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INTERNATIONAL ADVISORY COMMITTEE A. Carrington (Southampton, UK), Chair Emeritus J. M. Brown (Oxford, UK), Chair P. Casavecchia (Perugia, Italy) R. Colin (Brussels, Belgium) S. D. Colson (Richland, USA) R. F. Curl (Houston, USA) E. Hirota (Kanagawa, Japan) W. E. Jones (Halifax, Canada) M. Larsson (Stockholm, Sweden) S. Leach (Paris, France)
A. J. Merer (Vancouver, Canada) T. A. Miller (Columbus, USA) D. A. Ramsay (Ottawa, Canada) F. S. Rowland (Irvine, USA) T. C. Steimle (Tempe, USA) I. Tanaka (Tokyo, Japan) J. J. ter Meulen (Nijmegen, Netherlands) B. A. Thrush (Cambridge, UK)
LOCAL ORGANIZING COMMITTEE Yuan Tseh Lee (Honorary Chairman) Kopin Liu (Honorary Cochair) Yuan-Pern Lee (Chairman) Xueming Yang (Cochair)
Bor-Chen Chang Huan-Cheng Chang Kuo-Mei Chen Yit-Tsong Chen Bing-Ming Cheng Po-Yuan Cheng Su-Yu Chiang Eric Wei-Guang Diau Jia-Jen Ho Tong-Ing Ho
Sheng-Hsien Lin (Honorary Cochair) I-Chia Chen (Cochair)
Yen-Chu Hsu J.-M. Jim Lin King-Chuen Lin Wei-Tzou Luh J.-B. Nee Chi-Kung Ni Wen-Bih Tzeng Chin-hui Yu Niann-Shiah Wang
SYMPOSIUM VENUE The Grand Hotel 1, Sec. 4, Chung Shan N. Rd., Taipei 104, Taiwan TEL : 886-2-2886-8888 FAX : 886-2-2885-2885
SPONSORS National Science Council, Taiwan Academia Sinica, Taiwan Ministry of Education, Taiwan National Tsing Hua University, Taiwan
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Content
List of Invited Lectures 1
List of Posters 3
Abstracts of Invited Lectures 13
Abstracts of Posters 45
Poster Session A: Monday Evening 47
Poster Session B: Tuesday Evening 85
Poster Session C: Wednesday afternoon 123
Index of Authors 161
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1
List of Invited Lectures
No. Authors and Title pp.
M1 Suzuki, Toshinori Chemical Dynamics Studied by Time-Resolved Photoelectron Imaging
15
M2 Taylor, Mark; Muntean, Felician; McCoy, Anne; Barbera, Jack; Sanford, Todd; Rathbone, Jeff; Andrews, Django; Lineberger, W. Carl Time Resolved Solvent Rearrangement Dynamics
16
M3 Leone, Stephen R.; Müller, Astrid; Plenge, Jürgen; Haber, Louis; Clark, James Ultrafast X-Rays: Time-Resolved Photoelectron Processes in Molecular Dissociation
17
M4 Meijer, Gerard Manipulation of Molecules with Electric Fields
18
M5 Chou, Yung-Ching; Huang, Cheng-Liang; Ni, Chi-Kung; Kung, A. H.; Hougen, Jon T.; Chen, I-Chia Rotationally Resolved Spectra of Transitions Involving Motion of the Methyl Group of Acetaldehyde in the System à 1A" – X~ 1A'
19
M6 Chervenkov, S.; Georgiev, S.; Siglow, K.; Braun, J.; Chakraborty, T.; Wang, P.; Neusser, H. J. High Resolution Mass Selective UV Spectroscopy of Molecules and Clusters
20
M7 Choi, Jong-Ho Reaction Dynamics of Atomic Oxygen with Hydrocarbon Radicals
21
M8 Troya, Diego; Schatz, George C. Theoretical Studies of Reactions of Hyperthermal O(3P)
22
T1 Rowland, F. Sherwood Hydrocarbons in the Atmosphere
23
T2 Akimoto, Hajime Atmospheric Measurements of OH and HO2 Radicals in a Marine Boundary Layer
25
T3 Curl, Robert F.; Han, Jiaxiang; Hu, Shuiming; Brown, John; Chen, Hongbing; Thweatt, David Infrared Laser Spectroscopy and Chemical Kinetics of Free Radicals
26
T4 Zhu, R. S.; Xu, Z. F.; Lin, M. C. Ab Initio Studies of Free Radical Reactions of Interest to Atmospheric Chemistry
27
T5 Pollack, Ilana B.; Konen, Ian M.; Li, Eunice X. J.; Lester, Marsha I. Significant OH Radical Reactions in the Atmosphere: A New View
28
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W1 Balaj, O. Petru; Balteanu, Iulia; Beyer, M. K.; Bondybey, Vladimir E.
Free Electrons: The Simplest Free Radicals of them All 29
W2 Merkt, Frédéric High-Resolution Photoelectron Spectroscopic Studies of Ions and Radicals
30
W3 Vilesov, Andrey F. Helium Droplets as a Unique Nano-Matrix for Molecules and Molecular Aggregates
31
W4 Bonhommeau, D.; Viel, A.; Halberstadt, N. Non-adiabatic Dynamics of Ionized Neon Clusters inside Helium Nanodroplets
32
W5 Momose, Takamasa Free Radicals in Quantum Crystals: A Study of Tunneling Chemical Reactions
33
R1 Zhou, Jingang; Shiu, W.; Zhang, B.; Lin, Jim J.; Liu, Kopin From Pair Correlation to Reactive Resonance in Polyatomic Reactions
34
R2 Skodje, Rex T. State-to-State-to-State Dynamics of Chemical Reactions: The Control of Detailed Collision Dynamics by Quantized Bottleneck States
35
R3 Brouard, Mark The Stereodynamics of Photon-Initiated Reactions
36
R4 Aoiz, F. J.; Bañares, L.; Barr, J.; Torres, I.; Pino, G. A.; Amaral, G. A. Photodissociation Dynamics of Polyatomic Molecules Containing Sulfur: An Experimental Study
37
R5 Ni, Chi-Kung Photodissociation of Simple Aromatic Molecules Studied by Multimass Ion Imaging Techniques
38
F1 Kerenskaya, Galina; Schnupf, Udo; Heaven, Michael C. Spectroscopy and Dynamics of NH Radical Complexes
39
F2 Hutson, Jeremy M.; Soldán, Pavel Molecules in Cold Atomic Gases: How do They Interact?
40
F3 Steimle, Timothy C. Optical Stark and Zeeman Spectroscopy of Transition Metal Containing Radicals
41
F4 Hsu, Yen-Chu The Bending Vibrational Levels of C3-Rare-Gas Atom Complexes and C2H2+
42
F5 Maier, John P. Electronic Spectra of Carbon Chains and their Relevance to Astrophysics
43
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3
List of Posters Monday Evening, 26 July, 2004
No. Authors and Title pp.
A1-01 Laperle, Christopher M.; Mann, Jennifer E.; Continetti, Robert E. Three-Body Dissociation Dynamics of the Low-Lying Rydberg States of H3
47
A1-02 Lin, Jim J.; Perri, Mark J.; Van Wyngarden, Annalise L.; Boering, Kristie A.; Lee, Yuan T. Reaction Dynamics of Isotope Exchange Reaction of Singlet Oxygen Atom with Carbon Dioxide Molecule: A Crossed Molecular Beam Study
48
A1-03 Tseng, Chien-Ming; Dyakov, Yuri A.; Huang, Cheng-Liang; Mebel, Alexander M.; Lin, Sheng Hsien; Lee, Yuan T.; Ni, Chi-Kung Photoisomerization and Photodissociation of Aniline and 4-Methylpyridine
49
A1-04 Zhou, Weidong; Yuan, Yan; Zhang, Jingsong H-atom Elimination of n-Propyl and iso-Propyl Radicals: A Photodissociation Study
50
A1-05 Lee, Shih-Huang; Lee, Yuan T. Studies of Photodissociation Dynamics Using Selective Photoionization
51
A1-06 Zhang, Bailin; Shiu, Weicheng; Lin, Jim J.; Liu, Kopin Imaging the Mode-Correlation of Product Pairs: OH + CD4 → CD3 (000 Q, 202 Q) + HOD(ν1 ν2 0)
52
A1-07 Dyakov, Yuri A.; Mebel, Alexander M.; Lin, S. H.; Lee, Yuan T.; Ni, Chi-Kung Photodissociation of 4-Picoline, Aniline and Pyridine: Ab Initio and RRKM Study
53
A1-08 Lee, Yin-Yu; Dung, Tzan-Yi; Lee, Shih-Huang; Pan, Wan-Chun; Chen, I-Chia; Lin, Jr-Min; Yang, Xueming; Lee, Yuan T. Isomeric Species CH2SH and CH3S Formation from Photodissociation of Methanethiol at 157 nm
54
A1-09 Wu, Chia-Yan; Wu, Yu-Jong; Lee, Yuan-Pern Photodissociation of Fluorobenzene (C6H5F) at 193 nm Monitored with Time-resolved Fourier-transform Infrared Emission Spectroscopy
55
A1-10 Chen, Wei-Kan; Ho, Jr-Wei; Cheng, Po-Yuan Ultrafast Photodissociation Dynamics of Acetone S2 State at 195 nm
56
A1-11 Castillo, J. F.; Aoiz, F. J.; Banares, L.; Vazquez, S.; Martinez-Nuñéz, E.; Fernandez-Ramos, A. Quasiclassical Trajectory Studies of the F + CH4 Reaction Using an Ab Initio Potential Energy Surface Constructed by Interpolation
57
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A1-12 Eskola, Arkke; Seetula, Jorma; Timonen, Raimo Kinetics of the Reactions of Methyl Radical with HCl and DCl at Temperatures 188 – 500 K: Tunneling
58
A1-13 Tseng, S. Y.; Huang, C. L.; Wang, T. Y.; Wang, N. S.; Xu, Z. F.; Lin, M. C. Kinetics of the NCN + NO Reaction
59
A1-14 Wu, Di; Wang, Bing-Qiang; Li, Zhi-Ru; Hao, Xi-Yun; Li, Ru-Jiao; Sun, Chia-Chung Single-electron Hydrogen Bonds in the Methyl Radical Complexes H3C⋅⋅⋅HF and H3C⋅⋅⋅HCCH: an ab initio Study
60
A1-15 Hela, P. G.; Shih, H.-T.; Cheng, C.-H.; Chen, I-C. Dynamics of Photoluminescence in Bistriphenylene
61
A1-16 Chang, Chih-Wei; Diau, Eric Wei-Guang; Chang, I-Jy Ultrafast Interfacial Electron Transfer Dynamics of the TiO2 Nanostructures Functionalized by the Ru2+ Complexes
62
A1-17 Hancock, G.; Morrison, M.; Saunders, M. Time Resolved FTIR Emission Studies of Molecular Dynamics
63
A2-01 Katoh, Kaoru; Sumiyoshi, Yoshihiro; Ueno, Taketoshi; Endo, Yasuki Fourier-Transform Microwave Spectroscopy of CCCl and CCCCCl
64
A2-02 Kobayashi, Kaori; Saito, Shuji Isotope Study of the CCO Radical in its 3Σ- Ground State by Microwave Spectroscopy
65
A2-03 Lin, Chia-Shih; Chang, Wei-Zhong; Hsu, Hui-Ju; Chang, Bor-Chen New Dispersed Fluorescence Spectra of Simple Halocarbenes in a Discharge Supersonic Free Jet Expansion
66
A2-04 Radi, Peter P.; Tulej, Marek; Knopp, Gregor; Beaud, Paul; Gerber, Thomas Double-Resonance Spectroscopy on HCO and H2CO by Two-Color Resonant Four-Wave Mixing
67
A2-05 Fink, E. H.; Ramsay, D. A. Near Infrared Emission Spectra of HO2 and DO2
68
A2-06 Evertsen, R.; Staicu, A.; van Oijen, J. A.; Dam, N. J.; de Goey, L. P. H.; ter Meulen, J. J. Cavity Ring Down Spectroscopy of CH, CH2, HCO and H2CO in a Premixed Flat Flame at both Atmospheric and Sub-atmospheric Pressure
69
A2-07 Yurchenko, Sergei N.; Carvajal, Miguel; Jensen, Per; Lin, Hai; Thiel, Walter Rotation-vibration Motion of Pyramidal XY3 Molecules Described in the Eckart Frame: Theory and Application to NH3
70
A2-08 Chen, Kuo-mei Resonance-enhanced Multiphoton Ionization Spectroscopy of CH3 and CD3. Two-photon Absorption Selection Rules and Rotational Line Strengths of the v3- and v4-Active Vibronic Transitions
71
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A2-09 Shayesteh, Alireza; Appadoo, Dominique R. T.; Gordon, Iouli; Bernath, Peter F. The Vibration-Rotation Emission Spectra of Gaseous ZnH2 and ZnD2
72
A2-10 Balfour, Walter J.; Brown, John M.; Wallace, Lloyd Identification and Characterization of Two New Electronic Transitions of the FeH Radical in the Infrared
73
A2-11 Ashworth, Stephen H.; Varberg, Thomas D.; Hodges, Philip J.; Brown, John M. Detection of the Electronic Spectra of FeCl2 and CoCl2 in the Gas Phase
74
A2-12 Merer, A. J.; Peers, J. R. D.; Rixon, S. J. Free Radicals in the Reaction Products of Zr with Methane: the Electronic Spectra of ZrC and ZrCH
75
A2-13 Tang, Sheunn-Jiun; Chou, Yung-Ching; Lin, Jim Jer-Min; Hsu, Yen-Chu The Bending Vibrational Levels of Acetylene Cation: A Case Study of the Renner-Teller Effects with Two Degenerate Bending Vibrations
76
A2-14 Yoshida, K.; Kanamori, H. High Resolution Spectroscopic Studies of Vibrational States in the Triplet Potential of Acetylene
77
A2-15 Lin, I-Feng; Kurniawan, Fendi; Chiang, Su-Yu Experimental and Theoretical Studies on Rydberg States of H2CS in the Region 130-220 nm
78
A2-16 Jacox, Marilyn E.; Thompson, Warren E. Infrared Spectra of Neutral and Ionic SO2H2 Species Trapped in Solid Neon
79
A2-17 Jochnowitz, Evan B.; Zhang, Xu; Nimlos, Mark R.; Varne, Mychel Elizabeth; Stanton, John F.; Ellison, G. Barney Polarized IR Spectrum of Matrix-Isolated Propargyl Radicals and Detection of HC≡CH-CH2OO
80
A2-18 Cardenas, R.; Bates, S. A.; Robbins, D. L.; Rittby, C. M. L.; Graham, W. R. M. Recent Progress in FTIR and DFT Studies on the Vibrational Spectra and Structures of Group IV Clusters
81
A2-19 Delaney, Cailin; Clar, Justin; Cohen, Jodi; Abrash, Samuel A. Photochemistry of HI-Allene Complexes in Argon Matrices
82
A2-20 van de Meerakker, S. Y. T.; Vanhaecke, N.; Meijer, G. Decelerating OH and NH Radical Beams
83
A2-21 Hu, Shui-Ming; Liu, An-Wen; He, Sheng-Gui; Zheng, Jing-Jing; Lin, Hai; Zhu, Qing-Shi Inter-bonds Crossing Dipole Moment and Stretching Vibrational Bands Intersities of the Group V Hydrides
84
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6
Tuesday Evening, 27 July, 2004
No. Authors and Title pp.
B1-01 Capozza, G.; Leonori, F.; Segoloni, E.; Balucani, N.; Stranges, D.; Volpi, G. G.; Casavecchia, P. Crossed Molecular Beam Studies of Radical-radical Reactions: O(3P) + C3H5 (Allyl)
85
B1-02 Balucani, N.; Capozza, G.; Segoloni, E.; Cartechini, L.; Bobbenkamp, R.; Casavecchia, P.; Bañares, L.; Aoiz, F. J.; Honvault, P.; Bussery-Honvault, B.; Launay, J.-M. The Dynamics of Prototype Insertion Reactions: Crossed Beam Experiments versus Quantum and Quasiclassical Trajectory Scattering Calculations on Ab Initio Potential Energy Surfaces for C(1D) + H2 and N(2D) + H2
86
B1-03 Lin, Ming-Fu; Dyakov, Yuri A.; Lin, Sheng-Hsien; Lee, Yuan T.; Ni, Chi-Kung Photodissociation Dynamics of Pyridine and C6HxF6-x (x = 1~4) at 193 nm
87
B1-04 Zhou, Weidong; Yuan, Yan; Zhang, Jingsong State-to-state Photodissociation Dynamics of OH Radical via the A2Σ+ State and Fine-structure Distributions of the O(3PJ) Product
88
B1-05 McCunn, L. R.; Miller, J. L.; Krisch, M. J.; Liu, Y.; Butler, L. J.; Shu, J. Molecular Beam Studies of the Photolysis of 2-Chloro-2-butene and the Subsequent Dissociation of the 2-Buten-2-yl Radical
89
B1-06 Shiu, Vincent W. C.; Lin, Jim J.; Liu, Kopin; Wu, Malcom; Parker, David H. Threshold is More Exciting: Seeing Reactive Resonance in a Polyatomic Reaction
90
B1-07 Martínez-Núñez, Emilio; Marques, Jorge M. C.; Vázquez, Saulo A. Dissociation of the Methanethiol Radical Cation Induced by Collisions with Ar Atoms: An Investigation by Quasiclassical Trajectories
91
B1-08 Obernhuber, Thorsten; Kensy, Uwe; Dick, Bernhard The Photodissociation Dynamics of t-Butylnitrite Initiated by Excitation to the S2 Electronic State
92
B1-09 Yang, Sheng-Kai; Chen, Hui-Fen; Liu, Suet-Yi; Wu, Chia-Yan; Lee, Yuan-Pern Photolysis of 2-Fluorotoluene at 193 nm: Internal Energy of HF Determined with Time-resolved Fourier-transform Infrared Emission Spectroscopy
93
B1-10 Cireasa, D. R.; Moise, A.; ter Meulen, J. J. Inelastic State-to-state Scattering of Oriented OH by HCl
94
B1-11 Castillo, J. F.; Aoiz, F. J.; Banares, L. Quasiclassical Trajectory Studies of the Cl + CH4 Reaction Using an Ab Initio Potential Energy Surface Constructed by Interpolation
95
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B1-12 Pimentel, André S.; Nesbitt, Fred L.; Payne, Walter A.; Cody, Regina J. Planetary Chemistry of C2H5 Radicals: Rate Constant for the CH3 + C2H5 Reaction at Low Temperatures and Pressures
96
B1-13 Chou, Sheng-Lung; Lee, Yuan-Pern; Lin, Ming-Chang Experimental Studies of the Rate Coefficients of the Reaction O(3P) + CH3OH at High Temperatures
97
B1-14 Li, Zhi-Ru; Wu, Di; Li, Ru-Jiao; Hao, Xi-Yun; Wang, Bing-Qiang; Sun, Chia-Chung Electron Donor-Acceptor Bonds in the Methyl Radical Complexes H3C-BH3, H3C-AlH3 and H3C-BF3: an ab initio Study
98
B1-15 Liu, Kuan Lin; Cheng, Chao Han; Tang, Kuo-Chun; Chen, I-Chia Rapid Intersystem Crossing in Highly Phosphorescent Iridium Complexes
99
B1-16 Luo, Liyang; Chiang, Chia-Chen; Diau, Eric Wei-Guang; Lin, Ching-Yao Ultrafast Electron Transfer and Energy Transfer Dynamics of Porphyrin- TiO2 Nanostructures
100
B1-17 Yin, Hong-Ming; Sun, Ju-Long; Cong, Shu-Lin; Han, Ke-Li; He, Guo-Zhong The Internal Energy Distribution and Alignment Properties of the CH3O (X) Fragment by the Photodissociation of CH3ONO at 355 nm
101
B2-01 Suma, Kohsuke; Sumiyoshi, Yoshihiro; Endo, Yasuki Fourier-transform Microwave Spectroscopy and FTMW-millimeter-wave Double Resonance Spectroscopy of XOO (X = Cl, Br) Radicals
102
B2-02 Han, Huei-Lin; Chu, Li-Kang; Lee, Yuan-Pern Detection of Infrared Absorption of Gaseous ClCS Using Time-resolved Fourier-transform Spectroscopy
103
B2-03 Fan, Haiyan; Ionescu, Ionela; Annesley, Chris; Xin, Ju; Reid, Scott A. On the Renner-Teller Effect and Barriers to Linearity and Dissociation in HCF(Ã1 A")
104
B2-04 Colin, Reginald; Liu, Ching-Ping; Lee, Yuan-Pern Detection of Predissociated Levels of the SO B 3Σ- State using Degenerate Four-wave Mixing Spectroscopy
105
B2-05 Elliott, N. L.; Fitzpatrick, J. A. J.; Chekhlov, O. V.; Ashworth, S. H.; Western, C. M. Electronic Structure from High Resolution Spectroscopy
106
B2-06 Dagdigian, Paul J.; Nizamov, Boris; Teslja, Alexey Cavity Ring-Down Spectroscopy of Polyatomic Transient Intermediates: H2CN and H2CNH
107
B2-07 Pollack, Ilana B.; Konen, Ian M.; Li, Eunice X. J.; Lester, Marsha I. Significant OH Radical Reactions in the Atmosphere: A New View
108
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B2-08 Muramoto, Yasuhiko; Ishikawa, Haruki; Mikami, Naohiko First Observation of the B~ (1A1) State of SiH2 and SiD2 Radicals by the OODR Spectroscopy
109
B2-09 Bernath, P.; Bauschlicher, C. W.; Dulick, M.; Ram, R. S.; Burrows, A. Metal Hydrides in Astronomy
110
B2-10 O'Brien, Leah C.; Hardimon, Sarah Fourier Transform Spectroscopy of Gold Oxide, AuO
111
B2-11 Balfour, Walter J.; Li, Runhua; Jensen, Roy H.; Shephard, Scott A.; Adam, Allan G. The First Observation of the Rhodium Monofluoride Molecule Jet-cooled Laser Spectroscopic Studies
112
B2-12 Miller, Terry A. Spectroscopy of Free Radicals in Hydrocarbon Oxidation
113
B2-13 Chou, Yung-Ching; Chen, I-Chia; Hougen, Jon T. Anomalous Splittings of Torsional Sublevels Induced by the Aldehyde Inversion Motion in the S1 State of Acetaldehyde
114
B2-14 Lee, P. C.; Yang, J. C.; Nee, J. B. Absorption Spectra of O2 and NO in 105-200 nm Wavelength Region Measured by using a Supersonic Jet
115
B2-15 Willitsch, Stefan; Innocenti, Fabrizio; Dyke, John M.; Merkt, Frédéric Rovibronic Energy Level Structure of the Two Lowest Electronic States of the Ozone Cation
116
B2-16 Lo, Wen-Jui; Chen, Hui-Fen; Chou, Po-Han; Lee, Yuan-Pern Isomers of OCS2: IR Absorption Spectra of OSCS in Solid Argon
117
B2-17 Zhang, Xu; Kato, Shuji; Bierbaum, Veronica M.; Ellison, G. Barney Gas-Phase Reactions of Organic Radicals and Diradicals with Ions
118
B2-18 Larsson, M.; McCall, B. J.; Huneycutt, A. J.; Saykally, R. J.; Geballe, T. R.; Djurić, N.; Dunn, G. H.; Semaniak, J.; Novotny, O.; Al-Khalili, A.; Ehlerding, A.; Hellberg, F.; Kalhouri, S.; Neau, A.; Paál, A.; Thomas, R.; Österdahl, F. H3+ Dissociative Recombination and the Cosmic-Ray Ionisation Rate towards ζ Persei
119
B2-19 Oguchi, T.; Hattori, T.; Matsui, H. The Reaction Mechanism of O(1D) with Ethylene: the Product Yield Measurements of OH, CH2CHO and H atom
120
B2-20 Geppert, W. D.; Thomas, R.; Ehlerding, A.; Hellberg, F.; Österdahl, F.; Millar, T. J.; Semaniak, J.; af Ugglas, M.; Djuric, N.; Larsson, M. Dissociative Recombination of Astrophysically Important Isoelectronic Ions
121
B2-21 Peterka, Darcy S.; Kim, Jeong Hyun; Wang, Chia C.; Ahmed, Musahid; Neumark, Daniel M. Photoelectron Spectroscopy of Nitric Oxide Doped in Helium Droplets
122
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9
Wednesday Afternoon, 28 July, 2004
No. Authors and Title pp.
C1-01 Capozza, G.; Leonori, F.; Segoloni, E.; Volpi, G. G.; Casavecchia, P. Dynamics of HCCO and CH2 Radical Formation from the Reaction O(3P) + C2H2 in Crossed Beams using Soft Electron Impact Ionization for Product Detection
123
C1-02 Capozza, G.; Segoloni, E.; Volpi, G. G.; Casavecchia, P. Towards the "Universal" Product Detection in Crossed Beam Reactive Scattering Experiments using Soft Electron Impact Ionization: Dynamics of Vynoxy, Acetyl, Methyl, Formyl, and Methylene Radicals and Ketene Formation from the Reaction O(3P) + C2H4
124
C1-03 Liu, Chen-Lin; Hsu, Hsu Chen; Ni, Chi-Kung Photodissociation of I2+ Studied by Velocity Map Imaging
125
C1-04 Higashiyama, Tomohiko; Ishida, Masayuki; Honma, Kenji Dynamics of Reaction, Y(2D3/2, 5/2) + O2(X3Σ−g) → YO(A2Π) + O(3PJ), Studied by Crossed Beam-chemiluminescence Technique
126
C1-05 Miller, J. L.; McCunn, L. R.; Krisch, M. J.; Butler, L. J.; Shu, J. Molecular Beam Studies of the Dissociation and Isomerization of Radical Isomers: The Influence of the Electronic Wavefunction in the Dissociation Dynamics of Vinoxy Radicals
127
C1-06 Chang, Chushuan; Luo, Chu-Yung; Liu, Kopin Mode- and State-selected Photodissociation of OCS+ by Time-sliced Velocity Mapping Image Technique
128
C1-07 Martínez-Núñez, Emilio; Vázquez, Saulo A. Quasiclassical Trajectory Study of the 193 nm Photodissociation of CF2CHCl
129
C1-08 Fujimura, Yo; Tamada, Hisashi; Imai, Yoshiyuki; Mitsutani, Kazuya; Kajimoto, Okitsugu Reinvestigation of O(1D)+H2O Reaction: Examination of the Contribution of Excited States
130
C1-09 Bahou, Mohammed; Lee, Yuan-Pern Photodissociation Dynamics Investigated with a Pulsed Slit-jet and Time-resolved Fourier-transform Spectroscopy
131
C1-10 Lee, Sheng-Jui; Chen, I-Chia Ab Initio Studies for Dissociation Pathway and Isomerization of Crotonaldehyde
132
C1-11 Ho, Jr-Wei; Yang, Chia-Ming; Lai, Ta-Jen; Cheng, Po-Yuan The Use of Ultrafast Photodissociation as a Probe for Studies of Electronic Energy Transfer Dynamics
133
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C1-12 Oum, Kawon; Sekiguchi, Kentaro; Luther, Klaus
The Role of Radical-Molecule Complexes in the Recombination Kinetics of Benzyl Radicals
134
C1-13 Alam, M. S.; Rao, B. S. M.; Janata, E. Reactions of •OH and H• with Aliphatic Alcohols: A Pulse Radiolysis Study
135
C1-14 Cheng, Mu-Jeng; Chu, San-Yan Substituent Effect on Structure and Bonding of Bertrand Diradical (X2P)2(BY)2
136
C1-15 Guss, Joseph; Kable, Scott Characterisation of the CCl2 Ã State
137
C1-16 Kumae, Takashi; Arakawa, Hatsuko Assessment of Training Effects on Levels of Serum Total Anti-oxidative Activity in Matured Rats using Luminol-dependent Chemiluminescence
138
C1-17 Dong, Feng; Whitney, Erin; Zolot, Alex; Deskevich, Mike; Nesbitt, David J. High Resolution Spectroscopy and Reaction Dynamics of Free Radicals
139
C2-01 Katoh, Kaoru; Sumiyoshi, Yoshihiro; Endo, Yasuki; Hirota, Eizi FTMW and FTMW-MMW Double Resonance Spectroscopy of the CH3OO Radical
140
C2-02 Juances-Marcos, Juan Carlos; Althorpe, Stuart C. Geometric Phase and the Hydrogen-Exchange Reaction
141
C2-03 Fan, Haiyan; Ionescu, Ionela; Annesley, Chris; Xin, Ju; Reid, Scott A. Polarization Quantum Beat Spectroscopy of HCF(Ã1A"): 19F and 1H Hyperfine Structure, Zeeman Effect, and Singlet-triplet Interactions
142
C2-04 Liu, Ching-Ping; Reid, Scott A.; Lee, Yuan-Pern Two-color Resonant Four-wave Mixing Spectroscopy of Highly Predissociated Levels in the à 2A1 State of CH3S
143
C2-05 Ahmed, K.; Balint-Kurti, G. G.; Western, C. M. Exploring the Potential Energy Surfaces of C3
144
C2-06 Zhang, Guiqiu; Chen, Kan-Sen; Merer, Anthony J.; Hsu, Yen-Chu; Chen, Wei-Jan; Sadasivan, Shaji; Liao, Yean-An; Kung, A. H. Perturbations in the à 1Πu, 000 Level of C3
145
C2-07 Marshall, Mark D.; Greenslade, Margaret E.; Davey, James B.; Lester, Marsha I. Partial Quenching of Orbital Angular Momentum in the OH-Acetylene Complex
146
C2-08 Fujii, Asuka; Miyazaki, Mitsuhiko; Ebata, Takayuki; Mikami, Naohiko Infrared Spectroscopy of Large-sized Protonated Water Cluster Cations: Development of the 3-Dimensional Hydrogen Bond Network with Cluster Size
147
C2-09 Luh, Wei-Tzou Electronically-excited Singlet States of LiH
148
C2-10 O'Brien, Leah C.; O'Brien, James J. Intracavity Laser Spectroscopy of NiH
149
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11
C2-11 Jakubek, Zygmunt J.; Nakhate, Sanjay; Simard, Benoit; Zachwieja, Mirek Spectroscopy of Si+NH3 and Si-PH3 Reaction Products: Rovibronic Structure of the Ground Electronic States of SiNSi and PH2
150
C2-12 Varberg, Thomas D.; Le Roy, Robert J. Isotope Dependence and Born-Oppenheimer Breakdown in Mid- and Far-Infrared Spectra of Cadmium Hydride
151
C2-13 Baek, Dae Youl; Wang, Jinguo; Doi, Atsushi; Kasahara, Shunji; Baba, Masaaki; Katô, Hajime Doppler-free Two-photon Excitation Spectroscopy and the Zeeman Effect of the 1011401 Band of the S1 1B2u←S0 1A1g Transition of Benzene-d6
152
C2-14 Huang, Cheng-Liang; Liu, Chen-Lin; Ni, Chi-Kung; Hougen, Jon T. Electronic Spectra of Molecules with Two C3v Internal Rotors: Torsional Analysis of the A 1Au – X 1Ag LIF Spectrum of Biacetyl
153
C2-15 Willitsch, Stefan; Dyke, John M.; Merkt, Frédéric Rotationally Resolved Photoelectron Spectrum of NH2 and ND2: Rovibrational Energy Level Structure of the 1
1Aa~+ and 13BX~ + States
154
C2-16 Wu, Yu-Jong; Chou, Chun-Pang; Lee, Yuan-Pern Isomers of CNO2: Infrared Absorption of ONCO in Solid Neon
155
C2-17 Chou, Chun-Pang; Wu, Yu-Jong; Lee, Yuan-Pern IR Spectroscopy of Ge(NO) and Ge(NO)2 Isolated in Solid Argon
156
C2-18 Ehlerding, A.; Geppert, W.; Zhaunerchyk, V.; Hellberg, F.; Thomas, R.; Arnold, S. T.; Viggiano, A. A.; Semaniak, J.; Österdahl, F.; af Ugglas, M.; Larsson, M. Dissociative Recombination of Hydrocarbon Ions
157
C2-19 Thomas, R. D.; Ehlerding, A.; Geppert, W.; Hellberg, F.; Larsson, M.; Rosen, S.; Zhaunerchyk, V.; Bahati, E.; Bannister, M. E.; Vane, C. R.; Petrignani, A.; van der Zande, W. J.; Andersson, P.; Pettersson, J. B. C. The Effect of Bonding on the Fragmentation of Small Systems
158
C2-20 Hu, Qichi; Hepburn, John Dynamics and Spectroscopy of Threshold Photoion-Pair Formation
159
C2-21 Chen, Chun-Cing; Wu, Hsing-Chen; Tseng, Chien-Ming; Yang, Yi-Han; Chen, Yit-Tsong; One- and Two-photon Excitation Vibronic Spectra of 2-methylallyl Radical at 4.6-5.6 V
160
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Abstracts of Invited Lectures
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Chemical Dynamics Studied by Time-Resolved Photoelectron Imaging
Toshinori Suzuki Chemical Dynamics Laboratory, Discovery Research Institute
RIKEN (Institute of Physical and Chemical Research) Wako, Saitama 351-0198, JAPAN
As the Born-Oppenheimer approximation indicates, chemical change is driven by
electrons. Observation of rapid changes of electronic state or electron configuration during the
course of chemical reaction will be essential for elucidating the dynamics. In the last decade,
solid-state ultrafast laser technology has been well established to allow various types of
pump-probe experiments of chemical reactions; however, further efforts seemed to be
necessary to directly observe electronic dynamics. We have combined femtosecond
pump-probe ionization method with two-dimensional imaging of photoelectron scattering
distribution to observe electronic dephasing processes in real-time. In addition to the
electronic dynamics, vibrational, and rotational wavepacket motions vary the kinetic energy
and ejection angle of photoelectrons, which makes time-resolved photoelectron imaging to be
a powerful tool for studying chemical dynamics. In this talk, we will present the method,
some recent results, problems, and future possibilities.
“Non-adiabatic dynamics effects in Chemistry revealed by time-resolved charged particle imaging”, T.
Suzuki and B.J. Whitaker, Int. Rev. Phys. Chem. 20, 313 (2001).
“Time-resolved photoelectron spectroscopy and imaging”, T. Suzuki in Modern Trends in Chemical
Reaction Dynamics, Advanced Series in Physical Chemistry, (World Scientific, 2004).
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Time Resolved Solvent Rearrangement Dynamics
Mark Taylor1, Felician Muntean1, Anne McCoy2, Jack Barbera, Todd Sanford, Jeff Rathbone, Django Andrews, and W. Carl Lineberger1
1JILA and Department of Chemistry and Biochemistry, Boulder, CO, USA 1JILA Visiting Fellow, 2003; Permanent Address, Ohio State University, Columbus, OH, USA
A femtosecond negative ion-neutral-positive ion charge reversal apparatus is
employed to investigate transient neutral species evolving along a reaction coordinate. We
report studies of the rearrangement dynamics of Cu(OH2) and Cu(OH2)2 produced by
photodetachment of the corresponding anion. Negative ion photoelectron imaging
spectroscopy is employed to characterize the initial anion. Following a controlled delay
period, a second ultrafast tunable laser pulse (photon energy close to that of the Cu 2P excited
state) initiates resonant multiphoton photoionization of the time-evolving Cu···OH2 complex.
The time-resolved Cu+ and Cu+(OH2) signals provide information both on the prompt
dissociation of the complex and on the slower (10s of ps) energy redistribution between
internal rotational and radial modes of the evolving complex. Calculations of the time
evolution of the anion geometric configuration on the neutral potential energy surface yield
deeper insight into the nature of the rearrangement process and the energy flow within the
complex. Recent studies on other partially solvated systems will be briefly discussed.
Supported by NSF and AFOSR
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Ultrafast X-Rays: Time-Resolved Photoelectron Processes in Molecular Dissociation
Stephen R. Leone, Astrid Müller, Jürgen Plenge, Louis Haber, and James Clark
Departments of Chemistry and Physics and Lawrence Berkeley National Laboratory University of California, Berkeley, CA 94720 USA
[email protected] http://chem.berkeley.edu/people/faculty/leone/leone.html
Radical chemistry and production are investigated by ultrafast time-resolved photoelectron spectroscopy. High-order harmonics of a Ti:sapphire laser are produced in the vacuum ultraviolet or soft x-ray spectral region to serve as the probe pulses for valence shell and core level photoelectron spectra of transient and dissociating species. Soft x-ray femtosecond pulses are generated by focusing intense 800 nm pulses into a rare gas pulsed jet of Ar or Ne, producing the probe photons at every odd harmonic of 800 nm with energies up to 100 eV. Photofragmentation dynamics of small molecules is initiated with visible or ultraviolet pulses from the same master laser system. Two types of time-resolved photoelectron spectroscopies, x-ray photoelectron (XPS) and valence band photoelectron (PES), probe between different potential surfaces of the molecules. Diatomic molecules, such as bromine, are excited to a repulsive dissociative state or a bound electronic state, and selected harmonics are used to obtain time-resolved photoelectron spectra. The resulting bromine atom radicals are detected as they are produced in real time, and these signals are related to the timescale for the free atomic species to be formed. The wave packet amplitude on the dissociative state is observed and related to the above threshold ionization processes in the molecule, which occur simultaneously. Relative ionization cross sections are determined as a function of probe wavelength. New experiments emphasize dissociation and intramolecular processes in polyatomic molecule systems. Results are presented for the production and characterization of the harmonics, including spectral bandwidth determinations, temporal resolution, and the use of the harmonics for stable-molecule and dissociating-state core level and valence shell photoelectron spectroscopy. Related high resolution studies of molecules and radicals are performed at the Chemical Dynamics Beamline of the Advanced Light Source. A recirculating-linac-based concept for ultrafast x-ray pump-probe science is being developed, and the potential for studies with this possible future facility are also discussed.
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Manipulation of Molecules with Electric Fields
Gerard Meijer
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
and FOM Institute for Plasmaphysics Rijnhuizen,
Edisonbaan 14, NL-3439 MN Nieuwegein, The Netherlands During the last years we have been experimentally exploring the possibilities of manipulating neutral polar molecules with electric fields [1]. Arrays of time-varying, inhomogeneous electric fields have been used to reduce in a stepwise fashion the forward velocity of molecules in a beam. With this so-called 'Stark decelerator', the equivalent of a LINear ACcelerator (LINAC) for charged particles, one can transfer the high phase-space density that is present in the moving frame of a pulsed molecular beam to a reference frame at any desired velocity; molecular beams with a computer-controlled (calibrated) velocity and with a narrow velocity distribution, corresponding to sub-mK longitudinal temperatures, can be produced. These decelerated beams offer new possibilities for collision studies, for instance, and enable spectroscopic studies with an improved spectral resolution; first proof-of-principle high-resolution spectroscopic studies have been performed. These decelerated beams have also been used to load neutral ammonia molecules in an electrostatic trap at a density of (better than) 107 mol/cm3 and at temperatures of around 25 mK. In another experiment, a decelerated beam of ammonia molecules is injected in an electrostatic storage ring. The package of molecules in the ring can be observed for more than 50 distinct round trips, corresponding to 40 meter in circular orbit and almost 0.5 sec. storage time, sufficiently long for a first investigation of its transversal motion in the ring. A scaled up version of the Stark-decelerator and molecular beam machine has just become operational, and has been used to produce decelerated beams of ground-state OH and electronically excited (metastable) NH radicals. The NH radical is particularly interesting, as an optical pumping scheme enables the accumulation of decelerated bunches of slow NH molecules, either in a magnetic or in an optical trap. By miniaturizing the electrode geometries, high electric fields can be produced using only modest voltages. A micro-structured mirror for neutral molecules that can rapidly be switched on and off has been constructed and used to retro-reflect a beam of ammonia molecules with a forward velocity of about 30 m/s. This holds great promise for miniaturizing the whole decelerator, trap and storage ring for future applications.
References
[1] H.L. Bethlem and G. Meijer, Int. Rev. Phys. Chem. 22, 73 (2003)
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Rotationally Resolved Spectra of Transitions Involving Motion of the
Methyl Group of Acetaldehyde in the System A~ 1A″− X~ 1A′
Yung-Ching Chou,1 Cheng-Liang Huang,1 Chi-Kung Ni2, A. H. Kung2, Jon T. Hougen3, and
I-Chia Chen1 1Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 30013, 2Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan 106
3Optical Technology Division, National Institute of Standards and Technology, Gaithersburg,
Maryland 20899-8441
Fluorescence excitation spectra, at resolution 0.02 cm-1, in the system A~ 1A″− X~ 1A′
were recorded for acetaldehyde in a supersonic jet. We performed full rotational analysis of
bands n000 1514
+ and n000 1514
− , for n = 0 – 5, in which 140+ and 140- denote the two inversion
tunneling components of the aldehyde hydrogen out of plane bending, in the vibrational
ground state of A~ 1A″. Torsional levels from the lowest energy to beyond the methyl
torsional barrier up to 370 cm-1 are assigned. These high energy states lying above the
torsional barrier display character between the limits of torsional vibrational motion and free
internal rotor motion, so that the close-lying 5A2 and 6A1 states mix for K > 0, and K states in
the E sublevel are widely split. Anomalous transitions (∆Ka = 0, ∆Kc = 0) to A sublevels are
observed for bands 4000 1514
+ and 3000 1514
− . The positions of A and E sublevels in 140-15n
cannot be fitted with a program involving only interaction of torsion and rotation,
furthermore for n = 0–1 states the A/E splitting is reversed from those in 140+15n.
Interaction with inversion evidently varies the splitting of torsional sublevels and the K
structure.
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High Resolution Mass Selective UV Spectroscopy of Molecules and Clusters S. Chervenkov, S. Georgiev, K. Siglow, J. Braun, T. Chakraborty, P. Wang, and H. J. Neusser
Physikalische und Theoretische Chemie, Technische Universität München,
Lichtenbergstr. 4, D-85748 Garching, Germany Rotationally resolved UV spectra of molecular clusters in the gas phase have been measured with 100 MHz resolution and mass selection in a resonance-enhanced two-photon ionization process [1]. Analyzing the complex rotational structure of the vibronic bands of hydrogen-bonded clusters of aromatic molecules with water we have found information on the water position and the intermolecular vibrational dynamics. Results are presented for water complexes of benzonitrile, indole, and 4-fluorostyrene. Recently the technique has been successfully applied to flexible molecules of biological importance: the neurotransmitters ephedrine [2] and 2-phenylethanol. To better understand the conformational dynamics and the role of the intramolecular hydrogen bonds for the conformational stability we performed ab initio calculations. Combining pulsed high resolution and pulsed field ionization techniques we were able to resolve individual high Rydberg states (45 < n < 110) for the first time in a polyatomic molecule, benzene, and its van der Waals complexes with Ne, Ar, and Kr [1]. The series limits represent the individual rotational states of the respective radical cation yielding structural information on the van der Waals distance of the noble gas atom and on spin orbit coupling in the benzene radical cation induced by the external heavy noble gas atom.
Mass analyzed pulsed field threshold ionization (MATI) of bunches of very high Rydberg states is a powerful method for vibrational spectroscopy of radical cations and their production with defined internal energy. The mass selectivity allows us to detect with high precision the dissociation threshold of van der Waals bound aromatic radical cations with noble gases [3-5] and of hydrogen-bonded aromatic molecule-water complexes 3-methylindole-water and –benzene [6]. The ionization of the complex leads to strengthening of the hydrogen bond by factor of three caused by the additional charge.
[1] H. J. Neusser, K. Siglow, Chem. Rev. 100, 3921 (2000). [2] S. Chervenkov, P. Q. Wang, J. E. Braun, H. J. Neusser, submitted to J. Chem. Phys. [3] H. Krause, H. J. Neusser, J. Chem. Phys. 97, 5923 (1992). [4] J. E. Braun, H. J. Neusser, Mass Spectrom. Rev. 21, 16 (2002) [5] S. Georgiev, T. Chakraborty, H. J. Neusser, J. Phys. Chem. 108, 3304 (2004) [6] S. Georgiev, H. J. Neusser, Chem. Phys. Letters 189, 24 (2004)
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Reaction Dynamics of Atomic Oxygen with Hydrocarbon Radicals
Jong-Ho Choi
Department of Chemistry, Korea University, Seoul 136-701, Korea
The reaction dynamics of ground-state atomic oxygen (O(3P)) with propargyl (C3H3) radicals
have first been investigated by applying laser induced fluorescence (LIF) spectroscopy in a
crossed beam configuration. New exothermic channels (1) and (2) were observed, and the
nascent internal state distributions of some products showed substantial bimodal internal
excitations.
O(3P) + C3H3 → C3H2 + OH (1)
→ C3H2O + H (2)
We also performed ab initio, RRKM (Rice-Ramsperger-Kassel-Marcus) and prior
calculations to characterize the reaction mechanism and energy partitioning. It has been
found out that the surprising difference in the potential energy surfaces for the two reactions
plays a critical role in understanding the reaction mechanisms. We hope this work sheds
some light on the gas-phase atom-radical dynamics at the molecular level, which has been
very little explored so far.
[1] H.C. Kwon, J.H. Park, H. Lee, H.K. Kim, Y.S. Choi, and J.H. Choi*, J. Chem. Phys.
(Communications) 116. 2675 (2002).
[2] J.H. Park, H. Lee, H.C. Kwon, H.K. Kim, Y.S. Choi, and J.H. Choi*, J. Chem. Phys. 117.
2017 (2002).
[3] J.H. Park, H. Lee, Y.S. Choi, and J.H. Choi*, J. Chem. Phys. 119, 8966 (2003).[4]. H. Lee,
S.K. Joo, L.K. Kwon, J.H. Park, Y.S. Choi, and J.H. Choi*, J. Chem. Phys. (Communications)
119, 9337 (2003).[5] H. Lee, S.K. Joo, L.K. Kwon, and J.H. Choi*, J. Chem. Phys. 120, 2215
(2004).
[6] S.K. Joo, L.K. Kwon, H. Lee, and J.H. Choi*, J. Chem. Phys. 120, 7976 (2004).
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Theoretical Studies of Reactions of Hyperthermal O(3P)
Diego Troya and George C. Schatz
Department of Chemistry, Northwestern University, Evanston, IL 60208-3113 USA
Recently, Tim Minton at Montana State has performed a series of crossed molecular
beam experiments involving the reaction of hyperthermal oxygen atoms (several eV energies)
with H2, methane, ethane, propane and with polymer surfaces. These experiments are of
importance as they relate to the interaction of O(3P) found in low earth orbit with the
polymer-containing surfaces of space craft. This talk will describe a series of computational
simulations designed to model these reactions. The calculations are based on direct dynamics
calculations in which the MSINDO semiempirical electronic structure method is used to
determine forces for each time step in classical molecular dynamics simulations. For our
gas/surface simulations we also use QM/MM (quantum mechanics/molecular mechanics)
calculations in which the portions of the polymer that are close to the O atom are treated as
quantum atoms and the rest are described with molecular mechanics. We have calibrated the
quality of the MSINDO potential surface through extensive calibration with higher quality ab
initio calculations.
Although hydrogen abstraction to give OH plus an alkyl radical is the expected product
for O + alkane reactions, our hyperthermal results show that collision energies above 2 eV
lead to new reaction pathways, including addition of the O atom with H elimination to
produce alkoxy radicals, direct C-C bond breakage, direct water formation as well as aldehyde
formation. In certain cases we have been able to determine the importance of excited state
potential surfaces in the dynamics, as well as intersystem crossing effects. Collision induced
dissociation can play a role in some cases, and we have been able to show how angular
distributions for certain reactions switch from backward to forward peaked as collision energy
is increased.
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Hydrocarbons in the Atmosphere
F. Sherwood Rowland Departments of Chemistry and Earth System Science
University of California Irvine, California, 92697, U.S.A. The local presence of hydrocarbons in the atmosphere has been known for about two
centuries, with identification of specific compounds beginning about a century ago. However, the first confirmation that methane is present everywhere in the troposphere is generally attributed to Migeotte's spectroscopic measurements in 1948. Quantitative measurements of the simultaneous atmospheric presence of O3 and O2 demonstrate that the molar ratio is about 10-6, far in excess of a calculated thermodynamic equilibrium between them of 10-30. Similarly, the calculated thermodynamic equilibrium concentration of methane in the presence of O2 and H2O should be 10-140 times that of carbon dioxide. The atmosphere is thus far from equilibrium, in the former case because of the constant influx of solar radiation, and in the latter because many of the minor components such as methane are present in detectable amounts only because of ongoing emissions from biological sources. The reactive removal of volatile hydrocarbons from the atmosphere is primarily the consequence of attack by hydroxyl radicals, which are formed by ultraviolet attack on tropospheric ozone in (1) with the formation of O(1D) atoms which react with water vapor, as in (2). Hydroxyl radicals can attack saturated hydrocarbons by abstracting H in (3), and the residual R radical immediately adds an O2 molecule to form RO2 in (4). Hydroxyl radical formation is favored O3 + hυ → O(1D) + O2 (1) O(1D) + H2O → 2 HO (2) HO + RH → H2O + R (3) R + O2 → RO2 (4) in the summer because of more hours of more intense sunlight, and in the tropics by higher humidity which favors (3) in competition with deexcitation by collisions with N2 or O2.
The average atmospheric lifetime for a molecule I whose primary sink is reaction with HO can be approximately estimated from its measured laboratory reaction rate k3i versus k3 for a compound of known atmospheric lifetime. With a measured lifetime for anthropogenic methylchloroform, CH3CCl3, of five years, the alkanes have estimated lifetimes of 8 years for methane, 2 months for ethane, 2 weeks for propane, and a few hours for ethylene. Because the rate of north/south mixing of the atmosphere is approximately 15 months, methane is the only simple hydrocarbon which survives long enough to provide substantial contributions in both northern and southern hemispheres before being oxidized by HO radicals. For molecules such as ethane and propane, a strong seasonal variation is observed in the temperate and polar latitudes with minimum concentrations in the summer. Because most hydrocarbons enter the atmosphere in the north, the concentrations there are much very much higher than in the south.
We began collecting atmospheric samples in remote locations on both sides of the equator in 1978. Our measurements of methane in 1979 showed slightly higher concentrations than in 1978, indicating that its global concentration was rising. Continuation of this series of measurements have shown an increase from a global average of 1.52 ppmv in 1978 to 1.78 ppmv in 2003. Observations of methane from ice cores by other research groups show a gradual increase toward present levels from 0.75 ppmv at the beginning of the industrial revolution two centuries ago. The warming of the atmosphere by accumulation of
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anthropogenic gases was expanded in the 1970s from a "carbon dioxide problem" to a "greenhouse gas problem", with the experimental observation of significant increases over time of methane, nitrous oxide, the chlorofluorocarbons (CFCs), and tropospheric ozone as additional contributors to the trapping of outgoing infrared radiation. Water vapor is actually the major absorber of outgoing infrared radiation, but its atmospheric concentration responds to the temperature of the world's oceans, and increases as the Earth warms. With the assumption that all of the infrared radiation emitted by the Earth escapes to space, a simple calculation of the required average temperature for the Earth to emit enough infrared radiation to balance the incoming solar energy gives a temperature of −18°C. With an average Earth temperature of +14°C, this leads to a calculation of +32°C for the natural greenhouse effect. The calculation of a projected temperature increase of 1.4°C to 5.8 °C during the 21st century is the estimate of the incremental temperature increase which will accrue with the increases in global atmospheric concentrations of carbon dioxide, methane, nitrous oxide, CFCs, tropospheric ozone, water vapor and in various aerosols.
The RO2 radicals from (4) can react with NO in reaction (5) to form NO2, and its subsequent photolysis produces O atoms and then ozone. A very minor product of reaction (5) leads to the formation of alkyl nitrates, RONO2, which therefore become a marker for the production of ozone from the main channel of (5) + (6). We have investigated the hydrocarbon composition of the air RO2 + NO → RO + NO2 (5) NO2 + hυ → NO + O →→ O3 (6) in many cities around the world, and have observed not only the importance of vehicular traffic for the release of reactive hydrocarbons and nitrogen oxides, but also the importance of liquefied petroleum gas (typically C3 and C4 alkanes) in creation of urban ozone through reactions (4) to (6). We have also measured very high concentrations of alkane hydrocarbons in the rural southwest United States as the consequence of hydrocarbon leakage from the oil and gas industries. These alkanes have been accompanied by elevated alkyl nitrates, demonstrating that enough NO is present in these to trigger ozone formation even in these non-urban environments. We have also participated in numerous aircraft- and ship-based experiments which have led to other observations of hydrocarbons and their reactions. These include: (1) their formation by biomass burning, as measured both on the ground and in plumes
thousands of miles from the location of the burning; (2) removal by chlorine atom reaction in the near-absence of tropospheric ozone at altitudes
below 500 feet above frozen Hudson Bay (Canada); and (3) increased production of isoprene and alkanes accompanying CO2 decreases during "iron
fertilization" experiments in the Southern Ocean. All of these experiments have been performed in collaboration with Professor Donald R. Blake and various members of our research group, and with support from NASA and/or DOE, NSF, NASDA (Japan) and the Comer Foundation.
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Atmospheric Measurements of OH and HO2 Radicals in a Marine Boundary Layer
Hajime Akimoto
Atmospheric Composition Research Program Frontier Research System for Global Change, Yokohama, Japan
[email protected] The OH and HO2 radicals are the most important players of atmospheric reactions since
they are the key carriers of chain reactions of tropospheric photochemistry. Therefore, the
comparison between the observed and model-calculated concentrations of OH/HO2 radicals
can provide the most direct validation of tropospheric photochemical theory. Due to the very
low concentration of OH radicals (the order of 106 radicals/cm3 or less), however, reliable
measurement of these radicals has long been delayed since the pioneering attempt in 1970s.
Development of new technology enabled reliable measurement of these radicals on the
ground as well as in the aircraft since the middle of 1990’s. Since then three techniques has
been practically used in the ambient atmospheric application; laser-induced fluorescence(LIF),
differential optical absorption spectroscopy (DOAS), and chemical ionization mass
spectrometry (CIMS).
We developed a laser-induced fluorescence instrument and successfully implemented it in
field campaigns at three remote islands of Japan (Oki, Okinawa and Rishiri Island). At Cape
Hedo of Okinawa Island, the observed daytime level of HO2 agreed closely well with the
model-calculated results constraint to observed concentrations of NOx, hydrocarbonds,
aldehydes, CO, etc. which control “fast photochemistry” to generate and destroy HOx radicals.
This fact suggests that the photochemistry at Cape Hedo, Okinawa is well described by the
current mechanism.
In contrast, at Rishiri Island, the observed daytime concentration of HO2 was consistently
much lower than the model-calculated values in both 2000 and 2003 campaigns. Possible
processes that reduced the daytime HO2 are studied here, with the possibilities of (1)
heterogeneous loss of HO2 on aerosol surfaces, (2) unexpectedly fast HO2+RO2 reactions, and
(3) possible role of iodine chemistry. Analysis of simultaneous measurements of OH and HO2
radicals provides further discussion of unknown factors of atmospheric photochemistry.
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Infrared Laser Spectroscopy and Chemical Kinetics of Free Radicals
Robert F. Curl, Jiaxiang Han, Shuiming Hu, John Brown, Hongbing Chen, & David Thweatt Department of Chemistry, Rice Quantum Institute, Rice University, Houston, TX 77005
Our research has two aims: the observation and analysis of the infrared spectra of free
radicals and the investigation of their chemical kinetics. The degenerate CH stretching
fundamental of CH3O is our current interest. The upper state of the degenerate CH stretch
should consist of four subsystems corresponding to the four possible choices of the signs of l
and Σ relative to Λ. Significant progress has been made on this spectrum. Two sets of
subsystems have been observed in the jet-cooled spectrum and J values assigned to the lines
of their p-labeled component subbands. In addition, several apparently isolated subbands
have been assigned to p and J values. However, it is not clear at this time whether both of the
two assigned subsystems belong to the degenerate CH stretch even though they clearly have
perpendicular rotational selection rules. The spectra observed and our efforts to make sense of
them will be described. The infrared kinetic spectroscopy method is also used to explore
radical kinetics. A specific system of current interest is the determination of the product
yields of reactions of O(1D) with CH4. We have discovered significant hot atom effects even
at buffer gas (He) pressures above 10 Torr.
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Ab Initio Studies of Free Radical Reactions of Interest to Atmospheric Chemistry
R. S. Zhu, Z. F. Xu and M. C. Lin
Department of Chemistry, Emory University Atlanta, GA 30322, USA
Free radical reactions involving HOx, NOx, SOx and ClOx play their pivotal roles in
various aspects of atmospheric chemistry from acid rains to O3-formation in the troposphere
and O3-destruction in the stratosphere. Until recently prediction of their reaction rates and
product-branching ratios over a wide range of P,T-conditions had been difficult and unreliable.
Recent progress made in energy prediction by means of practically reliable computational
methods and rate constant calculations for barrierless radical-radical association processes by
solution of energy- and pressure-dependent master equation coupling all accessible quantum
states of multiple reactive intermediates allows us to estimate rate constants and
product-branching ratios to within kinetic accuracy. Several examples studied in our
laboratory on reactions of some of the aforementioned radicals will be discussed.
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Significant OH Radical Reactions in the Atmosphere: A New View
Ilana B. Pollack, Ian M. Konen, Eunice X. J. Li, and Marsha I. Lester Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323 USA
The three-body OH + NO2 + M → HONO2 + M association reaction is of fundamental
importance in atmospheric chemistry because it is an important sink of reactive HOx and NOx
radicals that directly affect the ozone budgets of the troposphere and stratosphere. Until very
recently, HONO2 was believed to be the only product of the OH + NO2 reaction. However, a
surprisingly large discrepancy between OH kinetic loss measurements performed at high and
low pressures has lead several groups to suggest that peroxynitrous acid (HOONO), a less
stable isomer of HONO2, may be a secondary product of this reaction and the coupled HO2 +
NO reaction.
Recently, this laboratory produced HOONO by reaction of photolytically generated
OH and NO2 radicals, stabilized the intermediate in a pulsed supersonic expansion, and
identified the trans-perp (tp) conformer of HOONO through infrared action spectroscopy in
the OH overtone region.[1] Extensive rotational band structure associated with the OH
overtone transition yields structural parameters and its transition dipole moment, which are in
good accord with ab initio values. The infrared overtone excitation provides sufficient
energy to break the O-O bond of tp-HOONO, producing OH (v=0) fragments that are detected.
The internal energy distribution of the OH fragments is consistent with a prior distribution,
and enables an accurate determination of the HOONO binding energy. The
spectroscopically derived value is in good accord with recent theoretical results and a kinetic
estimate of its stability. Comparisons will be made with previous infrared studies of
HOONO conformers isolated in Ar matrices [2] and more recent studies in a discharge flow
tube.[3,4] Many issues concerning the formation, isomerization, dissociation, and yield of
HOONO under jet-cooled and atmospheric conditions will be discussed in the oral and poster
presentations.
[1] I. B. Pollack, I. M. Konen, E. X. J. Li, and M. I. Lester, J. Chem. Phys. 119, 9981 (2003). [2] B. M. Cheng, J. W. Lee, and Y. P. Lee, J. Phys. Chem. 95, 2814 (1991); W.-J. Lo and Y. P.
Lee, J. Chem. Phys. 101, 5494 (1994). [3] S. A. Nizkorodov and P. O. Wennberg, J. Phys. Chem. A 106, 855 (2002). [4] B. D. Bean, A. K. Mollner, S. Nizkorodov, G. Nair, M. Okumura, S. P. Sander, K. A.
Peterson, and J. S. Francisco, J. Phys. Chem. A 107, 6974 (2003).
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Free Electrons: The Simplest Free Radicals of them All
O. Petru Balaj1, Iulia Balteanu1, M. K. Beyer1 and Vladimir E. Bondybey1,2, 1Institute für Physicalishe Chemie, Technische Universität München, Garching
2Department of Chemistry, University of California, Irvine Free radicals are usually defined as highly reactive species with unpaired electrons. Electrons themselves are highly reactive and unpaired and can therefore be considered to be the simplest free radicals. In the almost two hundred years since Humphrey Davy first noted the blue color appearing when sodium is dissolved in ammonia, free electrons in solutions have been extensively studied. More recently it was shown, that solvated gas phase electrons1 can also be generated, and we have found that a laser vaporization source developed in our laboratory with supersonic expansion, produces very cleanly hydrated electron clusters e!(H2O)n with n − 12-100 for studies by Fourier Transform Ion Cyclotron Resonance (FT-ICR) Mass Spectrometry. Even in the absence of collisions the trapped clusters gradually disappear due to heating by the black body infrared background radiation, and interesting size dependent competition between the loss of ligands and electron detachment. The finite clusters with exactly known composition are a very convenient medium for electron reaction studies, since unlike bulk solution “pulsed electrolysis” experiments they are not plagued by the effects of minor impurities. We will discus and describe here briefly the rich, multifaceted chemistry of the electron clusters, whose reactions can be crudely classified into several categories: a) Many simple, nonpolar molecules and atoms just contribute to cluster fragmentation b) Polar molecules capable of forming strong, hydrogen bonded networks can be exchanged for the water ligands, and gradually replace part or even all of the aqueous shell c) Reactions with species such as O2 or CO2, which can attach the free electron forming an anion stabilized strongly by hydration, result in replacement of the ionic core of the cluster. d) With a number of species, for instance acetonitrile or HCl, a true “chemistry” is observed, where existing covalent bonds are broken and/or new ones formed. 1. M. Armbruster, H. Haberland, and H. G. Schindler, Phys. Rev. Lett. 47, 323 (1981) 2. M. K. Beyer, B. S. Fox, B. M. Reinhard and V. E. Bondybey, J. Chem. Phys. 115, 9288 (2001)
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High-Resolution Photoelectron Spectroscopic Studies of Ions and Radicals
Frédéric Merkt
ETH Zürich, Physical Chemistry, CH-8093 Zürich, Switzerland
Photoelectron spectroscopy (PES) represents a useful tool to study the photoionization
dynamics of molecules and to study the properties of molecular radicals and ions. In the past
years progress has been made that enables the recording of VUV PE spectra at high resolution
using several variants of the technique of pulsed-field-ionization zero-kinetic energy
(PFI-ZEKE) PES. In our experiments, we record such spectra by monitoring the field
ionization of very high Rydberg states (n > 150) located below each ionization threshold as a
function of the wavenumber of a narrow bandwidth VUV laser. In a first variant, carefully
designed electric field pulse sequences are used to achieve a high selectivity in the field
ionization process and to record PE spectra at a resolution of 0.06 cm-1 [1]. A second variant,
called Rydberg-state-resolved threshold ionization can be used to resolve the high Rydberg
states within each line in a PFI-ZEKE PE spectrum, enabling one to record photoelectron
spectra at a resolution limited by the bandwidth of the laser radiation used (in our case
250 MHz) [2]. Finally, millimeter wave spectroscopy can be used to record transitions
between high Rydberg states at sub MHZ resolution [3]. Our studies have enabled us to
resolve the complete rotational structure and in several cases the spin-rotational fine structure
and even the hyperfine structure in the PE spectra of molecules. A new source of cold radicals
in supersonic expansions has been developed that is compatible with the high-vacuum
requirement of our PFI-ZEKE PE spectrometers and which can be used to study a wide range
of radicals [4]. The talk will present a survey of these developments and illustrate them by PE
spectroscopic measurements carried out on hydride radicals such as NH2, CH2 and C2H5 and
on reactive molecules such as O3.
[1] U. Hollenstein, R. Seiler, H. Schmutz, M. Andrist, and F. Merkt, J. Chem. Phys. 114, 9840 (2001). [2] R. Seiler, U. Hollenstein, G. M. Greetham, and F. Merkt, Chem. Phys. Lett. 346, 201 (2001). [3] A. Osterwalder and F. Merkt, Int. Rev. Phys. Chem. 21, 385-403 (2002). [4] S. Willitsch, J.M. Dyke, and F. Merkt, Helv. Chim. Acta 86, 1152-1166 (2003).
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Helium Droplets as a Unique Nano-Matrix for Molecules and Molecular Aggregates
Andrey F. Vilesov
Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA
In this talk experiments on spectroscopy of molecules and molecular complexes in
helium droplets will be reviewed. Some recent developments include the introduction of
pulsed droplet beams and the application of pulsed infrared lasers to molecular spectroscopy
in droplets. The study of the phthalocyanine (Pc), Mg-Pc and Zn-Pc molecules in helium
droplets is reported. The electronic spectra in the vicinity of the band origins show low
energy vibronic bands. These bands correspond to vibrational modes of several helium
atoms localized by molecular interaction. In other experiments we used large helium
droplets of 105 – 107 atoms as hosts to assemble molecular clusters. The rotationally
resolved spectra of the ν1 and ν3 vibrational modes of (NH3)n clusters and the ν3 mode of
(CH4)n (n = 1 – 2x103) clusters in He droplets have been obtained. The quenching of the
molecular rotational motion and the development of the vibrational bands of molecular
clusters upon an increase in cluster size are studied.
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Non-adiabatic Dynamics of Ionized Neon Clusters inside Helium Nanodroplets
D. Bonhommeau, A. Viel, and N. Halberstadt
LPQ-IRSAMC, CNRS and University Paul Sabatier, 118 route de Narbonne, 31062 Toulouse, France
One of the most common experimental tools to study host molecules or clusters inside
helium nanodroplets is mass spectrometry, which implies an ionization step. This ionization
usually produces fragmentation of the host molecule or cluster. The purpose of this work is to
determine the role of the helium environment in the dissociation. Is there no effect since these
nanodroplets have been shown to be superfluid, or is any dissociation inhibited because of the
very high heat conductivity of superfluid helium? Ionized rare gas clusters constitute ideal
model systems to study these fragmentation processes. Ionization brings the cluster from the
neutral configuration with bond lengths typical of Van der Waals bonding to the ionic
surfaces where the equilibrium bond lengths are much shorter. The cluster ion is thus
produced in a configuration containing a large amount of internal energy and dissociates.
Experiments by Janda and coworkers [1] have shown that their fragmentation is significantly
hindered, and can even be caged, in helium nanodroplets.
We have set up a simulation [2] of the ionization-dissociation process of these rare gas
clusters in a helium nanodroplet, using the molecular dynamics with quantum transitions
(MDQT) method [3] to treat the inherently multi-surface nature of the dynamics. The
electronic part is evolved quantum-mechanically, while the coordinates of the atoms are
propagated classically, with hops between adiabatic surfaces allowed. The potential energy
surfaces are described in the diatomics in molecules (DIM) model. The helium environment is
described by an ad hoc model, using a friction force acting on atoms with velocities above the
Landau critical velocity. A reasonable range of values for the corresponding friction
coefficient is obtained by comparison with existing experimental measurements.
[1] B.E. Callicoatt, K. F¨orde, T. Ruchti, L. Jung, and K.C. Janda, J. Chem. Phys. 108,
9371 (1998). [2] D. Bonhommeau, A. Viel and N. Halberstadt, J. Chem. Phys., in press. [3] J.C. Tully, J. Chem. Phys. 93, 1061 (1990).
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Free Radicals in Quantum Crystals: A Study of Tunneling Chemical Reactions
Takamasa Momose
Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan e-mail: [email protected]
Solid parahydrogen is a unique matrix for the study of chemical reactions of cold
molecules.[1,2] By virtue of the softness of solid parahydrogen as a quantum crystal,
rotational motion of molecules in the crystal is well quantized as in the gas phase. Moreover,
molecules are mobile in the crystal, so that various chemical reactions occur in the crystal.
As a result, quantitative information on chemical reactions of nearly free molecules at liquid
He temperatures such as tunneling chemical reactions can be obtained directly from the
spectroscopy of molecules in solid parahydrogen.
In the present work, tunneling chemical reactions between deuterated methyl
radicals and the hydrogen molecule in a parahydrogen crystal have been studied by FTIR
spectroscopy. The tunneling rates of the reactions R + H2 → RH + H (R=CD3, CD2H, CHD2,
and CH3) in the vibrational ground state were determined directly from the temporal change
in the intensity of the rovibrational absorption bands of the reactants and products in each
reaction in solid parahydrogen observed at 5 K. The tunneling rate of each reaction was
found to differ definitely depending upon the degree of deuteration in the methyl radicals.
The tunneling rates thus determined were 3.3 ×10-6 s-1, 2.0×10-6 s-1, and 1.0 ×10-6 s-1 for the
systems of CD3, CD2H, and CHD2, respectively. Conversely, the tunneling reaction between
a CH3 radical and the hydrogen molecule did not proceed within a week's time. The upper
limit of the tunneling rate of the reaction of the CH3 radical was estimated to be 8×10-8 s-1.
The tunneling reaction rates are clearly faster for heavier isotopomers in these systems. The
"anomalous" deuteration effect will be discussed. 1. T. Momose, and T. Shida, Bull. Chem. Soc. Jpn, 71, 1 (1998). 2. T. Momose, H. Hoshina, M. Fushitani, and H. Katsuki, Vib. Spectrosc. 34, 95 (2004). 3. T. Momose, H. Hoshina, N. Sogoshi, H. Katsuki, T. Wakabayashi, and T. Shida, J. Chem. Phys. 108, 7334 (1998). 4. H. Hoshina, M. Fushitani, T. Momose, and T. Shida, J. Chem. Phys. 120, 3706 (2004).
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From Pair Correlation to Reactive Resonance in Polyatomic Reactions
Jingang Zhou, W. Shiu, B. Zhang, Jim J. Lin, and Kopin Liu
Institute of Atomic and Molecular Sciences, Academia Sinica, P. O. Box 23-166, Taipei,
Taiwan 106
A novel time-sliced velocity imaging technique has been developed and implemented in
crossed-beam scattering experiments. Using this new approach, a number of atoms/radicals
with methane, such as F, Cl, OH + CH4 etc., and its isotopic variants were investigated. What
revealed from these studies is the coincident information of the state-resolved pair-correlation
of the two products. The correlated state distributions and differential cross sections show
striking differences for various product pairs, which open a new way to unravel the
complexity of a typical polyatomic reaction.
In this talk, we will elucidate the concept of product pair correlation and highlight some
of the major findings. In addition, we will show how such kind of measurements leads to the
discovery of a reactive resonance in six-atom reactions of F + CH4 and F + CHD3.
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State-to-State-to-State Dynamics of Chemical Reactions: The Control of Detailed Collision Dynamics by Quantized Bottleneck States * (i-iii)
Rex T. Skodje1,2
1) Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
and 2) Department of Chemistry, University of Colorado
It has long been realized that the characteristics of the transition state of a chemical reaction
control the reaction rate constant. More recently, Truhlar and coworkers have established
that quantized bottleneck states (QBS), which lie at the maxima of adiabatic potential curves,
provide a basis to understand the energy dependence of the cumulative reaction probability.
In this presentation, we discuss new work that reveals that the control exerted by the QBS
extends even to highly detailed state-to-state differential cross sections of elementary
reactions. Using various isotopes of the H+H2 prototype reaction, we show how the
angular dependence and product distribution of the reactions can be rationalized in terms of
the properties of the QBS. The understanding of the (initial) state-to (transition) state-to
(final) state reaction dynamics not only provides a basis to observe the QBS, but also adds
predictive power to the study of reaction dynamics.
* This work was done in collaboration with SD Chao, M. Gustafsson, and the experimental group of XM Yang. i) S. A. Harich et al, Nature, 419, 281 (2002). ii) D. X. Dai, et al, Science, 300, 1730 (2003). iii) S. A. Harich, et al, J. Chem. Phys., 117, 8341 (2002).
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The Stereodynamics of Photon-Initiated Reactions
Mark Brouard*
The Physical and Theoretical Chemistry Laboratory,
Department of Chemistry, University of Oxford,
South Parks Road, Oxford OX1 3QZ, United Kingdom
Laser pump-probe techniques have been used to study the stereodynamics of photon initiated unimolecular and bimolecular processes. The experiments employ polarized photolysis radiation coupled with either laser-induced fluorescence (LIF) or resonantly enhanced multiphoton ionisation (REMPI) and velocity-map ion-imaging. Using the latter technique, we have recently characterized the O(3PJ) photofragments generated in the photodissociation of N2O at 193nm: N2O + hv N2 + O(3PJ) The dependence of the ion-images, and integrated image intensities, on laser pump-probe polarization geometry has enabled us to determine the electronic alignment of the ground state O-atom photofragments [1]. The data have been used to help identify the electronic channel responsible for spin-forbidden dissociation in this atmospherically important molecular system.
Our studies of bimolecular processes are of the photon-initiated type [2], as illustrated by the example HX + hv H + X H + H2O OH(2ΠΩ)+ H2 These measurements provide a route not just to product quantum state population distributions, but also to kinetic energy release distributions, which provide information about scalar pair correlations between the internal excitation in the probed fragment (OH in the above example) and the co-product (H2), to angular scattering distributions (a two vector (k,k’) correlation proportional to the differential cross-section), and angular momentum polarization distributions (a (k,k’,j’) three vector correlation proportional to the polarization dependent differential cross-sections). Examples will be provided from both our LIF and ion-imaging work. [1] M. Brouard, A.P. Clark, C. Vallance, O.S. Vasyutinskii, J. Chem. Phys. 119, 771, (2003). [2] M. Brouard, P. O'Keeffe, C. Vallance, J. Phys. Chem. A, 106, 3629, (2002). * email address: [email protected]
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Photodissociation Dynamics of Polyatomic Molecules
Containing Sulfur: An Experimental Study
F. J..Aoiz 1, L. Bañares, J. Barr, I. Torres, G. A. Pino, G. A. Amaral
Departamento de Química Física I. Facultad de Química. Universidad
Complutense de Madrid. 28040 Madrid. Spain
The photodissociation of the deuterated dimethyl sulfide, CD3SCD3 (DMS), and dimethyl
sulfoxide, CD3SOCD3, DMSO, have been studied at several wavelengths in the UV region
(204-227 nm) using REMPI and time-of-flight mass spectrometry (TOFMS) to measure TOF
profiles, rotational and vibrational REMPI spectra and rotational alignment of the CD3
fragment. The photodissociation of the DMS molecule has been studied in the first (215-230
nm) and the second (200-205 nm) absorption bands. In both cases, the analysis of the TOF
profiles indicates a strongly anisotropic photodissociation (β=-0.9) with a large fraction
(70-80% and 90%, respectively) of the available energy appearing as fragment recoil
translation. In the first absorption band, this fraction is strongly dependent on the excitation
wavelength, supporting the theoretical conjecture [1] that the photofragmentation occurs via
an indirect, albeit rapid, process, involving two strongly coupled excited electronic states and
a non-adiabatic decay [2]. The dissociation in the second absorption band seems to take place
in a single purely repulsive potential energy surface.
The analysis of the results for the photodissociation of DMSO shows that there exist, at least,
three channels leading to formation of CD3. The primary dissociation, S-C bond cleavage,
involves two competing channels with distinct translational energy distributions for the CD3
fragment. The major dissociation pathway, yielding relatively slow and isotropic CD3
fragments, proceeds in a statistical manner on the ground electronic surface following internal
conversion. The second channel (parallel transition) produces a small percentage of
anisotropic and faster CD3 through direct dissociation. By analysing the TOF profiles at
different polarization angles of the dissociation laser and the rotationally-state resolved CD3
REMPI spectra, it has been possible to identify the percentage of the anisotropic dissociation.
[1] M.R. Manaa and D. R. Yarkony, J. Am. Chem. Soc. 116,11444 (1994)
[2] J. Barr, I. Torres, L. Bañares, J. E. Verdasco, and F. J. Aoiz, Chem. Phys Lett. 373, 550
(2003).
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Photodissociation of Simple Aromatic Molecules Studied by Multimass Ion Imaging Techniques
Chi-Kung Ni
Institute of Atomic and Molecular Sciences, Academia Sinica, P. O. Box 23-166, Taipei,
Taiwan
An overview of our recent experimental studies of aromatic molecules using multimass
ion imaging technique will be presented. Photodissociation of several simple aromatic
molecules, including benzene, fluorobenzene, toluene, m-xylene, ethylbenzene,
propylbenzene, phenol, pyridine, 4-methylpyridine, and aniline at 248 nm or 193 nm were
investigated under collisionless condition. Photofragment translational energy distributions
and dissociation rates were recorded. They revealed new isomerization and dissociation
channels of these molecules. The experimental data will be discussed in reference to the ab
initio potential energy surfaces and statistical theory results.
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Spectroscopy and Dynamics of NH Radical Complexes
Galina Kerenskaya, Udo Schnupf, and Michael C. Heaven
Department of Chemistry, Emory University, Atlanta, GA 30322, USA
Spectroscopic and theoretical studies of the binary complexes of NH with He, Ne, and H2
are described. Interest in the NH-He complex stems from identification of NH(X) as a
promising candidate for studies of ultra-cold molecules (paramagnetic ground state with a
large rotational constant). With He buffer gas cooling the stability of NH in a magnetic trap
depends on the details of the NH+He interaction potential. We have probed this interaction
through studies of the A-X transition of NH-He. Preliminary observations appear to be in
good agreement with the results of recent high-level theoretical calculations1.
Studies of the A-X system of NH-Ne yield insights concerning the characteristic energy
level patterns of 3Σ and 3Π complexes. Theoretical predictions have been used to guide the
analysis of the congested ro-vibronic structure of NH(A)-Ne. The predictions were in
qualitative agreement with the observed structure, but systematic quantitative errors were
noted. Interestingly, contrasting errors were found for the singlet (a and c) and triplet (X and
A) potential energy surfaces.
Complexes of NH with H2 are of interest as they may be used to examine NH+H2→NH2+H
reaction dynamics. This reaction is endothermic for NH(X), so the existence of a stable
NH(X)-H2 complex is expected. Quenching data indicate that the reactions of NH(c) and
NH(A) with H2 do not encounter barriers. Preliminary work on NH-H2 shows that the
ground state complex may be generated in a jet expansion and detected via excitation of the
monomer A-X transition. The spectral features observed to date involve direct excitation of
the continuum. They define a ground state bond dissociation energy of "0D =35 cm-1.
Experiments are in progress to determine the primary decay channels for the non-fluorescent
quasi-bound levels of NH(A)-H2.
1. H. Cybulski, R. V. Krems, H. R. Sadeghpour, A. Delgarno, J. Klos, G. C. Groenenboom,
A. van der Avoird, D. Zgid and G. Chalasinski, work in progress.
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Molecules in Cold Atomic Gases: How do They Interact?
Jeremy M. Hutson and Pavel Soldán
Department of Chemistry, University of Durham, Durham DH1 3LE, United Kingdom There is great interest in cooling molecules and trapping them at temperatures below 1 milliKelvin and especially in producing quantum-degenerate gases of dipolar species. Over the last few years, several experimental methods have been developed to cool stable molecules and free radicals to temperatures of tens or hundreds of milliKelvin. These include buffer gas cooling in cryogenic helium [1], molecular beam decleration using switched electric fields [2], guiding of the cold fraction from a thermal gas [3], and crossed molecular beam scattering [4]. However, the cold molecules produced by such methods need further cooling to reach the ultracold regime below 1 milliKelvin. One promising candidate for this “second stage” cooling is to inject the cold molecules into a cold atomic gas of Rb or some other alkali metal and to rely on “sympathetic cooling” of the molecules. However, very little is known about the interactions between molecules and alkali metal atoms. We have investigated the interaction between Rb and polar molecules such as NH and OH. We have carried out ab initio electronic structure calculations to characterize the surfaces. The strength of the interaction is found to depend very strongly on the spin states involved. For example, if Rb and NH collide with their electron spins parallel, they interact on a quartet surface (4A''). The interaction is then dominated by dispersion forces and is relatively weak, with a well depth of 0.078 eV. If the two species are not spin-aligned, however, they can interact on the lowest doublet surface (2A''), which has a very much stronger interaction potential (well depth 1.372 eV) because it is an ion-pair state with an attractive Coulomb interaction at short range. The dispersion-bound doublet state crosses the ion-pair state at conical intersections at linear geometries. In this case, strong collisions can occur via a harpoon mechanism. This effect may be undesirable for sympathetic cooling, because it may enhance reorientation and three-body collision rates, but it might also be used for production of extremely polar ultracold molecular complexes. For RbNH, there are electronically excited states correlating with Rb (2P) that have reasonable Franck-Condon factors to both the low-energy continuum state Rb (2S) + NH(3Σ) and the ion-pair bound state Rb+NH–. It may thus be possible to form the very polar Rb+NH– species by stimulated Raman pumping or even by spontaneous emission. Similar deeply bound ion-pair states exist for other alkali atom – molecule pairs such as Rb–OH, but not for Rb–HF. References [1] J. D. Weinstein, R. deCarvalho, T. Guillet, B. Friedrich and J.M. Doyle, Nature 395, 148 (1998). [2] H. L. Bethlem and G. Meijer, Int. Rev. Phys. Chem. 22, 73 (2003). [3] S. A. Rangwala, T. Junglen, T. Rieger, P. W. H. Pinkse and G. Rempe, Phys. Rev. A 67, 043406 (2003). [4] M. S. Elioff, J. J. Valentini and D. W. Chandler, Science 302, 1940 (2003). [5] P. Soldán and J. M. Hutson, Phys. Rev. Lett. 163202 (2004).
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Optical Stark and Zeeman Spectroscopy of Transition Metal Containing Radicals
Timothy C. Steimle
Department of Chemistry and Biochemistry Arizona State University
Tempe, AZ 85287-1604, U. S. A.
Identification and characterization transition metal (TM) metal containing radical molecules formed in the reaction of TM atoms or clusters with simple gaseous reagents provide insight into corrosion and catalysis. As is evident from the multitude, and variety, of molecules identified using time-of-flight mass spectrometry, the difficulties of synthesizing these ephemeral molecules in the gas phase has largely been overcome by implementing the laser ablation/gaseous reagent supersonic expansion schemes. Generating collimated molecular beams and recording the resonant optical spectra at near natural linewidth limits for the multitude of diatomic molecules produced in these sources is now relatively straightforward. The ground and excited electronic state permanent electric dipole moments, extracted from analyzing these optical spectra recorded in the presence of a static electric field, have been used to establish trends in chemical bonding. The results of our Stark measurements for diatomic TM nitrides, oxides and carbides will be presented and compared with simple molecular orbital correlation models and sophisticated ab initio predictions.
The number of TM-containing polyatomic molecules for which ultrahigh resolution electronic spectra have been recorded and analyzed is relatively small due in part to the traditional reliance upon LIF detection. Most notable exceptions are the studies of the dihalides by the Oxford group [1] and the cyanides [2] and methylidynes [3] from by the UBC group. Recently detected of PtNH and ScCN will be given as examples from our laboratory. Efforts to apply the absorption-based technique of transient frequency modulation spectroscopy [4, 5] to the study of these TM containing polyatomic as well as other diatomic molecules will be summarized.
Although less frequently implemented, optical Zeeman spectroscopy can also provide valuable insight in the nature of the electronic states through the determination of magnetic g-factors. Results of our recent optical Zeeman spectroscopic measurements on the A 3Φ - X 3∆ band system (“γ-band”) of TiO and the A2Π/B2Σ+ - X2Σ+ band systems of calcium monohydride, CaH, will be presented. These molecules are proposed as probes of the ambient magnetic field in the sun [6]. The goal here is twofold: a) determine magnetic tuning rates for visible and near infrared spectral features, b) use the extracted g-factors to analyze the electronic state composition. 1. S. Ashworth and J.M. Brown, J. Mol. Spectrosc. 191, 276-285 (1998). 2. C.T. Kingston, A.J. Merer, T.D. Varberg, J. Mol. Spectrosc. 215(1), 106-127 (2002). 3. M. Barnes, A.J. Merer, and G.F. Metha, J. Mol. Spectrosc. 181, 168-179 (1997) 4. J.C. Bloch, R.W. Field, G.E. Hall, and T.J. Sears, J. Chem. Phys. 101, 1717-1720 (1994). 5. T.C. Steimle, M. L. Costen, G.E. Hall, and T. J. Sears, Chem. Phys. Lett, 319, 363-367
(2000). 6. S. V.Berdyugina, and S. K.Solanki, Astronomy and Astrophysics 385(2), 701-715 (2002)
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The Bending Vibrational Levels
of C3-Rare-Gas Atom Complexes and C2H2+ Yen-Chu Hsu1,2
1Institute of Atomic and Molecular Sciences, Academia Sinica, P. O. Box 23-166, Taipei 106, Taiwan, R. O. C.
2Department of Chemistry, National Taiwan University, Taipei 106, Taiwan, R. O. C.
Bending vibrations of polyatomic molecules have a strong influence on molecular dynamics since they can lift the degeneracies of electronic states and/or cause state mixings. They are not always easy to observe since they often have low frequencies. The bending levels of two molecular systems have been studied in this work: C3-rare gas van der Waals complexes and the acetylene cation, C2H2+. The bending vibrational levels (υb=1-10) of the ground states of the C3-rare gas complexes were probed by wavelength-resolved emission from several vibronic levels of the à state.[1] The level structure of the two bending vibrations of each complex, except that of C3-Ne, has been fitted to a perturbed harmonic oscillator model, where the potential function has the form θ+θ= 2221 coscos rVrVV ( r is the amplitude of the C3-bending motion and θ gives the orientation of the rare gas atom relative to the plane of the bent C3 molecule). The potential function of each complex, obtained from the model fit, will be compared with that from our ab initio calculations. The trans- and cis