high resolution photoelectron imaging iker león department of chemistry, brown university 68th...
TRANSCRIPT
High Resolution Photoelectron Imaging
Iker LeónDepartment of Chemistry, Brown University
68th International Symposium on Molecular SpectroscopyOHIO
June 2013
- Experimental set up Imaging
- Results
Au4-
Au2-
- Conclusions
Outline
- Introduction
More Au2- !!!
Introduction
PES of anions: - EA - Density of states - Electronic excitation energies
Electronic fingerprint
limited by the resolution of the electron energy analyzer
ZEKE (anions): - Resolution bellow cm-1
DifficultWigner threshold law -> limited to electrons leaving as s-wave
SEVI : - High detection efficiency - Resolution of few cm-1
- PAD
• D. M. Neumark, J. Phys. Chem. A 112, 13287 (2008).
combines the advantage of both
• S. J. Cavanagh, S. T. Gibson, M. N. Gale, C. J. Dedman, E. H. Roberts, and B. R. Lewis Phys. Rev. A 76, 052708 (2007).
3D presentation
Apparatus
• A. T. J. B. Eppink and D. H. Parker, Rev. Sci. Instrum. 68, 3477 (1997).
• D. Townsend, M. P. Minitti, and A. G. Suits, Rev. Sci. Instrum. 74, 2530 (2003).
Au-
Apparatus
* Bordas, C.; Paulig, F.; Helm, H.; Huestis, D. L. Rev. Sci. Instrum. 67, 2257 (1996)
ApparatusAnions are photodetached in a dc electric field which will project the photoelectron velocity distribution onto a detector
Au-
Apparatus
Initial velocity vector mapped on the same point on the detector
Abel inversion methods: the full three-dimensional (3D) information can be reconstructed
What do we obtain?
How?
Apparatus
Extract kinetic energy and angular distributions from the spatial appearance of the two-dimensional (2D) image
Apparatus
Results: Au2
-
Results: Au2-
* Leon, I.; Yang, Z.; Wang, L. S. J. Chem. Phys. 138, 184304 (2013)
Results: Au2-
* Leon, I.; Yang, Z.; Wang, L. S. J. Chem. Phys. 138, 184304 (2013)
Results: Au2-
* Leon, I.; Yang, Z.; Wang, L. S. J. Chem. Phys. 138, 184304 (2013)
Results: Au4
-
Y-Shaped
Vs.
Diamond
Results: Au4-
More Au2-
…
15400 15600 15800 16000 16200
Wavenumber / cm-1
Au-
2
2 3 4 5 2
1
0
1
2
3
internuclear distance R Å en
ergy
eV
• G. F. Gantefor, D. M. Cox, and A. Kaldor, J. Chem. Phys. 2, 854-858 (1991)
2 3 4 5 2
1
0
1
2
3
internuclear distance R Å
ener
gyeV
1.9 2.0 2.1 2.2 2.3
0.2
0.4
0.6
0.8
1.0
1.9 2.0 2.1 2.2 2.3
0.2
0.4
0.6
0.8
1.0
1.9 2.0 2.1 2.2 2.3
1
2
3
4
5
factor , 5 .
1.9 2.0 2.1 2.2 2.3
2
4
6
8
10
factor , 10.
1.9 2.0 2.1 2.2 2.3
0.2
0.4
0.6
0.8
1.0
factor , 1 .
1.9 2.0 2.1 2.2 2.3
0.5
0.5
1.0factor , 1 .
1.9 2.0 2.1 2.2 2.3
0.4
0.2
0.2
0.4
0.6
0.8
1.0factor , 0 .5
Conclusions
Conclusions
Good resolution: - low kinetic energy: 1.5 cm-1 - high kinetic energy: < 1% ∆E/E
Au2-: - success!
- good resolution at low and high kinetic energies - accurate EA determination - high detection efficiency
Au4-: - low frequency mode resolved
- accurate EA determination - anion and neutral vibrational information
high resolution PE imaging: electronic and vibrational information for size-selected clusters: cluster structure determination
Complementary to IR spectroscopy.
Thank you!