LINE PARAMETERS OF THE PH3 PENTAD IN THE 4-5 µm REGION

V. MALATHY DEVI and D. CHRIS BENNER

College of William and Mary

 

I.KLEINER

CNRS/IPSL-Universites Paris-ESt and Diderot, France

 

R. L. SAMS and T. A. BLAKE

Pacific Northwest National Laboratory

 

L. R. BROWN

Jet Propulsion Laboratory

L. N. FLETCHER

Department of Physics, University of Oxford

OverviewWhy are we interested in PH3 pentad?

Previous studies and energy levelsResonances & interactions in the pentadExperimental conditions & sample spectra

Preliminary results on Position and Intensity fits

Line shapes (widths, shifts, line mixing & speed dependence)

widths vs. J and KEmpirical fits for widths

Comparison of widths in n1 & n3 to n2 & n4 Conclusions and acknowledgments

Phosphine is a molecule of astrophysical and astronomical interest. It has been observed on both the Jupiter and Saturn

• It is a symmetric top molecule with a pyramidal structure; has 4 IR fundamental vibrational bands, 1, 2, 3 and 4.

• The most prominent absorption features in the pentad are the two strong overlapping bands 1 and 3 located at 2321.131 and 2326.877 cm-1.

• The other 3 bands in the pentad (22, 2+ 4, and 24) are weak and are located on the lower wavenumber side.

• The complicated rotational structures of the 1 and 3 give rise to strong Coriolis-type interaction between them. Other types of anharmonic interactions also occur among the various bands.

• The Coriolis interaction gives rise to many “forbidden” transitions and also results in large A+A- splittings.

The pentad region is revisited; because

• Accurate knowledge of line parameters for PH3 is important for Cassini/VIMS exploration of Saturn and for correct interpretation of Jovian observations by JUNO and ESA′s newly-selected mission, JUICE.

• A puzzling inconsistency in the mixing ratio derivations of PH3 with altitude

from Cassini VIMS and Cassini CIRS experiments were noticed by astronomers

and attributed it to the poor knowledge of PH3 spectroscopy in the pentad.

• Line parameters (e.g. positions and intensities) for all five bands in the 1930-

2440 cm-1 are measured to improve the spectroscopic database for remote

sensing of the giant planets.

• Analysis of high resolution, high S/N spectra of high purity PH3 recorded with the Bruker FTS at PNNL and the McMath-Pierce FTS on Kitt Peak are made.

• The strong 1 and 3 bands are recorded using very short absorption path cells (~ 1.05 cm).

A brief survey of earlier studies is outlined next

PRIOR STUDIES OF PH3 ( and S) IN THE PENTAD Band Parameter Investigators Instrument or

data usedResolution

(cm-1)Year

n1 and n3 Rovibrational and relative intensities

Baldacci et al. Grating Spectrometer

0.025-0.035 1980

n1 and n3 Line Intensities, few line widths

Lovejoy et al. Tunable diode laser

Doppler limited

1985

2n2 , n2+n4 Rovibrational Constants

Tipton et al. FTS 0.01 1986

2n2 , n2+n4,2n4, n1, n3

Pentad, Theoretical Modeling

Tarrago et al. Using FTS data 0.0054 1990

2n2 , n2+n4,2n4, n1, n3

Positions and int. (line-by-line simulation)

Tarrago et al. FTS 0.0054 1992

n1, n3, 2n4,n2+n4

Assignments and A+A- splittings

Ulenikov et al. FTS 0.005 2002

n1 and n3 Line intensities Suarez FTS 0.002 2002

n1, n3, 2n4,n2+n4

HITRAN 2000 update

Kleiner et al. Tarrago et al. line parameters

0.0054 2003

n1, n3, 2n4,n2+n4 Line Intensities Wang et al. FTS 0.005 2005

dyad, pentad, octad

Global Modeling Nikitin et al. FTS data from various sources

0.002-0.0115 2009

Development of the theoretical model and new programs G. Tarrago et al., J. Mol. Spectrosc.1990

22 2+4

l4

24

l4

1 3

l3

22 K-type

interaction Diag

Coriolis CoriolisFermi

Fermi Coriolis

2+4 l- type interaction

Diag

CoriolisFermi

CoriolisFermi

242 l- type interaction

Diag

CoriolisFermi

CoriolisFermi

1 K-type Interaction

Diag

Coriolis

3 l- type interaction

Diag

Previous studies (not exhaustive)• The Octad: The 8 vibrational bands shown on the left

Line positions at low resolution

(Maki et al., J Chem Phys, 1973)

Line positions and intensities, high resolution

(Butler et al., J Mol Spectrosc, 2006)

A Global analysis of the dyad, pentad and octad (Nikitin et al., J Mol Spectrosc, 2009)

• The pentad (middle left): 2n2, n2+n4, 2n4, n1, n3 bands

Line Positions: fit to an rms=0.009 cm-1 up to J=16

(Tarrago et al., J Mol Spectrosc, 1992,

Ulenikov et al., J Mol Spectrosc, 2002)

Intensities: modeled to an rms.= 13%

(Tarrago et al., J Mol Spectrosc, 1992)

•The dyad (bottom left): n2, n4 bands

Line Positions: fit to an rms.=0.0004 cm-1 up to J=22

(Fusina et al., J Mol Struct, 2000). Intensities: rms.=2%

(L.R. Brown et al., J Mol Spectrosc, 2002)

Lorentz self-broadened width coefficients

(J. Salem et al., J Mol Spectrosc, 2004)

Experimental conditions of PNNL and Kitt Peak spectra, two illustrative spectra recorded at PNNL

Bruker FTS at PNNL at 0.0022 cm-1

T = 298.2 K; Path length = 1.045 cm

Sample Pressures (Torr)2.048 4.24 10.152 22.46 50.11Spectra were used for n1, n3, 2n4 and n2+n4

McMath-Pierce FTS at 0.0115 cm-1

T= 289-294 K; Path length=425 cm

Sample Pressures (Torr)1.50 3.72 3.16 6.30 Spectra were used for the weak 2n2

mm5 room temperature spectra with the PNNL FTS were fit

simultaneously using the multispectrum fitting technique

3-4 Kitt Peak FTS were fit by single spectrum fitting

technique for 2n2 transitions

Top left (RED): 4.24 TorrBottom left (Blue):22.46 Torr

Preliminary Energy Fit Results and a comparisonBAND 0 (cm-1) # lines rms (cm-1)

2n2 1972.578 168 0.0033

n2+n4 2108.185 631 0.0027

2n4, l=0 2226.835 352 0.0034

2n4, l=±2 2234.835 644 0.0034

n1 2321.124 384 0.0030

n3 2326.797 812 0.0031

172 0.0011

657 0.0018

415 0.0011

657 0.0015

454 0.0017

980 0.0018

Nikitin et al., 2009

3287 line positions, up to J=14

67 floated parameters for the upper states; GS constants: fixed

Global fit:gs, dyad, pentad, octad

For the pentad:374 fixed parameters

144 floated parameters

INTENSITIY FITS1308 line intensities are fit with 19 adjustable

parameters; 6 leading terms of the dipole moment derivatives and 13 Herman-Wallis terms

Band # lines rms(%)

2n2 120 6.9

n2+n4 391 10.4

2n4 (l = 0) 141 10.2

2n4 (l = 2) 165 10.1

n1 159 9.2

n3 332 8.0

The higher pressure spectra allowed us to measure self-width and self-shift coefficients

Black: 2.048 Torr

Red: 4.24 Torr

Blue:10.152 Torr

Pink: 22. 46 Torr

Green: 50.11 Torr

)()1)(( 000 selfGasp

)()()( 0000 TTTT

2

000

01

000

0 ),)(()1)(,)((),(n

L

n

LL T

TTpselfb

T

TTpGasbpTpb

Some of the A+A- pairs of lines exhibited Line Mixing. A non Voigt line shape including line mixing and speed

dependence was used to fit the data.Line mixing was

measured applying the off diagonal relaxation matrix

formalism, e.g.;

[12C16O results: V. Malathy Devi et al., JQSRT 113 (2012)

1013-1033]

Line 1 at 2218.38533(1) cm-1

Line 2 at 2218.42965(1) cm-1

PP(13,9) pair K″=9 splittingSelf line mixing: 0.0291 (4)

cm-1 atm-1 at 296 K

LORENTZ SELF-BROADENED WIDTH COEFFICIENTS IN THE 3 BAND OF PH3

Self-broadened width coefficients (cm-1 atm-1 at

296 K) vs. Jm and Km

The term 0.05*(Jm-Km) helps trend recognition Jm and Km are max. J and K(a) Width vs. Jm for each

Km

(b) Width vs. Km for each Jm

Where no error bars are visible, the errors are smaller

then the font size used

EMPIRICAL POLYNOMIAL FITS FOR SELF WIDTHS IN THE 3 BANDLEFT PANELS: ALL TRANSITIONS EXCEPT J=K

RIGHT PANEL: ONLY J=K LINES

Left: (a) Widths vs. Jm and (b) Widths vs. Km (all lines except J=K )

Top: ONLY J=K LINES

The term 0.5* (Jm-Km) is used for trend recognition

Comparisons of widths in the 1 and 3 bands [PS] to the 2 and 4 bands

[Salem et al. J. Mol. Spectrosc. 223 (2004) 174-181]Transition J” K” Band [PS] Widtha [PS] Band [Salem et al.] Width (SDRP) a,b Ratio; [PS/Salem et al.]

QR 2 0 1 0.1105(3) 2 0.1121(46) 0.986±0.041

QR 2 1 1 0.1100(2) 2 0.1103(27) 0.997±0.024

QR 7 0 1 0.1085(2) 2 0.1102(29) 0.985±0.026

QR 7 1 1 0.1057(2) 2 0.1070(29) 0.988±0.027

QR 7 2 1 0.1073(2) 2 0.1079(41) 0.994±0.038

QR 7 5 1 0.1052(2) 2 0.0995(34) 1.057±0.037

QR 9 4 1 0.1022(2) 2 0.1044(24) 0.979±0.023

QR 10 2 1 0.1009(3) 2 0.1014(27) 0.995±0.027

QR 10 7 1 0.1047(12) 2 0.0988(23) 1.056±0.027

QR 12 2 1 0.0965(5) 2 0.0994(37) 0.971±0.036

QR 12 9 1 0.0882(19) 2 0.0945(28) 0.933±0.034

Mean & std. dev. 0.995±0.036PP 3 1 3 0.1131(1) 4 0.1123(28) 1.007±0.025

RP 4 1 3 0.1132(2) 4 0.1147(37) 0.987±0.032

RP 6 1 3 0.1169(2) 4 0.1113(30) 1.050±0.028

RP 7 0 3 0.1111(1) 4 0.1107(27) 1.004±0.024

PP 7 4 3 0.1071(1) 4 0.1086(28) 0.986±0.025

PP 8 5 3 0.1060(1) 4 0.1101(26) 0.963±0.023

RP 10 1 3 0.1042(2) 4 0.1054(38) 0.989±0.036

PP 11 11 3 0.0736(1) 4 0.0748(19) 0.984±0.025

Mean & std. dev. 0.996±0.023

a Units are cm-1 atm-1 at 298.2 K; b Speed-Dependent Rautian Profile.

CONCLUSIONS

o Over 4000 line positions and intensities are measured. o The rotational quantum numbers of measured lines go as high as J

″=16 and K″=15 in the 1 and 3 bands.

o The measured positions and intensities are modeled using new theoretical calculations in the pentad. The analyses are in progress.

o More than 800 Lorentz self-broadened widths and self-induced pressure shift coefficients are measured in several bands.

o Off-diagonal relaxation matrix elements are determined for a number of A+A- transitions with K″= 3, 6, and 9.

o Speed dependence parameters are also retrieved for several transitions.ACKNOWLEDGMENTS

NASA’s Outer Planetary Research Program supported the work performed at the College of William and Mary. Research at the Jet propulsion Laboratory (JPL), California Institute of Technology, was performed under contract with the National Aeronautics and Space Administration. The United States Department of Energy supported part of this research and was conducted at the W.R. Wiley Environmental Molecular Sciences laboratory, a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research and located at the Pacific Northwest National Laboratory (PNNL). PNNL is operated for the United States Department of Energy by the Battelle Memorial Institute under Contract DE-AC05-76RLO 1830. I. Kleiner wishes to thank the financial support by ANR-08-BLAN-0054 for this project. L.N. Fletcher acknowledges the support by a Glasstone Science Fellowship at the University of Oxford.

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