LINE PARAMETERS OF THE PH 3 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

Overview Why are we interested in PH 3 pentad? Previous studies and energy levels Resonances & interactions in the pentad Experimental conditions & sample spectra Preliminary results on Position and Intensity fits Line shapes (widths, shifts, line mixing & speed dependence) widths vs. J and K Empirical fits for widths Comparison of widths in 1 & 3 to 2 & 4 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 and cm -1. The other 3 bands in the pentad (2 2, 2 + 4, and 2 4 ) 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 PH 3 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 PH 3 with altitude from Cassini VIMS and Cassini CIRS experiments were noticed by astronomers and attributed it to the poor knowledge of PH 3 spectroscopy in the pentad. Line parameters (e.g. positions and intensities) for all five bands in the 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 PH 3 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 PH 3 ( and S) IN THE PENTAD BandParameterInvestigatorsInstrument or data used Resolution (cm -1 ) Year 1 and 3 Rovibrational and relative intensities Baldacci et al.Grating Spectrometer and 3 Line Intensities, few line widths Lovejoy et al.Tunable diode laser Doppler limited 1985  2, Rovibrational Constants Tipton et al.FTS  2, 2 + 4,  4, 1, 3 Pentad, Theoretical Modeling Tarrago et al.Using FTS data  2, 2 + 4,  4, 1, 3 Positions and int. (line-by-line simulation) Tarrago et al.FTS , 3,  4, Assignments and A+A- splittings Ulenikov et al.FTS and 3 Line intensitiesSuarezFTS , 3, 2 4, HITRAN 2000 update Kleiner et al.Tarrago et al. line parameters , 3, 2 4, Line IntensitiesWang et al.FTS dyad, pentad, octad Global ModelingNikitin et al.FTS data from various sources

Development of the theoretical model and new programs G. Tarrago et al., J. Mol. Spectrosc l l l 3 2 K-type interaction Diag Coriolis Fermi Coriolis l- type interaction Diag Coriolis Fermi Coriolis Fermi 2 42 l- type interaction Diag Coriolis Fermi Coriolis Fermi 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): 2 2, 2 + 4, 2 4, 1, 3 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): 2, 4 bands Line Positions: fit to an rms.= 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 cm -1 T = K; Path length = cm Sample Pressures (Torr) Spectra were used for 1, 3, 2 4 and McMath-Pierce FTS at cm -1 T= K; Path length=425 cm Sample Pressures (Torr) Spectra were used for the weak 2 2 mm 5 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 2 2 transitions Top left (RED): 4.24 Torr Bottom left (Blue):22.46 Torr

Preliminary Energy Fit Results and a comparison BAND 0 (cm -1 ) # lines rms (cm -1 ) 2   +  , l = , l =±   Nikitin et al., 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 FITS 1308 line intensities are fit with 19 adjustable parameters; 6 leading terms of the dipole moment derivatives and 13 Herman-Wallis terms Band # lines rms(%) ( l = 0) ( l = 2)

The higher pressure spectra allowed us to measure self-width and self-shift coefficients Black: Torr Red: 4.24 Torr Blue: Torr Pink: Torr Green: Torr

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.; [ 12 C 16 O results: V. Malathy Devi et al., JQSRT 113 (2012) ] Line 1 at (1) cm -1 Line 2 at (1) cm -1 P P(13,9) pair K″=9 splitting Self line mixing: (4) cm -1 atm -1 at 296 K

LORENTZ SELF-BROADENED WIDTH COEFFICIENTS IN THE 3 BAND OF PH 3 Self-broadened width coefficients (cm -1 atm -1 at 296 K) vs. J m and K m The term 0.05*(J m -K m ) helps trend recognition J m and K m are max. J and K (a) Width vs. J m for each K m (b) Width vs. K m for each J m Where no error bars are visible, the errors are smaller then the font size used

EMPIRICAL POLYNOMIAL FITS FOR SELF WIDTHS IN THE 3 BAND LEFT PANELS: ALL TRANSITIONS EXCEPT J=K RIGHT PANEL: ONLY J=K LINES Left: (a) Widths vs. J m and (b) Widths vs. K m (all lines except J=K ) Top: ONLY J=K LINES The term 0.5* (J m -K m ) 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) ] Transition J” K” Band [PS]Width a [PS]Band [Salem et al.] Width (SDRP) a,b Ratio; [PS/Salem et al.] QR (3) (46)0.986±0.041 QR (2) (27)0.997±0.024 QR (2) (29)0.985±0.026 QR (2) (29)0.988±0.027 QR (2) (41)0.994±0.038 QR (2) (34)1.057±0.037 QR (2) (24)0.979±0.023 QR (3) (27)0.995±0.027 QR (12) (23)1.056±0.027 QR (5) (37)0.971±0.036 QR (19) (28)0.933±0.034 Mean & std. dev ±0.036 PP (1) (28)1.007±0.025 RP (2) (37)0.987±0.032 RP (2) (30)1.050±0.028 RP (1) (27)1.004±0.024 PP (1) (28)0.986±0.025 PP (1) (26)0.963±0.023 RP (2) (38)0.989±0.036 PP (1) (19)0.984±0.025 Mean & std. dev ±0.023 a Units are cm -1 atm -1 at 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 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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