1. HIGH-RESOLUTION ANALYSIS OF VARIOUS PROPANE BANDS: MODELING OF TITAN'S INFRARED SPECTRUM J.-M. Flaud

2. Propane - Historical Perspective First identification of C 3 H 8 on Titan came from Voyager IRIS (Maguire et al. Nature,1981) Although multiple bands identified, the S/N was poor, Only the 26 band at 721 cm -1 was ever used for VMR determination (papers by Coustenis et al.)

3. CIRS Titan Spectrum Instrument and mission Titan spectrum CIRS composition - overview

4. Cassini Composite Infrared Spectrometer (CIRS) CIRS

5. When starting the study: -line data only publicly available (GEISA 1992 and later) for the v 26 mode at 748 cm -1, based on unpublished measurements by S. Daunt. -Medium resolution lab absorption spectra courtesy of S. Sharpe, PNNL recorded at room temperature Propane has 27 IR modes with low energy modes: v 14 (216 cm -1 ), v 27 (268 cm -1 ), v 9 (369cm -1 ) lots of strong hot bands Propane: spectroscopic data

6. CIRS Propane Band Detections:13-11 μm

7. CIRS Propane Band Detections:11-9 μm

8. CIRS Propane Band Detections:8-6 μm

9. We included in our study a new set of propane lines for several bands v 19 (1338), v 18 (1376),),{v 24,v 4 }(1472)in the region 1300-1500 cm -1, as measured and modeled by Flaud, Lafferty and Herman, J. Chem. Phys(2001). We checked the fundamental mode v 26 intensities in GEISA and found that they are about x 2.38 too high; probably because the band sum was scaled to lab spectra that includes hot bands These enable an independent measurement of the propane abundance from a different CIRS focal plane (FP4) to the v 26 (FP3). Propane: New spectroscopic data Need of line by line list to model the spectra

10. CIRS Propane Band Detections: 8-6 μm

11. 24 1 5151 17 1 4141 24 1 HWHW 5151 CACA HWHW 17 1 CBCBC HWHW 4141 CACA FC HWHW Hamiltonian matrix used to calculate the {24 1, 5 1,17 1, 4 1 } interacting states of propane. H W : Watson-type Hamiltonian. C A, C B, C C : a-, b-, c-type Coriolis interactions. F: Fermi-type interaction

12. Mixing coefficients of the J 0,J and J 1,J levels of the 4 1 state into the 24 1 state of propane. The different mixing coefficients lead to an inversion of the J 0,J and J 1,J states starting at J=15.

13. Central region of the C-type jet-cooled ν 24 band of propane. Because of the strong A-type Coriolis interaction with the levels of 4 1, the Rq 0 and p Q 1 lines of ν 24 are highly perturbed.

14. RegionCoustenis et al.(2007) Vinatier et al.(2007) This work ν 26 (748 cm -1 )5.0(1.0)4.5(1.5)4.2(0.5) ν 18 (1376 cm -1 )5.7(0.8) ν 24 (1472 cm -1 )16.4(0.8) Propane abundances on Titan

15. Propane – Summary All four bands of propane tentatively identified by IRIS are now clearly seen by CIRS at much higher S/N. In addition 3-4 further bands have now been detected. Abundances retrieved here agree well with previous results for ν 26, and with new ν 18 measurement. ν 24 measurement in very poor agreement: probably due to continuum fitting and/or aliasing. v 26 needs to be re-measured for: - Better modeling and better accuracy - Missing hotbands,.

16. Hamiltonian matrix used to calculate the {26 1, 9 2 } interacting states of propane. 26 1 9292 HWHW CACA 9292 CACA HWHW Vibrational State26 1 9292 Number of levels1062741 J max 5846 K max 3126 0.0000≤δ<0.000378.5%70.6% 0.0003≤δ<0.000613.3%18.1% 0.0006≤δ<0.00126.4%7.3% 0.0004≤δ<0.00351.8%4.0% Std, Deviation (10 -3 cm -1 ) 0.41

18. The lines marked with a ‘*’ belong to the 9 cold band

20. Titan spectra average, 30S–30N latitude, 100–150km,(black line) compared to three models: (i)C2H2, C2H6 and HCN only (no propane); (ii) GEISA 2003 propane atlas; (iii) This work Residuals Spectra (χ2 reduces from 6.9 to 2.4)

21. RegionCoustenis et al.(2007) Vinatier et al.(2007) This work ν 26 (748 cm -1 )5.0(1.0)4.5(1.5)4.2(0.5) 6.6(0.7) ν 18 (1376 cm -1 )5.7(0.8) Propane abundances on Titan

22. Propane – Next Steps Need further theoretical work and lab spectroscopy to measure line positions and intensities and model the remaining bands: ν 8 – 860 cm -1 v 21 – 922 cm -1 v 20 – 1054 cm -1 v 7 – 1157 cm -1

23. PROPANE AND TITAN I would like to thank: W. J. Lafferty, F. Kwabia, C. A. Nixon, D. E. Jennings, B. Bézard, N. A. Teanby, P. G. J. Irwin, T. M. Ansty, A. Coustenis, F. M. Flasar.

24. High resolution analysis of the ethylene-1- 13 C spectrum in the 8.4–14.3-μm region J.-M. Flaud, W.J. Lafferty, Robert Sams, V. Malathy Devi, Journal of Molecular Spectroscopy 259 (2010) 39–45

25. Hamiltonian matrix used to calculate the {10 1, 8 1, 7 1, 4 1, 6 1 } interacting states of ethylene -1- 13 C 10 1 8 1 7171 4141 6161 10 1 HWHW Herm conj 8181 CACA HWHW 7171 CACA FHWHW 4141 CBCBC HWHW 6161 CACA CACA CBCB HWHW

26. Range of quantum numbers observed for experimental energy levels and a statistical analysis of the results of the energy level calculation for the 10 1, 8 1, 7 1 and 4 1 ro-vibrational levels of ethylene -1- 13 C Vibrational State10 1 8 1 7 1 4 1 Number of levels20524170857 J Max 27284429 K Max 118187,8 series mainly 0.000≤δ<0.00188.3%97.5%95.6%86% 0.001≤δ<0.00211.2%2.5%4.2%11.3% 0.002≤δ<0.00330.5%0.2%1.8% Std, Deviation (10 -3 cm -1 ) 0.48

27. Mixing coefficients of the K a =7 and 8 rotational levels of 4 1 onto the 7 1 state for mono- 13 C ethylene

28. .A portion of the mono- 13 C ethylene spectrum showing absorption lines of the forbidden ν 4 band. Lines involving the K a = 8 upper state levels of 4 1 are seen only because they borrow their intensity from the p Q 10 line of the strong ν 7 band. Unlabeled strong lines are the ν 7 transitions.

29. Mono- 13 C ethylene in Titan Problem: Discrepancy of ~40% in measured absolute intensities between high and low resolution spectra!!!

30. CONCLUSION More high resolution spectroscopic work is needed for a lot of “difficult” molecules (Lots of vib-rot interactions, tunneling effects,…) in order to provide line by line lists (including hot bands) Or For “heavy” molecules cross sections measurements (Various P and Ts) PROBLEM: BOTH require a lot of work!!