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Holger S. P. Müller , B. J. Drouin, J. C. Pearson, L. R. Brown, I. Kleiner, R. L. Sams

Toward a global model of low-lying vibrational states of methyl cyanide, CH 3 CN: the v 4 = 1 state at 920 cm –1 and its interactions with nearby states. Holger S. P. Müller , B. J. Drouin, J. C. Pearson, L. R. Brown, I. Kleiner, R. L. Sams. 11th International HITRAN Conference; VIII-7.

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Holger S. P. Müller , B. J. Drouin, J. C. Pearson, L. R. Brown, I. Kleiner, R. L. Sams

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  1. Toward a global model of low-lying vibrational states of methyl cyanide, CH3CN: the v4 = 1 state at 920 cm–1and its interactions with nearby states Holger S. P. Müller, B. J. Drouin, J. C. Pearson, L. R. Brown, I. Kleiner, R. L. Sams 11th International HITRAN Conference; VIII-7

  2. Motivation • important molecule in InterStellar Medium (ISM), • especially hot cores, and in CircumStellar Envelopes (CSE) − 5 isotopic species detected, incl. CH2DCN; 13CH313CN + ?? − hot band transitions of vibrationally excited states detected − v8 – v8 hot band transitions detected for 13C species − used as temperature probe (esp. hot cores) − considered to be a weed species • present in planetary atmospheres (Titan, Earth)

  3. E / cm−1 v6 = 1 v8 = 4 v7=v8=1 v3 = 1 1200 v4=v8=1 v8 = 3 v7 = 1 v4 = 1 800 v8 = 2 400 v8 = 1 v = 0 0 Low-Lying Vibrational States of CH3CN

  4. The ν4 Band of CH3CN • ν4 = ν(C–C), parallel band • favorable frequency region for remote sensing • weak band strengths: ν44.8 cm–2 atm–1; ν8 (4.4), 2ν8 (6.2), ν7 (11.7) ν6 etc (94)

  5. ν4:PNNL, p = 30Pa, l = 19m, res.: 0.00164cm−1 • ~1050 lines, Jmax = 56, Kmax = 12; current unc.: 0.1 mK intensities, broadening, and selected positions: C. P. Rinsland et al., JQSRT109 (2008) 974 • v = 0 for 6 isotopologs: H. S. P. Müller et al., A&A506 (2009) 1487 • v8≤ 2: H. S. P. Müller et al., 62nd Ohio Symp, 2007, WG03 Previous and Present Work • ν4,ν7, 3ν8:A. M. Tolonen et al., JMSp 160 (1993) 198 • (parameters for v7 = 1 and v8 = 3 mostly from this study) • v4 = 1: J. Cosleou et al., JMSp146 (1991) 49 + ref.; ≤ 460 GHz • NEW:JPL & U Köln, ~310 lines, ≤ 1.439 THz, Jmax = 79, Kmax = 16

  6. Rotational Spectrum of CH3CN at the Level of CH3C15N ×13CH3CN, K = 10, 9 + CH313CN, K = 9, 8 ♥ CH3CN, v8 = 1, k = –15, 17 ▼ CH2DCN, K = 9

  7. 13CH313CN: Intensity ≈ CH3CN @ 2000 cm–1

  8. E / cm−1 15 1200 15 14 12 10 10 800 5 10 5 400 l = −1 l = +1 Aζ q22 5 0 v8 = 1 K Level Structure of v = 0 and v8 = 1 v = 0

  9. E / cm−1 1750 15 15 14 14 1500 10 15 15 13 13 11 10 1250 10 1000 l = +1 l = −1 l = +2 l = 0 l = −2 Interactions between v8 = 1 and v8 = 2Detail of the K Level Structure v8 = 2 v8 = 1

  10. –3 –1 +1 +3 –1 v8 = 3 +1 v7 = 1 v4 = 1 –2 0 +2 v8 = 2 Perturbations of v4 = 1 by Nearby States –2, 1 K = 7, 5; J = 40, 41 –1, –1 K > 20 0, 3 K = 8, J = 65, 66 –2, 1 K = 7, 5; J > 75 1, –2 K = 5, 6; J = 73 3, 0 K = 5, 8; J = 57 = ΔK, Δl 0, 0 K > 20

  11. Interaction of v4 = 1, K = 5 with v8 = 2, K = 80 @ J' = 57

  12. The region of v4 = 1, J = 63 – 62

  13. Section of the Fortrat Diagram

  14. Interaction Parameters (MHz) Involving v4 = 1

  15. Acknowledgements • H.S.P.M. and the CDMS are supported by the Bundesminiterium für Bildung und Forschung (BMBF) administered through Deutsches Zentrum für Luft- und Raumfahrt (DLR; the German space agency). • I.K. thanks the Programme National de Plane´tologie (PNP, France) for their funding of the project. • Part of the research at the Jet Propulsion Laboratory (JPL), California Institute of Technology, was performed under contract with the National Aeronautics and Space Administration. • Part of the experimental work was performed 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 Pacific Northwest National Laboratory. PNNL is operated for the United States Department of Energy by the Battelle Memorial Institute under Contract DE-AC05-76RLO 1830.

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