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+ TERAHERTZ SPECROSCOPY OF METHYLAMINE R. A. Motiyenko, L. Margulès Laboratoire PhLAM, Université Lille 1, France V.V. Ilyushin, E.A. Alekseev Insitute.

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Presentation on theme: "+ TERAHERTZ SPECROSCOPY OF METHYLAMINE R. A. Motiyenko, L. Margulès Laboratoire PhLAM, Université Lille 1, France V.V. Ilyushin, E.A. Alekseev Insitute."— Presentation transcript:

1 + TERAHERTZ SPECROSCOPY OF METHYLAMINE R. A. Motiyenko, L. Margulès Laboratoire PhLAM, Université Lille 1, France V.V. Ilyushin, E.A. Alekseev Insitute of Radio Astronomy, NASU, Kharkov, Ukraine B. Drouin, S.Yu Jet Propulsion Laboratory J. Cernicharo, B. Tercero Centro de Astrobiologia (CSIC-INTA), Madrid Spain

2 + Interstellar methylamine  Precursor of glycine NH 2 CH 2 COOH CH 3 NH 2 +CO 2 mixture irradiated by UV: Bossa et al. A&A 506 (2009) 601; Lee et al. ApJ 697 (2009) 428; Holtom et al. ApJ 626 (2005) 940  12 CH 3 NH 2 detected in Sgr B2 and Orion KL at 3 mm: Kaifu et al. ApJ 191 (1974) L135 in cm wave range: Fourikis et al. ApJ 191 (1974) L139  Detected in the atmosphere of Jupiter Kuhn et al. Geophys. Res. Lett. 4 (1977) 203 Intense spectrum extending far beyond 1 THz Good candidate for Herschel and SOFIA observations T = 293 K T = 150 K T = 50 K

3 + Rotational spectroscopy Two large amplitude motions: CH3 torsion NH2 inversion (wagging) Ohashi and Hougen, J. Mol. Spec (1987) – effective rotational-tunneling Hamiltonian Ilyushin et al., J. Mol. Spec (2005) – extension of the model, fit within experimental accuracy of microwave and IR data Ilyushin and Lovas, J. Phys. Chem. Ref. Data 36 (2007) – accurate predictions and intensity calculation up to 500 GHz for all transitions with J<30 Motiyenko, Margulès and Ilyushin, 66th OSU Symposium, FA08, Columbus 2011 – 13CH3NH2 spectra up to 1 THz,

4 + Tunneling splittings A 1, A 2, B 1, B 2, E 1, E 2  Each energy level is labeled by the values of usual quantum numbers J and K=K a and by an overall torsion-wagging- rotation symmetry species of G 12 PI group: A 1, A 2, B 1, B 2, E 1, E 2 E E 1+1 E 1-1 E 2+1 E 2-1  Additional labeling occurs for E symmetry species in order to distinguish between positive and negative K in a symmetric rotor basis set: E 1+1, E 1-1 and E 2+1, E 2-1 E2E2 E1E1 E 2+1 E 2-1 E 1+1 E 1-1 A2A2 A1A1 B2B2 B1B1 J, K a Selection rules: A 1 ↔ A 2 ; B 1 ↔ B 2 ; E 1 ↔ E 1 ; E 2 ↔ E 2 more than 10 transitions for each J and K a 11 1 B B MHz 11 1 E E MHz 11 1 A A MHz 11 1 E E MHz 11 1 E E MHz 11 1 B B MHz 11 1 A A MHz 11 1 E E MHz 11 1 E E MHz 11 1 E E MHz

5 + Lille sub-mm wave spectrometer Active sextupler 75 – 105 GHz//+15 dBm Absorbing cell SR7270 DSP Lock- in amplifier InSb Bolometer Amplifier Synthesizer Agilent E8257D GHz Ethernet hub x6 x2: 150 – 215 GHz x3: 225 – 315 GHz x5: 400 – 530 GHz x6: 500 – 630 GHz x9: 750 – 945 GHz xNxN N=2, 3, 5, 6(2x3), 9(3x3)

6 The JPL experimental setup PC FM Rf Synthesizer Multiplier chain Si detector Lock-in Sample cell Pump Reference 30 mTorr CH 3 NH 2 ×6×6 ×2×2 ×3×3 Frequency Multiplier Submillimeter Spectrometer (FMSS) …

7 6/23/2011Low Temperature Lineshape of HD GHz → GHz New THz Source for Spectroscopy Power Spectrum Under purged conditions

8 + The spectra 13 CH 3 NH 2 12 CH 3 NH 2 Lille : 500 – 630 GHz Lille : 775 – 945 GHz JPL : 1061 – 1093 GHz JPL : 1575 – 1625 GHz JPL : 2550 – 2660 GHz A = MHz A = MHz b Q 1 K = 6 - 5

9 + transition FIR freq. cm-1 FIR freq. MHz THz freq. MHz Diff. 1612E E B1511B E E B1910B A12 A E1-1239E A1910A E1+112 E B12 B E2-112 E E1+1239E E1-112 E B239B E E B1611B E E B2010B A 12A E1-1249E A2010A B 12B A249A E E B1711B E E E E FIR vs THz measurements Ohashi et al. J. Mol. Spec. 126 (1987) 443 – 459

10 + The Hamiltonian K, K’ K K’ 0 1 J 0 1 J off diagonal contributions for K=1 The Hamiltonian matrix n =1: nontunneling motion n = 2, 4, 6…: tunneling involving wagging n = 3, 5, 7…: tunneling involving torsion Ohashi and Hougen, J. Mol. Spec (1987)

11 + Nuclear quadrupole hyperfine structure Hyperfine splittings Fit f hf Rotational frequencies f rot Global fit (Dr. Ohashi code) Expectation values Hyperfine constants Torsional- Wagging- Rotational parameters Two-step fitting scheme: 1.Hyperfine splittings to get pure rotational transitions 2.Rotational transitions to get torsional-wagging-rotational parameters 1406 hyperfine components were used to determine 587 rotational frequencies and 2 hyperfine constants rms = MHz, wrms = 0.45

12 + The results 12 C spectra recorded and analyzed up to 2.6 THz 12 C Dataset consisting of 3868 lines 2540 microwave-terahertz lines 1328 FIR lines 80 parameters fitted RMS = MHz, WRMS = 1.05 Major problems come from K>13 lines: new K-dependent terms should be included into the model 13 C species has not been detected in Orion survey of J. Cernicharo (upper limits for column densities will be provided in the paper to be publsihed) 13 CH 3 NH 2 12 CH 3 NH 2 A (MHz) (61) (95) B (MHz) (13) (12) C (MHz) (13) (12) wagging h 2v (MHz) (11) (89) h 4v (MHz)2.7313(10)2.7422(12) q2q (40) (49) f2f (66) (20) torsion h 3v (MHz) (15) (14) h 5v (MHz) (68) (72) f3f (14) (16)

13 Dr. N. Ohashi for providing his code for methylamine CNES Programme National de Physico-Chimie du Milieu Interstellaire - CNRS ANR-08-BLAN-0054 Acknowledgements Actions sur projets PCMI


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