Transcript HMT.pptx
HIGH RESOLUTION SPECTROSCOPY OF HEXAMETHYLENETETRAMINE (HMT) C6N4H12 V. BOUDON, Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 5209 CNRS-Université de Bourgogne, 9. Av. A. Savary, BP 47870, F-21078 Dijon Cedex, France O. PIRALI, Ligne AILES – Synchrotron SOLEIL, L’Orme des Merisiers, F-91192 Gif-sur-Yvette, France and Institut des Sciences Moléculaires d’Orsay, UMR 8214 CNRS-Université Paris-Sud, Bât. 210, 91405, Orsay Cedex, France 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 Contents I. The HMT molecule II. IR spectroscopy at SOLEIL III. Theoretical model IV. Band analyses and simulations V. Conclusions and perspectives 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 I. The HMT molecule 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 Hexamethylenetetramine (HMT) HTM is similar to adamantane1 (C10H16) with four C–H groups substituted by N atoms Td (tetrahedral) symmetry 25 normal modes: Vapor pressure @ 296 K ≤ 7 μbar 1See ν1 to ν4: A1 (Raman) ν5: A2 (Inactive) ν6 to ν10: E (Raman) ν11 to ν16: F1 (Inactive) ν17 to ν25: F2 (IR / Raman) O. Pirali, V. Boudon, J. Oomens and M. Vervloet, J. Chem. Phys. 156, 024310 (2012) 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 II. IR spectroscopy at SOLEIL 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 AILES beamline at SOLEIL High Resolution Absorption Spectroscopy in the Far-IR Interferometer Synchrotron beam entrance Multipass cell : Max = 200m Bolometer detectors Maximum spectral resolution = 0.001 cm-1 Spectral range= 7-1000 cm-1 Multipass White cell: L = 151.748 m Ambiant temperature (T = 296 K) 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 III. Theoretical model H Pk all indexes v v ' K ,n v v ' (A1g ) tsKs,n R Vss ' ' 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 Theoretical model – Tensorial formalism Systematic expansion of effective Hamiltonian and transition moment up to any order and for any polyad scheme, thanks to group theory and tensorial methods H Pk all indexes v v ' K ,n v v ' tsKs,n R Vss ' ' Parameters Rotation (A1g ) Vibration All interactions are automatically included Vibrational extrapolation Global analyses 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 IV. Band analyses and simulations 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 The 670 cm–1 band (ν24) 2470 assignments, Jmax = 119 dRMS = 0.353 × 10–3 cm–1 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 The 1015 cm–1 band (ν22) 4904 assignments, Jmax = 90 dRMS = 0.357 × 10–3 cm–1 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 The 1015 cm–1 band (ν22) : P branch detail 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 The 1015 cm–1 band (ν22): rovibrational levels 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 The 1241 cm–1 band (ν21) 3411 assignments, , Jmax = 82 dRMS = 0.371 × 10–3 cm–1 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 The 1362 cm–1 band (ν20) 2623 assignments, Jmax = 70 dRMS = 0.442 × 10–3 cm–1 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 The 1462 cm–1 band (ν19) 1224 assignments, Jmax = 86 dRMS = 0.698 × 10–3 cm–1 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 IV. Conclusions and perspectives 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 Problems with the 820 cm–1 band (ν23) This band looks simple, but resists to analysis! Nearby perturbator? • P and R clusters deploy in oposite directions • Strange “comb” Q branch 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 Perspectives: HMT in interstellar space and comets? http://www.astrochem.org/sci/Hexamethylenetetramine.php 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 Perspectives: HMT on Titan? In a paper submitted to Icarus, C. He, G. Lin, A. Smith, (2012) “NMR Identification of Hexamethylenetetramine and Its Precursor in Titan Tholins: Implications for Titan Prebiotic Chemistry”, HMT appears to the main species arising from tholin synthsesis: This scheme makes sense, since méthanimine (H2C=NH) was: 1. Observed in situ (ion mass spectroscopy, Yelle et al. FD 147 2010) 2. Observed in lab plasmas of N2-CH4 (Carrasco et al. 2012, Icarus) 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012