Spectroscopy of jet-cooled methane in the lower icosad region: Empirical assignments of low-J″ spectral lines from two-temperature analysis

Milan Mašát (1) , Petr Pracna (2) , Didier Mondelain (3) , Samir Kassi (3) , Alain Campargue (3) , Ondrej Votava (4)

1 IPC - J. Heyrosky´ Institute of Physical Chemistry
2 J. Heyrovsky institute of Physical Chemistry
3 LAME-LIPhy - LAsers, Molécules et Environnement
4 J. Heyrovsky Institute of Physical Chemistry

Complete 12CH4 spectrum in the lower icosad spectral range (7050-7350 cm‑1) has been measured in supersonic jet at 28 K for the first time using direct absorption tunable diode laser spectrometer. Due to efficient rotational cooling only spectral lines with lower rotational quantum number J < 4 are observed in the spectrum. Spectral lines in the supersonic jet spectra have been matched with those in liquid nitrogen cooled cell spectra (81 K) and two-temperature method for empirical lower state rotational quantum number assignments has been applied to obtain accurate experimental values of the lower state rotational quantum numbers J″. Especially positions of lines with of J″ = 0 are relevant for vibrational band origin determination, as they are unambiguously the R(0) transitions of the respective bands.

Domaines: Optique [physics.optics]

Milan Mašát, Petr Pracna, Didier Mondelain, Samir Kassi, Alain Campargue, et al.. Spectroscopy of jet-cooled methane in the lower icosad region: Empirical assignments of low-J″ spectral lines from two-temperature analysis. Journal of Molecular Spectroscopy, 2013, 291, pp.9-15. ⟨10.1016/J.JMS.2013.06.002⟩. ⟨hal-00997630⟩