Spectroscopy of jet-cooled methane in the lower icosad region: Empirical assignments of low-J '' spectral lines from two-temperature analysis
Abstrakt
Complete (CH4)-C-12 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.
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