High-resolution spectrum of the ν9 band and reinvestigation of the ν8 band of cis-CH3ONO

Abstract

The infrared spectrum of methyl nitrite CH3ONO has been recorded at a spectral resolution of 0.003cm−1 using a Fourier-transform spectrometer Bruker IFS125HR. The ν8 band of the cis isomer has been reinvestigated in the 780–880cm−1 spectral range to complete the study made by Goss et al. (2004) [3] and to fit the internal rotor splittings. The BELGI-IR program, which enables us to treat an isolated infrared band for asymmetric molecules containing one internal methyl rotor has been used for the analysis and predictions of spectra. Finally 1036 lines (913 A-type and 123 E-type lines for J≤50 and Ka≤28) have been assigned for the cis isomer and fitted with a standard deviation of 0.00047cm−1.Furthermore, for the first time, the ν9 band of cis-CH3ONO was investigated in the 540–660cm−1 spectral range and rather large internal rotation splittings were also observed at higher J values. For the ν9 band, the effective approach performed with the BELGI-IR program allowed us to analyze and reproduce 682 lines up to J=50 and Ka=18 with a standard deviation of 0.00051cm−1. The multiple vibration–rotation–torsion interactions, which are likely to occur between the excited v9=1 and v8=1 states and the torsional manifolds are discussed.