Fourier transform infrared and tunable diode laser spectra of the 13C12CH6 ν12 torsion–vibration–rotation band: Frequencies, intensities, and barriers to internal rotation

Abstract

High resolution spectra in the 12.2 μm region of the ν12 fundamental of the minor isotopomer 13C12CH6 have been recorded. Torsional Coriolis interaction of the excited v12=1 state with the close lying excited torsional v6=3 state leads to observed splittings of up to several tenths of cm−1 in ν12 near the crossing region at KΔK=−18. Torsional splittings measured with a high resolution tunable diode spectrometer (TDL) and more than 2200 lines measured with a Fourier transform spectrometer (FTS) have been analyzed in a global nonlinear least squares fit to a symmetric top Hamiltonian. The standard deviation of the overall fit is 5.5×10−4 cm−1. From 17 intensity measurements of individual lines, a square dipole moment of R2v=7.45(29)×10−4 D2 has been derived for the ν12 fundamental.