Fourier transform spectroscopy of torsionally excited C-13 methanol in the CO-stretching band

Torsionally excited n=1 and n=2 subbands of the CO‐stretching fundamental have been assigned in the Fourier transform infrared spectrum of 13CH3OH recorded at a resolution of 0.002 cm−1. For the n=1 torsional state, subbands with K values up to 7 have been identified for A torsional symmetry and up to 5 for E symmetry. For n=2, four subbands have so far been assigned. Subband origins have been obtained by fitting the observed wave numbers to J(J+1) power‐series expansions. The expansion parameters represent the data compactly to close to the experimental uncertainty in the absence of line blending or perturbations. Significant downshifting of the n=1 origins is observed, correlated closely with proximity to the n=0 OH‐bending state. J‐localized perturbations have been observed and characterized for several subbands. Two of the far‐infrared laser lines optically pumped by the 10R(14) CO2 laser line have been assigned.