Torsion-Vibration-Rotation Interactions in Methanol. IV. Microwave Spectrum of CH3OH in the Excited CO Stretching State

Abstract

The ${\text{K=2← 1\hspace{0.17em}E}}_1\mathrm{\hspace{0.17em}Q}$ branch and the $J_K{\text{=1}}_0{\text{← 0}}_0\mathrm{\hspace{0.17em}A‐E}$ doublet have been observed for the first excited CO stretching mode in the microwave spectrum of normal methanol. A value for the excited state barrier to internal rotation of $\text{397.9± 3\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}$ is required to reproduce the Q‐branch origin frequency of 47 929.9 MHz, with reasonable limits on geometry changes assumed. This value is consistent with previous infrared results.