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

The K=2← 1 E1 Q branch and the JK=10← 00 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 397.9± 3 cm−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.