BARRIER TO INTERNAL ROTATION IN AN EXCITED VIBRATIONAL STATE OF METHANOL
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Date
1972
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Ohio State University
Abstract
A weak Q branch strating with a J=1 line at 26 256.80 MHz has been observed in the microwave spectrum of normal methanol. The Q branch has been assigned to the K = 0 $\leftarrow 1 E_{2}$ transition in an excited vibrational state, on the basis of the Stark effects and the observation of the $1_{1}$ $\leftarrow O_{0}$ and $1_{0}$ $\leftarrow O_{0} E_{2}$ lines at 21 900.08 and 48 156.93 MHz respectively. The excited vibrational state has anergy of $933\pm 150$ $cm^{-1}$, and is most probably the $CH_{3}$ in-plane rocking mode. A value for the excited state barrier to internal rotation of $557 \pm 35$ $cm^{-1}$ is required to reproduce the Q-branch origin frequency, with reasonable limits on geometry changes assumed. This is an increase of 50\% over the ground state value of $376 cm^{-1}$.
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Author Institution: Department of Physics, University of New Brunswick