INFRARED BAND SHAPES III. VARIATION OF MOMENTS OF INERTIA WITH STATE
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Date
1954
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Ohio State University
Abstract
We have studied the effect of changes in the moments of inertia with vibrational state upon the shapes of unresolved infrared absorption bands for several of the most favorable cases. The simplest problems are those arising for parallel bands of linear molecules and for those parallel bands of symmetric rotors for which a sharp Q-branch is observed. We have derived formulas for the computation of the value of $\frac{{B}^{\prime\prime}-{B}^{\prime}}{{B}}$ from the ratio of the heights of the maxima of the P and R branches of such bands. Parallel bands which do not show a sharp Q-branch present a less tractable problem, but with the aid of a computing machine the band envelope to be expected from any given combination of parameters may be constructed. It should then be possible to use this procedure to obtain at least approximate values of the moment changes. In dealing with perpendicular bands it is necessary to allow not only for changes in the moments but also for Coriolis interactions. Again the problem is simplified when the band has a sharp Q-branch, while the general case is susceptible to attack using computing machines. Some applications of such calculations will be shown.
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Author Institution: Department of Chemistry, Purdue University