NEW HIGH DISPERSION MEASUREMENTS ON $CD_{4}$
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Date
1952
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Ohio State University
Abstract
The infrared spectrum of $CD_{4}$ has been examined from $900 cm^{-1}$ to $7000 cm^{-1}$ with the University of Tennessee prism-grating spectrograph, utilizing gratings of 15,000, 7200, and 3600 lines per inch. In order to detect overtone and combination bands, the lead sulfide region was mapped using a multiple reflection cell 50 cm in length with up to forty traversals. About twenty bands were resolved, including those originally measured by Nielsen and $Nielsen.^{1}$ These bands, $\nu_{3}, \nu_{4}$, and $\nu_{1} + \nu_{4}$, were observed at considerably higher resolving power, and a more complex structure seemed to be indicated than was shown in the original measurements. In particular, the rotational lines in the high-frequency branch of the fundamental vibration, $\nu_{4}$, were resolved into multiplets. Because of the Coriolis interaction between the modes, $\nu_{2}$ and $\nu_{4}$, it is possible for the normally infrared inactive mode, $\nu_{2}$, to appear in the infrared if the two modes of vibration are of approximately the same frequency. A band identified as $\nu_{2}$ was observed at $1092 cm^{-1}$ whereas $\nu_{4}$ appeared at $996 cm^{-1}$. This value for the band center differs considerably from the value obtained from the Raman spectrum of the first overtone, $2\mu_{2}$. An analysis of the rotational structure has been made for the vibrational states, $\nu_{2}, \nu_{3}, \nu_{4}, 2\nu_{3}$, and $\nu_{1} + \nu_{4}$, taking into account the Coriolis interaction between vibration and rotation, but not the K-splitting of the rotational lines. Rotational analysis is progressing on other bands, but because of the overlapping of bands, it has been possible to identify only a few lines near the band centers up to the present time.
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Author Institution: Department of Physics, The University of Tennessee