ROTATIONAL STRUCTURE OF THE $\nu_{3}$ RAMAN BAND OF METHANE
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Date
1951
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Publisher
Ohio State University
Abstract
A multiple reflection Raman tube was used with a quartz spectrograph, giving a dispersion of $25.7 cm^{-1} /mm$ at $\lambda 2537$, to study the fine structure of the $\nu_{3}$ band of methane at a pressure of four atmospheres. Seventy-five lines in the band were resolved, and evidence for most of the fifteen theoretically predicted sub-branches was found. Various combination relations were used to calculate the molecular constants from the frequencies of selected, unblended, Raman lines and the infrared frequencies of Nielsen and $Nielsen.^{1}$ The analysis gave three different rotational constants $B^{+}_{1}, B^{0}_{1}$ and $B_{1}^{-}$ for the upper vibrational state and, surprisingly, three different values for the ground state. The average rotational constants are $B_{1} = 5.207, D_{1} = 1.6 \times 10^{-4}$ and $B_{0} = 5.244$, and $D_{0} = 1.3 \times 10^{-4}$. The values of $\mu_{0}$ and $\zeta_{3}$ were found to be 3018.1 $cm^{-1}$ and 0.055. $^{1}$ A. H. Nielsen and H. H. Nielsen, Phys. Rev. 48, 864 (1935)
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Author Institution: Department of Physics, University of Toronto