SPECTROSCOPY OF $C_{3}$ AND $SiC_{2}$ MOLECULES IN NEON AND ARGON MATRICES
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Date
1963
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Ohio State University
Abstract
“The spectrum of the $C_{3}$ molecule trapped in neon and argon matrices at $4^{\circ} K$ and $20^{\circ} K$ has been studied in absorption in the infrared and near-ultravoilet regions and in fluorescence in the visible region. Many features of the well-known cometary emission spectrum beginning at 4050\AA and strikingly reproduced in the neon absorption spectrum. $C$ substitution has also been used to prove that $C_{3}$ is isolated is isolated under the extreme conditions prevailing during the preparation of the matrices. Analysis of the near-ultraviolet bands yields the excited-state frequencies: $\nu_{1} = 1100\;cm^{-1},\;\nu’_{2} = 420\;cm^{-1},\;\nu’_{3} = ?$. Fluorescence and infrared measurements give the ground-state frequencies: $\nu_{1}’’ = 1235\;cm^{-1}\;\nu_{3}’’ = 2042\;cm^{-1}$. Our ultraviolet spectra are in accord with the low bending frequency, $\nu_{2}’’ \cong 70\;cm^{-1}$, recently proposed by Gausset, Herzberg, Lagerquist, and $Rosen.^{1}$ Other complexities in the spectrum indicate that the observed transition may be $^{3}\Pi_{u} \longleftrightarrow X ^{3} \Sigma_{g}^{-}$- rather than the expected $^{1} \Pi_{u} \longleftrightarrow {^{1}}\Sigma_{g}^{+}$. A similar study has been made of the $SiC_{2}$ molecule which has been observed in stellar spectra and produced in the laboratory by $Kleman^{2}$. The matrices have been prepared by trapping the vapour effused from hot silicon carbide. The absorption spectrum in a neon matrix begins at 4963{\AA} (as compared to 4977{\AA} in the gas) and contains some weak bands not observed by Kleman. The matrix may also exhibit the spectra of the $Si_{2},\;Si_{2}C$, and $Si_{2}C_{3}$ molecules, depending upon the conditions of vaporization. “
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$^{2}$B. Kleman, Astrophys, J. 125, 162 (1956). $^{1}$L. Gausset, G. Herzberg, A. Lagerquist and B. Rosen, Faraday Society (in press)
Author Institution: Union Carbide Research Institute
Author Institution: Union Carbide Research Institute