ESRAND OPTICAL STUDIES OF THE $M^{+}C_{2}^{-}$ AND $C_{4}$ MOLECULES
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Date
1974
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
In the course of a search for ESE spectrum of $C_{2}^{-1}$ isolated in its $^{2}\Sigma_{g}^{+}$ ground state the ion pairs $M^{+}C_{2}^{-}(M^{+} = li^{+}$, $Na^{+}$, $K^{+}$, $Cs^{+}$) have been formed at $4^{\circ} K$ by the photolysis of a matrix consisting of 1\% M and 1\% $C_{2}H_{2}$ in $Ar.^{2}$ Isotopic substitutions iondicate a triangular conformation with equivalent C atoms. An estimate of spin densities in $^{13}C_{2}^{-}$ has been derived from the observed hyperfine splittings. Infrared and electronic spectra of the ion pairs demonstrate the variation of the $C_{2}^{-}$ vibrational frequency in the ground state and in the excited $^{2}\Sigma_{u}^{+}$ state as a function of the alkali $cation.^{3}$ $C_{4}$ has been prepared by the photolytic dissociation of 1\% $C_{4}H_{2}$ (diacetylene) in an argon matrix. The ESR spectrum consisting of the $\Delta$M = 1 (xy, and $xy_{2}$) and $\Delta$M = 2 transitions confirms that $C_{4}$ is linear and has a $^{3}\Sigma_{g4}^{-}$ ground state in agreement with the MO calculations of Pitzer and Clement. A value for the zero-field splitting constant $D = 0.224 cm^{-1}$ has been determined.
Description
$^{1}$ G. Herzberg and A. Lagerqvist, Can. J. Phys. 46, 2362 (1968). $^{2}$ D.E. Milligan, M. E. Jacox, and L. Abouaf-Marguin, J. Chem. Phys. 46, 4562 (1967); 51, 1952 (1969). $^{3}$ L. Andrews and R. R. Smardzewski, J. Chem. Phys. 58, 2258 (1973).
Author Institution: Department of Chemistry, University of Florida
Author Institution: Department of Chemistry, University of Florida