LASER INDUCED FLUORESCENCE SPECTROSCOPY OF THE $C_{4}H$ AND $C_{4}D$ RADICALS
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Date
1996
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Publisher
Ohio State University
Abstract
Laser-induced-fluorescence spectra of the $C_{4}H$ and $C_{4}D$ radicals have been observed for the first time. The molecules were generated in a supersonic jet by an electric discharge of $C_{2}H_{2}$ or $C_{2}D_{2}$ diluted in Ar. Fourteen and thirteen vibronic bands were observed for $C_{4}H$ and $C_{4}D$ respectively, in the near UV region (24000 - 25000 $cm^{-1}$). The bands were assigned to the $^{2}\Sigma-^{2}\Sigma$ or $^{2}\Pi-^{2}\Sigma$ type and several $^{2}\Sigma-^{2}\Sigma$ bands were subjected to rotational analyses. The determined rotational constants for the lower state agree with those for $C_{4}H/C_{4}D$ in the ground vibrational level in the $X^{2}\Sigma$ state, which were reported in a previous microwave study $^{a,b}$. The spin-orbit splittings in the $^{2}\Pi-^{2}\Sigma$ bands are 16 and $12 cm^{-1}$ for $C_{4}H$ and $C_{4}D$, respectively, leading a conclusion that the excited electronic state for the observed band system is $^\Pi$. The present observation is consistent with a recent CASSCF $study^{c}$, which predicted the $B^{2}\Pi$ state with the excitation energy of $24500 cm^{-1}$.
Description
$^{a}$C. A. Gottlieb, E. W. Gottlieb, P. Thaddeus, and M. Kawamura, Astrophys. J. 275, 916 (1983). $^{b}$D. R. Woodward, J. C. Person, C. A. Gottlieb,and C. A. Thaddeus, Astrophys. J. 333, L29 (1988). $^{c}$A. L. Sobolewski and L. Adamowicz, J. Chem. Phys. 102, 394 (1995).
Author Institution: Department of Pure and Applied Sciences, College of Arts and Sciences, The University of Tokyo; Department of Chemistry, Graduate School of Science, Kyoto University
Author Institution: Department of Pure and Applied Sciences, College of Arts and Sciences, The University of Tokyo; Department of Chemistry, Graduate School of Science, Kyoto University