THE 5340{\AA} BANDS OF THIOCARBONYL CHLORIDE.

$^{d}$In parentheses, the change from the ground state structure.Author Institution: Department of Chemistry, Vanderbilt UniversityThe first singlet-singlet $\pi^{\ast}\leftarrow n$ transition of thiocarbonyl chloride, $CSCl_{2}$, gives rise to a system of bands whose origin occurs near 5340 {\AA}. Vibrational structure associated with the $^{35}Cl_{2}CS$ and $^{35}Cl^{37}ClCS$ isotopes has been analyzed in some detail. The pure electronic jump is forbidden as an electric dipole transition, $^{v}A_{2}\leftarrow|\rightarrow^{e}A_{1}$, and the bands observed are mainly vibronic $B_{2}\leftarrow A_{1}$ combinations. The organization of the spectrum is similar to that of the corresponding band system of formaldehyde, the resemblance being accentuated by the fact that the $^{1}A_{2}$ state of thiocarbonyl chloride is non-planar with similar geometry to the $^{1}A_{2}$ state of $CH_{2}O$. Some parameters of the excited state are collected in the table below. Fundamental Frequencies and Probable Structure of Excited $(^{1}A_{2}) Cl_{2}CS$ [FIGURE] $$\begin{array}{lllll}rCS,\ \AA& 1.73 (+0.10)^{a}& \nu_{1},\ CS\ stretch& & 907.4\\rCCl,\ \AA & 1.77 (+0.02)&\nu_{2},\ CCl\ stretch&&480.0\\\angle ClCCl& 119^{\circ}(+8,0^{\circ})& \nu_{3}, CCl_{2}bend&&245.0\\&&\nu_{4},\ CCl_{2}\ wag&\nu_{4}=1& \quad 0.42\\ Out-of-plane\, angle\Bigg\}&32^{\circ}(+32^{\circ})\\&&&\nu_{4}=2&279.6 \\T_{0}(^{35}Cl_{2}CS)&18715.89&& \nu_{4}= 3&292.5\\T_{0}(^{35}Cl^{37}ClCS)&18716.32&&\nu_{4}= 4& 447.0\end{array}$