Knowledge Bank

The first singlet-singlet $\pi \ast \leftarrow n$ transition of thiocarbonyl chloride, $CSCl2$, gives rise to a system of bands whose origin occurs near 5340 {\AA}. Vibrational structure associated with the $\mathrm{<mrow\; data-mjx-texclass="ORD">35</mrow>}Cl2CS$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">35</mrow>}Cl37ClCS$ isotopes has been analyzed in some detail. The pure electronic jump is forbidden as an electric dipole transition, , and the bands observed are mainly vibronic $B2\leftarrow A1$ 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 $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A2$ state of thiocarbonyl chloride is non-planar with similar geometry to the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A2$ state of $CH2O$. Some parameters of the excited state are collected in the table below. Fundamental Frequencies and Probable Structure of Excited $(1A2)Cl2CS$ [FIGURE] $$\begin{array}{lllll}rCS,\ \AA& 1.73 (+0.10)^{a}& \nu_{1},\ CS\ stretch& & 907.4\rCCl,\ \AA & 1.77 (+0.02)&\nu_{2},\ CCl\ stretch&&480.0\\angle ClCCl& 119^{\circ}(+8,0^{\circ})& \nu_{3}, CCl_{2}bend&&245.0\&&\nu_{4},\ CCl_{2}\ wag&\nu_{4}=1& \quad 0.42\ Out-of-plane, angle\Bigg}&32^{\circ}(+32^{\circ})\&&&\nu_{4}=2&279.6 \T_{0}(^{35}Cl_{2}CS)&18715.89&& \nu_{4}= 3&292.5\T_{0}(^{35}Cl^{37}ClCS)&18716.32&&\nu_{4}= 4& 447.0\end{array}$$