Knowledge Bank

The far infrared beamline of the Canadian Light Source synchrotron facility has been used to record three rotationally resolved vibrational bands of 1,1-dichloroethylene in the $500-1000$ cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ range, at $0.00096$ cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ resolution. These correspond, for the H$2$C$=$C$\mathrm{<mrow\; data-mjx-texclass="ORD">35</mrow>}$Cl$2$ isotopologue, to an $a$-type band (CCl$2$ antisymmetric stretch) at $796.0$ cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$, a $b$-type band (CCl$2$ symmetric stretch) at $603.0$ cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$, and a $c$-type band (CH$2$ wag) at $868.6$ cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$. Anharmonic frequency calculations at the MP2/6-311++G(2d,2p) level, combined with rotational and centrifugal distortion constants from a millimeter wave study of the ground state, nderline{\textbf {50a}}, (1995), 347-351.}, were an invaluable aid in facilitating the spectroscopic assignment for this asymmetric top ($\kappa =-0.58$). Analysis of the $796$ cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ band is nearly complete, giving well determined excited state rotational and centrifugal distortion constants. Results of this analysis and progress with analysis of the other two bands will be presented.