Knowledge Bank

Large numbers of ‘hot’ bands in the first electronic absorption system of $CS2$ have been photographed at high resolution. Their rotational analysis has given accurate vibrational, rotational and $\ell$-type doubling constants for the higher overtones of the bending vibrations of $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}CS2$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CS2$- For $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CS2$ the data cover those levels with $v2\le 4,\ell \le 2$, but for $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}CS2$ where 40 m-atm absorbing path was attained, the data extend to levels with $v2\le 6,\ell \le 3$. The great strength of these `hot’ bands results from the change of S-C-S bond angle in the transition, (which is $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}A2(3\Delta u)–-1\Sigma g+)$, and from the angle-dependence of the transition moment.