Knowledge Bank

The emission spectra of both $H2S+$ and $D2S+$ have been obtained using the controlled electron energy technique of Horani and Leach. The spectra are assigned to a $A^{2} A_{1} - X^{2} B_{1} $ transition by analogy with $NH2$, $PH2$ and $AsH2$. The decrease and subsequent increase of the bending vibrational intervals in the $A2A1$ state of $H2S+$ and $D2S+$ indicates a barrier to linearity of c.a. $4600cm-1$. A rotational analysis of several bands of the spectrum of both the hydride and the deuteride has been carried out and structures derived for both the lower and the upper states. The spectrum is complicated owing to the combined effects of large amplitude vibration, Renner interaction and spin-orbit interaction on the energy levels of the excited state. Many forbidden lines are observed of the type $\Delta J \not= \Delta $N, owing to the fact that the spin-orbit coupling in the ground state is case b and in the excited state tending towards case a. Several sub-bands are absent when $v2\prime \ge 5$ and this is thought to be due to predissociation of the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}A1$ state by a $\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}A2$ state.