Knowledge Bank

Extensive series of new emission bands of $SiH+$ and $SiD+$ spectrum have been observed in the region 170 nm -- 200 nm from a high frequency discharge through a mixture of a trace of $SiCl4$ in helium and hydrogen. This spectrum has been recorded at high resolution by a 6.6 m vacuum spectrograph. Rotational and vibrational analyses are carried out and molecular constants of the electronic states are determined. The rotational structure follows a simple $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma -1\Sigma$ transition. Ten bands of $SiH+$ and fifteen bands of $SiD+$ are explained as transitions between three new excited electronic levels and the lowest $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi 0$ state predicted from theoretical $calculations.1$ The carrier of the spectrum is confirmed by the observed isotopic effect.