The Band Spectrum of HS

The absorption spectrum of HS is obtained by passing repeated flashes from a source of continuous background through a discharge tube in which HS radicals are formed from ${\mathrm{H}}_2$S by pulses of radiofrequency current synchronized to precede immediately the flashes. The spectrograms obtained show only one band at 3237A. The rotational structure indicates that the ground state is an inverted ${}_{}{}^2{}_{}{}^{}\Pi$, and the excited state a ${}_{}{}^2{}_{}{}^{}\Sigma$. Because of the strong $\Lambda \Sigma$ coupling in the ${}_{}{}^2{}_{}{}^{}\Pi$ state the doublet is wide, and since the Boltzmann factor greatly favors ${}_{}{}^2{}_{}{}^{}\Pi _{\frac{3}{2}}^{}{}_{}{}^{}$, only the strongest branch, $Q_2$, from the ${}_{}{}^2{}_{}{}^{}\Pi _{\frac{1}{2}}^{}{}_{}{}^{}$ state is found. From ${}_{}{}^2{}_{}{}^{}\Pi _{\frac{3}{2}}^{}{}_{}{}^{}$ the ${}_{}{}^Q{}_{}{}^{}P_{21}^{}{}_{}{}^{}$ and ${}_{}{}^R{}_{}{}^{}Q_{21}^{}{}_{}{}^{}$ satellite branches as well as $P_1$, $Q_1$ and $R_1$ are found. For the ${}_{}{}^2{}_{}{}^{}\Pi$ ground state the best values of the constants obtained are $B_0^{}{}_{}{}^{\prime \prime }=9.47\mathrm{}$; $D_0^{}{}_{}{}^{\prime \prime }=-0.001\mathrm{}$ and $A=-378.6\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$. The constants for the excited ${}_{}{}^2{}_{}{}^{}\Sigma$ state are $B_0^{}{}_{}{}^{\prime }=8.30\mathrm{}$; $D_0^{}{}_{}{}^{\prime }=-0.00078\mathrm{}$, and $\gamma =0.32\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$. The origin of the 0,0 band is at 30,659.1 ${\mathrm{cm}}^{-1\mathrm{}}$.