LASER EXCITATION SPECTRUM AND MICROWAVE OPTICAL DOUBLE RESONANCE SPECTRUM OF THE $3^{1}_{0}$ BAND IN THE $\tilde{a}^{3}A_{2}-\tilde{X}^{1}A_{1}$ SYSTEM OF $H^{2}CS$

Author Institution: Institute for molecular ScienceThe CW dye laser excitation spectrum of the $3_{0}^{1}$ band in the $\tilde{a}^{3}A_{2}-\tilde{X}^{1}A_{1}$ transition of $H_{2}CS$ was observed in the region 15280 to $15400 cm^{-1}$ with Doppler-limited resolution. $H_{2}CS$ was generated by thermally decomposing $(CH_{2})_{3}S$. The observed spectrum was analyzed to yield precise values for the rotational constants, the centrifugal distortion constants, and the spin-spin and spin-rotation interaction constants in the triplet state and for the band origin. Transitions with $K_{a}^{\prime}=4$ and5 revealed the effect of the c-type Coriolis interaction between the $v^{1}_{3}=1$ and $v^{1}_{6}-1$ states. Through the analysis of this Coriolis interaction the $\nu_{3}-\nu_{6}$ difference was determined to be $99.322 cm^{-1}$. Fifteen K-type doubling transitions of $K_{a}=1$ and 2 and two a-type R branch transitions with $K_{a}=1$ in the $\tilde{a}$ state were observed by a microwave or radio-frequency optical double resonance technique. Two K-type doubling transitions of $K_{a}=1$ and two R branch transitions were resolved into three hyperfine components. From the observed splitting the proton hyperfine constants were determined to be $a_{F}=27.7(25)$, $T_{bb} + T_{cc} =12.8(44)$, and $T_{bb}-T_{cc}=7.89(19)$ with one standard errors in parentheses