Laser excitation spectrum and microwave optical double resonance spectrum of the 31 band in the ã 3A2–X̃ 1A1 system of H2CS: The hyperfine structure of the ã 3A2 state

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Abstract
The dye laser excitation spectrum of the 310 band in the ã 3A2 ← X̃ 1A1 transition of H2CS was observed in the region 15 280 to 15 400 cm−1 with Doppler‐limited resolution. The observed spectrum was analyzed to yield precise values for the rotational constants, the centrifugal distortion constants, and the spin–spin and the spin‐rotation interaction constants in the upper triplet state and for the band origin. Transitions with Ka′=4 and 5 revealed the effect of the c‐type Coriolis interaction between the v3′=1 and v6′=1 states, which, when analyzed, allowed determination of the ν3−ν6 difference to be 99.341 cm−1. 15 K‐type doubling transitions and two a‐type R branch transitions in the ã state were observed by a microwave or radio‐frequency optical double resonance technique, of which two K‐doubling transitions of Ka=1 and two R branch transitions (all F3 components) were resolved into three hyperfine components. From the observed splittings the proton hyperfine coupling constants were determined to be aF=27.7(25), Tbb+Tcc=12.8(44), and Tbb−Tcc=7.89(19) MHz with one standard errors in parentheses.