摘要
Ethylthio (C2H5S) radicals were formed on laser photolysis at 248 nm of diethyl disulfide (C2H5SSC2H5) or ethyl mercaptan (C2H5SH) in a free‐jet expansion. The fluorescence excitation spectrum was recorded in the spectral region 398–432 nm. The origin lies at 23 519.6 cm−1, approximately 799 cm−1 greater than previously reported. Two main progressions with spacings near 420.5 cm−1 (C–S stretch) and 256.0 cm−1 (CCS bend) are dominant. Additional active fundamental vibrational modes of the B̃ state are at 718.4, 862.8, 1054.6, 1158.9, and 1203.3 cm−1. Observation of hot bands enables accurate determination of four low‐lying vibrational modes of the ground state at 271.9, 296.0, 478.3, and 672.4 cm−1. The dispersed fluorescence was recorded in the spectral region 415–525 nm. We identified several additional vibrational modes of the X̃ state at 890, 957, 1075, 1257, 1290, 1470, 2950, and 3050 cm−1. Theoretical calculations at the MP2 level were performed to predict vibrational frequencies of both B̃ and X̃ states, and for the latter state were also with the B3‐LYP density functional theory; the results agree satisfactorily with experimental observations.