Laser sideband spectroscopy in the ν 4 fundamental of silane, SiH 4

Abstract

We performed direct frequency reading IR spectroscopy in the ν 4[R_(14), A2(1) ← A1(1)] transition-frequency region of SiH 4 around 945.950 cm −1 by electrooptic mixing the stabilized CO 2-laser line P(20) with a tunable millimeter-wave signal. Power of as much as 100 μW was available in the tunable sideband allowing direct detection of the IR signal. Two strong absorption lines were observed at (945.972 ± 0.001) cm −1 and at (945.995 ± 0.001) cm −1; their pressure broadening rates were found out to differ from each other by a factor of about 2. Accuracy in absolute IR-frequency assessment of better than 10 −3 cm −1 was achieved simultaneously providing providing 10 −4 cm −1 resolution.