The overtone spectrum of carbonyl sulfide in the region of the ν1+4 ν3 and 5 ν3 bands by ICLAS-VECSEL

Abstract

The high-resolution overtone spectrum of OCS has been recorded in the region of the ν 1+4 ν 3 and 5 ν 3 bands by intracavity laser absorption spectroscopy based on an optically pumped vertical external cavity surface emitting laser (VECSEL). The extremely weak ν 1+4 ν 3 band at 8954.87 cm −1 was found to be isolated. The 5 ν 3 band at 10080.91 cm −1 is accompanied by two weaker bands at 9933.53 and 10114.02 cm −1 assigned to the 12 04–00 00 and 04 04–00 00 bands, respectively. In addition, the 01 15–01 10 hot band was detected together with the extremely weak band heads of the R branch of the 02 0,25–02 0,20 hot bands. Finally, the 5 ν 3 band of the 16O 12C 34S minor isotopomer, present in natural abundance in the sample, was also observed and rotationally analyzed. Effective state parameters could be retrieved by standard band-by-band rotational fitting of the line positions, leading to a typical rms of 0.006 cm −1 . The observed line positions were compared to the predictions of the global model described by Rhaibi et al. [J. Mol. Spectrosc. 191 (1998) 32–44]. In general, the agreement is excellent, close to the experimental uncertainty ( 0.01 cm −1 ) thus confirming the high predictive ability of this effective Hamiltonian model. Weak but significant deviations up to 0.1 cm −1 were, however, identified for two rotational levels of the highly excited 2,16 0,0 dark state, observed through a local interaction with the 00 05 state. In the case of the 16O 12C 34S isotopomer, the predicted line wavenumbers of the 5 ν 3 band were globally overestimated by about 0.04 cm −1 . The new data have been included in the corresponding global model, leading to almost unchanged values of the molecular parameters and a statistical agreement with the experiment.