Local Mode Effects on the High-Resolution Overtone Spectrum of H2S around 12 500 cm−1

The overtone spectrum of H 2 S has been studied by intracavity laser absorption spectroscopy in the wavenumber region 12 270–12 670 cm −1 . The rovibrational analysis has provided upper state rotational parameters for the three interacting vibrational states, (401), (104), and (024), observed in the region. The rotational levels of the first two states, constituting the local mode pair 41 ± , are strongly coupled by a strong H 22 type interaction. The (024) state is observed via a local perturbation. Altogether, 399 rovibrational lines have been assigned, including 172 rotational upper state sublevels which have been reproduced calculationally within the experimental accuracy of 0.015 cm −1 . A local mode type behavior is evidenced by the values of the rotational parameters.