Vibration–rotational spectroscopy of XH2and XH3type molecules near the local mode limit

The Overtone Spectrum of H2 32S near 13 200 cm-1

The intracavity laser absorption spectrum of H2 32S has been recorded near 13 200 cm-1 with an equivalent absorption pathlength of 25 km. The observed spectrum is assigned to the (50(+/-), v2 = 1) states constituting a local mode pair in strong H22-type interaction. The rovibrational analysis has allowed the assignment of 210 lines involving 86 rotational upper state levels which have been reproduced with a rms of 0.023 cm-1 close to the experimental accuracy. A perturbation affecting one line is assigned to a local interaction with the (40(+/-), v2 = 3) local mode pair. The influence of the bending excitation on the local mode character of the (n0(+/-), v2 = 1) stretch-bend combination levels is discussed on the basis of the values of the rotational constants and of the H22 interaction parameters. Copyright 1999 Academic Press.

The H2S Spectrum around 0.7 µm

The overtone spectrum of H2S has been recorded by intracavity laser spectroscopy in the 14100-14400 cm-1 spectral region. The rovibrational analysis was performed allowing one to assign not only lines involving the pair of interacting states {(402), (303)} ({(60(+), 0), (60(-), 0)} in local mode notation), but also lines involving the interacting states {(322), (223)} ({50(+), 2), (50(-), 2)} in local mode notation). Indeed, apart from the strong H22 interactions that link the rotational levels of the states (60(+/-), 0) on the one hand, and the rotational levels of the states (50(+), 2) on the other hand, we observe that the rotational levels of the two pairs of states interact strongly through anharmonic and Coriolis-type resonances. These resonances transfer intensity to lines involving the (50(+), 2) pair of states. Altogether 80 rotational upper-state levels have been observed and reproduced satisfactorily using an Hamiltonian matrix that takes explicitly into account the various interactions and assumes the same vibrational energy and rotational constants for the two components of the local mode pairs. The following band centers have been obtained: nu0 (60(+), 0) = 14291.122 cm-1 and nu0 (50(+/-), 2) = 14284.705 cm-1. Finally a local mode-type behavior is evidenced by the values of the Hamiltonian constants, and refined vibrational local mode parameters are obtained. Copyright 1998 Academic Press.