High resolution spectroscopic study of H2Se (40+,0) A1 and (40-, 0) B2 stretching states: normal mode and local mode analysis

High resolution spectra of the coupled and degenerate (40+, 0) A1 and (40-, 0) B2 (the local mode pair) states of H2Se are reported. The vibration–rotation transitions of H2 n Se (n = 80,78) were assigned by using the ground state combination differences and least-squares fits to yield the rotational and coupling constants for the two stretching states with degenerate band origins: υ0 (40+, 0) = 8894·504cm-1; υ0 (40-, 0) = 8894·504cm-1. Several striking local 0 0 mode limit effects and the formation of fourfold rovibrational energy clusters are observed and discussed.