Vibrational Analysis and Isotope Effects in Hydrogen Selenide

Values of the band origins for the near-infrared rotation—vibration bands v1+v2, v2+v3, 2v1+v3, v1+2v3, 3v1, and 3v1+v3 of H280Se were determined directly from their respective PPJ (J) and RRJ (J) lines. A vibrational analysis of the band origins of these six bands, of four previously analyzed combination bands, and of the three fundamentals led to values for the zero-order frequencies, anharmonic constants, and the interaction matrix element for a second-order resonance between levels of the type (v1, v2, v3) and (v1−2, v2, v3+2). Values for the isotopic band center separations Δv0≡v0 (H280Se) —v0 (H2iSe) and for ΔC0≡80C0−iC 0, where i=82, 78, 77, and 76, were obtained from the observed isotopic separations of the PPJ (J) and RRJ (J) lines for several bands. These empirical values of Δv0 are compared with a set of theoretical values calculated using Krimm's approximate isotopic frequency rule and the vibrational constants for H280Se. Values of iA0, iB0, and iC0 were calculated by combining our values of 80A0, 80B0, and 80C0 with our empirical values of ΔC0 and with values of Δ(A0−C0) and Δ(A0−B0) obtained from Oka and Morino's analysis of the microwave data of Jache, Moser, and Gordy. An equilibrium H–Se–H bond angle of 90° 34′ and an H–Se bond length of 1.460 Å were calculated using a set of α's which were obtained from the rotational constants of 2v1, v1+v3, v1+v2+v3, and the ground state constants.