Isotope Substitution in Near Local-Mode H₂X Molecules: Stretching Fundamental Bands of HDSe

The high-resolution FTIR spectrum of the HDSe molecule in the presence of H₂Se and D₂Se was recorded on ⁸⁰Se monoisotopic and natural samples in the 1500-2900 cm_-1 region and theoretically analyzed in the regions of the stretching fundamental bands ν₁ and ν₃ near 1692 and 2351 cm^-1, respectively. The analysis was performed starting from derived isotopic relations between vibration-rotation, anharmonic, centrifugal distortion, and other parameters which reveal high predictive power. Strong resonance interactions between the states (100) and (020) are taken into account, and sets of parameters which reproduce the experimental rotation-vibration energies of the (100) and (001) states with a mean accuracy of 0.00008 and 0.00009 cm^-1, respectively, for the HD⁸⁰Se species, were obtained. For the less abundant species, for which some higher order terms were constrained, slightly worse agreement was achieved. The refined spectroscopic parameters are very close to their predicted values.