Potential energy and dipole moment functions of the HCS radical

Abstract

The three-dimensional MCSCF CI potential energy, electric dipole and electronic transition moment functions have been calculated for the X2A′ and A2A″ electronic states of the HCS radical. These states adiabatically correlate with the two components of a 2Π electronic state for linear configurations and their ro-vibronic spectra exhibit the Renner-Teller effect. Such spectra have been evaluated from variational ro-vibronic wavefunctions, which take into account both anharmonicity effects and rotation-vibration coupling. The nuclear and electronic angular momentum couplings have also been considered. Spectroscopic constants for the X2A′ and A2A″ states calculated by perturbation theory are given. The calculated equilibrium geometries are: ReCH: 1.083 Å (X), 1.063 Å (A), ReCS: 1.573 Å (X), 1.557 Å (A) and αeHCS: 131.8° (X), 180° (A), respectively. The electronic barrier to linearity in the electronic ground state is calculated to be 3063 ± 200 cm-1. The fundamental vibrational band origins and intensities (at 300 K) in the electronic ground state of HCS are predicted to be: 3104 cm-1/6 cm-2 atm-1 (CH stretch), 1165 cm-1/43cm-2 atm-1 (CS stretch) and 871 cm-1/54 cm-2 atm-1 (bend). The fundamental frequencies are expected to be accurate to within about 30 cm-1, the vibrational intensities to within about 10 to 20%. The electric dipole moment μ0 (X) is calculated to be 0.85 ± 0.05 D. The K-reordering due to the electronic angular momentum coupling is discussed. Absolute line intensities (up to J″ = 9) have been calculated and are given for a few intense lines. © 1990.