Ab initio dipole moment function of H 2S

Abstract

We report new ab initio dipole moment surfaces (DMS) of the electronic ground state of the H 2S molecule. The two components of the dipole moment function have been evaluated using the coupled-cluster single and double excitations augmented by a perturbative contribution from connected tripled excitation (CCSD[T]) ab initio method. The rovibrational line intensities calculated with these ab initio DMS are in good agreement with the experimental data for fundamental ν 1, ν 2 , and ν 3 bands. Our calculations reproduce the observed anomalies in the intensity distributions of rovibrational bands of H 2S unlike the previous ab initio calculations. Since the DMS are very flat near the equilibrium geometry, the fundamental ν 1 and ν 3 bands are abnormally weak which makes the first principle intensity calculation a challenging problem.