High-level theoretical rovibrational spectroscopy of HCS+ isotopologues

- Highly accurate near-equilibrium potential energy surface for HCS+ from composite method.
- Effective spectroscopic parameters from variational calculations of rovibrational states.
- Analysis of the experimentally observed Fermi resonance.
- Prediction of spectroscopic parameters and band intensities for isotopologues.

In this work the rovibrational spectrum of the HCS+ molecular cation is revisited through high-level electronic structure and variational rovibrational calculations. A local potential energy function is built from explicitly correlated coupled-cluster results, incorporating corrections for core-valence, scalar relativistic and higher-order excitation effects. The computed spectroscopic parameters, based on variational calculations with Watson's isomorphic Hamiltonian for linear molecules lead to a nearly perfect agreement with experimentally reported values (Rosenbaum et al., 1989). Furthermore, the documented Fermi resonance within the (0,00,1)/(0,20,0) and (1,00,1)/(1,20,0) pairs of states is clarified. Based on a newly developed electric dipole moment function transition dipole moments of fundamental transitions are predicted for the most important isotopologues.

144