Investigation of vibrational states of the ArHCl+ cation in the electronic ground state Original Research Article

The potential energy surface (PES) of the electronic ground state of the ArHCl+ molecular ion is calculated by the multireference single- and double-excitation configuration interaction (MRD-CI) technique. An analytical representation of the potential energy data is obtained in the form of a power series. The vibrational eigenvalue problem is treated with high accuracy on the basis of the variational method using a direct product basis contracted in two steps (truncation/recoupling method). Unexpectedly for such a weakly bound system the spectrum turns out to be of a rather regular nature up to the first dissociation energy, allowing for an assignment of quantum numbers to a major part of the vibrational states. Furthermore, the wave functions are analysed together with several geometrical and energetic characteristics of the various vibrational states.