Ab initio vibrational spectra and structure of the ground state of HeScH2+

Potential energy and dipole moment surfaces of the (1)A' ground state of HeScH2+ have been calculated using both the internally contracted single and double excitation multireference configuration interaction and the coupled- cluster singles and doubles augmented by a perturbative treatment of triple excitations levels of theory. Analytical functions have been fitted to the discrete surfaces employing a multidimensional least squares approach. These analytical functions have subsequently been embedded within a rectilinear normal- coordinate vibrational Hamiltonian in order to calculate vibrational states and transition intensities for low- lying states of HeScH2+.