Ab initio potential energy surface and spectrum of the B(Π3) state of the HeI2 complex
Journal of Chemical Physics
The three-dimensional interaction potential for I 2 ͑B 3 ⌸ 0 u +͒ + He is computed using accurate ab initio methods and a large basis set. Scalar relativistic effects are accounted for by large-core relativistic pseudopotentials for the iodine atoms. Using multireference configuration interaction calculations with subsequent treatment of spin-orbit coupling, it is shown for linear and perpendicular structures of the complex that the interaction potential for I 2 ͑B 3 ⌸ 0 u +͒ + He is very well
... + He is very well approximated by the average of the 3 AЈ and 3 AЉ interaction potentials obtained without spin-orbit coupling. The three-dimensional 3 AЈ and 3 AЉ interaction potentials are computed at the unrestricted open-shell coupled-cluster level of theory using large basis sets. Bound state calculations based on the averaged surface are carried out and binding energies, vibrationally averaged structures, and frequencies are determined. These results are found to be in excellent accord with recent experimental measurements from laser-induced fluorescence and action spectra of HeI 2 . Furthermore, in combination with a recent X-state potential, the spectral blueshift is obtained and compared with available experimental values.