Photoassociation of He2 revisited
Résumé
A new theoretical study for the photoassociation of metastable helium is presented, based on fully ab initio short-range potentials. Optimization of the exponents of the Gaussian orbitals of a smaller basis set than employed previously allowed the calculation of potentials dissociating to He(2 3S)+He(2 3P) at the multi-reference configuration interaction level down to internuclear separations of 3.5 a0. The good agreement with observed near-dissociation levels obtained previously using extrapolated short-range potentials is confirmed and almost all levels observed to the red of the He D2 line, associated with the He 2 3S + 2 3P2 dissociation limit, are assigned. The agreement is less satisfactory with the levels observed to the red of the He D1 line, although vibrational levels have been found in the outer ultra-long-range well of a double-well potential with the He 2 3P1 dissociation limit. A semiclassical analysis is presented to explain the limited sensitivity of the near-dissociation binding energies to the short-range potential.