Ab initio calculation of the X 2Σ +u state of He +2 and adjustment governed by translational spectroscopic measurements

Results of ab initio CI calculations are presented for the ground state potential energy curve of He ⁺₂. In addition all possible quasibound vibrational rotational levels have been calculated. A comparison with experimentally observed levels for all isotopic combinations of He ⁺₂ at first showed relatively large discrepancies, especially for the level widths (one order of magnitude). Using several tentative assignments of vibrational and rotational quantum numbers to the observed levels, a procedure was developed to adjust the ab initio potential to fit the experimental data on both energy and lifetimes of the levels. The change in the dissociation energy necessary to accomplish this is 15 meV; moreover, in the bonding region between 1.3 and 3.5 bohr the analogous changes were everywhere than 1.0 meV.