SPECTROSCOPIC CONSTANTS AND DIPOLE-MOMENT FUNCTIONS OF THE 22 ELECTRON DICATIONS SINE++, PF++, SO++, NCL++, AND CAR++

The potential energy functions and spectroscopic constants of a series of eighteen 22 electron diatomic molecules with charge - 1, 0, + 1, and + 2 have been obtained using version 1 of the coupled electron pair approximation (CEPA-1) with a Gaussian basis set of 101 functions, containing both f orbitals and diffuse s and p orbitals. All of these except the negative ions have also been treated by singles and doubles configuration interaction (CI-SD) and by the latter including a size consistency correction [CI-SD (s)] with a slightly smaller basis set (93 functions) that omitted the diffuse s and p functions. Both methods [CEPA-1 and CI-SD (s)] produce values of r(e) and omega-e for the neutral and monocation species that give deviations from experiment that are both small and smoothly varying across the series. Corrections based on these deviations have been applied to the r(e) and omega-e values of the spectroscopically unknown dications, SiNe + +, PF + +, SO + +, NCl + +, and CAr + +, which possess either great kinetic stability, or in some cases, even thermodynamic stability, as published ab initio calculations have already demonstrated. Our estimated uncertainties for the corrected r(e) and omega-e values are different for the five dications, depending upon the available spectroscopically known comparison species and the consistency achieved between methods, but in the most favorable case (PF + +) they are +/- 0.002 angstrom and +/- 10 cm-1. The dipole moment functions of the doubly charged ions have been calculated for the first time (using CI-SD) and used to estimate the intensities of the rotational and vibrational spectra.