Metastable (3)Sigma sub g(-) Ground State of F2(2+) and the Bonding in MolecularDications

摘要

Large multireference configuration interaction (MR-CI) calculations on the F2++ion predict a 3/Eg ground state, metastable with respect to tunneling into the F+ + F+ nuclear continuum. The potential energy curve displays a 0.40 eV barrier at Rb = 1.607 A, between the local potential minimum (Re = 1.289 A) and the 3Pg(F+) + 3Pg(F+) asymptote at 7.69 eV lower energy. The potential barrier traps four quasibound vibrational levels, with a tunneling lifetime of 16 ms for v = 0. A Dunham analysis at the well minimum gives we=919.4 cm-1, wexe = 16.31 cm-1, Be = 1.073 cm-1, and alpha e = 0.0316 cm-1. In a departure from an earlier viewpoint, the origin of the barrier in this and other dications is interpreted as a sum of the e2/R Coulomb repulsion and the ordinary chemical bonding of the constituent ions. This model also explains the purely repulsive character found for the valence-excited 1 delta g and 1 Sigma + states.