Valence electronic states of SiH2+ by ab initio effective valence shell Hamiltonian

The ab initio second order effective valence shell Hamiltonian which is based on quasidegenerate many-body perturbation theory has been applied to the SiH2+ dication. From the characteristic properties of Hv, all the valence states are determined with a same accuracy. The four low lying quasibound states (X 2Σ+, A 2Π, a 4Π, C 2Σ+) are found for the dication. It is verified that the existence of some quasibound states is due to the interaction of an attractive state from ion-neutral pair asymptote with a same symmetry repulsive state from ion–ion pair asymptote. Since the experimental data are scarce, this work provides all theoretical spectroscopic properties of these quasibound states. Also the repulsive valence states are examined.