Theoretical study of spectroscopic constants and transition properties of silicon hydride cation

The potential energy curves and dipole moments for the lowest seven Λ−S states correlating to three dissociation limits Si+(P2u)+H(Sg2), Si+(Pg4)+H(Sg2), and Si(Dg1)+H+(Sg1) of SiH+ cation are computed using multi-reference configuration interaction plus Davidson corrections method with the AWCV5Z-DK basis set. By solving the radical Schrödinger equation, the spectroscopic parameters of these states are obtained, which are in excellent agreement with available experimental values. The spin-orbit coupling effect is taken into account in the computations via the Breit-Pauli Hamiltonian operator, which causes the seven Λ−S states to split into fifteen Ω states. It is the first time that the spin-orbit coupling calculation is carried out on SiH+. The spin-orbit coupling leads to avoided crossing between B1Δ2 and dΠ23 states, c3Σ1− and bΣ1+3 states, respectively. The B1Δ2 state has a double-well potential resulting from the avoided crossing. The potential energy curves and spectroscopic constants of the Ω electronic states are also depicted with the aid of the avoided crossing between electronic states of the same symmetry. In addition, the transition dipole moments, Franck-Condon factors and the radiative lifetimes for the XΣ1↔AΠ1, AΠ1↔BΔ1, aΠ3↔dΠ3, aΠ3↔cΣ−3, cΣ−3↔dΠ3, XΣ0++1↔aΠ0+3, and XΣ0++1↔aΠ13 transitions are obtained.