Ab initio study of spin-orbit interaction in the ground electronic states of XH (XÂ =Â C, Si, Ge and Sn) molecules

Electronic structure and spectroscopic properties for the ground electronic states of CH, SiH, GeH and SnH molecules were obtained using the multiconfigurational self-consistent field followed by spin-orbit multireference multistate perturbation theory. Spin-orbit splitting calculations for ground states of the four molecules were carried out with model core potential (MCP) and all-electron (AE) methods. MCP results are compared with corresponding AE values to estimate the accuracy of the saving cost MCP calculations. The potential energy curves, calculated for the Ω states CH(X12Π1/2 and X22Π3/2), SiH(X12Π1/2 and X22Π3/2), GeH(X12Π1/2 and X22Π3/2) and SnH(X12Π1/2 and X22Π3/2) using the MCP method, were fitted to analytical potential energy function using Murrell-Sorbie potential energy function. Based on the analytical potential energy function, force constants and spectroscopic constants for the Ω states were obtained.