Theoretical Study on the Spectroscopic Parameters and Transition Properties of MgH Radical Including Spin–orbit Coupling

An accurate theoretical study on the MgH radical is reported by adopting the high-level relativistic MRCI+Q method with a quintuple-zeta quality basis set. The reliable potential energy curves of the five \it \Lambda-S states of MgH are derived. Then the associated spectroscopic parameters are determined and found to be in good accordance with the available experimental results. The permanent dipole moments (PDMs) and the spin–orbit (SO) matrix elements of \it \Lambda-S states are computed. The results show that the abrupt changes of PDMs and SO matrix elements are attributed to the variations of electronic configurations at the avoided crossing point. The SOC effect leads to the five \it \Lambda-S states split into ten \it \Omega states and results in the double potential well of (2)1/2 state. Finally, the transition properties from the (2)1/2, (1)3/2 and (3)1/2 states to the ground state X^2\it \Sigma+1/2 transitions are obtained, including the transition dipole moments, Franck–Condon factors and radiative lifetimes.