Ab initio study on the ground and low-lying excited states of GaH

A multireference configuration interaction (MRCI) study has been carried out on GaH. Potential energy curves and spectroscopic constants of the X1Σ0++, a3Π0−,0+,1,2, A1Π1 and a Rydberg state of 1Σ+(II) are obtained. The observed open-structure absorption bands of GaH in the region 41 650–46 300 cm−1 can be ascribed to the transitions from this Rydberg state at about 45 000 cm−1 to the ground state. Breit–Pauli operator is used for spin–orbit coupling effect calculations. Four Ω components of the bound a3Π0−,0+,1,2 state are calculated for the first time. The transition properties of the excited states, including the transition dipole moments, the radiative lifetimes and the Franck–Condon factors, are predicted.