A 3Π0+–X 1Σ+0+ and B 3Π1–X 1Σ+0+ transitions of GaI: an MRDCI study

A multireference singles and doubles configuration interaction (MRDCI) study based on relativistic effective core potentials has been carried out on GaI. The ground state of GaI is X 1Σ+ with re=2.65 Å and ωe=196 cm−1. There is only one bound excited state (3Π) below an energy of 25 000 cm−1. Potential energy curves of 12 low-lying Λ-S states have been computed. The ground-state dissociation energy of GaI has been estimated to be 3.34 eV compared with the observed value of 3.47 eV. Spin–orbit coupling is included in the calculation. The splittings among the four Ω components of the 3Π state are small. Transition probabilities of two observed transitions: A 3Π0+–X 1Σ+0+ and B 3Π1–X 1Σ+0+ are calculated from CI energies and wavefunctions. The A–X transition has been found to be more probable than B–X. The radiative lifetimes of A and B states have been estimated.