An ab initio study of the ground and valence excited states of GaCl

All-electron relativistic calculations on the ground and valence excited states of the GaCl molecule have been performed using extended internally contracted multireference electron correlation techniques. The potential energy curves (PECs) of all the 12 A-S states and the 23 Omega states generated from them are plotted, and the spectroscopic constants (SCs) of bound states are fitted. This seems to be the first time that a study has been made of the spin-orbit coupling effects of valence states and the transition properties of A (3)Pi(0+), B (3)Pi(1) and C 1Pi(1) states of the GaCl molecule in a theoretical way. On comparison of the calculated results obtained from different multireference electron correlation methods, we find that the size-extensivity corrections improve the theoretical T-e, r(e) and omega(e) results significantly, and the multireference average quadratic coupled cluster method well reproduces the experimental values in most cases. The PEC shape and the SCs of the C (1)Pi(1) state are affected by both the avoided crossing rule among Q states of the same symmetry and the size-extensivity correction. The C (1)Pi(1) state has a very shallow potential well (v(max)(') = 2). The lifetime of the C(1)Pi(1) state is of the order of a nanosecond, while that of the A (3)Pi(0+) and B (3)Pi(1) states is of the order of a microsecond.