Relativistic and correlated all-electron calculations on the ground and excited states of AgH and AuH

We report relativistic all-electron multireference based perturbation calcu lations on the low-lying excited states of gold and silver hydrides. For Au H, we consider all molecular states dissociating to the Au(S-2)+H(S-2) and Au(D-2)+H(S-2) atomic limits, and for AgH, the states corresponding to the Ag(S-2)+H(S-2), Ag(P-2)+H(S-2), and Ag(D-2)+H(S-2) dissociation channels. S pin-free relativistic effects and the correlation effects are treated on th e same footing through the relativistic scheme of eliminating small compone nts (RESC). Spin-orbit effects are included perturbatively. The calculated potential energy curves for AgH are the first reported in the literature. T he computed spectroscopic properties agree well with experimental findings; however, the assignment of states does not correspond to our calculations. Therefore, we give a reinterpretation of the experimentally observed C (1) Pi, a (3)Pi, B (1)Sigma (+), b((3)Delta (1))1, D (1)Pi, c(1)(3)Pi (1), and c(0)((3)Pi (0)) states. A labeling suggested by us is a1, C0(+), b0(-), c2, B(3)Pi (+)(0), d(3)Pi (1), e1, f1 and g1, respectively. The spin-orbit sta tes corresponding to Ag(D-2)+H(S-2) have not well defined the Lambda and S quantum numbers, and therefore, they probably correspond to Hund's coupling case c. For AuH, we present a comparison of the calculated potential energ y curves and spectroscopic parameters with the previous configuration inter action study and the experiment. (C) 2000 American Institute of Physics. [S 0021-9606(00)31139-4].