Theoretical study of the spectra of CuH and CuD

Abstract

The electronic states of CuH correlating with the two lowest dissociation channels have been studied by ab initio methods. Potential energy curves, electric dipole (transition) moments, and spin–orbit coupling matrix elements are evaluated using correlated wave functions determined from the (relativistic) no-pair equation. The excited states of CuH and CuD cannot be characterized as pure spin states. By including spin–orbit coupling in the calculations, a one to one correspondence can be established between experimentally known term energies and computed level positions. The A 1Σ+ and B 3Π0+ states results from different linear combinations of 1 1Σ+ and 1 3Π0+. The 3Π state is found to have an inverted fine-structure pattern in contradiction to earlier assumptions. The experimentally known C1 and c1 states originate from admixtures of 1 3Δ and 1 1Π. The large coupling between LS states explains the intensity of the otherwise forbidden transitions from 3Π and 3Δ to the ground state. Among the states predicted from the present analysis is a low-lying 3Σ+ state which may be responsible for the bands observed in the red region.