Ab initio calculations on the ground and excited electronic states of neutral and charged palladium monoxide, PdO0,+,-

Multi-reference configuration interaction and coupled cluster calculations were carried out for the ground and several low-lying excited electronic states for PdO, PdO+, and PdO-. Spin-orbit coupling, core-correlation effects, and large correlation-consistent basis sets were employed. We report bond lengths, spectroscopic constants, energetics, and potential energy curves for all of the considered states. Our calculations settle the assignment for the previously recorded peaks of the experimental PdO- photoelectron spectrum. We found that the spin-orbit effects mix considerably the -S states of PdO, changing dramatically the order of its low-lying electronic states. The ground states of these species were found to be (4)sigma(-) for PdO+, (3)sigma(-) for PdO, and (2) for PdO-. Going from PdO to PdO+, the electron detaches from a sigma orbital which is localized on the metal. Going from PdO to PdO-, the additional electron attaches a orbital, which is more localized on oxygen. For PdO- we found six electronic states bound with respect to PdO.