Photoionization efficiency spectroscopy and density functional theory investigations of RhHo₂On (n=0–2) clusters

Abstract

The experimental and theoretical adiabatic ionization energies (IEs) of the rhodium-holmium bimetallic clusters RhHo₂On (n=0–2) have been determined using photoionization efficiency spectroscopy and density functional theory(DFT) calculations. Both sets of data show the IE of RhHo2O to be significantly lower than the values for RhHo₂ and RhHo₂O₂, which are found to be similar. This indicates that there are significant changes in electronic properties upon sequential addition of oxygen atoms to RhHo₂. The DFT investigations show that the lowest energy neutral structures are a C₂ᵥ triangle for RhHo₂, a C₂ᵥ planar structure for RhHo₂O where the O atom is doubly bridged to the Ho–Ho bond, and a C₂ᵥ nonplanar structure for RhHo₂O₂, where the O₂ is dissociative and each O atom is doubly bridged to the Ho–Ho bond in the cluster above and below the RhHo₂ trimer plane. Good correlation between the experimental and computational IE data imply that the lowest energy neutral structures calculated are the most likely isomers ionized in the molecular beam. In particular, the theoretical adiabatic IE for the dissociativeRhHo₂O₂ structure is found to compare better with the experimentally determined value than the corresponding lowest energy O₂ associative structure.