Photoionization efficiency spectroscopy and density functional theory investigations of RhHo2O(n) (n = 0-2) clusters.

The experimental and theoretical adiabatic ionization energies (IEs) of the rhodium-holmium bimetallic clusters RhHo(2)O(n) (n=0-2) have been determined using photoionization efficiency spectroscopy and density functional theory (DFT) calculations. Both sets of data show the IE of RhHo(2)O to be significantly lower than the values for RhHo(2) and RhHo(2)O(2), which are found to be similar. This indicates that there are significant changes in electronic properties upon sequential addition of oxygen atoms to RhHo(2). The DFT investigations show that the lowest energy neutral structures are a C(2v) triangle for RhHo(2), a C(2v) planar structure for RhHo(2)O where the O atom is doubly bridged to the Ho-Ho bond, and a C(2v) nonplanar structure for RhHo(2)O(2), where the O(2) is dissociative and each O atom is doubly bridged to the Ho-Ho bond in the cluster above and below the RhHo(2) 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 dissociative RhHo(2)O(2) structure is found to compare better with the experimentally determined value than the corresponding lowest energy O(2) associative structure.