Electronic Structure and Anion Photoelectron Spectroscopy of Uranium-Gold Clusters UAu n (-), n=3-7

A collaborative effort between experiment and theorytoward elucidatingthe electronic and molecular structures of uranium-gold clustersis presented. Anion photoelectron spectra of UAu n (-)(n = 3-7) were takenat the third (355 nm) and fourth (266 nm) harmonics of a Nd:YAG laser,as well as excimer (ArF 193 nm) photon energies, where the experimentaladiabatic electron affinities and vertical detachment energies valueswere measured. Complementary first-principles calculations were subsequentlycarried out to corroborate experimentally determined electron detachmentenergies and to determine the geometry and electronic structure foreach cluster. Except for the ring-like neutral isomer of UAu6 where one unpaired electron is spread over the Au atoms, all otherneutral and anionic UAu n clusters (n = 3-7) were calculated to possess open-shell electronswith the unpaired electrons localized on the central U atom. The smallerclusters closely resemble the analogous UF n species, but significant deviations are seen starting with UAu5 where a competition between U-Au and Au-Aubonding begins to become apparent. The UAu6 system appearsto mark a transition where Au-Au interactions begin to dominate,where both a ring-like and two heavily distorted octahedral structuresaround the central U atom are calculated to be nearly isoenergetic.With UAu7, only ring-like structures are calculated. Overall,the calculated electron detachment energies are in good agreementwith the experimental values.

Automated summary

This study presents a collaborative effort between experimental and theoretical approaches to elucidate the electronic and molecular structures of uranium-gold clusters. Anion photoelectron spectra of UAu n (-)(n = 3-7) were measured using different laser and photon energies, and first-principles calculations were performed to determine the geometry and electronic structure of each cluster. The results showed that smaller clusters resemble UF n species, but deviations start to appear starting with UAu5 due to the competition between U-Au and Au-Au bonding.