Exploring s–d, s–f, and d–f Electron Interactions in Ag_nCe⁺ and Ag_nSm⁺ by Chemical Reaction toward O₂

Abstract

We investigate gas-phase reactions of free Ag n Ce+ and Ag n Sm+ clusters with oxygen molecules to explore s–d, s–f, and d–f electron interactions in the finite size regime; a Ce atom has a 5d electron as well as a 4f electron, whereas a Sm atom has six 4f electrons without 5d electrons. In the reaction of Ag n Ce+ (n = 3–20), the Ce atom located on the cluster surface provides an active site except for n = 15 and 16, as inferred from the composition of the reaction products with oxygen bound to the Ce atom as well as from their relatively high reactivity. The extremely low reactivity for n = 15 and 16 is due to encapsulation of the Ce atom by Ag atoms. The minimum reactivity observed at n = 16 suggests that a closed electronic shell with 18 valence electrons is formed with a delocalized Ce 5d electron, while the localized Ce 4f electron does not contribute to the shell closure. As for Ag n Sm+ (n = 1–18), encapsulation of the Sm atom was observed for n ≥ 15. The lower reactivity at n = 17 than at n = 16 and 18 implies that an 18-valence-electron shell closure is formed with s electrons from Ag and Sm atoms; Sm 4f electrons are not involved in the shell closure as in the case of Ag n Ce+. The present results suggest that the 4f electrons tend to localize on the lanthanoid atom, whereas the 5d electron delocalizes to contribute to the electron shell closure.

Reactivity of cationic silver clusters with O2: a probe of interplay between clusters’ geometric and electronic structures

“…Ag n + species with n = 8, 10, 14, and 20 are inert, and the reactivity of n = 4 is very low, which is different from previous experimental observations. 36,39,40 3.2 Theoretical structures and electronic properties of Ag n…”

“…35,38,39 A recent experiment using an ion trap running at room temperature showed that the even-odd oscillation in the reactivity of Ag n + ends at n = 10, and all larger sizes are highly reactive. 40 In these previous experiments, cluster etching paths and reactive odd sizes of Ag n + are hints that extra energies could be ubiquitous in reaction systems, facilitating the crossing of barriers associated with bond breakages or spin accommodation requirements. The reactivity of clusters under relatively violent conditions could partially mask the effects of their intrinsic geometric or electronic characteristics.…”

Virtual Issue on Experiment–Theory Synergies in the Study of Metal and Metal-Containing Clusters

“…Hydrogen storage is an additional compelling topic for study using experimental cluster models combined with theory, as in studies reported by Poutsma et al and Lushchikova et al These studies can be further extended with pure DFT calculations that consider the impact of doped clusters as reported by Charkin et al in which the location-dependent activity of the dopant atom can be explored. A recent experimental study on O 2 reactions with lanthanide-doped Ag n + clusters reported by Arakawa et al might inspire theoretical activity on the role of the close-lying 4f, 5d, and 6s electrons on lanthanides in cluster reactivity.…”