title: Photoabsorption of Ag(n)(N∼6-6000) nanoclusters formed in helium droplets: transition from compact to multicenter aggregation.
abstract: Ag(N) clusters with up to thousands of atoms were grown in large He droplets and studied by optical spectroscopy. For N≲10(3) the spectra are dominated by a surface plasmon resonance near 3.8 eV and a broad feature in the UV, consistent with absorption by individual metallic particles. Larger clusters reveal unexpectedly strong broad absorption at low frequencies, extending down to ≈0.5 eV. This suggests a transition from single-center to multicenter formation, in agreement with estimates of cluster growth kinetics in He droplets. Moreover, the spectra of large clusters develop a characteristic dispersion profile at 3.5-4.5 eV, indicative of the coexistence of localized and delocalized electronic excitations in composite clusters, as predicted theoretically.
authors.affiliation: Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA.
authors.forename: Evgeny
authors.initials: E
authors.lastname: Loginov
authors.forename: Luis F
authors.initials: LF
authors.lastname: Gomez
authors.forename: Naihao
authors.initials: N
authors.lastname: Chiang
authors.forename: Avik
authors.initials: A
authors.lastname: Halder
authors.forename: Nicholas
authors.initials: N
authors.lastname: Guggemos
authors.forename: Vitaly V
authors.initials: VV
authors.lastname: Kresin
authors.forename: Andrey F
authors.initials: AF
authors.lastname: Vilesov