Zero-kinetic-energy photoelectron
spectroscopy
of Ar(2p)-excited argon
clusters
A. Knop, H.W. Jochims, A.L.D. Kilcoyne, A.P. Hitchcock1, E. Rühl
Institut für Physikalische
und Theoretische Chemie, Freie Universitãt Berlin, Takustrasse 3,
D-14195 Berlin, Germany
Received 17 February 1994; in final form 29 April 1994
Zero-kinetic-energy photoelectron (ZEKE) spectra of atomic argon and argon clusters are recorded in the Ar(2p) excitation regime. Characteristic shifts of the Ar(2p) ionization energies are observed as a function of cluster size. The maximum of the zero-kinetic-energy photoelectron band (Ar(2p3/2)) is found at 248.9±0.1 eV, whereas the corresponding band in the ZEKE spectrum of a cluster beam of average cluster size of approximately 750 atoms occurs at 247.94 ± 0.01 eV. An enhanced ZEKE yield in the Ar(2p) continuum is attributed to inelastic scattering of the photoelectron within individual clusters. These results are compared to Ar(2p) spectroscopic studies of argon atoms, argon clusters and solid argon. Based on our analysis of the Ar(2p) ZEKE spectrum of large clusters, the Ar(2p3/2) ionization energy of solid argon is predicted to be 247.7±0.1 eV.
ã
1994 Elsevier Science B.V. All rights reserved