Zero-kinetic-energy photoelectron spectroscopy of Ar(2p)-excited argon clusters

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(2p32)) 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 …