K-shell spectroscopy of Ar clusters

Total ion yield spectra of a supersonic beam of Ar clusters have been recorded in the Ar K-shell (1s) spectral region using synchrotron radiation. The spectrum of the cluster component of beams containing argon clusters of mean size N̄≊400 atoms is similar to that of the x-ray absorption spectrum of solid Ar. Analysis of the Ar 1s extended x-ray absorption fine structure (EXAFS) indicates an average first shell Ar–Ar distance in the cluster similar to that of the solid, but there is an increased Debye–Waller (disorder/thermal motion) term as well as changes in the higher coordination shell signals.Time-of-flight mass spectra and photoion–photoion coincidence (PIPICO) spectra of argon cluster beams are reported and the charge separation mechanisms of multiply charged argon clusters are discussed. The results are compared to those from recent studies of the Ar 2p spectra of Ar clusters.