Frustration of direct photoionizations of argon clusters irradiated with intense EUV-FEL pulses

Abstract

We have measured the kinetic energies of fragment ions from Ar clusters (average cluster size <N> ∼ 10 to 600) exposed to intense extreme ultraviolet free-electron laser pulses (λ ∼ 61nm, I ∼ 1.3×1011 [W/cm2]). We found that the average kinetic energy of fragment ions was saturated for <N> ≳ 200.