Abstract

Though the nature of intense, short pulse laser interactions with single atoms and solid targets has been the subject of extensive experimental and theoretical investigation over the last 15 years, only recently has the nature of intense laser interactions with van der Waals bonded atomic clusters of 20 -100 Å been addressed in experiments. These experiments have suggested that the laser-cluster interaction is much more energetic than that of isolated atoms, producing bright x-ray emission (100 - 5000 eV photons) when a low density gas containing clusters is illuminated [1,2]. While experiments have indicated indirect evidence for keV electron production in the cluster through time resolved x-ray spectroscopic data [2], until recently no direct data on the exact nature of the kinetic energies produced by the intense irradiation of clusters existed. In this paper we present the first energy distribution measurements of both electrons and ions resulting from the interaction of a femtosecond laser pulse with van der Waals bonded clusters. We find that the cluster is rapidly heated by collisional inverse bremsstrahlung. This heats a sizable fraction of the electrons in the cluster to a temperature above 1 keV. The super-heated cluster then explodes, ejecting ions with substantial kinetic energy. In fact, ions with energy up to 1 MeV are produced in Xe clusters.

© 1997 Optical Society of America