Two-dimensional effects in the hydrodynamic expansion of xenon clusters under intense laser irradiation

The inherently two-dimensional nature of the hydrodynamic expansion of large xenon clusters irradiated by intense laser fields is shown in measurements of ion and electron emission as a function of laser pulse duration. These reveal correlation between a resonance in energy absorption by the clusters and asymmetry in cluster expansion. An extension of the hydrodynamic model accounts for the observations; an earlier interpretation of the electron spectrum is found to be incorrect.