Interaction of Intense Laser Pulses with Noble Gas Clusters and Droplets

A series of experiments have been performed to investigate the time dependent interaction of intense laser pulses with mass-limited noble-gas clusters and droplets. The laser-cluster interaction was explored using a variable pulse width arrangement whereas the dynamics of the droplets were investigated using a pump probe scheme. The plasma evolution was assessed by monitoring x-ray and extreme ultraviolet emission, as well as light scattering. The observed time scales for clusters and droplets are understood in terms of two time scales natural to the plasma dynamics. We also present, in the case of clusters, a 1D hydrodynamic model of the interaction in which the laser field is treated self-consistently. We find that nonuniform expansion of the heated material results in long-time resonance of the laser field at the critical density plasma layer. These simulations explain the dependence of generation efficiency on laser pulse width.