Short wavelength generation from atomic clusters

We report the generation of both incoherent and coherent short-wavelength radiation which results from the unique interaction of an intense laser pulse with atomic clusters. The atomic clusters are produced by a pulsed gas jet. In the higher intensity regime (1015 endash 1017 W/cm2) the laser pulse ionizes and heats the atomic cluster resulting in a novel plasma with ∼1 keV electron temperatures. This plasma strongly emits incoherent x-rays in the 20 endash 500 A wavelength range. Using laser pulses at intensities of 1014 W/cm2, high order harmonics are created which, when compared to single atom gases, yield a higher appearance intensity for a given harmonic order, stronger non-linear dependence of harmonic signal on laser intensity, higher-order harmonics, and reduced saturation of the harmonic signal at high laser intensity. copyright 1996 American Institute of Physics