We investigate the heating of the quasifree electrons in large rare-gas clusters ($N$ exceeding ${10}^5$ atoms) by short laser pulses at moderate intensities ($I\simeq {10}^{15}\mathrm{W}{\mathrm{cm}}^{-2}$). We identify elastic large-angle backscattering of electrons at ionic cores in the presence of a laser field as an efficient heating mechanism. Its efficiency as well as the effect of collective electron motion, electron-impact ionization, and cluster charging are studied employing a mean-field classical transport simulation. Results for the absolute x-ray yields are in surprisingly good quantitative agreement with recent experimental results.

• Received 28 June 2005

DOI:https://doi.org/10.1103/PhysRevLett.96.013203