Ultrashort-pulse laser plasmas: Fraction of hot electrons escaping from the target and electron spectra in planar and spherical geometry

摘要

Hot electrons generated upon interaction of ultrashort, intense laser pulses with solid targets have many applications in various fields of physics. In this paper a simple theory is developed which allows calculation of the fraction of electrons which escape from the target and the altered electron energy distribution at a distance from the target. The theory is worked out in planar and spherical geometry. It is exact if the electrons are instantaneously generated. In planar geometry all particles eventually return to the target. In spherical geometry, however, a fraction of the electrons are found to escape and, moreover, the electron energy spectrum at large distances approaches an asymptotical one. Two examples of initial electron distributions are treated in detail, viz., an exponential and a Lorentzian distribution. (c) 2005 American Institute of Physics.