Avalanche ionization of an atomic gas in a laser radiation field with a time-dependent intensity

A theoretical analysis was made of the evolution of an electron avalanche in a laser radiation field with an arbitrarily time-dependent power density. The electron diffusion equation in the energy space was used to determine the distribution function. The avalanche growth rate averaged over a pulse was determined for an arbitrary time dependence q(t). It was found that when the laser pulse duration was greater than the electron-atom energy relaxation time, the growth rate depended strongly on the pulse time profile.