Js. Roman et al., Relativistic quantum dynamics of a localized Dirac electron driven by an intense-laser-field pulse - art. no. 063402, PHYS REV A, 6406(6), 2001, pp. 3402
The Volkov solutions for the Dirac equation are used to describe the dynami
cs of an electronic wave packet interacting with a very strong laser pulse
in the relativistic regime. By means of a projection method we explore the
regimes of long and short laser wavelength compared to the wave packet dime
nsions. Comparisons with classical electron trajectories show that the beha
vior of the expectation value of the operators becomes different as we ente
r to the short-wavelength regime. In addition, a study of the wave packet e
volution shows unexpected features in this regime. The calculations are com
pleted with an analysis of the total wave function in terms of the dynamics
of its positive and negative energy components.