Influence of zitterbewegung on relativistic harmonic generation

Harmonic generation from one-electron ions exposed to a strong laser pulse has been calculated numerically using the Dirac equation for studying the r ole of relativistic contributions from the nucleus. For the laser parameter s employed here magnetic field contributions are negligible,justifying a on e-dimensional model potential. In comparison to the relativistic Schrodinge r theory, slightly more radiation of high harmonic order is predicted in mo derately charged ions. This difference is attributed to the presence of neg ative energy states in Dirac theory, which allows for stimulated zitterbewe gung (laser-induced transitions between positive and negative energy states ) of the electron.