Photoelectron angular distributions of excited atoms in intense laser fields

Abstract

Angular distributions of photoionization differential rates for an atom in arbitrary excited states ionized by intense laser fields with arbitrary polarization are reported. Relativistic effects are incorporated into the Keldysh theory, yielding semi-analytical expressions of ionization rates for hydrogenic initial states in intense linear, circular, and elliptical laser polarizations. Angular distributions are compared for different angular momentum quantum numbers, magnetic quantum numbers, and Keldysh parameters $\ensuremath{\gamma}$. The angular distributions are shown to depend strongly on $\ensuremath{\gamma}$, thus also reflecting the influence of relativistic effects. The sign of the magnetic quantum number, corresponding to different electron rotations, is shown to have a significant effect on photoelectron angular distributions in circularly polarized laser fields.