Quantum beats in photoionization from a coherent superposition of fine-structure levels

Abstract

We present a theory of quantum beats in photoionization from a coherent superposition of $D_{\frac{3}{2},5.2\mathrm{}}$ levels in alkali-metal atoms. The semiclassical density-matrix formalism is used to describe both the excitation of the $D_{\frac{3}{2},\frac{5}{2}}$ levels by a two-photon resonant pulse and the subsequent photoionization by a delayed probe pulse. Quantum beats occur in the ionization signal as a function of the delay of the probe pulse. The depth of modulation is determined for different light polarizations.