Electronic dynamics and frequency effects in circularly polarized strong-field physics

We analyze, quantum mechanically, the dynamics of atomic ionization with a strong, circularly polarized, laser field. We show that the main source for non-adiabatic effects, defined as the deviations from the static-field configuration with corresponding instantaneous amplitude, is connected to an effective barrier lowering due to the laser frequency. Such non-adiabatic effects manifest themselves through ionization rates and yields that depart up to more than one order of magnitude from a static-field configuration which we take as a reference for comparison. As a rule of thumb, such non-adiabatic manifestations get stronger with increasing laser frequency. Beyond circular polarization and atomic targets, these results show the limits of standard instantaneous-static-field like-interpretation of laser-matter interaction and the great need for including time-dependent electronic dynamics.