Evolution of Rydberg angular momentum wavepackets in half-cycle pulses

We study the redistribution of Rydberg states subject to half-cycle electromagnetic pulses as a function of the field strength and the duration of the pulses. It is found that the survival probability exhibits oscillations which are associated with the almost recurrent propagation of the electronic wavepacket in angular momentum space. The classical and quantal origin of the different Stark beat frequencies is discussed. The dependence of the beats on the shape of the pulse and effects due to a non-hydrogenic core are analysed. The momentum transferred by the field is identified as a fundamental variable for the excitation function.