Theoretical treatment of quantum beats in the argon nf autoionizing states.

An experimental poster, presented in parallel with this theoretical study, observes quantum beats between different autoionizing nf Rydberg states, as a function of the time delay between an ultrafast laser excitation of those states and a subsequent short laser pulse that can photoionize the nf states.  To describe this experiment theoretically, multichannel quantum defect theory (MQDT) is implemented in combination with time-dependent perturbation theory to predict the observed oscillations in the angular distribution and in the angle-integrated energy-dependent photoelectron yield. Interference between the different quantum pathways as a function of the time delay results in an signal oscillating at frequencies equal to the difference between the quasi-discrete nf energies.  The experimental signatures can be understood by including terms in the theoretical description up to second order in the field strength.

This work was funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award Number DE-SC0010545