UC Berkeley

The autoionization dynamics of the (²P_1/2)ns/d Rydberg states in krypton are investigated using spatially isolated wave-mixing signals generated with a short train of subfemtosecond extreme ultraviolet (XUV) pulses and noncollinear, few-cycle near infrared pulses. Despite ubiquitous quantum beat oscillations from XUV-induced coherences within the excited-state manifold, these wave-mixing spectra allow for the simultaneous evaluation of autoionization lifetimes from a series of Rydberg states above the first ionization potential. Experimentally measured lifetimes of 22 ± 8 fs, 33 ± 6 fs, and 49 ± 6 fs for the wave-mixing signals emitting from the (²P_1/2)6d/8s, (²P_1/2)7d/9s, and (²P_1/2)8d/10s resonances compare favorably with lifetimes for the (²P_1/2)6d, 7d, and 8d Rydberg states determined from spectral linewidths. Analysis of the quantum beats reveals that the enhancement of wave-mixing pathways that couple the (²P_1/2)nd states to themselves leads to individual reporter state-dependent decays in the wave-mixing signals. The results demonstrate the promise of wave-mixing spectroscopies with subfemtosecond XUV pulses to provide valuable insights into processes governed by electronic dynamics.