Autoionization Dynamics of (2P1/2)ns/d States in Krypton Probed by Noncollinear Wave Mixing with Attosecond Extreme Ultraviolet and Few-Cycle Near Infrared Pulses

The autoionization dynamics of the (<sup>2</sup>P<sub>1/2</sub>)ns/d Rydberg states in krypton are investigated using wave-mixing signals generated with subfemtosecond XUV pulses and noncollinear, few-cycle NIR pulses. Despite quantum beat oscillations from the XUV-induced coherence, these wave-mixing spectra allow for the simultaneous evaluation of autoionization lifetimes from a series of Rydberg states. Experimentally measured lifetimes for the wave-mixing signals emitting from the (<sup>2</sup>P<sub>1/2</sub>)6d/8s, 7d/9s, and 8d/10s resonances compare favorably with lifetimes for the (<sup>2</sup>P<sub>1/2</sub>)6d, 7d, and 8d Rydberg states determined from spectral linewidths. Analysis of the quantum beats reveals that the enhancement of wave-mixing pathways leads to 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.<br>