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

Abstract

The autoionization dynamics of the (2 P1/2)ns/d Rydberg states in krypton are investigated using spatially-isolated wave-mixing signals generated with a short train of subfemtosecond XUV pulses and noncollinear, few-cycle near infrared (NIR) pulses. Despite ubiquitous quantum beat oscillations from the XUV-induced coherences within the excited-state manifold, these wavemixing 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 (2 P1/2)6d/8s, (2 P1/2)7d/9s, and (2 P1/2)8d/10s resonances compare favorably with lifetimes for the (2 P1/2)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 (2 P1/2)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. I.

Coupled nuclear–electronic decay dynamics of O2 inner valence excited states revealed by attosecond XUV wave-mixing spectroscopy

“…50 These effects are interesting in their own right but make it difficult to extract lifetime information when the pulse duration is similar to the lifetime of interest. To disentangle this complexity, we recently developed attosecond non-collinear wavemixing spectroscopy with one attosecond XUV pulse and two non-collinear fewfemtosecond NIR pulses [17][18][19][20][21][22][23] . The advantage of the technique is that it spatially isolates the nonlinear response from the combined linear and nonlinear response of ATA and yields a background-free homodyne measurement that can be more cleanly interpreted than ATA.…”

“…It has been used to probe the electronic and vibrational structure in atoms and molecules [17][18][19] , and we utilized it recently to measure autoionization lifetimes in Kr. 21 In this work, we report the first application of attosecond XUV wave-mixing spectroscopy to the fast-decaying dynamics in a molecule, specifically the O2 3s…”

“…The experimental apparatus for attosecond non-collinear wave-mixing spectroscopy with attosecond XUV pulses has been described previously [21][22][23] and is shown in Figure 2. Briefly, a commercial Ti-sapphire laser system (Femtopower HE, Femtolasers) is used to produce 2 mJ, 22 fs NIR pulses at a 1 kHz repetition rate, which are then spectrally broadened in a 2 m long stretched hollow core fiber of 500 μ inner diameter filled with 2 bar of neon gas.…”

“…5,[8][9][10][11][12] However, the advent of ultrafast light sources in the XUV region of the spectrum has enabled direct measurements of excited state lifetimes through novel spectroscopic techniques, thereby opening new windows into the decay mechanisms of these states. [13][14][15][16] In this paper, we employ the recently developed method of attosecond XUV wave-mixing spectroscopy [17][18][19][20][21][22][23] to very short-lived (<10 fs) Rydberg states of O2 and, in conjunction with state-of-the-art theory, unravel the interplay between autoionization and predissociation with vibrational state-specificity.…”

Coupled Nuclear-Electronic Decay Dynamics of O2 Inner Valence Excited States Revealed by Attosecond XUV Wave-Mixing Spectroscopy

“…It has been used to probe the electronic and vibrational structure in atoms and molecules [17][18][19] , and we utilized it recently to measure autoionization lifetimes in Kr. 21 In this work, we report the first application of attosecond XUV wave-mixing spectroscopy to the fast-decaying dynamics in a molecule, specifically the O2 3s Rydberg state. Spatially isolated wave-mixing signals are observed from this Rydberg state and the transient behavior of these signals is measured.…”