Nonresonant coherent amplitude transfer in attosecond four-wave-mixing spectroscopy

• Published in: Physical review. A 2023-02, Vol.107 (2), Article 023526
• Main Authors: Gaynor, James D., Fidler, Ashley P., Kobayashi, Yuki, Lin, Yen-Cheng, Keenan, Clare L., Neumark, Daniel M., Leone, Stephen R.
• Format: Article
• Language: English
• Subjects: ATOMIC AND MOLECULAR PHYSICS; atomic orbital; autoionization & auger processes; four-wave mixing; high-harmonic generation; light-matter interaction; optical coherence
• ISSN: 2469-9926; 2469-9934
• DOI: 10.1103/PhysRevA.107.023526

Attosecond four-wave mixing (FWM) spectroscopy using an extreme ultraviolet (XUV) pulse and two noncollinear near-infrared (NIR) pulses is employed to measure Rydberg wave packet dynamics resulting from XUV excitation of a 3s electron in atomic argon into a series of autoionizing 3s–1np Rydberg states ~29 eV. The emitted signals from individual Rydberg states exhibit oscillatory structure and persist well beyond the expected lifetimes of the emitting Rydberg states. These results reflect substantial contributions of longer-lived Rydberg states to the FWM emission signals of each individually detected state. A wave packet decomposition analysis reveals that coherent amplitude transfer occurs predominantly from photoexcited 3s–1 (n + 1) p states to the observed 3s–1np Rydberg states. The experimental observations are reproduced by time-dependent Schrödinger equation simulations using electronic structure and transition moment calculations. Finally, the theory highlights that coherent amplitude transfer is driven nonresonantly to the 3s–1np states by the NIR light through 3s–1 (n + 1)s and 3s–1 (n – 1)d dark states during the FWM process.