Non-resonant Coherent Amplitude Transfer in Attosecond Four-Wave Mixing Spectroscopy

TL;DR

This study demonstrates non-resonant coherent amplitude transfer in attosecond four-wave mixing spectroscopy, revealing long-lived Rydberg state contributions and wavepacket dynamics in atomic argon through experimental and theoretical analysis.

Contribution

It introduces a novel observation of non-resonant coherent amplitude transfer in four-wave mixing, supported by experimental data and Schrödinger equation simulations.

Findings

Long-lived Rydberg states contribute to four-wave mixing signals.

Coherent amplitude transfer occurs predominantly from 3s-1(n+1)p to 3s-1np states.

Theoretical modeling confirms non-resonant amplitude transfer driven by near-infrared light.

Abstract

Attosecond four-wave mixing spectroscopy using an XUV pulse and two noncollinear near-infrared pulses is employed to measure Rydberg wavepacket dynamics resulting from extreme ultraviolet excitation of a 3s electron in atomic argon into a series of autoionizing 3s-1np Rydberg states around 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 four wave mixing emission signals of each individually detected state. A wavepacket 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 Schr\"odinger equation simulations using electronic structure and transition moment calculations. The theory highlights that coherent amplitude transfer is driven non-resonantly to the 3s-1np states by the near-infrared light through 3s-1(n+1)s and 3s-1(n-1)d dark states during the four-wave mixing process.