Strong-Field-Assisted X-ray Second Harmonic Generation

TL;DR

This paper theoretically demonstrates x-ray second harmonic generation driven by strong-field high harmonic generation from core electrons, proposing it as a new spectroscopic tool for atomic and molecular studies with potential for attosecond x-ray pulse generation.

Contribution

It introduces a novel theoretical framework for x-ray SHG via strong-field-driven HHG from core electrons, merging attosecond laser technology with nonlinear x-ray methods.

Findings

Confirmation of HHG-XSHG from atomic core electrons.

Broadband multi-peak structure with a spectral cutoff in the x-ray regime.

Potential for probing core-electron dynamics and generating attosecond x-ray pulses.

Abstract

We theoretically demonstrate x-ray second harmonic generation (SHG) with strong-field-driven high harmonic generation (HHG) from core electrons in gas-phase atoms, highlighting its potential as a powerful spectroscopic tool for studying atomic and molecular systems. Our simulations confirm the generation of HHG with x-ray SHG (HHG-XSHG) from atomic core electrons through the rescattering of electrons from x-ray two-photon excitation and subsequent tunneling ionization in an optical laser field. The resulting HHG-XSHG spectrum features a broadband multi-peak structure and a distinct spectral cutoff in the x-ray regime. These findings indicate that HHG-XSHG is a valuable technique for probing core-electron dynamics, generating attosecond x-ray pulses, and exploring nonlinear interactions, effectively merging laser-driven attosecond technology with nonlinear x-ray methodologies provided by x-ray free-electron lasers.