Coherent nonlinear X-ray four-photon interaction with core-shell electrons

Area of Science:

• Atomic and Molecular Physics
• Ultrafast Spectroscopy
• Quantum Electronics

Background:

• Coherent nonlinear light-matter interactions with X-rays enable ultrafast spectroscopy at atomic resolution.
• X-ray four-wave mixing offers insights into electronic state coupling, electron motion, and dynamics.
• Current methods face limitations in achieving site and state selectivity for complex systems.

Purpose of the Study:

• To demonstrate coherent, background-free four-photon interactions with core-shell electrons using X-ray pulses.
• To explore X-ray four-wave mixing for atomic-scale multidimensional correlation spectroscopy.
• To establish a foundation for studying localized electron dynamics with high resolution.

Main Methods:

• Utilizing single broadband X-ray pulses from a free-electron laser.
• Performing all-X-ray four-wave mixing measurements on gaseous neon.
• Employing multicolour time-delayed X-ray pulse schemes.

Main Results:

• Successfully demonstrated coherent, background-free four-photon interactions with core-shell electrons.
• Observed X-ray four-wave mixing signals arising from doubly resonant nonlinear Raman processes.
• Generated 2D spectral maps (photon-in/photon-out) for atomic-scale correlation spectroscopy.
• Showcased the feasibility of ultrafast time-domain extensions using time-delayed pulses.

Conclusions:

• The developed X-ray four-wave mixing technique provides atomic-scale insights into electron dynamics.
• This methodology advances multidimensional correlation spectroscopy.
• Potential applications include studying biomolecules, quantum materials, and advancing energy conversion and quantum technologies.