Super-resolution stimulated X-ray Raman spectroscopy.

Area of Science:

• Atomic and Molecular Physics
• Ultrafast X-ray Science
• Quantum Optics

Background:

• Intense X-ray pulse propagation in dense media yields phenomena like X-ray lasing and stimulated X-ray Raman scattering (SXRS).
• SXRS is theoretically crucial for launching/probing valence-electron wavepackets and developing nonlinear X-ray spectroscopies.
• Previous SXRS experiments lacked spectroscopic detail, and theoretical models required difficult-to-achieve phase-coherent attosecond pulses.

Purpose of the Study:

• To demonstrate stimulated X-ray Raman scattering (SXRS) with high spectroscopic precision.
• To probe valence-excited states in neon with exceptional joint energy-time resolution.
• To develop a new approach for nonlinear X-ray spectroscopy beyond current limitations.

Main Methods:

• Utilized broadband X-ray pulses and a novel covariance analysis of incident and scattered Raman pulses.
• Achieved super-resolution conditions by outperforming incident bandwidth and instrumental energy resolution using 18,000 single shots.
• Employed ab initio propagation simulations to support experimental findings.

Main Results:

• Demonstrated SXRS with spectroscopic precision, resolving valence-excited states in neon at 0.1 eV-40 fs resolution.
• Revealed the competition between X-ray lasing in ions and stimulated Raman scattering in neutrals.
• Achieved significantly enhanced signal collection efficiency and a broad excitation window, surpassing spontaneous Raman scattering by orders of magnitude.

Conclusions:

• The stochastic SXRS approach provides a powerful new tool for nonlinear X-ray spectroscopy.
• This method enables tracking elementary events that govern chemical outcomes with high fidelity.
• The demonstrated super-resolution technique opens new avenues for ultrafast dynamics studies in atomic and molecular systems.