Attosecond delays in X-ray molecular ionization.

Area of Science:

• Atomic and Molecular Physics
• Quantum Dynamics
• Ultrafast Science

Background:

• The photoelectric effect exhibits attosecond delays, offering insights into molecular dynamics.
• Sub-femtosecond light pulses enable the study of photoionization dynamics.
• Time-resolved core-level photoionization measurements were previously limited by X-ray source availability.

Purpose of the Study:

• To measure time-resolved X-ray photoemission delays of core-level electrons.
• To investigate the complex dynamics of core-level photoionization using attosecond X-ray pulses.
• To explore contributions to photoemission delays, including electron trapping and scattering.

Main Methods:

• Utilized attosecond soft X-ray pulses from a free-electron laser.
• Performed measurements of X-ray photoemission delay near the oxygen K-shell threshold in NO.
• Scanned the K-shell threshold region to analyze delay spectra.

Main Results:

• Observed unexpectedly large X-ray photoemission delays for core-level electrons, up to 700 attoseconds.
• Found that the delay spectrum is richly modulated, indicating complex electronic processes.
• Identified contributions from transient electron trapping, Auger-Meitner electron collisions, and multi-electron scattering.

Conclusions:

• X-ray attosecond experiments can resolve time-resolved core-level photoionization dynamics.
• The observed delays and spectral modulations provide a detailed view of electron correlations.
• This work opens new avenues for studying molecular dynamics with high temporal resolution.