Laser-induced inner-shell excitations through direct electron re-collision versus indirect collision

Area of Science:

• Atomic Physics
• Quantum Dynamics
• X-ray Spectroscopy

Background:

• Inner-shell excited atoms exhibit rapid radiative and non-radiative decay.
• Direct time-domain studies of these dynamics are essential for understanding fundamental processes.
• Previous research has focused on indirect methods due to the fast decay rates.

Purpose of the Study:

• To investigate the excitation and ionization dynamics of inner-shell electrons using laser-induced electron re-collision.
• To measure the influence of laser intensity and ellipticity on emitted x-ray spectra.
• To establish a pump-probe capability for studying core-hole dynamics at their natural timescale.

Main Methods:

• Utilized few-cycle infrared laser pulses to induce electron re-collision.
• Analyzed the emitted x-ray spectra as a function of laser intensity and ellipticity.
• Performed numerical simulations to interpret experimental observations.

Main Results:

• Observed distinct dependencies of x-ray emission spectra on laser parameters for different atomic systems.
• Identified competing excitation mechanisms contributing to x-ray emission.
• Demonstrated that direct re-collision excitation differs from indirect collisions.

Conclusions:

• The study provides direct time-domain insights into inner-shell excited atom decay processes.
• Laser intensity and ellipticity significantly influence x-ray emission, with system-dependent variations.
• Understanding these excitation mechanisms is key for advanced pump-probe experiments.