Attosecond time-resolved autoionization of argon.

Area of Science:

• Atomic physics
• Quantum mechanics
• Ultrafast spectroscopy

Background:

• Autoionization is a fundamental process where an atom with excess energy decays by ejecting an electron.
• Fano resonances describe the interference between a discrete state and a continuum of states, crucial for understanding atomic spectra.
• Previous studies have explored laser-matter interactions, but the specific effects of intense fields on autoionization resonances require further investigation.

Purpose of the Study:

• To experimentally investigate the influence of intense few-cycle near-infrared laser pulses on argon autoionization resonances.
• To elucidate the underlying mechanisms responsible for the observed modifications in resonance parameters.
• To understand the strong-field dynamics of autoionizing states in atoms.

Main Methods:

• Utilizing attosecond transient absorption spectroscopy to probe atomic dynamics with high temporal resolution.
• Employing isolated few-cycle near-infrared laser pulses to induce strong-field effects.
• Performing numerical simulations to interpret experimental observations and explore theoretical underpinnings.

Main Results:

• Observed significant modifications in the peak position, intensity, linewidth, and shape of the 3s3p⁶np ¹P Fano resonance series (26.6-29.2 eV) of argon.
• Experimentally confirmed the splitting of the 3s3p⁶4p ¹P line under intense laser fields.
• Numerical simulations accurately reproduced the experimental findings, attributing the splitting to the coupling of two short-lived highly excited states.

Conclusions:

• Intense laser fields dynamically alter the autoionization spectrum of argon atoms.
• The observed spectral splitting is a direct consequence of strong-field induced coupling between excited atomic states.
• Attosecond spectroscopy provides a powerful tool for probing ultrafast dynamics in laser-driven atomic systems.