Intensity-dependent two-electron emission dynamics in nonsequential double ionization by counter-rotating two-color...

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Mechanics
• Laser-Matter Interactions

Background:

• Nonsequential double ionization (NSDI) is a fundamental process in strong-field physics.
• Understanding electron emission dynamics in intense laser fields is crucial for attosecond science.
• Previous studies have explored single and double ionization in various laser configurations.

Purpose of the Study:

• To investigate the nonsequential double ionization of helium.
• To analyze the electron momentum distributions under counter-rotating two-color circularly polarized laser fields.
• To explore the influence of laser intensity on ionization dynamics and electron release times.

Main Methods:

• Utilized a three-dimensional classical ensemble model.
• Simulated the behavior of helium atoms interacting with counter-rotating two-color circularly polarized laser fields.
• Analyzed the momentum distribution of the emitted electrons at different laser intensities.

Main Results:

• At moderate intensity, electron momentum distribution shows a maximum in the middle of the negative vector potential triangle sides.
• At high intensity, a double-triangle structure is observed, attributed to different electron release times after recollision.
• At low intensity, a shift from the middle is observed due to a narrow emission time window for the first electron.

Conclusions:

• Laser intensity significantly dictates the electron momentum distribution in NSDI of helium.
• The observed double-triangle structure at high intensity provides insights into electron recollision and release dynamics.
• Low-intensity ionization reveals prevalent double-recollision events and NSDI from doubly excited states.