Manipulating twisted electrons in strong-field ionization

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Mechanics
• Strong-Field Physics

Background:

• Strong-field ionization is a fundamental process where intense laser fields liberate electrons from atoms or molecules.
• Vortex interferences in photoelectrons have been observed in experiments involving counter-rotating circularly polarized laser pulses.
• Understanding the orbital angular momentum (OAM) of photoelectrons is crucial for interpreting these interference patterns.

Purpose of the Study:

• To investigate the discrete orbital angular momentum (OAM) of photoelectrons generated via strong-field ionization.
• To provide an alternative interpretation of experimental observations of vortex interferences in strong-field ionization.
• To establish a connection between electron OAM and interference phenomena in strong-field ionization.

Main Methods:

• Utilized the strong-field approximation (SFA) to derive an interference condition for electron vortices.
• Performed computations using SFA, Qprop, and R-Matrix methods for a neon target.
• Analyzed the OAM of photoelectrons across different computational approaches.

Main Results:

• Derived an interference condition for vortices that shows excellent agreement with photoelectron momentum distributions.
• Identified a small number of discrete vortex states localized in specific energy regions.
• Demonstrated that vortices arise from the interference of pairs of twisted electron states, with OAM related to spiral arms.

Conclusions:

• The study establishes a direct link between photoelectron OAM and vortex interference patterns in strong-field ionization.
• A semiclassical relation for OAM was determined by recreating vortices with pairs of twisted electrons.
• Proposed methods for direct OAM measurement and its application in time-resolved imaging of photo-induced dynamics.