Influence of long-range Coulomb interaction in velocity map imaging

Area of Science:

• Atomic and Molecular Physics
• Chemical Physics
• Quantum Mechanics

Background:

• Velocity-map imaging (VMI) typically approximates photoelectron trajectories as ballistic, neglecting residual Coulomb fields.
• This approximation simplifies image analysis but fails when long-range forces significantly influence electron paths.

Purpose of the Study:

• To demonstrate the necessity of including long-range Coulomb interactions in VMI analysis.
• To analyze two distinct scenarios in isolated atoms and molecules where this approximation breaks down.

Main Methods:

• Theoretical analysis of photoelectron trajectories under Coulomb interactions.
• Interpretation of experimental velocity-map imaging data.

Main Results:

• Slow photoelectrons from neutral systems exhibit complex image structures and central glories due to attractive Coulomb potentials.
• Photodetachment from multiply charged anions shows features explained by tunnel detachment through repulsive Coulomb barriers, even when standard VMI is valid.

Conclusions:

• The standard VMI approximation is insufficient for accurate analysis in cases involving significant Coulomb interactions.
• Accounting for attractive and repulsive Coulomb potentials is vital for understanding photoelectron dynamics and interpreting VMI data in specific atomic and molecular systems.