Absolute Differential Positronium-Formation Cross Sections

Area of Science:

• Atomic and Molecular Physics
• Quantum Chemistry
• Positron Scattering

Background:

• Positronium (Ps) formation is a key process in positron-atom/molecule collisions.
• Understanding Ps formation cross sections is crucial for various applications, including materials science and fundamental physics.
• Previous experimental data for differential cross sections near 0° were limited.

Purpose of the Study:

• To provide the first absolute experimental determination of differential cross sections for ground-state positronium formation.
• To investigate the angular distribution of positronium formation for various targets (He, Ar, H2, CO2).
• To compare experimental results with theoretical predictions and analyze target-specific emission propensities.

Main Methods:

• Absolute measurements of differential cross sections using a high-resolution positron beam.
• Scattering experiments conducted at low angles (near 0°) to probe forward emission.
• Analysis of the ratio between differential and integrated cross sections.

Main Results:

• First absolute experimental differential cross sections for ground-state positronium formation are reported for He, Ar, H2, and CO2.
• Experimental data are compared with existing theoretical models.
• A higher propensity for forward emission of positronium was observed for Helium and Hydrogen molecule targets compared to Argon and Carbon Dioxide.

Conclusions:

• The experimental data provide a benchmark for theoretical calculations of positronium formation.
• The observed forward scattering asymmetry highlights target-specific effects in the positronium formation mechanism.
• Further theoretical and experimental investigations are warranted to fully understand the nuances of positronium formation dynamics.