Double-to-single target ionization ratio for electron capture in fast p-He collisions

Area of Science:

• Atomic and Molecular Physics
• Collision Physics
• Quantum Mechanics

Background:

• Transfer ionization (TI) is a fundamental process in ion-atom collisions.
• Understanding TI mechanisms is crucial for plasma physics and astrophysics.
• Previous studies have explored TI but lacked detailed separation of contributions.

Purpose of the Study:

• To experimentally determine absolute cross sections for transfer ionization (TI) in proton-helium collisions.
• To separate and analyze the contributions of Thomas (TTI) and kinematic (KTI) transfer ionization.
• To investigate the velocity dependence of both TTI and KTI processes.

Main Methods:

• Utilized the CRYRING ion storage ring with an internal gas-jet target.
• Employed a recoil-ion-momentum spectrometer for precise measurements.
• Analyzed proton-helium collisions in the energy range of 2.5-4.5 MeV.

Main Results:

• Measured absolute cross sections for TI, separating TTI and KTI components.
• Observed that the probability of electron emission in KTI decreases with increasing collision velocity.
• Found that the velocity dependence of the TTI cross section aligns with theoretical predictions of v(-11) scaling.

Conclusions:

• The experimental data provide a detailed understanding of TI mechanisms in p-He collisions.
• Kinematic TI electron emission approaches photoionization shakeoff values at higher velocities.
• The observed TTI velocity scaling validates theoretical models in this collision regime.