Pauli Shielding and Breakdown of Spin Statistics in Multielectron Multi-Open-Shell Dynamical Atomic Systems

Area of Science:

• Atomic and Molecular Physics
• Quantum Mechanics
• Chemical Physics

Background:

• Electron capture in ion-atom collisions is crucial for understanding atomic processes.
• Doubly excited states in multielectron systems present complex theoretical challenges.
• Previous studies on carbon ion collisions lacked consensus on spin statistics and cascade effects.

Purpose of the Study:

• To determine C^{3+} cross sections for electron capture from helium and hydrogen.
• To investigate the formation of doubly excited C^{3+} states (1s2s2p).
• To resolve controversies regarding the ratio R of cross sections for ^{4}P and ^{2}P_{±} states and the influence of cascades.

Main Methods:

• Utilized zero-degree Auger projectile spectroscopy for experimental analysis.
• Employed a three-electron close-coupling semiclassical approach for theoretical calculations.
• Focused on swift C^{4+} (1s2s ^{3}S) ion collisions.

Main Results:

• Resolved a long-standing puzzle concerning the ratio R of cross sections for ^{4}P and ^{2}P_{±} states.
• Demonstrated that the frozen core approximation is inadequate for multielectron systems.
• Experimental and theoretical results are consistent.

Conclusions:

• The study clarifies the underlying physics of electron capture in complex quantum systems.
• A novel 'Pauli shielding' effect, stemming from the Pauli exclusion principle, is proposed to explain the observed ratio R.
• Findings necessitate a re-evaluation of theoretical approaches for electron capture in multielectron ions.