Sequential Synchronous Mechanism for Double-Electron Capture: Insights into Unforeseen Large Cross Sections in...

Area of Science:

• Atomic and Molecular Physics
• Chemical Physics
• Quantum Mechanics

Background:

• Electron capture cross sections are crucial for understanding ion-molecule interactions.
• Low-energy collisions often exhibit complex dynamics not predicted by simple models.
• Energetically unfavorable reactions typically show minimal cross sections.

Purpose of the Study:

• To investigate the unexpectedly large double electron capture cross sections in Sn^{3+} + H_{2} collisions.
• To elucidate the underlying charge transfer mechanism responsible for the observed cross sections.
• To explain the unusual energy dependence of the reaction at low energies.

Main Methods:

• Experimental measurement of double electron capture cross sections at low energies (<50 eV/u).
• Theoretical modeling using propagation of vibrational wave packets.
• Calculations performed on coupled multiple potential energy surfaces.

Main Results:

• Observed remarkably large double electron capture cross sections (on the order of 10^{-15} cm^{2}).
• Identified a novel charge transfer mechanism driven by simultaneous ion motion and molecular vibration.
• Revealed an unusual energy dependence of the cross sections that is explained by the new mechanism.

Conclusions:

• The study reveals a new charge transfer mechanism in ion-molecule collisions.
• This mechanism explains large, unexpected cross sections in energetically unfavorable reactions.
• Insights into the interplay of nuclear and electronic motion in low-energy collisions were gained.