Low-energy state-selective charge transfer by multiply charged ions

Area of Science:

• Atomic and Molecular Physics
• Plasma Physics
• Astrophysical Chemistry

Background:

• Accurate charge-transfer cross-section data are crucial for modeling astrophysical environments and fusion plasmas.
• Existing theoretical models often struggle to predict these cross-sections accurately, especially at low energies.

Purpose of the Study:

• To present a novel experimental method combining radiofrequency-guided ion beams and photon emission spectroscopy.
• To measure state-selective charge-transfer cross-sections for helium ions (He2+) and nitrogen ions (N5+) colliding with molecular hydrogen.
• To provide benchmark data for advancing theoretical descriptions in astrophysics and fusion energy research.

Main Methods:

• Utilized a combined radiofrequency-guided ion beam and photon emission spectroscopy technique.
• Investigated ion collision energies ranging from 1000 eV/amu down to 5 eV/amu.
• Obtained absolute state-selective cross-section values.

Main Results:

• Measured state-selective charge-transfer cross-sections for He2+ and N5+ on molecular hydrogen.
• Observed significant, orders-of-magnitude differences between experimental results and theoretical predictions.
• Demonstrated the method's capability to probe low-energy collision regimes.

Conclusions:

• The experimental data serve as critical benchmarks for validating and improving theoretical models of charge transfer.
• The developed method offers a powerful tool for state-selective charge-transfer measurements in astrophysically and fusion-relevant energy ranges.
• Discrepancies underscore the limitations of current theoretical approaches and the need for further development.