Absolute cross sections of single and double electron capture for C⁴⁺ colliding with He, O₂, N₂, and CH₄

Institute of Modern Physics, Key Laboratory of Nuclear Physics and Ion-Beam Application (MOE), Fudan University, Shanghai 200433, China

^★ Corresponding author. bingshengtu@fudan.edu.cn; brwei@fudan.edu.cn

Received: 22 July 2025
Accepted: 13 September 2025

Abstract

Context. Charge exchange between solar wind C⁴⁺ ions and neutrals drives soft X-ray and extreme ultraviolet emissions in astrophysical environments. Laboratory studies of charge exchange processes provide accurate atomic structure parameters, which are essential for the modeling of astrophysical plasmas.

Aims. We aim to measure the absolute charge exchange cross section of C⁴⁺ colliding with He, O₂, N₂, and CH₄ for their potential applications in astrophysical plasma modeling, as such processes take place between fast solar wind and neutral gases in planetary atmospheres.

Methods. The experiments were performed on a 150 kV highly charged ion collision apparatus at Fudan University. The C⁴⁺ ions were generated from a 14.5 GHz electron cyclotron resonance ion source, collided with the target gas in the gas cell, and detected by a position-sensitive detector. We utilized the growth rate approach to investigate the electron capture cross section data.

Results. We provide new absolute electron capture cross section data of C⁴⁺ colliding with He, O₂, N₂, and CH₄ in the energy range of 2.3–33.3 keV/u or 671–2535 km/s, with experimental uncertainties of 9% and 10% for single- and double-electron capture, respectively. The measured single-electron capture cross sections for C⁴⁺+He show significant deviations from existing theoretical calculations. Conclusions. We obtained the absolute single- and double-electron capture cross sections of C⁴⁺ colliding with He, O₂, N₂, and CH₄. These new data significantly deviate from the predictions of current modeling approaches.