Measurement of Absolute Single and Double Electron Capture Cross Sections for O⁶⁺ Ion Collisions with CO₂, CH₄, H₂, and N₂

Abstract

The absolute electron capture cross sections for single and double charge exchanges (CEs) between the highly charged ion O6+ and CO2, CH4, H2, and N2, the dominant collision processes in the solar wind, have been measured in the energies from 7 keV · q (2.63 keV u−1) to 52 keV · q (19.5 keV u−1). These measurements were carried out in the new experimental instrument setup at Fudan University, and the errors of the cross sections for single and double CEs at the 1σ confidence level were about 11% and 16%, respectively. Limited agreement is achieved with single electron capture results calculated by the classical overbarrier model. These cross section data are useful for the simulation of ion–neutral processes in astrophysical environments and to improve the present theoretical model of fundamental atomic processes.

Single- and Double-electron Capture Cross Sections for O6+ Ion in Collisions with H2 Molecules

“…In Figure 2, our total SEC cross sections for O 6+ ion in collisions with H 2 molecule are presented as a function of impact energy, together with available experimental data (Crandall et al 1977(Crandall et al , 1979Phaneuf et al 1982;Dijkkamp et al 1985;Machacek et al 2014;Han et al 2021). The present results are also listed in Table 2.…”

“…In the former experiment, total SEC cross sections were also measured by means of charge-state analysis at 0.5-5 keV u −1 . More recently, both total SEC and DEC cross sections were measured by Machacek et al (2014) at 1.17 and 2.33 keV u −1 and Han et al (2021) for energies ranging from 2.63 to 19.50 keV u −1 . Though with different apparatuses, electron cyclotron resonance ion source was used in both experiments, and cross sections for ions in different charge states due to the electron-capture process were measured by applying an appropriate potential field to deflect the ions (see also Greenwood et al 2001 andZhang et al 2018 for more details about the experiments).…”

“…Though with different apparatuses, electron cyclotron resonance ion source was used in both experiments, and cross sections for ions in different charge states due to the electron-capture process were measured by applying an appropriate potential field to deflect the ions (see also Greenwood et al 2001 andZhang et al 2018 for more details about the experiments). Despite extensive experimental studies on O 6+ and H 2 collisions, only very few data are available for state-resolved SEC processes limited in the energy range of 0.007-10 keV u −1 (Dijkkamp et al 1985;Lubinski et al 2000), and the DEC ones for energies within 1-20 keV u −1 (Machacek et al 2014;Han et al 2021). From the theoretical point of view, investigating this collision system remains challenging due to the strong coupling between various channels, the multicenter features of the H 2 molecular target, and the role of the electronic correlation, notably in the important two-electron processes invoked just above.…”

Uncertainties in Atomic Data for Modeling Astrophysical Charge Exchange Plasmas

“…The improvement in the momentum measurement technique allows nl selectivity, and for a few cases, it might even be able to resolve the spin state. The state-of-the-art measurement accuracy is about 11% for both the total and nl-resolved cross sections [83].…”

Uncertainties in Atomic Data for Modeling Astrophysical Charge Exchange Plasmas

“…The improvement in the momentum measurement technique allows nl selectivity, and for a few cases, it might even be able to resolve the spin state. The state-of-the-art measurement accuracy is about 11% for both the total and nl-resolved cross sections [85].…”