Abstract
Relevant uncertainties of theoretical atomic data are vital to determining the accuracy of plasma diagnostics in a number of areas, including, in particular, the astrophysical study. We present a new calculation of the uncertainties on the present theoretical ion-impact charge exchange atomic data and X-ray spectra, based on a set of comparisons with the existing laboratory data obtained in historical merged-beam, cold-target recoil-ion momentum spectroscopy, and electron beam ion traps experiments. The average systematic uncertainties are found to be 35–88% on the total cross sections, and 57–75% on the characteristic line ratios. The model deviation increases as the collision energy decreases. The errors on total cross sections further induce a significant uncertainty to the calculation of ionization balance for low-temperature collisional plasmas. Substantial improvements of the atomic database and dedicated laboratory measurements are needed to obtain the current models, ready for the X-ray spectra from the next X-ray spectroscopic mission.
Highlights
Charge exchange plasma can be found in a broad range of astrophysical environments, including, in particular, the interfaces where the solar wind ions interact with neutrals in comets and planetary atmospheres [1,2,3,4], but potentially in supernova remnants [5,6], star-forming galaxies [7,8], active galactic nuclei [9], and clusters of galaxies [10,11]
The SPEX atomic data do not constitute one uniform set of theoretical calculations, but a mixture of three different types of approaches: (1) the rates derived with the empirical scaling reported in Gu et al [13] (G16 hereafter), which was based on a numerical approximation to a collection of historical theoretical and experimental rates; (2) the multi-channel Landau-Zener method reported in Mullen et al [36]
The G16, MCLZ, and RCMD calculations utilized in the SPEX code do not fully reproduce the measurements, with notable, and likely velocity-dependent discrepancies in both total cross sections, state-resolved cross sections, and line ratios in the X-ray spectra
Summary
Charge exchange plasma can be found in a broad range of astrophysical environments, including, in particular, the interfaces where the solar wind ions interact with neutrals in comets and planetary atmospheres [1,2,3,4], but potentially in supernova remnants [5,6], star-forming galaxies [7,8], active galactic nuclei [9], and clusters of galaxies [10,11]. A recent comparison using the data from the EBIT measurements [33] showed that the model and the laboratory spectra differ significantly in both line energies and strengths, for the L-shell charge exchange between nickel ions and neutral particles. Another recent example is that the COLTRIMS measurement by Xu et al [34] showed that the model calculations might differ from the measurements by 20–50% for the state-selective cross sections of Ne8+ and Ne9+ charge exchange. Throughout the paper, the errors are given at a 68% confidence level
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
