Line ratios for soft-x-ray emission following charge exchange betweenO8+and Kr

Abstract

Lyman spectra and line ratios are reported for soft X-ray emissions following the charge exchange process in 293 km/s, 414 km/s, 586 km/s, and 1256 km/s O 8+ and Kr collisions. Lyman series from Ly-α to Ly-ε were resolved for the O 7+ ion using a high resolution X-ray quantum microcalorimeter detector. It is found that the observed line ratios are dependent on the nl distribution of the captured electron, and the Ly-α and Ly-β X-ray emissions are enhanced. Moreover, by comparing the measured line ratios to the constructed theoretical single charge exchange line ratios for O 8+

A High Spectral Resolution Study of the Soft X-Ray Background with the X-Ray Quantum Calorimeter

“…But there is the promise of major improvements in the near future. We have already used this same XQC payload as a detector on the merged beam collision facility at Oak Ridge National Laboratories to make some preliminary measurements of line ratios from charge exchange as a function of velocity that illustrate limitations of current calculations (Defay et al 2013;Fogle et al 2014;Seely et al 2017). The installation has now been greatly improved and will soon be collecting better data on lines from ion-neutral pairs of astrophysical interest.…”

Measurement of n-resolved State-selective Charge Exchange in Ne(8,9)+ Collision with He and H2

“…More recently, significant progress in CX studies has been made with high-resolution X-ray microcalorimeters (Defay et al 2013;Fogle et al 2014;Seely et al 2017;Betancourt-Martinez et al 2018;Zhang et al 2019) and crystal spectrometers (Beiersdorfer et al 2005(Beiersdorfer et al , 2018(Beiersdorfer et al , 2019Lepson et al 2017). For instance, by measuring Lyβ/Lyα line ratios for X-ray emission in C 6+ -He electron capture at solar wind velocities, Defay et al (2013) clarified n = 3 capture being dominant, which later on was correctly reproduced by Cumbee et al (2017), while in a previous solar wind model Koutroumpa (2007) only assumed the dominant capture.…”

“…On the other hand, it is really difficult to encounter the triple coincidence of high-resolution X-rays, scattered projectiles, and target recoil ions. The X-ray emission from singly excited ions following autoionizing double-electron capture cannot be distinguished from the SEC (Hasan et al 2001;Seely et al 2017), which results in a softening of the spectrum due to the contribution of the autoionizing double-electron capture. Therefore, experimental and theoretical advances in obtaining nl-resolved state-selective cross sections is increasingly important for precise measurement and high-fidelity modeling.…”

Uncertainties in Atomic Data for Modeling Astrophysical Charge Exchange Plasmas

“…In Figure 5, we plot the comparison of the line ratio calculations and experiments for C VI and O VIII. The experimental data are taken from the beam-gas measurements by Andrianarijaona et al [75] for C VI and Seely et al [76] for O VIII. A caveat of the comparison is that these experiments used the Kr atom as a target, while the original theoretical calculations are based on capture from H atom.…”

“…Comparison of experimental and theoretical line ratios for the C 6+ (left) and O 8+ (right) reactions. The experimental data from Andrianarijaona et al[75] and Seely et al[76] are plotted as data points, and the predictions from G16, MCLZ, and RCMD are shown in black, red, and blue curves. The dashed curves show the calculations of C 6+ and O 8+ collisions with H atoms, and the solid lines show the collisions with Kr atoms obtained using the scaling of Leung & Kirchner[77].…”