X-ray emission measurements following charge exchange between C6+and He

Abstract

X-ray spectra following charge-exchange collisions between C 6+ and He are presented for collision energies between 460 and 32 000 eV/u. Spectra were obtained at the Oak Ridge National Laboratory Multicharged Ion Research Facility using a microcalorimeter x-ray detector capable of fully resolving the C VI Lyman series lines through Ly-γ . These line ratios are sensitive to the initial electron distribution and test our understanding of the charge-exchange process. In addition, these line ratios are important for identifying charge exchange in astrophysical contexts involving the interaction of solar wind ions with neutrals. Our measurements are performed at collision velocities (300-2500 km/s) which overlap most of the solar wind range. Additional data of this type can be combined with computations to provide an extensive set of reliable line ratios and absolute cross sections for the interpretation of a variety of astrophysical situations.

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

“…Laboratory measurements of charge exchange emission spectra have demonstrated that the relative strength of different emission lines changes significantly over the range of solar wind velocities (e.g. Defay et al 2013). There are also large uncertainties and variabilities in the metal ion content of the solar wind.…”

Radiance line ratios Ly-β/Ly-α, Ly-γ/Ly-α, Ly-δ/Ly-α, and Ly-ε/Ly-α for soft X-ray emissions following charge exchange between C6+ and Kr

“…Previously, our measurements of C 6+ + He, reported by Defay et al [5], were compared with predictions by the Atomic-Orbital Close-Coupling (AOCC) calculations of Fritsch and Lin [6] and Molecular-Orbital Close-Coupling (MOCC) calculations of Kimura and Olson [7]. The experimentally determined Ly-b/Ly-a ratio is in good agreement with the AOCC predictions at higher collision energies (velocities above 1500 km/s) while the MOCC predictions exhibit the trend of the measured ratios at low collision energies.…”

“…The experiment was conducted at ORNL-MIRF with the same experimental setup used for C 6+ + He by Defay et al [5] and Fogle et al [10]. Fully stripped 13 C is produced in the permanent magnet Electron Cyclotron Resonance (ECR) ion source [23], magnetically selected to form a beam of 13 C 6+ and then accelerated or de-accelerated off the high voltage platform to produce collisions with Kr at the solar wind velocities (300-2500 km/s).…”

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

“…The sketch of the experimental setup can be seen in Fig. 1 and is identical to that used in other measurements [16][17][18].…”

“…X-ray spectra and line ratios measurements can be used to test our understanding of CX collision mechanisms. For example, our previous line ratio measurements [16,17] for C 6+ on He and H 2 collisions have been compared to recent theoretical line ratios constructed from calculations using the TC-BGM method. The satisfactory agreement with our line ratio measurements confirm the predictions that a statistical l distribution occurs at low velocities, while the l distribution shifts to maximum l at high velocities [10].…”