X-ray Emission Following Charge Exchange Between Slow Highly Charged Ions and Atomic H and Its Astronomical Application

Experimental and theoretical research on X-ray emissions following charge exchange between slow highly charged ions and atomic Hydrogen supply vital atomic data for the study of diagnosing and modeling plasmas in non-equilibrium astrophysical environment. In the present paper, employing the semiclassical multi-channel Landau-Zener (MCLZ) method, we calculated the total cross-section of bare and hydrogenic C, N, and O ions charge exchange with hydrogen atoms, and compared it with previously reported experimental results. In \rm C^5+ + H collision, theoretically calculated cross-sections have large differences with experimental cross-sections. We also compared state-selective cross-sections calculated by classical MCLZ and quantum-mechanical molecular orbital close-coupling (QMOCC) methods in the solar wind ion velocity (or energy) range. For capture to n = 3 shell, MCLZ calculated state-selective cross-section increases with collision energy increasing; For capture to n = 4 shell, MCLZ calculated state-selective cross-section decreases with collision energy increasing; It is lower than two magnitudes as the QMOCC method calculated cross-section at the low energy end. Finally, using the Kronos program package developed in the astrophysical field, we calculated the X-ray emission spectrum, line ratio, and hardness ratio of charge exchange of 1 keV·u⁻¹ \rmO^8++\rmH by means of the recommended cross-section by Janev Atomic Data and Nuclear Data Tables, 1999, 55(2): 201, and contrast with the MCLZ method calculated results. We consider that the MCLZ calculation combine with l distribution model has a large uncertainty, which could affect the accuracy of the astrophysical environment modeling. It is required to develop a more accurate full quantum theory.