State-selective Charge Exchange in 19.5-100 keV amu-1 O6+ Collision with He and H2

The cross sections of state-selective charge exchange (CX) between highly charged ions and neutrals are important for modeling extreme ultraviolet and soft X-ray emissions in many astrophysical objects with hot plasma impacting cold media. By using cold-target recoil-ion momentum spectroscopy, we measure O6+ CX collisions with He and H-2 in the collision energy range of 19.5 to 100 keV amu(-1). The relative cross sections of state-selective single CX are reported for electron capture into O5+(1s(2)nl) n = 2, 3, 4, 5, >= 6 and n = 3, 4, 5, >= 6 for He and H-2, respectively. With the collision energy increasing to 100 keV amu(-1), the main capture channel shifts to higher n for both target species as compared to available theoretical results. We also report state-selective cross sections for double CX with He, where doubly excited states of O4+(1s(2)nln'l') with nln'l' being 2s(2) (S-1), 2s(2)p (P-1), 2p(2) (D-1), and 2p(2) (S-1) [symmetric configurations] and 2s3l, 2p3l-2s4l, and 2s5l-2p5l [asymmetric configurations] are distinguished. It is found that the contributions of doubly excited states with asymmetric configurations are dominant and symmetric configurations increasingly come into play with the increase of collision energy. The present results provide experimental benchmarks available for theoretical calculations.

Automated summary

State-selective charge exchange (CX) cross sections between O6+ ions and He/H-2 were measured using cold-target recoil-ion momentum spectroscopy. The cross sections for electron capture into specific excited states of O5+ ions were reported for different collision energies. Additionally, state-selective cross sections for double CX with He were obtained, distinguishing between symmetric and asymmetric configurations of doubly excited states. The results provide experimental benchmarks for theoretical calculations.