Measurement and calculation of absolute single- and double-charge-exchange cross sections for O6+ ions at 1.17 and 2.33 keV/u impacting He and H-2

Abstract

Absolute single- and double-charge-exchange cross sections for the astrophysically prominent O6+ ion with the atomic and molecular targets He and H2 are reported. These collisions give rise to x-ray emissions in the interplanetary medium, planetary atmospheres, and comets as they approach the sun. Measurements have been carried out using the Caltech Jet Propulsion Laboratory electron cyclotron resonance ion source with O6+ at energies of 1.17 and 2.33 keV/u characteristic of the slow and fast components of the solar wind. Absolute charge-exchange (CE) data are derived from knowledge of the target gas pressure, target path length, incident ion current, and charge-exchanged ion currents. These data are compared with results obtained using the n-electron classical trajectory Monte Carlo method. The radiative and Auger evolution of ion populations following one- and two-electron transfers is calculated with the time-dependent collisional-radiative code nomad using atomic data from the flexible atomic code. Calculated CE emission spectra for 100Å<λ<1400Å are reported as well and compared with experimental sublevel spectra and cross sections.