ABSOLUTE SINGLE AND MULTIPLE CHARGE EXCHANGE CROSS SECTIONS FOR HIGHLY CHARGED C, N, AND O IONS COLLIDING WITH CH4

Absolute charge exchange (CE) cross sections have been measured for single and multiple exchanges between the highly charged ions (HCIs) Cq+ ( -->q = 3–6), Nq+ ( -->q = 4–7) and Oq+ ( -->q = 5–7) colliding with the target methane (CH4) present in comet and planetary atmospheres. Measurements were made at collision energies of 7×q keV (1.8-3.5 keV amu−1), representative of the fast component of the solar wind. The HCIs are produced in a 14 GHz electron cyclotron resonance ion source. Absolute cross sections are measured using the retarding potential analyzer method, with knowledge of the target length, density, and projectile currents. Comparison is made with results of the classical trajectory Monte Carlo method, and the classical overbarrier model.