Photon emission resulting from collisions of O5+ with CO

Abstract As part of an investigation of the interactions between solar-wind ions and cometary gases, UV/X-ray and optical measurements of the photons resulting from collisions of O 5+ with CO have been made. Although O 5+ is not a major solar-wind ion, its interaction with CO yields information applicable to other solar-wind ion interactions. The data show general agreement with the “over-the-barrier” model prediction that electrons are likely to be captured into the n  = 4 levels of the resulting O 4+ ion. Not only are the UV/X-ray lines measured in the 10–20 nm range with the UV/X-ray spectrometer consistent with this prediction, but the general lack of optical lines in the optical spectrometer range of 350–850 nm support the model for O 5+ –CO collisions. Only one optical line may be attributed to the decay of excited O 4+ ions while most of the observed optical lines are attributable to atomic and molecular excitation of the CO target.