Electronic excitation and charge transfer processes in collisions of H{sup +}, H{sub 2}{sup +}, and H{sub 3}{sup +} ions with carbon monoxide at typical solar-wind velocities

• Published in: The Astrophysical journal 2014-01, Vol.780 (2)
• Main Authors: Werbowy, S., Pranszke, B.
• Format: Article
• Language: English
• Subjects: ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CARBON MONOXIDE; COLLISIONS; COMETS; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; CROSS SECTIONS; DISTRIBUTION; EXTREME ULTRAVIOLET RADIATION; HYDROGEN; HYDROGEN IONS 1 PLUS; ION-MOLECULE COLLISIONS; LUMINESCENCE; MOLECULAR IONS; MOLECULES; PHOTONS; SOLAR WIND; SPECTRA
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/780/2/157

Luminescence in the 200-580 nm spectral region was observed in the collisions of H{sup +}, H{sub 2}{sup +}, and H{sub 3}{sup +} with CO in the 50-1000 eV projectile energy range. Using computer simulations, we have identified emission of the following products in the observed spectra: the CO{sup +}(A-X) comet-tail system, CO{sup +}(B-X) first negative system, CO{sup +}(B-A) Baldet-Johnson system, and CO(b-a) third positive system. Also, an emission from atomic hydrogen (H{sub β} line at 486nm) has been observed. From the analysis of the experimental spectra, we have determined the absolute emission cross-sections for the formation of the observed products. Computer simulations gave the excited-product population distributions over vibrational and rotational energy levels. The vibrational level distribution from the CO{sup +}(A-X) comet-tail system is compared with the data for CO excited by 100 eV electrons and extreme ultraviolet radiation (XUV) photons. We have used these data to analyze the excitation conditions in the comet Humason (1961e). From the vibrational population distributions observed in the comet, we found that this distribution can be reproduced if electrons produce 25%, protons 70%, and XUV photons produce 5% of the emitting molecules. We find that the ratio of the CO{sup +}(B-X) emission to the sum of two main emissions (CO{sup +}(A-X)+CO{sup +}(B-X)) is velocity dependent and does not depend on the projectile ion type. For small velocities (below 100 km s{sup –1}) the ratio is about 5%, while for higher velocities it increases to 30%. For these data, we have found an empirical formula that satisfactorily describes the experimental data: R = R {sub max}(1 – v {sub th}/v), (where R {sub max} = 33%, v {sub th} = 87 km s{sup –1}). This could be used to infer the velocity of ions producing the observed emission of CO{sup +} products.