AAS 204th Meeting, June 2004
Session 73 Solar and Stellar Coronae
SPD Poster, Thursday, June 3, 2004, 9:20am-4:00pm, Ballroom

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[73.09] Measurement of the Absolute Electron Impact Excitation Cross Section for the C III 117.6 nm Transition

A. Daw, P. H. Janzen, L. D. Gardner, J. L. Kohl (Harvard-Smithsonian Center for Astrophysics)

An inclined beams arrangement is being used to measure the absolute cross section for electron impact excitation of the C2+ (2s2p 3Po - 2p2 3P) transition for energies below threshold to 15 eV above. These cross sections determine the EIE rate coefficients required for astrophysical applications. Ions are produced in a 5 GHz Electron Cyclotron Resonance (ECR) ion source. A modulated beams technique with inclined electron and ion beams is being used. The radiation from the excited ions at a wavelength of 117.5 nm is detected using an absolutely calibrated optical system that subtends slightly over pi steradians. The population of the C2+ metastable state in the incident ion beam is determined experimentally. The measured cross sections will be presented and compared to those predicted by theory. This work is supported by NASA Supporting Research and Technology grants NAG5-9516 and NAG5-12863 in Solar and Heliospheric Physics and by the Smithsonian Astrophysical Observatory.

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