Inclined Beams Measurements of Electron Impact Excitation at the Harvard-Smithsonian CfA

Details Inclined Beams Measurements of Electron Impact Excitation at the Harvard-Smithsonian CfA Inclined Beams Measurements of Electron Impact Excitation at the Harvard-Smithsonian CfA

May 2008

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008aas...212.0316g&link_type=abstract

American Astronomical Society, AAS Meeting #212, #3.16; Bulletin of the American Astronomical Society, Vol. 40, p.186

Physics

Scientific paper

The analysis of absolute spectral line intensities and intensity ratios with spectroscopic diagnostic techniques provides empirical determinations of plasma parameters in astrophysical objects. Since spectral line intensities and their ratios are controlled by the excitation rate coefficients for the electron temperature of the observed astrophysical structure, it is imperative that one have accurate values for the relevant rate coefficients. The technique employed at CfA utilizes a modulated beam of a single ion species, which is crossed at 45 degrees with a similarly modulated electron beam. Photons from the decay of ions excited by collisions with the electrons are collected synchronously with the beams' modulation pattern by an absolutely calibrated optical system. We will illustrate our experimental approach by discussing our current measurements of EIE in C2+ (2s2 1S0 - 2s2p 1Po1), which dominates the emission of CIII 97.7 nm in the Sun. Since the wavelength of the decay photons is below the transmission cutoff of window materials, our new detection system utilizes an open microchannel plate detector and a spherical mirror coated with Al/MgF2/B4C. These new components have been thoroughly calibrated at the wavelengths relevant to this experiment and at wavelengths relevant to forthcoming measurements in O4+. The latest research results will be reported. This work is supported by NASA Supporting Research and Technology grant NNG06GE49G in Solar and Heliospheric Physics and by the Smithsonian Astrophysical Observatory.

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