25 November 1999 Ionization-excitation of He following electron and proton impact: a polarization study using an EUV polarimeter
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New experimental results are presented on measurements of the degree of linear polarization for ionization-excitation of He following electron and proton impact on a He gas target. These measurements have been performed using an optically characterized molybdenum/silicon (Mo/Si) multilayer mirror (MLM) polarimeter whose reflection and polarization characteristics have been optimized for the 304 angstrom wavelength region. In particular, the polarization of the photon emission from the decay of HeII (2p) 2P0 yields (1s) 2S with a wavelength of 304 Angstrom (Lyman (alpha) of HeII) has been measured for electron impact energies ranging from threshold to 1500 eV. These results are compared with polarization measurements of HeII Lyman (alpha) following proton impact on He for 187 to 460 keV beam energy corresponding to 2.7 a.u. less than v less than 4.3 a.u. projectile velocities. The integral alignment parameter A0 is also provided for negatively and positively charged particle impact to elucidate similarities and differences in the collision dynamics of two electron targets such as helium. Such results are of importance for astrophysical and laboratory plasma diagnostics.
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Hocine Merabet, Hocine Merabet, Annette Siems, Annette Siems, Reinhard F. Bruch, Reinhard F. Bruch, Stephan Fuelling, Stephan Fuelling, Matthew Bailey, Matthew Bailey, "Ionization-excitation of He following electron and proton impact: a polarization study using an EUV polarimeter", Proc. SPIE 3764, Ultraviolet and X-Ray Detection, Spectroscopy, and Polarimetry III, (25 November 1999); doi: 10.1117/12.371076; https://doi.org/10.1117/12.371076

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