Berlin 2014 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 25: Poster: Electron scattering and recombination
A 25.3: Poster
Dienstag, 18. März 2014, 16:30–18:30, Spree-Palais
New method of measuring metastable states for electron impact on light targets at all scattering angles — •Marvin Weyland1,2, Alexander Dorn1, Hans Rabus2, Xueguang Ren1,2, Thomas Pflüger1,2, and Woon Yong Baek2 — 1Max-Planck-Institute for Nuclear Physics, Heidelberg, Germany — 2Physikalisch-Technische Bundesanstalt, Braunschweig, Germany
We apply a new method of measuring differential cross sections for metastable atom production by electron impact. A crossed beam setup with a supersonic helium jet and a pulsed electron beam at energies close to the excitation threshold of 19.82 eV is used. Measuring the momentum vectors of the metastable atoms instead of the scattered electrons removes common restrictions to the accessible scattering angles while reaching high detection efficiency. At impact energy of 22.2 eV we can distinguish between excitation of the 23S-state and 21S- or 23P-state. Using a photoemission electron source we reach an impact energy resolution of 200 meV at about 1 µA peak current. Results are compared with simulations of the experiment, using convergent-close-coupling (CCC) and R-matrix-pseudo-state (RMPS) calculations of differential scattering angles. Experimental results agree best with RMPS calculations. Although used here only with helium as a target, the instrument can be used to measure excitation cross sections in many light targets.