Hamburg 2009 – scientific programme

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A: Fachverband Atomphysik

A 34: Poster II

A 34.20: Poster

Thursday, March 5, 2009, 16:30–19:00, VMP 9 Poster

Spin-resolved electron scattering from lead (Pb) and europium (Eu) atoms — •Volker Hamelbeck and G. Friedrich Hanne — Physikalisches Institut, 48149 Münster, Germany

The interactions between low-energy spin-polarised electron beams and atomic as well as molecular targets have comprehensively been studied in our group. An interesting aspect of this field are collision experiments on heavy open-shell metal atoms such as Pb and Eu where spin-orbit and exchange effects occur simultaneously. This is still a difficult task for theory.
For a description of these processes, the scattering parameters S_P, S_A, T^→ and U^→ are introduced. Through the polarisation function S_A the spin-dependence of the DCS is quantified. The other parameters are determined by measurement of P^→ and P^→′, the electron polarisation before and after scattering respectively. These cover distinct effects such as exchange (T_x,T_y,T_z) and rotation (U_xz,U_zx) of the electron spin during scattering.
In our experiments, the spin-polarised electron beam is guided from a GaAs source to the collision centre where it hits the heavy metal vapour emanating from an oven. A rotatable spectrometer is used to collect the scattered electrons whose spin polarisation is determined in a Mott-detector, subsequently.
In the case of low energy electron scattering from Pb, the angular distribution of the spin asymmetry function S_A shows a significant dependence on the energy between 11 eV and 14 eV. For Eu, first results of S_A and the exchange parameter T_y are presented.