A Source of Polarised Electrons for the Study of Polarisation Effects in Polarised Electron-Atom Scattering

Abstract

A source of polarised electrons suitable for use in a crossed-beam electron/atom scattering experiment has been built. The electrons were polarised by scattering them elastically from mercury atoms in a crossed-beam experiment. The electron polarisation was investigated for electron energies between 6 eV and 44 eV in the angular range from 30o to 130o. Spin analysis was performed by means of a 100 keV Mott scattering experiment from a gold target at a scattering angle of 120o. The intensity of the polarised electron beam was monitored simultaneously with the polarisation measurements. A maximum polarisation of (67.2 ± 8.2)% was obtained for an incident electron energy of 14 eV at a scattering angle of 95o. However, as a source of polarised electrons, the optimum conditions were obtained when the electron energy was 13 eV at a scattering angle of 95o. Under these conditions an electron polarisation of (62.7 ± 8.0)% was measured with an electron current in the alkali interaction region of 3.10-12A. Comparison with the results of previous theoretical and experimental studies of electron polarisation in low energy scattering from mercury show good agreement with the polarisation values and differential cross-sections.