Longitudinal Spin Asymmetry in (e, 2e) Processes on Atoms by Relativistic Electrons

摘要

The investigation of (e, 2e) processes on atoms by spin-polarized electron offers a sensitive tool for stringent test of theories by probing different physical mechanisms like exchange scattering, spin-orbit coupling of both bound and continuum states, orbital orientation and alignment etc as well as their interplay. Recently, a number of relativistic (e, 2e) experiments on atoms have been performed by using transversely polarized electron beam and unpolarized target to measure spin asymmetries. The transverse spin asymmetry in an (e, 2e) experiment is measured by measuring coincident cross sections and is defined in terms of relative cross section difference: A = (d~3σ↑ - d~3σ↓)/(d~3σ↑ + d~3σ↓), where d~3σ↑ and d~3σ↓ are triple differential ionization cross section of K-shell for impinging electron with spin polarization up and down the scattering plane respectively. The experimental spin-asymmetry measured on K-shell Ag~1, on L-shell of Au~2, on K-shell of Cu, Ag and Au~3 has been interpreted to be caused by spin dependent forces. Whereas the spin asymmetry on the 2 p_(3/2) sub-shell of U are interpreted in terms of the fine structure effect. Recently, Bhullar and Sud have predicted asymmetry in (e, 2e) process on atoms by longitudinally polarized relativistic electrons. The longitudinal spin asymmetry in (e, 2e) process on atoms has not been measured so far. Longitudinal spin asymmetry in (e, 2e) process on an atom from K-shell at first sight might surprise. We present a schematic diagram of the (e, 23) ionization process on atoms in Fig. 1 to understand the asymmetry in (e, 2e) process better.