SYMMETRICAL SCATTERING IN ELECTRON AND POSITRON-IMPACT IONIZATION OF METASTABLE 2S-STATE HYDROGEN-ATOMS

Triple differential cross sections for ionization of hydrogen atoms in the metastable 2s-state by the impact of electrons and positrons have been calculated for coplanar symmetric geometry. In this calculation a multiple scattering theory due to Das [10] and Das and Seal [11] has been used. An analysis of the results reveals that unlike scattering from the ground state, scattering from 2s-state is essentially a highe r order process except for the binary collision direction. Moreover, h ere, the cross section results for 2s-state are much larger compared t o those for scattering from the ground state. It is also found that th e ionization mechanism at large scattering angles for ionization from the 2s-state is different from that for ionization from the ground sta te.