Electron Impact Ionisation of Metastable 2s-state Hydrogen Atoms

The triple differential cross section for ionisation of hydrogen atoms in the metastable 2s-state by electrons of 250 eV incidence energy has been calculated following the multiple scattering theory of Das and Seal (1993). The results are compared with the first Born results and with the results of some other theories. Additional features are noted in the cross section curves of the present calculation. These offer wider scope for the experimental study of ionisation of hydrogen atoms in their metastable states.