(e, 2e) differential cross section of the ionization of hydrogen (2s, 2p0, 2p+or-1) by electron impact: the influence of the final state correlation

The differential cross section of the ionization of hydrogen in its n=2 degenerate state by electron impact is investigated theoretically by applying the correlated double continuum wavefunction satisfying the exact asymptotic conditions. The levels 2p 0 , 2p +or-1 , being energetically undistinguishable from the 2s in a coincidence detection, contribute equally to the differential cross section and show some interesting interference structures. The comparison of the results with those obtained by simpler procedures like Coulomb projected first Born calculations shows the importance of having the correct asymptotic behaviour in the final state, specially for small scattering angles. This work constitutes a necessary step for future calculations concerning complex atoms, whose wavefunctions could be constructed by 2p 0 , 2p +or-1 orbitals.