Electron-hydrogen-atom elastic and inelastic scattering with screened Coulomb interaction around the n=2 excitation threshold

The effects of Coulomb interaction screening on electron-hydrogen-atom elastic and excitation scattering around the n = 2 threshold have been investigated by using the R-matrix method with pseudostates. The elastic and excitation collision strengths show dramatic changes when the interaction screening length D varies from infinity to 3.8 a.u., as a result of the convergence of S-1,S-3 Feshbach resonances to the varying 2s threshold and of the transformation of P-1,P-3 and D-1 Feshbach resonances into shape-type resonances when they pass across the 2s and 2p threshold at certain critical value of D, respectively [S. B. Zhang et al., Phys. Rev. Lett. 104, 023203 (2010)]. The resonance parameters for a large number of D in the range D = infinity-3.8 a.u. are presented. It is observed that the P-1,P-3 and D-1 resonance contributions to the elastic and excitation collision strengths decrease rapidly with decreasing D after the resonance passes the critical D value. The contribution of a S-1(e) Feshbach resonance to the elastic or excitation collision strength changes into a cusp after the resonance merges into its parent 2s state and immerses into the background with the further decrease of D.