Differential ionization of a one-electron target under bare-ion impact: Application to proton-impact ionization of atomic hydrogen

A single-center coupled pseudostate approximation originally used by McGovern et al. [Phys. Rev. A 79, 042707 (2009)] to study differential ionization under ion impact is extended to take account of electron exchange. The approximation is fully quantal and includes the interaction between the projectile and target nuclei as well as post-collisional interactions between the ionized electron and the two nuclei. Calculations are presented for proton-impact ionization of atomic hydrogen at 75 keV. These include fully (triple) differential cross sections which illustrate how the post-collisional interaction switches from being dominated by the interaction between the ejected electron and the target nucleus to being dominated by the electron interaction with the projectile nucleus (charge exchange to the continuum). Comparison is made with some measurements of the double differential cross section with respect to ejected electron energy and proton scattering angle. While overall agreement between theory and the experimental data is encouraging, detailed agreement is lacking. The need for more experimental work is emphasized.

Figure 1

Laboratory frame TDCS (in a.u.) for proton impact ionization of atomic hydrogen at 75 keV in coplanar geometry and for an ejected electron energy, $E$, of 5 eV. (a) Forward scattering of the proton. The direction of the momentum transfer $\mathbf{q}$, see (53), is indicated in (b) and (c). The approximations are as described in (58).

Figure 2

Laboratory frame TDCS (in a.u.) for proton impact ionization of atomic hydrogen at 75 keV in coplanar geometry and for an ejected electron energy, $E$, of 10 eV. (a) Forward scattering of the proton. The direction of the momentum transfer $\mathbf{q}$, see (53), is indicated in (b) and (c). The approximations are as described in (58).

Figure 3

Laboratory frame TDCS (in a.u.) for proton impact ionization of atomic hydrogen at 75 keV in coplanar geometry and for an ejected electron energy, $E$, of 16.395 eV. (a) Forward scattering of the proton. The direction of the momentum transfer $\mathbf{q}$, see (53), is indicated in (b) and (c). The approximations are as described in (58).

Figure 4

Laboratory frame TDCS (in a.u.) for proton impact ionization of atomic hydrogen at 75 keV in coplanar geometry and for an ejected electron energy, $E$, of 26.395 eV. (a) Forward scattering of the proton. The direction of the momentum transfer $\mathbf{q}$, see (53), is indicated in (b) and (c). The approximations are as described in (58).

Figure 5

Laboratory frame TDCS (in a.u.) for proton impact ionization of atomic hydrogen at 75 keV in coplanar geometry and for an ejected electron energy, $E$, of 36.395 eV. (a) Forward scattering of the proton. The direction of the momentum transfer $\mathbf{q}$, see (53), is indicated in (b) and (c). The approximations are as described in (58).

Figure 6

Laboratory frame double differential cross section (59) for proton impact ionization of atomic hydrogen at 75 keV and for ejected electron energies $E$ as indicated. The approximations are as described in (58). INCO, red solid curve; CO, blue solid curve; $T$, black dashed curve; $P$, green dashed curve. The experimental data are from [18, 19].