Antiproton stopping in atomic targets

Abstract

Stopping powers of antiprotons in H, He, Ne, Ar, Kr, and Xe targets are calculated using a semiclassical time-dependent convergent close coupling method. The helium target is treated using both frozen-core and multiconfiguration approximations. The electron-electron correlation of the target is fully accounted for in both cases. Double ionization and ionization with excitation channels are taken into account using an independent-event model. The Ne, Ar, Kr and Xe atom wave functions are described in a model of six p-shell electrons above a frozen Hartree-Fock core with only one-electron excitations from the outer p-shell allowed. Results obtained for helium in the multiconfiguration treatment are in better agreement with experimental measurements than other theories.

Antiproton stopping inH2andH2O

“…Recently we have applied a semiclassical timedependent convergent close-coupling (CCC) method to calculations of antiproton stopping powers in the atomic targets of H, He, Ne, Ar, Kr, and Xe [17]. For H we obtained excellent agreement with other theoretical calculations while for He our results were in best agreement with experiment when compared to other theories.…”

Electron correlations in the antiproton energy-loss distribution in He

“…The first moment of this distribution, referred to as stopping cross section, and the second moment, the straggling cross section, are compared with other theoretical predictions and experiment when available. We have addressed the well-known discrepancy between several theoretical predictions [5,24,25] and experimental data for the stopping cross section forp [26,27] and µ − [57]. While we find slightly improved agreement with thep experiment at high energies well above the stopping power maximum, the discrepancies to the data persist at lower energies while our TDCC results are in good accord with the recent CCC calculation [5] Both the stopping cross section and the straggling cross section are shown to be influenced by electron correlation effects.…”

“…In order to quantify the role of correlations in the DET distribution and to compare with previous non-perturbative calculations for stopping [5,24,25,35] we perform in parallel mean-field simulations. For the calculation of the DET distribution, they involve two separate approximations to be kept track of.…”

“…These are to be distinguished from true multi-electron transitions (SI-EX and DI) for which models [5,24,25] based on SAE approximations, TDDFT or convergent close coupling calculations have been invoked, in addition to, the independent event model (IEM) thereby neglecting explicitly correlated transitions. Such dynamical correlations are fully accounted for by the present TDCC simulation.…”

Proton-beam stopping in hydrogen

“…The single-centre CCC approach has previously been applied to the calculation of stopping cross sections for antiproton collisions with atoms and molecules [17][18][19] and to the calculation of scattering cross sections for antiproton-hydrogen collisions [20,21]. Additionally, the two-centre CCC approach has been applied to the calculation of scattering cross sections for proton-hydrogen collisions [22][23][24].…”