Theoretical description of two- and three-particle interactions in single ionization of helium by ion impact

In this work we calculate doubly differential cross sections (DDCS) for single ionization of helium by highly charged ion impact. We study the importance of two-particle interactions in these processes by considering the cross sections as a function of all two-particle subsystems momenta. Experimental DDCSs were obtained recently from kinematically complete experiments on single ionization of He by $100\mathrm{MeV}∕\mathrm{amu}$ ${\mathrm{C}}^{6+}$ and $3.6\mathrm{MeV}∕\mathrm{amu}$ ${\mathrm{Au}}^{24,53+}$ impact. Furthermore, we evaluated the importance of three-particle interactions by plotting the squared momenta of all three collision fragments simultaneously in a Dalitz plot. Using the first Born and distorted-wave approximations for fully differential cross sections, together with Monte Carlo integration techniques, we were able to reproduce the main features observed in experimental data and to assess the quality of the models implied by the different employed approximations.

Figure 1

Definition of the Dalitz plot for the ion-impact ionization case. See the text for details.

Figure 2

Experimental doubly differential cross sections (DDCS) for $100\mathrm{MeV}∕\mathrm{amu}$ ${\mathrm{C}}^{6+}+\mathrm{He}$, extracted from Ref. 1. (a) DDCS as a function of the magnitudes of the electron momentum $\left(k\right)$ and of the projectile momentum transfer $\left(q\right)$, (b) DDCS as a function of the magnitudes of the electron $\left(k\right)$ and recoil-ion $\left(p_r\right)$ momenta, and (c) DDCS as a function of the magnitudes of the recoil-ion momentum $\left(p_r\right)$ and of the projectile momentum transfer $\left(q\right)$.

Figure 3

Theoretical DDCSs for $100\mathrm{MeV}∕\mathrm{amu}$ ${\mathrm{C}}^{6+}+\mathrm{He}$ using FBA (see the text for details). (a) $\mathrm{DDCS}(q,k)$, (b) $\mathrm{DDCS}(p_r,k)$, and (c) $\mathrm{DDCS}(q,p_r)$.

Figure 4

Idem Fig. 2 for $3.6\mathrm{MeV}∕\mathrm{amu}$ ${\mathrm{Au}}^{53+}+\mathrm{He}$.

Figure 5

Theoretical DDCSs for $3.6\mathrm{MeV}∕\mathrm{amu}$ ${\mathrm{Au}}^{53+}+\mathrm{He}$ using CDW-EIS without taking into account $N$-$N$ interaction (see the text for details). (a) $\mathrm{DDCS}(q,k)$, (b) $\mathrm{DDCS}(p_r,k)$, and (c) $\mathrm{DDCS}(q,p_r)$.

Figure 6

Experimental Dalitz plots for (a) $100\mathrm{MeV}∕\mathrm{amu}$ ${\mathrm{C}}^{6+}+\mathrm{He}$ and (b) for $3.6\mathrm{MeV}∕\mathrm{amu}$ ${\mathrm{Au}}^{53+}+\mathrm{He}$.

Figure 7

Theoretical Dalitz plots for $100\mathrm{MeV}∕\mathrm{amu}$ ${\mathrm{C}}^{6+}+\mathrm{He}$ using (a) FBA and (b) CDW-EIS theory without taking into account the $N$-$N$ interaction (see text).

Figure 8

Theoretical Dalitz plots for $3.6\mathrm{MeV}∕\mathrm{amu}$ ${\mathrm{Au}}^{53+}+\mathrm{He}$ using (a) CDW-EIS theory without take into account the $N$-$N$ interaction and (b) CDW-EIS theory including the $N$-$N$ interaction (see text).