Projectile-target core interaction in single ionization of helium by 100-MeV/u ${\text{C}}^{6+}$ and 1-GeV/u ${\text{U}}^{92+}$ ions

We consider single ionization of helium by very fast highly charged ions. The ionization is treated as a three-body problem which involves the “active” target electron, the target core (consisting of the target nucleus and the “passive” target electron) and the projectile ion. In contrast to the previous studies of this process, in which the interaction between the projectile and the target core was treated as a purely Coulomb one, we describe this interaction using the same core potential which acts on the active electron and which has both Coulomb and short-range parts. According to our results the deviation of the interaction between the projectile and the target core from the purely Coulomb law has on overall a weak effect on the ionization dynamics. In particular, we show that the account of this deviation does not enable one to get any better agreement with experimental data on the fully differential cross section for the electron emission into the so-called perpendicular plane.

Figure 1

The FDCS for single ionization of helium by 100-MeV/u ${\text{C}}^{6+}$ projectiles plotted as a function of the polar emission angle. The cross section is given in the scattering plane. The electron emission energy ${\epsilon }_k=6.5\text{eV}$ and the total momentum transfer $q=0.65\text{a}\text{.u}\text{.}$ Symbols: experimental data from [2]. Solid curve: results obtained by including into the interaction between the projectile and the target core the full expression (1). Dashed curve: the projectile-target core interaction is modeled by the Coulomb part of Eq. (1) only. Dotted curve: the first Born results.

Figure 2

Same as in Fig. 1 but for the electron emission energy of 17.5 eV and the total momentum transfer of 1.43 a.u.

Figure 3

Same as in Fig. 1 but the cross section is given in the perpendicular plane. Besides, the dashed-dotted curve displays results of the calculation in which the interaction between the projectile and the active electron is described within the rCDW-EIS but the projectile-target core interaction is completely ignored.

Figure 4

The FDCS for single ionization of helium by 1-GeV/u ${\text{U}}^{92+}$ projectiles plotted as a function of the polar emission angle. The cross section is given in the scattering plane. The electron emission energy ${\epsilon }_k=2\text{eV}$ and the total momentum transfer $q=0.65\text{a}\text{.u}\text{.}$ Symbols: experimental data from [7]; these data have been fit to the maximum of the solid curve. Solid curve: results obtained by including into the interaction between the projectile and the target core the full expression (1). Dashed curve: the projectile-target core interaction is modeled by the Coulomb part of Eq. (1) only. Dotted curve: the first Born results.

Figure 5

Same as in Fig. 4 but for the electron emission energy of 10 eV and the total momentum transfer of 1 a.u.

Figure 6

Same as in Fig. 5 but the cross section is given in the perpendicular plane. Besides, the dashed-dotted curve displays results of the calculation in which the interaction between the projectile and the active electron is described within the rCDW-EIS but the projectile-target core interaction is completely ignored.

Figure 7

The doubly differential cross section $d^2\sigma /d{\epsilon }_{k}dQ$ for single ionization of helium by 100-MeV/u ${\text{C}}^{6+}$ projectiles given as a function of the transverse momentum transfer $Q$ at a fixed value of the emission energy (${\epsilon }_k=6.5$ and ${\epsilon }_k=37.5\text{eV}$ for the upper and lower panels, respectively, of the figure). Left panels of the figure: solid curves are results obtained by including into the interaction between the projectile and the target core the full expression (1); dashed curves show the results obtained when the projectile-target core interaction is modeled by the Coulomb part of Eq. (1) only; dotted curves are the first Born results. Right panels: the same as in the left panels plus experimental data from [2].

Figure 8

The doubly differential cross section $d^2\sigma /d{\epsilon }_{k}dQ$ for single ionization of helium by 1-GeV/u ${\text{U}}^{92+}$ projectiles given as a function of the transverse momentum transfer $Q$ at a fixed value of the emission energy (${\epsilon }_k=10$ and ${\epsilon }_k=40\text{eV}$ for the upper and lower panels, respectively, of the figure). Solid curve: results obtained by including into the interaction between the projectile and the target core the full expression (1). Dashed curve: the projectile-target core interaction is modeled by the Coulomb part of Eq. (1) only. Dotted curve: the first Born results.