Collision dynamics in electron-capture processes with excitation

We have measured the projectile scattering-angle dependency for various electronic final states for single-electron capture in $\text{p}+\text{He}$ and ${{}^3\text{H}\text{e}}^{+}+\text{He}$ collisions at incident energies between 60 and 630 keV/u. We find pronounced peak structures in the scattering-angle dependence of some of the ratios of different capture channels. We interpret this as experimental evidence that an excitation process of the target is caused by a transverse momentum transfer that leads to an additional projectile deflection.

Figure 1

(Color online) Ratio $R_{TE}$ of transfer excitation and ground-state transfer of the differential cross-sections $d\sigma /d{\theta }_P^{\prime }$ in $\text{p}+\text{He}$ and ${\text{He}}^{+}+\text{He}$ collisions at projectile energies of 60–630 keV/u. Black squares represent data for proton, and the red circles for ${\text{He}}^{+}$ impact. All error bars show the statistical standard deviations. Scattering angles for ${{}^3\text{H}\text{e}}^{+}$ are multiplied by their mass to be comparable with the proton data. The line is a $B$-spline fit to guide the eye.

Figure 2

(Color online) Ratio $R_{TI}$ of transfer ionization and ground-state transfer of the differential cross-sections $d\sigma /d{\theta }_P^{\prime }$ in $\text{p}+\text{He}$ and ${\text{He}}^{+}+\text{He}$ collisions at projectile energies of 60–630 keV/u. Black squares represent data for proton, and the red circles for ${\text{He}}^{+}$ impact. All error bars show the statistical standard deviations. Scattering angles for ${{}^3\text{H}\text{e}}^{+}$ are multiplied by their mass to be comparable with the proton data. The line is a $B$-spline fit to guide the eye.

Figure 3

(Color online) Ratio $R_{PE}$ of electron capture into an excited state of the projectile and ground-state transfer of the differential cross-sections $d\sigma /d{\theta }_P^{\prime }$ in $\text{p}+\text{He}$ and ${\text{He}}^{+}+\text{He}$ collisions at projectile energies of 60–630 keV/u. Black squares represent data for proton, and the red circles for ${\text{He}}^{+}$ impact. All error bars show the statistical standard deviations. Scattering angles for ${{}^3\text{H}\text{e}}^{+}$ are multiplied by their mass to be comparable with the proton data. To guide the eyes $B$-splines connect the different points.