Small-Angle Differential Cross Sections for Symmetrical Resonant Charge Exchange in Molecular Hydrogen

Abstract

We measured state selective scattering angle distributions in non-dissociative-state single electron capture in $\{5,7.5,10\}$ keV/u, $\left[{\mathrm{H}}^{+}+{\mathrm{H}}_2\right]$ and $\left[{\mathrm{H}}_2^{+}+{\mathrm{H}}_2\right]$ collisions, using Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS). In our measurements, range of the scattering angle was small where diffraction effect is expected to take place, and, the ground state electron capture - symmetrical resonant channel for the ${\mathrm{H}}_2^{+}$ projectile and near resonant channel for the ${\mathrm{H}}^{+}$ projectile - was fully resolved from other channels. We analyzed the data considering ${\mathrm{H}}_2^{+}$ and ${\mathrm{H}}_2$ possess two independent-identical scattering centers and exhibit multi center interference effect. By comparing these equal-velocity collisions, we investigated the atomic nature of the individual scattering centers. We observed Fraunhofer diffraction from a circular aperture like patterns with equal fringe widths, for both the projectiles, in ground state channel. We applied a simple toy model to reconstruct the circular apertures.