Channeling of molecular ions with relativistic energy

When energetic ions are injected into a single crystal parallel to a crystal axis or plane, they proceed in an open space guided by the crystal potential without colliding with atoms in the atomic plane or string, which is called channeling. We aimed to study dynamics of molecular ions, H2+, of 160 MeV/u and their fragment ions, H+ ions in a Si crystal under the channeling condition. The molecular ions, H2+, are soon ionized, i.e. electron-stripped in the crystal, and a pair of bare nuclei, H+ ions, travels in the crystal potential with mutual Coulomb repulsion. We developed a 2D position sensitive detector for the angular-distribution measurement of the H+ ions transmitted through the crystal, and observed the detailed angular distribution. In addition we measured the case of H+ on incidence for comparison. As a result, the channeled component and non-channeling were clearly separated. The incident angular divergence is critical to discuss the effect of Coulomb explosion of molecular H2+ ions. (author)