Experimental Method for Testing the Potential of Moving Ions in Solids

Molecular ions, which define the initial separation between nuclei, are used as a probe of the potential established by swift ions in solids. Employing 75-300-keV ${\mathrm{H}}_2^{+}$ and He${\mathrm{H}}^{+}$ ions one observes that a large fraction of clusters do not explode in solid targets whose thickness is much greater than the mean electron-loss distance. The results are consistent with the view that protons moving in solids carry bound electrons.