Energy Spectra of Dissociation and Recombination Products of H2+ Emergent from Ultra Thin Carbon Films below the Bohr Velocity

Using the University of Chicago Scanning Transmission Ion Microscope and techniques described elsewhere, we have measured the energy spectra of recombined H+2, dissociation H+, and H+ in coincidence with H0 from H+2 beams traversing 15-45 Å carbon films at 12.5 keV/H. We have compared these spectra to spectra of transmitted single H+ with the same incident speed. The spectra of H+2 are consistent with the two protons of H+2 losing energy in the film as if they were independent single protons. Furthermore, the widths of such spectra show that H+2 recombination takes place randomly and without regard to the energy of the two partners. For the thinnest films the dissociation spectra exhibit three peaks, a central peak representing nonrepulsive states of H+2, and two outside peaks for the repulsive 2p¿u molecular state of H+2. The central peak, corresponding to dissociations with approximately zero energy release, has the same shape and width as that of a single proton energy loss peak. The relative heights of the three peaks are about the same as those reported by Laubert and Chen and Gaillard et al. at much higher energies.