Abstract
The electronic stopping cross section of slow hydrogen projectiles in large-band-gap insulators has been measured at energies of a few keV. Even at velocities as low as , we find no influence of the band gap on the velocity dependence of , contrary to the case of gaseous targets with similar minimum excitation energy. The magnitude of and its essentially linear velocity dependence allow us to arrive at the following conclusion: Electron promotion processes contribute substantially to stopping due to formation of molecular orbitals. This points towards the existence of a bound electron state at a proton that moves slowly in an insulator. A simple model based on the calculation of molecular orbital correlation diagrams for the H/LiF collision system supports the idea of local reduction of the band gap of an insulating target.
- Received 1 July 1997
DOI:https://doi.org/10.1103/PhysRevLett.79.4112
©1997 American Physical Society