Coulomb heating of channeled H/sup + sub 2/ and H/sup + sub 3/ molecules in Si

Abstract

Si-K x-ray and backscattering yields have been measured as a function of the projectile entrance angle for atomic and molecular (H2 + and H3 +) hydrogen ions channeling at kinetic energies of 150 keV per proton along the Si k100l crystal direction. A large enhancement of the x-ray production has been observed for well-aligned H3 + molecule beams. It is shown that this effect results from the Coulomb explosion of the molecule fragments during the channeling motion. Moreover, the shape and intensity of the measured angular distribution allows a quantitative determination of the corresponding heating of the transversal ion motion (2.6±0.6 eV for H2 + and 5.1±0.8 eV for H3 + molecules) in the channel. These values are consistent with the stored potential energies per particle and they depend significantly on the collective wake forces and molecular alignment conditions.