The Coulomb explosion of molecular ions in channeling conditions

The backscattering energy spectra of protons have been measured with 650 keV/atom H+, H2+ and H3+ beams irradiating Si crystal in <1 0 0> and <1 1 0> directions. The Coulomb explosion of molecules on entering a crystal results in significant modification of the transverse energy distribution of channeled protons, the molecular fragments. This shows itself as a significant increase of the dechanneling rate as compared with the case of atomic ion beam. Relative to H+, the observed backscattering yield for H2+ and H3+ is substantially higher, up to 30% in the latter case. The data show that the Coulomb explosion appears to be more effective for H3+ molecular ions. The measurement results are compared with the corresponding computer simulation. The calculations demonstrate, particularly, the character of coordinated motion of the molecular fragments predetermined by the correlated initial conditions at the crystal surface