Coulomb heating of channeled C+ and C2+ molecules in Si

Abstract

Si x-ray and backscattering yields have been measured as a function of the C⁺ and C₂⁺ entrance angle along the Si ‹100› channel in an energy interval between 900 and 2200 keV/atom. A significant enhancement of the x-ray production has been observed for the well-aligned C₂⁺ beam in comparison with the monoatomic case. It is shown that this effect results from the Coulomb explosion of the molecule during the channeling motion. By combining the Rutherford backscattering channeling (RBS-C) and the x-ray results we were able to determine the value of the transverse energy transfer as a function of the beam energy due to the break up process (Coulomb heating). This energy increases monotonically from 14 eV for 900 keV/atom up to 30 eV for 2200 keV/atom. In addition, we were able to predict the theoretical Coulomb heating values by combining calculations and simulations, the theoretical-experimental agreement, within the experimental errors, being quite reasonable.