Interplay between the Coulomb explosion and vicinage effects studied usingH2+molecules under channeling conditions

Abstract

The aim of this work is to investigate how the mean energy loss and straggling due to ${{\mathrm{H}}_{2}}^{+}$ molecules interacting with silicon are affected by the Coulomb explosion and vicinage effects. To that end, a SIMOX-type sample made up of $^{18}\mathrm{O}$ and with an appropriate $^{18}\mathrm{O}$ marker grown over the surface of crystalline Si was employed, allowing to carry out the measurements through the $^{18}\mathrm{O}(p,\ensuremath{\alpha})^{15}\mathrm{N}$ resonant reaction at $151.2\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$ under channeling and random directions. The results show that the mean energy loss associated with the Coulomb explosion and vicinage effects are similar and amount each to about 2% of the total mean energy loss. The comparison of the energy straggling obtained for molecular beams at random and the well-aligned $⟨100⟩$ direction shows a larger value for the aligned case, which is interpreted as a result of the Coulomb explosion along the channel direction. The experimental results are also discussed in terms of Monte Carlo simulations.