On the molecular effect in hydrogen molecular ions penetration through thin films

Penetration of low energy (2–12 keV) hydrogen molecular ions (H2+) and single protons through thin (40 Å) carbon films is simulated using molecular dynamic approach. It is shown that the width of energy loss spectra for the case of H2+ penetration is larger than that for H+H+ spectra (a “molecular effect”) as it was previously observed in experiments [1]. This is explained by the molecular ions dissociation in the first few monolayers of the target. A simple semi-analytical model accounting for the molecular effect is provided. Results of simulations are compared with experiments.