Energy loss of swift H+2 and H+3 molecules in gold : vicinage effects

Abstract

We present experimental and theoretical results of vicinage effects due to the interaction of H+ 2 and H+ 3 molecules with thin gold foils. High-energy-resolution backscattering experiments were carried out at energies ranging from 80 up to 200 keV per nucleon for the H+ 2 molecules and up to 140 keV per nucleon for the H+ 3 molecules. The results show small enhancements (about 5% and 15% for H+ 2 and H+ 3 molecules, respectively) of the stopping ratios. The values obtained by the simulation code SEICS indicate small vicinage effects as well and are in satisfactory agreement with the experimental data. Moreover, the same simulations carried out for carbon foils yield relatively higher stopping ratios. The differences between the vicinage effects obtained for C and Au are interpreted in terms of different excitation spectra of each material. Finally, our results obtained for Au are in clear disagreement with those reported in the seminal work of Brandt, Ratkowski, and Ritchie [Phys. Rev. Lett. 33, 1325 (1974)].