PNNL

Abstract

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. We present experimental chemical sputtering results for D+, D+2 and D+3 ions incident on ATJ graphite in the energy range 5–60 eVD-1, and compare them with simulations for deuterated amorphous carbon impacted by neutral D, D2 and D3. The measured methane yields/D for the different species compared at the same energy/D diverge below about 60 eVD-1, the incident triatomic molecular ions leading to the largest yields/D, and the atomic ions to the smallest, reaching a factor of two difference at 10 eV/D. The measured yields/D are in reasonable agreement with molecular dynamics simulations over the entire calculated energy range. The model surfaces were prepared by D, D2 and D3 impacts in a way that mimics the experiment. For D2 incident at energies below 15 eV/D, the simulations show a strong dependence of the sputtering yields on the vibrational state of the incident projectile.