The depth distribution of 40-keV 133Xe ions in various single crystals

Abstract

The marked difference previously observed in the depth distribution profiles of 40-keV 133Xe ions in the best channeling directions of tungsten and gold has prompted a more detailed investigation into the effect of various crystal properties on these profiles. We find that the major differences are: (i) a much smaller fraction of the ions remains channeled in gold; (ii) a maximum range is observable in gold at 20 °K but not at room temperature; and (iii) the maximum range in gold is much larger than in tungsten.The effects of crystal structure and of mean vibrational amplitude on the depth distribution have been studied. Depth-distribution profiles in gold resemble those in other similar f.c.c. metals, such as copper and aluminium. On the other hand, in iridium, an f.c.c. metal whose thermal vibrational amplitude is almost identical with that of tungsten and tantalum, the profiles resemble those in the b.c.c. metals much more closely than those in the f.c.c. metals.It is concluded that the mean vibrational amplitude of the lattice plays a major role in determining the depth-distribution profile, whereas the maximum range of channeled particles is determined mainly by the electron density along the mid-channel axis.