Number,
\(N_{\rm{imp}}\), of energetic particles of a specified type incident on a solid within a surface area
\(A\) and stopped within the solid divided by
\(A\).
\(D_{\rm{imp}} = N_{\rm{imp}}/A\).
Note: Particles that are not stopped within the solid are either backscattered or transmitted.
Source:
PAC, 2020, 92, 1781. 'Glossary of methods and terms used in surface chemical analysis (IUPAC Recommendations 2020)' on page 1805 (https://doi.org/10.1515/pac-2019-0404)