Energy loss of a particle scattered at a given depth in the sample, and detected at a given angle, by the product of the atomic density of the sample atoms and the depth of scattering.
Source:
PAC, 2020, 92, 1781. 'Glossary of methods and terms used in surface chemical analysis (IUPAC Recommendations 2020)' on page 1835 (https://doi.org/10.1515/pac-2019-0404)