Number of ions sputtered from a sample divided by the number of ions incident with a given mass, energy, charge, and angle of incidence.
Source:
PAC, 2020, 92, 1781. 'Glossary of methods and terms used in surface chemical analysis (IUPAC Recommendations 2020)' on page 1845 (https://doi.org/10.1515/pac-2019-0404)