In
atomic spectroscopy, mass of analyte converted into free atoms in the atomizer divided by mass of analyte entering the dispersion device.
Source:
PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 726 (https://doi.org/10.1515/pac-2019-0203)