Measuring instrument for measuring the number of electrons, or an intensity proportional to that number, as a function of the electron kinetic energy.
Source:
PAC, 2020, 92, 1781. 'Glossary of methods and terms used in surface chemical analysis (IUPAC Recommendations 2020)' on page 1824 (https://doi.org/10.1515/pac-2019-0404)