Any technique in which the sample is bombarded with X-rays and photoelectrons produced by the sample are detected as a function of energy.
for Chemical Analysis) refers to the use of this technique to identify elements, their concentrations, and their chemical state within the sample.
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook