{"term":{"id":"08747","title":"particle flux density","longtitle":"IUPAC Gold Book - particle flux density","doi":"10.1351\/goldbook.08747","code":"08747","status":"current","synonym":"<em>synonyms<\/em>: fluence rate (obsolete), photon flux density","definitions":[{"id":1,"text":"Number of particles (or photons) incident on a plane perpendicular to the incident radiation per unit time per unit area.","notes":{"1":"Particle flux density is identical with the product of the particle density and the average speed of the particles.","2":"The SI unit of flux density is \\(\\pu{m-2 s-1}\\).","3":"Often an indication of the type of incident particles is wrongly added to the unit of flux density, e.g., the neutron flux density is sometimes indicated as n \\(\\pu{cm-2 s-1}\\). As 'n' is not a unit, it is metrologically unacceptable and therefore not recommended."},"sources":["PAC, 2021, 93, 69. 'Vocabulary of radioanalytical methods (IUPAC Recommendations 2020)' on page 91 (https:\/\/doi.org\/10.1515\/pac-2019-0302)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/08747\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/08747\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/08747\/plain"},"citation":"Citation: 'particle flux density' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351\/goldbook.08747","license":"The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/) for individual terms.","collection":"If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .","disclaimer":"The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.","accessed":"2026-06-13T13:26:41+00:00"}}