Title: photonic efficiency
Long Title: IUPAC Gold Book - photonic efficiency
DOI: 10.1351/goldbook.14057
Status: current

Definition
Ratio of the rate of the photoreaction measured for a specified time interval (usually the initial conditions) to the rate of incident photons within a defined wavelength interval inside the irradiation window of the reactor.

Notes
1) A quantity called formal quantum efficiency (FQE) is sometimes used as synonymous for photonic efficiency and calculated from the known spectral distribution of the excitation source and the known absorption spectrum of the reaction system. It is calculated as the ratio between the rate of reaction and the incident photon flux.
2) When monochromatic radiation is used, formal quantum efficiency is \(\xi\); otherwise formal quantum efficiency \(\neq \xi\).
3) Mathematical definition: \[\xi = \frac{{\rm{d}}n/{\rm{d}}t}{\int_{\lambda_{1}}^{\lambda_{2}} q_{n,\rm{p},\lambda}^{0}{\rm{d}}\lambda}\] when using the incident spectral photon flux, chemical amount basis, \(q_{n,\rm{p},\lambda}^{0}\) with \(n\) (mol) the amount of substance produced or consumed, and \[\xi = \frac{{\rm{d}}N/{\rm{d}}t}{\int_{\lambda_{1}}^{\lambda_{2}} q_{\rm{p},\lambda}^{0} {\rm{d}}\lambda}\] when using the incident spectral photon flux, number basis, \(q_{\rm{p},\lambda}^{0}\) with \(N\) the number of entities produced or consumed. The superscript 0 (zero) emphasises the fact that the incident number of photons (prior to absorption) is used.

Related Terms
- photocatalytic efficiency: https://goldbook.iupac.org//terms/view/14044
- photonic yield: https://goldbook.iupac.org//terms/view/14058
- relative photonic efficiency: https://goldbook.iupac.org//terms/view/14084

Source
- PAC, 2011, 83, 931. 'Glossary of terms used in photocatalysis and radiation catalysis (IUPAC Recommendations 2011)' on page 974 (https://doi.org/10.1351/PAC-REC-09-09-36)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/14057/html
- json: https://goldbook.iupac.org/terms/view/14057/json
- xml: https://goldbook.iupac.org/terms/view/14057/xml

Citation: Citation: 'photonic efficiency' 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.14057
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Accessed: 2026-06-21T17:49:02+00:00