Title: pre-exponential factor
Long Title: IUPAC Gold Book - pre-exponential factor
DOI: 10.1351/goldbook.P04811
Status: current
Index: quantity

Definition
Coefficient in front of the exponential factor expressing the empirical temperature dependence of the rate coefficient, \(k\), on temperature, \(T\), \(k=A\ \exp (- E_{\rm{a}}/R\ T)\), where \(E_{\rm{a}}\) is the activation energy.

Related Terms
- Coefficient: https://goldbook.iupac.org/terms/view/C01124
- activation: https://goldbook.iupac.org/terms/view/A00093
- rate coefficient: https://goldbook.iupac.org/terms/view/R05137

Sources
- Green Book, 2nd ed., p. 56 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)
- PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 177 (https://doi.org/10.1351/pac199668010149)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/P04811/html
- json: https://goldbook.iupac.org/terms/view/P04811/json
- xml: https://goldbook.iupac.org/terms/view/P04811/xml

Citation: Citation: 'pre-exponential factor' 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.P04811
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Accessed: 2026-06-28T22:56:07+00:00