Title: tunnelling
Long Title: IUPAC Gold Book - tunnelling
DOI: 10.1351/goldbook.T06531
Status: current

Definition
The process by which a particle or a set of particles crosses a barrier on its potential-energy surface without having the energy required to surmount this barrier. Since the rate of tunnelling decreases with increasing reduced mass, it is significant in the context of isotope effects of hydrogen isotopes.

Related Terms
- isotopes: https://goldbook.iupac.org//terms/view/I03331
- potential-energy surface: https://goldbook.iupac.org//terms/view/P04780
- reduced mass: https://goldbook.iupac.org//terms/view/R05214

Source
- PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1174 (https://doi.org/10.1351/pac199466051077)

Related Reference
- PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2282 (https://doi.org/10.1351/pac199668122223)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/T06531/html
- json: https://goldbook.iupac.org/terms/view/T06531/json
- xml: https://goldbook.iupac.org/terms/view/T06531/xml

Citation: Citation: 'tunnelling' 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.T06531
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Accessed: 2026-05-18T10:23:34+00:00