06531 IUPAC Gold Book - tunnelling 10.1351/goldbook.T06531 T06531 current synonym: quantum-mechanical tunnelling 1 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. 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 PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1174 (https://doi.org/10.1351/pac199466051077) PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2282 (https://doi.org/10.1351/pac199668122223) https://goldbook.iupac.org/terms/view/T06531/html https://goldbook.iupac.org/terms/view/T06531/json https://goldbook.iupac.org/terms/view/T06531/plain 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 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. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . 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. 2026-05-18T10:21:31+00:00