04979 IUPAC Gold Book - quantized internal energy 10.1351/goldbook.Q04979 Q04979 current 1 The quantized internal energy of a molecule in its electronic ground or excited state can be approximated with sufficient accuracy for analytical purposes by: \[E_{\rm{int}}=E_{\rm{el}}+E_{\rm{vib}}+E_{\rm{rot}}\] where \(E_{\mathrm{el}}\) is the electronic, \(E_{\mathrm{vib}}\) the vibrational and \(E_{\mathrm{rot}}\) the rotational energy, respectively. excited state https://goldbook.iupac.org//terms/view/E02257 internal energy https://goldbook.iupac.org//terms/view/I03103 PAC, 1988, 60, 1449. 'Nomenclature, symbols, units and their usage in spectrochemical analysis - VII. Molecular absorption spectroscopy, ultraviolet and visible (UV/VIS) (Recommendations 1988)' on page 1452 (https://doi.org/10.1351/pac198860091449) https://goldbook.iupac.org/terms/view/Q04979/html https://goldbook.iupac.org/terms/view/Q04979/json https://goldbook.iupac.org/terms/view/Q04979/plain Citation: 'quantized internal energy' 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.Q04979 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. 2026-04-18T03:23:40+00:00