Potential energy gap between @R05163@ and the @T06468@, sometimes involving the zero point energies, but usually not.
Sources: Green Book, 2nd ed., p. 56 [Terms] [Book] PAC, 1996, 68, 149. (A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)) on page 189 [Terms] [Paper]
Citation: 'threshold energy' in IUPAC Compendium of Chemical Terminology, 3rd ed. International Union of Pure and Applied Chemistry; 2006. Online version 3.0.1, 2019. https://doi.org/10.1351/goldbook.T06366 RISBibTexEndNote