Term: bifurcation
https://doi.org/10.1351/goldbook.08145

Definition:
Feature on a potential-energy surface whereby a minimum-energy reaction path (MERP) emanating from a saddle point (corresponding to a transition structure) splits in two and leads to alternative products without intervening minima or secondary barriers to overcome. A bifurcation arises when the curvature of the surface in a direction perpendicular to the MERP becomes zero and then negative; it implies the existence of a lower-energy transition structure with a transition vector orthogonal to the original MERP.

Source: PAC, 2022, 94, 353. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 2021)' on page 370 (https://doi.org/10.1515/pac-2018-1010)

Citation: 'bifurcation' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.08145

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