Term: separability assumption
https://doi.org/10.1351/goldbook.S05611

Definition:
This expression refers to the assumption, essential to conventional transition-state theory, that the energy of the system may be expressed as the sum of components associated with different degrees of freedom. In transition-state theory it is assumed that the energy of the motion of the system through the dividing surface of the potential-energy (reaction) surface is separable into various components. In many practical calculations it is assumed that the energy of the system is separable into electronic, vibrational, rotational and translational energy.

Related Terms:
1) transition-state theory (http://doi.org/10.1351/goldbook.T06470).
2) dividing surface (http://doi.org/10.1351/goldbook.D01823).
3) potential-energy (reaction) surface (http://doi.org/10.1351/goldbook.P04780).
4) degrees of freedom (http://doi.org/10.1351/goldbook.D01572).

Source: PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 186 (https://doi.org/10.1351/pac199668010149)

Citation: 'separability assumption' 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.S05611

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