transition coordinate

https://doi.org/10.1351/goldbook.T06455
The @[email protected] at the @[email protected] corresponding to a vibration with an imaginary frequency. Motion along it in the two opposite senses leads towards the reactants or towards the products.
Source:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1174 [Terms] [Paper]