intrinsic activation energy, Ea,i

https://doi.org/10.1351/goldbook.I03134
If Ea,1 and Ea,- 1 are the
activation energies
for a reaction in forward and reverse directions, the lesser of the two is sometimes called the intrinsic
activation
energy. It is the
activation
energy for the reaction in the exothermic direction.
Source:
PAC, 1996, 68, 149. (A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)) on page 170 [Terms] [Paper]