activation energy (Arrhenius activation energy)

https://doi.org/10.1351/goldbook.A00102
An empirical parameter characterizing the exponential temperature dependence of the rate coefficient, k, Ea = RT^2.(d(lnk)/dT), where R is the gas constant and T the thermodynamic temperature. The term is also used for threshold energies in electronic potential surfaces, in which case the term requires careful definition.
Source:
Green Book, 2nd ed., p. 55 (https://dev.goldbook.iupac.org/files/pdf/green_book_2ed.pdf)