activated state

https://doi.org/10.1351/goldbook.08141
In theories of unimolecular reactions an energized chemical species, often characterized by the superscript \(^{\ddagger}\), where the excitation is specific and the molecule is poised for reaction.
Notes:
  1. Often used as a synonym for activated complex or transition state, but not restricted to transition-state theory.
  2. This is distinct from an energized molecule, often characterized by the superscript \(^{*}\), in which excitation energy is dispersed among internal degrees of freedom.
  3. This is not a complex according to the definition in this Glossary.
Source:
PAC, 2022, 94, 353. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 2021)' on page 357 (https://doi.org/10.1515/pac-2018-1010)