Electron that is out of the thermal equilibrium with its environment and has enough kinetic energy to overcome potential barriers to travel between different regions of a molecule or
lattice.
Source:
PAC, 2022, 94, 15. 'Glossary of terms relating to electronic, photonic and magnetic properties of polymers (IUPAC Recommendations 2021)' on page 35 (https://doi.org/10.1515/pac-2020-0501)