active state

of a surface photoadsorption centre
https://doi.org/10.1351/goldbook.13990
Electronically excited surface centre, or a surface centre (surface site) with a trapped photogenerated charge carrier that interacts with species at the solid/liquid, liquid/liquid, solid/gas, or liquid/gas interfaces with formation of, e.g., chemisorbed species.
Source:
PAC, 2011, 83, 931. (Glossary of terms used in photocatalysis and radiation catalysis (IUPAC Recommendations 2011)) on page 939 [Terms] [Paper]