chain carrier

https://doi.org/10.1351/goldbook.C00949
A species, such as an atom or @F02519@, which is involved in @C00959@ is known as a chain @C00859@.
Source:
PAC, 1996, 68, 149. (A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)) on page 156 [Terms] [Paper]