https://doi.org/10.1351/goldbook.S05868
A
stable
paramagnetic
group
(typically a nitryl radical) that is attached to a part of a molecular entity
whose microscopic environment is of interest and may be revealed by the electron spin resonance
(ESR) spectrum of the spin label
. When a simple paramagnetic
molecular entity is used in this way without covalent attachment
to the molecular entity of interest it is frequently referred to as a 'spin probe'.