Electron
paramagnetic resonance
(
EPR) and/or electron spin
resonance
(
ESR) is defined as the form of
spectroscopy concerned with microwave-induced transitions between magnetic energy levels of electrons having a net spin and orbital
angular momentum. The term electron
paramagnetic resonance and the symbol
EPR are preferred and should be used for primary indexing.
Source:
PAC, 1989, 61, 2195
(Recommendation for EPR/ESR nomenclature and conventions for presenting experimental data in publications (Recommendations 1989))
on page 2196