An electron spin resonance spectrometer is disclosed which includes a sample and a reference arm (16, 18). The sample arm has a circulator (30) for directing radiation to a resonator (22) in which a sample for analysis is deposited and for receiving radiation from the resonator and directing it to a...http://www.google.se/patents/US4803624?utm_source=gb-gplus-sharePatent US4803624 - Electron spin resonance spectrometer
