Electron paramagnetic resonance spectrum of radical pairs in ultraviolet irradiated (Nh₄)₂s₂0₈ single crystals

Irradiation of (NH₄)₂S₂0₈ single crystals with ultraviolet (UV) light produces two kinds of radical pair, I and II. Radical pair I is stable at room temperature, and can be produced via UV irradiation at room temperature. The electron paramagnetic resonance (EPR) spectrum exhibited by radical pair I is similar to that of SOJ pairs in UV irradiated K₂S₂0₈ crystals observed previously, and can be identified similarly. Radical pair II can be produced by UV irradiation and detected by EPR only at low temperatures. Radical pair II, which could be identified as SOJ pairs, exhibits a limited lifetime at room temperature. A rigorous method has been developed for analysing the EPR spectra exhibited by these radical pairs.