EPR: The Bruker ESP 300 EPR spectrometer works in X band. It has a dual-mode ER4116DM resonator which allows the measurement of parallel and perpendicular mode EPR transitions. Optical illumination of a sample is possible through an 8 mm i.d. hole on the cavity front. The spectrometer is housed with OXFORD ESR900 cryostat which is capable of lowering the experimental temperature down to 4 K.