A MULTICHANNEL SPECTROMETER FOR CORRELATED EPR-OPTICAL ABSORPTION ANALYSIS OF PHOTOCHROMIC PROCESSES IN CRYSTALS

A fast optical fiber multichannel spectrometer that has been developed for simultaneous measurements of EPR and optical absorption of defect s in crystals is described. The setup is designed for establishing cor relations between both phenomena by observing their changes under vary ing pump light energies. In this way optical bands are assigned to the defects causing them. After this calibration step, the pump-light-ind uced variations of the band intensities alone serve to unravel the res ponsible charge transfer processes. The speed of the spectrometer 14 m s for one spectrum in the range 400 nm to 1100 nm - is the basis for s uch experiments. A special scheme for evaluation of the spectra allows a fast overview of the phenomena occuring on the atomic level. Exampl es based on two types of photochromic BaTiO3 crystals are given. The e xtension of this type of spectroscopy to other fields, where correlati on between EPR and optical phenomena is essential, is discussed.