Electron paramagnetic resonance study of Eu2+ centers in melt-grown CsBr single crystals

摘要

The structure of Eu2+ monomer centers in CsBr single crystals is investigated using electron paramagnetic resonance (EPR) spectroscopy. These centers are produced by heating the melt-grown crystals above 600 K in vacuum followed by a rapid quench to room temperature (RT) or 77 K. The angular dependence of their EPR spectrum demonstrates that these centers have cubic symmetry. At RT the EPR spectrum decays by aggregation of the Eu2+ ions. This strongly contrasts with the situation for CsBr:Eu needle image plates synthesized by physical vapor deposition, where the Eu2+-related EPR spectrum was observed to exhibit long-term stability at RT.