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Electron paramagnetic resonance study of copper impurity charge-states in PbWO4 scintillator |
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| Authors: | A Hofstaetter V V Laguta B K Meyer M Nikl J Rosa R Y Zhu |
| Institution: | a Physics Institute, University of Giessen, Heinrich-Buff-Ring 16, Gissen D 35392, Germany b Institute for Problems of Material Science, Ukrainian Academy of Sciences, Krjijanovskogo 3, Kiev 03142, Ukraine c Institute of Physics, AS CR, Cukrovarnická 10, Prague 162 53, Czech Republic d 256-48, HEP, California Institute of Technology, Pasadena, CA 91125, USA |
| Abstract: | The study of two types of Cu2+ centres observed in nominally pure PbWO4 crystals grown by Bridgman and Czochralski methods was carried out by electron paramagnetic resonance (EPR). One of centres, called Cu2+(I), arises after oxygen compensation, while the second one, called Cu2+(II) requires, in addition, infrared illumination at low temperatures, being thermally stable only up to 22–23 K. The EPR spectra of both Cu2+ centres are described by rhombic symmetry g-tensors with the Z-principal axis lying close to, or in the (ab) plane of the crystal. It is proposed that in both centres the Cu2+ ions substitute for Pb2+ ions. The additional reduction of the local crystal-field symmetry is connected with a CuWO4 wolframite-type lattice distortion for the Cu(I) and a Jahn–Teller distortion of the regular PbWO4 lattice for the Cu(II). It was also found that either IR irradiation or thermal heating activate the transfer of an electron between two closely spaced Cu2+ centres. |
| Keywords: | Electron paramagnetic resonance Tungstates Defects |
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