METHOD FOR THE DETERMINATION OF PHOTOSTIMULABLE DEFECT CENTER CONCENTRATIONS, PRODUCTION-RATES, AND EFFECTIVE FORMATION ENERGIES

A new method is proposed to determine radiation-induced defect center concentrations in solids which exhibit photostimulable luminescence. The technique relies on the determination of the number of photons released by spontaneous and photostimulated luminescence. A comparison with the x-ray-absorbed energy yields the effective formation energy of spontaneous luminescence photons and photostimulable centers. The method is applied representatively to BaFBr:Eu2+, which is utilized commercially as photostimulable x-ray storage phosphor in image plates for x-ray, gamma-ray, electron, and neutron radiography. It is shown that in the utilized material on average 8 photostimulable F(Br-) centers. (color centers based on bromine vacancies) and about 5 spontaneously emitted photons are generated by the absorption of 1 keV x-ray energy. Taking recent investigations into account which show that the x-ray generation of spontaneous luminescence and photostimulated luminescence centers is accompanied by the creation of approximately 36 nonphotostimulable defect centers, an average formation energy of about 20 eV per defect center can be calculated.