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. T he technique relies on the determination of the number of photons rele ased by spontaneous and photostimulated luminescence. A comparison wit h the x-ray-absorbed energy yields the effective formation energy of s pontaneous luminescence photons and photostimulable centers. The metho d is applied representatively to BaFBr:Eu2+, which is utilized commerc ially 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. (c olor centers based on bromine vacancies) and about 5 spontaneously emi tted photons are generated by the absorption of 1 keV x-ray energy. Ta king recent investigations into account which show that the x-ray gene ration of spontaneous luminescence and photostimulated luminescence ce nters is accompanied by the creation of approximately 36 nonphotostimu lable defect centers, an average formation energy of about 20 eV per d efect center can be calculated.