Radiation quenching of F-center emission in ruby

The only red luminescence intrinsic to chromium ions is observed in ruby crystals with a chromium concentration on the order of 0.01 weight percent. If the ruby has been previously irradiated with high-energy electrons to a fluence of 1017 cm^-2, F and F⁺ emissions appear. These emissions disappear during irradiation by X-rays. The luminescence intensity (I) follows a linear decay on log(I) vs. log(time). The decay kinetics are the same at both room and liquid nitrogen temperatures. Four thermoluminescence (TL) peaks are present for electron-irradiated crystals after UV-exposure, also. These peaks, which have an electronic nature, also disappear under irradiation by X-rays. New evidence supports the idea that the origin of both phenomena is the same.