Molecular Luminescence from Electron-Irradiated Alkali-Halides

The ultraviolet (uv) emission composed of vibronic lines emitted from electron-irradiated alkali halides was investigated. It was observed only from the surface layers of NaCl and KCl among various alkali halides (alkali=Li, Na and K; halogen=F, Cl and Br, except LiBr). It was also found that the intensity of the uv emission increases as the irradiation dose is increased, and that the uv emission spectra of electron-irradiated NaCl and KCl coincide well with those of X-ray irradiated NaCl:CN and KCl:CN, respectively. These results suggest that the uv emission is attributed to CN - introduced from the ambience into the surface layer of the crystals during electron irradiation. The difference in the appearance of the uv emission among alkali halides is explained in terms of the size of the halogen-ion vacancy and the emission mechanism.