X-Ray Generation of Color Centers in Zone-Refined KCl and KBr

The techniques of zone purification of KCl and KBr crystals are described, and the success of this technique in removing impurities such as hydroxyl ions and divalent cations is demonstrated. A comparison of the defects introduced into zone-purified salts and commercial salts by x irradiation at room temperature and at liquid-helium temperature is given. Studies of the optical bleaching of F, H, and VK centers by F-band light at liquid-helium temperature gives evidence of the spatial proximity of these centers.