Electron Spin Resonance of Colloid Centres in Lithium Hydride

Lithium hydride becomes additively coloured by exposure to ultraviolet light. An optical absorption band is produced at 6500 Å. From the position and general behaviour of the absorption band it may be assumed that this is due to colloidal particles comparable in size with the wavelength of visible light. It is supposed that the coloration process follows the Gurney-Mott theory of the photographic process. The irradiated specimens also exhibit a symmetrical, temperature-independent electron spin resonance absorption. This resonance is attributed to conduction electrons in colloidal particles which are small compared with the skin depth at 9000 Mc/s.