An electron spin resonance study of photoproduced trivalent iron and divalent vanadium in silver chloride

A method is described which allows Fe 2+ and V 3+ to be formed in the same specimen of silver chloride. Exposure to blue or to red light produces Fe 3+ and V 2+ . The effect of blue light is explained in terms of hole capture by Fe 2+ and electron capture by V 3+ whereas that of red light is explained in terms of a charge‐transfer absorption by the trivalent forms of iron and vanadium. A re‐arrangement in the environment of Fe 3+ occurs on warming to about 203° K. After blue irradiation at 93° K some of the V 2+ is believed to be associated with two silver‐ion vacancies. A re‐orientation of the vacancies is observed on warming to about 110 and at about 150° K a further re‐orientation takes place and one vacancy is removed. Photoproduced Fe 3+ and V 2+ are stable at 93° K. At room temperature they decay at the same rate with a half life which is of the order of minutes.