Examination of Colored Alkali Halides for Photoelectric Hall Effect

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Abstract
Five additively colored alkali halides have been examined for photoelectric Hall effect by means of two different arrangements, a single cross-electrode set-up and Tartakowsky's divided electrode method. The consistently null results obtained were checked by using zincblende, a substance of known photoelectric galvanomagnetic properties, in both arrangements. From the upper limit assigned to the Hall effect, it was computed that the mean free path of photoelectrons in rocksalt is not much greater than the dimensions of a lattice cell—in agreement with Von Hippel's result for the electronic mean free path on the basis of electrical breakdown experiments. This interpretation of the null result was supported by the fact that the large initial surge of electron current in KCl and KBr at the outset of illumination also showed no Hall effect. The magnetic deflection of photoelectric current reported in rocksalt by Tartakowsky was not found, either for additively or photochemically colored specimens.