The Photo-Electric and Thermionic Properties of Iron

Abstract

The photo-electric properties of metals which have undergone a thorough outgassing process by heat treatment have not been extensively studied.DuBridge,' Warner2 and Kazda3 have studied the photo-electric character- istics of platinum, tungsten and mercury, respectively, taking particular outgassing precautions.An effort is being made in this laboratory to extend the study to other metals.The investigations reported in the present paper have yielded some interesting results for pure iron.Others in this laboratory are at the present time working with molybdenum, tantalum and cobalt.The present paper is a preliminary report of investigations of the following phenomena:(1) The variation of the photo-electric sensitivity of iron as it undergoes an extended process of outgassing by heat treatment.(2) The effect of crystallographic changes on the photo-electric sensitivity of thoroughly outgassed iron.(3) The effect of a crystallographic change on the thermionic emission from outgassed iron.(4) The variation of the long wave-length limit through the outgassing process.The apparatus was similar to that used by DuBridgel and consisted essentially of a narrow strip of iron suspended inside a nickel receiving cylinder, the whole being enclosed in a Pyrex tube which was connected through a liquid air trap and a mercury cut-off to the pumps.A quartz window, sealed directly on the pyrex tube served to admit the radiations from a quartz mercury arc.The pressures could be measured by a Mc- Leod gauge or an ionization manometer of the type described by Dushman and Found.4The electrolytic iron, used in this work, was supplied by Professor Watts of the chemical engineering department of the University of Wis-