Spectro-Photoelectrical Effects in Argentite the Production of an Electromotive Force by Illumination

Abstract

Electromotive force produced by illumination of argentite.—If argentite (${\mathrm{Ag}}_2$S) is connected in a closed circuit with a galvanometer and one surface of contact is illuminated, an e.m.f. is produced which increases with the intensity, reaching a limit of about.013 volt for 600 candle-meters and over. On continued exposure, marked fatigue is shown, the e.m.f. decreasing in a few minutes to half value. By use of a monochromatic illuminator and a suitable intensity control, the e.m.f. was found to show a sharp maximum for about 1μ. The results were found independent of the contacts used whether Cu, Al, Fe, Sn, Ag or water. The effect is clearly not thermoelectric. Various samples showed similar results. No transmitted light effect was observed. Six other minerals showed the effect to a greater or less extent, including molybdenite (Mo${\mathrm{S}}_2$) and acanthite (${\mathrm{Ag}}_2$S).