Structure of the Lines of the Arc Spectrum of Silver

Abstract

THE fine structure of the more important lines of the arc spectrum of silver was examined by means of a reflecting echelon grating of high resolving power. This instrument and its mounting have been pre viously described¹. The light source was a tube of fused silica fitted with external electrodes similar to those used by me in the investigation of the structures of the arc lines of indium¹, thallium², and gallium³, excited by means of a high frequency oscillator. The discharge tube was filled with neon at a pressure of about 0.5 mm. of mercury, and the capillary portion of the tube contained a small quantity of silver chloride. The capillary was heated to a temperature of about 600° C. All the lines examined were found to be simple. The half-value width of the lines was determined by obtaining two images of the line under investigation on the same plate, making two exposures at different pressures of the air surrounding the echelon grating ; the separation of the images at the smallest pressure difference at which the two images could still be resolved was measured and taken to be the half-value width of the line.