Photometric Study of the Appearance of Spectral Lines in a Condensed Spark

Abstract

The time interval between the time of appearance in a condensed spark discharge of the arc lines 4678A, 4722A, 4811A (${2}^{3}{P}_{012}\ensuremath{-}{2}^{3}{S}_{1}$) of zinc, 4680A, 4800A, 5086A (${2}^{3}{P}_{012}\ensuremath{-}{2}^{3}{S}_{1}$) of cadmium, the air lines 4347A, 4631A and 5001A was measured visually, using the Kerr cell method developed by Beams. A photographic method was developed whereby it was possible to determine from photometric measurements the variation of the intensity of an individual line with the time after the beginning of the spark. The time of first appearance, or zero intensity, is inferred from the extrapolation of the curves showing the intensity as a function of the time. The arc lines of zinc appear simultaneously. The arc lines of cadmium appear simultaneously but definitely earlier than the zinc arc lines. The air lines appear simultaneously but earlier than the arc lines. The spark lines appear simultaneously but earlier than the arc lines and later than the air lines of the respective elements. The results of the visual and photographic methods do not agree. Neither method gives information that in the case of zinc or cadmium, an electron remains in the ${2}^{3}{S}_{1}$ state for a longer time before dropping to the ${2}^{3}{P}_{0}$ state than before dropping to the ${2}^{3}{P}_{1}$ or the ${2}^{3}{P}_{2}$ state.