Intensity of Spectrum Lines

Abstract

VERY little attention has been paid in the past to the accurate measurement of the optical intensity of spectral lines in vacuum tubes under different conditions, probably on account of the considerable experimental difficulties. Hence I may, perhaps, be allowed to indicate a relation I have obtained between the optical intensity, current strength, and pressure of the glowing gas. Throughout the whole experimental range, using the so-called “electrode less” tube—with wholly external mercury electrodes, when the current is of a slowly oscillating character—the optical intensity, with an end-on tube, is accurately proportional to the readings of a thermo-galvanometer in series, and over a more limited range of measurement, at constant current, is inversely proportional to the pressure of the gas.