Line Shapes in the Method of Intersecting Energy Levels

The first part of this work is a study of the changes of intensity of the resonance fluorescence from mercury vapour as a small magnetic field H is applied either parallel or anti-parallel to the direction of the incident light. The changes follow either a Lorentzian or a dispersion-type function of the Zeeman splitting of the excited state, according to the orientations of polarizer and analyser in the beams of light. In an experiment with an additional oscillatory field at a frequency ω 0 , similar curves are observed in the region H = H 0 /2. ( H 0 is the field for which ω 0 is the Larmor frequency.) The observations are relevant to a recently developed technique in which intensity changes of this sort are used to make precision measurements in spectroscopy. The Lorentzian line shape is usually observed. The possibility of obtaining line profiles of other shapes was pointed out by Franken.