Proposal for Measuring Lamb Shifts by the Study of Modulated, Fluorescent Light

Abstract

A method is proposed for measuring the interval between two atomic energy levels of different parity. The method is related to optical radio-frequency double resonance and level-crossing experiments in that the behavior of atoms in excited states is deduced from observations of the fluorescent light. In contrast with the oscillating electric field ordinarily used to stimulate transitions between states of opposite parity, a small, static electric field is required. The rate at which atoms are excited is required to be modulated; consequently, the fluorescent light will be modulated. The amplitude of modulation will depend on the parameters. A general expression is derived. Two cases are of particular interest: (1) A resonance effect is predicted if the frequency of modulation matches the interval between the perturbed levels. This effect could best be studied for frequencies much greater than the combined natural widths of the levels. (2) For frequencies smaller than the natural width, a level-crossing effect is predicted whose peak occurs at the point of intersection of the unperturbed levels. The method might be applied to measure intervals between the $2s$ and $2p$ levels in hydrogen. Estimates are given of the required fields and frequencies.