Microwave Double-Resonance Experiments

Abstract

Double quantum transitions and certain changes in line intensities which can be ascribed to relaxation effects have been observed in a Stark‐effect spectrometer in which the absorbing gas was exposed to two microwave fields simultaneously. The general features of the line shape predicted by Javan for a three‐level system in the presence of two irradiating fields have been clearly observed in OCS and propylene oxide. Studies of various transitions in these molecules indicate the presence of either a double quantum emission or absorption line depending upon the energy‐level scheme in question. Observation of both zero‐field and Stark transitions has revealed certain expected changes in line intensities. Several experimental arrangements for microwave double resonance are described and applications of this technique to the identification and confirmation of complex rotational spectra are discussed.