The Absorption of Microwaves by Gases

Abstract

The absorption by ammonia of electromagnetic waves having a length in the one-centimeter range has been known for some years. An investigation has been made to determine whether other gases show similar absorption for microwaves and as a result fourteen additional gases have been found whose absorption is comparable to that of ammonia. Among these gases are dimethyl ether, a variety of amines and alkyl halides, and several others. Measurements on the absorption coefficient and dielectric constant of these gases taken at 1.25 cm at room temperature and a pressure of one atmosphere are given. The frequency at which the absorption coefficient attains its maximum value may be inferred from the curve: absorption coefficient vs. pressure. Data on the absorption of several gas mixtures are given. Possible molecular mechanisms adequate to account for the large absorptions observed are discussed together with the conclusions reached.