Evaluation of Molecular Quadrupole Moments from Microwave Spectral Line Breadths. I. Theoretical

Abstract

The breadths of microwave spectral lines in gas mixtures may arise from several different interactions. It is shown that when the radiating molecule is the linear molecule OCS, polarizability interactions predominate, but when the radiating molecule is NH3 undergoing inversion, quadrupole moment interactions predominate. Consequently, NH3 is a particularly suitable molecule to use as a ``probe'' to measure quadrupole moments of other molecules. An improved theoretical analysis leads to a revision of previously published molecular quadrupole moments.