Collision Broadening of Rotational Absorption Lines. III. Broadening by Linear Molecules and Inert Gases and the Determination of Molecular Quadrupole Moments

Abstract

A recently developed theory of the pressure broadening of microwave absorption lines resulting from transfer of rotational energy in molecular collisions has been applied to calculations of the linewidth of rotational absorption lines of a number of linear and symmetric-top molecules broadened by collisions with linear molecules and inert-gas atoms. In such cases, shorter-range forces such as dipole–quadrupole, quadrupole–dipole, quadrupole–quadrupole, and dispersion interactions are important as well as dipole–dipole interaction. In general, the agreement between the theoretical calculations and previously reported measurements is quite satisfactory. The application of the experimental technique as a method for determining molecular electric quadrupole moments is analyzed, and values for the molecular quadrupole moments of OCS, N2O, NO, CO2, N2, and H2 are obtained from earlier data.