Collision Broadening of Rotational Absorption Lines. VI. Pressure Broadening of Microwave Absorption Spectra Involving Oxygen

Abstract

The pressure broadening of microwave absorption lines by collisions involving O₂ has been investigated using a method presented earlier for analyzing and evaluating microwave linewidth parameters under conditions where impact‐theory assumptions are valid. A value of (1.16 ± 0.12) D· Å was obtained for the molecular quadrupole moment of O₂ from linewidth data for broadening of NH₃ inversion lines by O₂. This value is in reasonably good agreement with values determined by other methods, and should constitute an upper limit to the true value since only dipole–quadrupole interaction was considered in the linewidth calculations, This value of the molecular quadrupole moment of O₂ was used to calculate linewidth parameters for H₂O–O₂ broadening, OCS–O₂ broadening, N₂O–O₂ broadening, O₂–O₂ self‐broadening, and the broadening of the 9– line of O₂ by various foreign gases. These results are in general smaller than the experimental values, suggesting that the effects of higher‐order interactions are important in collisions with O₂.