Microwave radii in nonresonant spectra

The microwave cross section σ for Debye-like spectra resulting from overlapping lines at high pressures is computed. The main idea is a modification of Anderson's model, by which the cross section is computed for an effective line instead of computing it for the single overlapping lines. This gives a natural explanation of the observed reduction of σ compared to σ for the isolated lines. Complete numerical calculations are carried out for the case of Debye spectra of symmetric-top molecules. Agreement with experiment is satisfactory.