Absolute calibration of millimeter-wavelength spectral lines

A detailed analysis of the chopper-wheel method of calibrating the intensity of a millimeter-wavelength spectral line is presented. Special techniques were used to construct a receiver which eliminates most of the usual calibration difficulties. The zenith atmospheric extinction between 3.5 mm and 2.6 mm wavelength was measured, and the intensities of six spectral lines in this range were absolutely calibrated with an estimated uncertainty (1 sigma) of 7 percent. The effects of the antenna power pattern on the corrected antenna temperature T*/sub A/ are calculated for several simple models of the source brightness distribution. (auth)