The Accuracy of Measurements of the Spectral-Line Frequencies in the Studies of the Rotational Transitions of the 16 O 12 C 32 S Molecule in the Millimeter and Submillimeter Wave Ranges

The absolute error of determining the center frequency of the molecule spectral line during a single measurement, which is obtained by fitting the line shape to the model profile, is usually significantly smaller than the statistical spread in the frequencies of the repeated measurements. We discuss the possible causes of the systematic errors leading to an increase in the uncertainty of measurements of the line-center frequency. For an example of the multiple spectral measurements of the rotational transitions of the 16 O 12 C 32 S molecule in the millimeter- and submillimeter-wave ranges (with a frequency of up to 522 GHz), by the Lamb-dip method, we determine the absolute error of the performed measurements, which amounts to 0 . 4 kHz. New precision values of the center frequencies of the rotational transitions of the 16 O 12 C 32 S molecule and more accurate values of the rotational constants, which are calculated using the measured frequencies, are presented.