Intensity measurements in microwave spectroscopy the "antimodulation" method

Abstract

Principle and theoretical background are presented of a new method for the precision measurement of absolute and relative peak intensities of microwave absorption lines. This method, called the “antimodulation” method, can be used with any spectrometer employing molecular modulation. In the present research the antimodulation method has been applied in the 1.25 cm wavelength region with a Stark-cavity spectrometer of novel design. As a check on the possibilities of the antimodulation method measurements have been performed on seven lines arising from the J = 1 → 2 rotational transition in carbonyl sulphide (OCS), But for the l-doublet lines, results of both absolute (standard error 2.5 percent) and relative (error 1–2 percent) measurements are in good agreement with calculated values. The measured intensities of the l-doublet lines are about 15 percent too low. This discrepancy cannot be explained by experimental errors. A possible refinement of the theory is suggested to explain the difference.