AN IMPROVED MICROWAVE SPECTROMETER FOR LINEWIDTH MEASUREMENTS

A microwave spectrometer capable of determining linewidth data with repeatability better than 2% for spectral lines of intensities of 10 -6 and 10-7 cm-1 has been developed. The technique of source modulation has been utilized effectively to produce molecular transition without resorting to the conventional technique of Stark modulation. This scheme of source modulation has enabled the use of an absorption cell of any reasonable length to be used. The cells employed in this investigation were 6.1, 15.2, and 30.5 m in length. Data on signal-to-noise ratios for spectral lines of 10-4, 10-5, and 10 -6 cm-1 intensity are given to demonstrate the merit of an increased cell length. A circular waveguide rather than the conventional rectangular waveguide is utilized as the absorption cell. © 1969 The American Institute of Physics.