Microwave Spectroscopy in the Region of Three to Five Millimeters

Abstract

Exploratory investigations in the region of the electromagnetic spectrum between 3.3- and 5-mm wave-length have shown that useful work can be done here with available sources and detectors. Higher rotational transitions of BrCN and ICN have been observed with satisfactory signal-to-noise ratios at pressures low enough to resolve the nuclear quadrupole splittings. These measurements indicate that the minimum detectable absorption is ${10}^{-5\mathrm{}}$ neper per cm with the present spectroscope. The $B_0$ value of HCN has been determined as 1.4789 ${\mathrm{cm}}^{-1\mathrm{}}$, in agreement with infra-red results. The quadrupole coupling factor for the nitrogen nucleus in this molecule has been found to be 4.7 mc.