Microwave Spectra of the Free Radicals OH and OD

Abstract

Experiments are reported on the microwave spectra of the free OH radical. The radicals are produced by an electric discharge in concentrations near 10% at pressures of approximately 0.1 mm Hg. The spectra are detected by Zeeman modulation. They are due to direct transitions between the $\Lambda$-doublet levels of each rotational state in the ground vibrational level of the molecule. Spectra due to ${\mathrm{O}}^{16}$H, ${\mathrm{O}}^{18}$H, and ${\mathrm{O}}^{16}$D in ${}_{}{}^2{}_{}{}^{}\Pi _{\frac{1}{2}}^{}{}_{}{}^{}$ and ${}_{}{}^2{}_{}{}^{}\Pi _{\frac{3}{2}}^{}{}_{}{}^{}$ states have been observed in the 7.7 to 37 kMc/sec region. Intensity of the lines ranges from about 5×${10}^{-6\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$ to 5×${10}^{-8\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$.