The microwave spectrum of the PH2 radical

Three rotational transitions, 1₁₀ ← 1₀₁, 2₂₀ ← 2₁₁, and 3₃₀ ← 3₂₁, of the PH₂ radical in the ground vibronic state were observed in the mm-wave region, by using a source-frequency modulation spectrometer with a 1-m-long free space cell. The PH₂ radical was generated directly in the cell by glow discharge in a mixture of phosphine and oxygen. Thirty four fine and hyperfine components were measured for the three transitions. An analysis of the observed spectra, combined with far-infrared and mid-infrared laser magnetic resonance spectra and laser-induced fluorescence spectra obtained by other works, improved the rotational and spin-rotation interaction constants in precision. The observed hyperfine structure gave the magnetic hyperfine coupling constants for both P and H nuclei and also the P nuclear spin-rotation interaction constants.