Microwave spectrum of the PHD radical: fine and hyperfine structure

Furuya and Saito studied the microwave spectrum of the monodeuterated species of PH2 in the 180-360 GHz region, using a high-sensitivity millimeter-wave spectrometer. The radical was generated in a free space absorption cell by a hollow-cathode discharge in a mixture of H2 and D2 over red phosphorus flakes, placed in the pyrex glass cell. Molecular constants including hyperfine coupling terms for the P and H nuclei were determined precisely by a least-squares analysis of observed spectral lines. Based on the molecular axis rotation by a deuterium substitution of PH2 for PHD, the hydrogen hyperfine coupling tensor for PH2 was derived from the axial components of PH2 and PHD for the first time. The principle value for the magnetic hyperfine coupling constant for the hydrogen nucleus was determined to be 14.12 and -19.58 MHz along the principal axes in plane. One of the principal axes was found to make an angle of 3.69º with the P-H bond