The microwave spectrum of the PF radical in the ground X 3Σ− electronic state

Abstract

The microwave absorption spectrum of the PF radical in the X 3Σ− state was detected by using a source modulation microwave spectrometer. The radical was produced in a free space cell by a dc glow discharge in a mixture of PH3 and CF4. Five rotational transitions with N=1 ← 0 up to 5 ← 4 were observed in the frequency region of 44 to 171 GHz and were least-squares analyzed to determine the rotational constant, the centrifugal distortion constant, the spin–spin coupling constant with its centrifugal distortion term, the spin-rotation coupling constant, and the magnetic hyperfine coupling constants for both phosphorus and fluorine nuclei. A centrifugal correction term was found to be necessary for the c magnetic hyperfine constant of phosphorus in order to achieve a good fitting of the observed spectrum. The present data agree with, but considerably improve the accuracies of ground-state molecular constants which Douglas and Frackowiak derived from high-resolution emission spectra. The spin density and the s character of the unpaired-electron orbital were calculated from the observed magnetic hyperfine coupling constants to be 91.3% and 0.88% for P and 9.1% and 0.17% for F.