Radio-Frequency Spectrum of Phosphine (PH3)

The electric resonance spectrum of phosphine (PH3) was measured at zero electric field for three rotational states, J=4, 5, and 7 with K=3. In addition, the J=K=2 and J=K=1 spectra were observed at several values for the electric field. The dipole moment (debye) is 0.57395±0.0003. The magnetic hyperfine constants (kilohertz) are cα=−114.90±0.13, cβ=−116.38±0.32 for the spin—rotation interaction of the 31P nucleus, and ζ α=8.01±0.08,ζβ=7.67±0.19 for the spin—rotation interaction of the 1H nuclei. The α constant is the mean interaction in the x and y directions, and the β constant is the interaction about the molecular z axis. No inversion doubling was observed (Δ〈1 kHz). The K=3 levels have K-doubling fine structure as predicted by Nielson and Dennison, but the magnitude does not agree with their formula.