Radio-Frequency Spectrum of Phosphine (PH3)

The electric resonance spectrum of phosphine (PH₃) was measured at zero electric field for three rotational states, $\text{J=4}$ , 5, and 7 with $\text{K=3}$ . In addition, the $\text{J=K=2}$ and $\text{J=K=1}$ spectra were observed at several values for the electric field. The dipole moment (debye) is $\text{0.57395±0.0003}$ . The magnetic hyperfine constants (kilohertz) are $c_{\alpha }{\text{=−114.90±0.13, c}}_{\beta }\text{=−116.38±0.32}$ for the spin—rotation interaction of the ³¹P nucleus, and ${\zeta }_{\alpha }{\text{=8.01±0.08,ζ}}_{\beta }\text{=7.67±0.19}$ 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 ($\text{Δ〈1}$ kHz). The $\text{K=3}$ levels have K‐doubling fine structure as predicted by Nielson and Dennison, but the magnitude does not agree with their formula.