Electron Diffraction Study of the Structure of Phosphine

The structure of gaseous phosphine was investigated by the sector-microphotometer method of electron diffraction. It was found that the length of the P–H bond was rg (0) = 1.437±0.004 A and the root-meansquare amplitude of vibration was 0.085±0.008 A where the quoted uncertainties represent standard errors. The asymmetry of the stretching vibration was estimated and used to deduce the approximate equilibrium bond length, re∼1.419 A. The H–H distance, while observed, was not sufficiently accurate to provide a useful value of the bond angle. The diffraction values are compared with spectroscopic values considering briefly the effect of the zero-point vibrations on each.