THE P-31 SHIELDING IN PHOSPHINE

The temperature dependence of the phosphorus shielding in phosphine has been remeasured in the range 300-400 K in samples with densities in the range 7-30 amagat. The shielding surfaces are calculated using the localized orbital-local origin (LORG) method of Hansen and Bouman in terms of the symmetry coordinates for the molecule. These surfaces are used to calculate the rovibrationally averaged P-31 shielding. The calculated temperature dependence and the deuterium-induced isotope shift for phosphine are in agreement with experiment. The shapes of the P-31 in PH3 and the N-15 in NH3 shielding surfaces are very similar. With the exception of the inversion coordinate, the remarkable similarity of the surfaces becomes obvious when the shielding functions are scaled by the values of <r-3>np for the ground states of the neutral P and N atoms.