The experimental phosphorus 2p spectrum of PF3 shows vibrational structure corresponding to the symmetric phosphorus-fluorine stretching mode, with a fundamental frequency of 121.7 meV. In addition, the spectrum shows that the 2p(3/2) peak is a doublet split by 146 meV. This molecular-field splitting arises because the anisotropic molecular environment lifts the threefold degeneracy of the 2p orbitals. The observed vibrational structure is compared with that predicted by theory, either treating the core hole explicitly or using the equivalent-cores approximation to simulate the effects of the core hole. Ab initio calculations of the molecular-field splitting that include core-valence electron correlation predict a value in good agreement with the experimental value.