The equilibrium geometries, vibrational frequencies, and infrared and Raman intensities for P4O6 and P4O10 were calculated using the Hartree-Fock self-consistent-field method. The computed geometries are in good agreement with experimental measurements. Scaling the nb initio vibrational frequencies of P4O10 to account for anharmonicity and neglect of electron correlation yields values that agree with experimentally observed transitions, confirming the previous assignment of the spectrum. The energy ordering of the computed vibrational levels for P4O6 differs, in part, from assignments based on experimental data. A new assignment that is in agreement with both the computations and the experiments is suggested; this requires the reassignment of four of the fundamental vibrations. The infrared emission spectrum produced by burning red phosphorus in air was recorded and the observed peaks assigned to P4O10 transitions. The experimental relative intensities of the fundamental vibrations agree well with the computed relative intensities.