Vibrations of Tetrahedral Pentatomic Molecules Part III. Comparison with Experimental Data. Part IV. Isotopic Shifts

Part III. Various specific assumptions as to intramolecular forces are discussed from the point of view of the general theory and are compared with experimental data. C${\mathrm{H}}_4$ is found to be the only molecule even approximately to obey valence forces. For some other molecules satisfactory results are obtained by postulating an additional repulsive force inversely proportional to some power of the distance between the corner atoms.