The vibration spectra of crystals

Summary

The eigenfrequeneies of lithium and sodium fluorides have been theoretically evaluated and their observed spectroscopic behaviour is found to be in accord with the results. The greater disparity in the atomie weights of metal and halogen in the case of lithium fluoride than in sodium fluoride leads to some interesting differences in behaviour between the two substances. In both cases, however, the frequeney of maximum absorption doesnot correspond with the oscillation of the metal and halogen atoms against each other, but agrees with that of the oscillations in which only the fluorine atoms move, the metal atoms remaining at rest.