On the Structure and Interpretation of the Infrared Absorption Spectra of Crystals

An experimental and theoretical investigation of the absorption spectrum of MgO in the near infrared is reported. Part A is devoted to the experimental results, which were obtained by use of a rocksalt spectrometer. They show that the fundamental absorption is accompanied by a great deal of secondary structure. In Part B an interpretation of the results of A is undertaken on the basis of a quantum-mechanical treatment of anharmonic potential forces. On this basis, it is shown that a cubic crystal of the MgO type should not possess but a single near infrared absorption as previous calculations had indicated, but should possess an extremely complicated secondary structure. In Part C the possibilities of obtaining a quantitative correlation between experiment and theory are discussed and it is concluded that the former must be made the object of additional refinements.