Infrared intensities of lattice vibrations in molecular crystals

T. Luty, R. W. Munn

    Research output: Contribution to journalArticlepeer-review

    Abstract

    From the dynamic multipoles model an expression is derived for the dipole moment derivative governing the intensity of infrared absorption by lattice modes in molecular crystals. The result depends on non-local susceptibilities which take proper account of the local electric field in a way consistent with dielectric theory. It is shown that the non-local rsponse follows naturally from microscopic lattice dynamical theory. It arises from dipolar coupling and is intimately connected with the delocalized exciton states produced by the same mechanism. Intensities calculated for the iodine crystal are inproved by including the local field, but a point quadrupole field proves too anisotropic to yield the measured intensity ratio. The treatment shows that infrared intensities can be used to obtain unique effective molecular polarizabilities.

    Original languageEnglish
    Pages (from-to)295-302
    Number of pages8
    JournalChemical Physics
    Volume43
    Issue number3
    DOIs
    Publication statusPublished - 1 Nov 1979

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