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Physical State Influences on the Intensity of Infrared Absorption Bands

Volume 17, Number 2 (March 1963) Page 47-50

Sharpless, Norman E.; Gregory, Dolores A.

Using chloranil as a model, the intensities of various bands in the infrared spectrum have been investigated as functions of the particle size of the crystals. As the particles become larger, the values of molar absorptivity appear to approach the value found for a single crystal As the particle size approaches zero, the values increase. The molar absorptivities in solution are higher than those observed for the smallest particles investigated, and the plots of molar absorptivity as function of size may be extrapolated to the solution values as possible limits. It appears that there is no orientation of particles in the pellets, while x-ray diffraction data indicate no changes in crystal structure but do show some evidence of the formation of a solid solution. The frequencies of the various bands are independent of the sizes of the particles.