Knowledge Bank

A spectroscopic study of naphthalene was made with the intention of making a vibrational analysis. Polarized spectra of single crystals were taken, and they suggest that infrared dichroic effects in some molecular crystals may be interpreted by an oriented-gas'' model. This model does not agree in all details with the predictions of the space group analysis, e.g., it fails to predict splitting due to space group coupling. Evidence that this splitting is present but unresolved in the infrared spectrum of solid naphthalene has been obtained. Supporting experiments were preformed which bear on the interpretation of the polarized spectra. Optical studies of naphthalene were conducted to verify the absence of significant elliptical polarization for the crystal orientations studied. Mixed crystals of naphthalene in anthracene were studied in an attempt to provide additional evidence on the utility of the oriented-gas'' model. Very dilute mixed crystals offer opportunity to study the spectral changes which occur when a molecule is placed within a crystal potential field but not adjacent to identical molecular systems. The dichroism observed for the absorption of naphthalene at $779cm-1$ in dilute mixed crystals in anthracene will be described.