Electronic States of Heavily Doped Molecular Crystals—Naphthalene. II. Experimental

Abstract

The energy states and optical spectra of heavily doped mixed crystals are investigated. Studies are made for the following binary systems: (1) naphthalene-h8 and -d8, (2) naphthalene-h8 and -ad1, and (3) naphthalene-h8 and -bd1 , corresponding to strong, medium, and weak perturbations, respectively. In addition to ordinary absorption spectra at 4°K, band-to-band transitions at both 4 and 77°K are also analyzed with emphasis on their relations to cooperative excitation and over-all density-of-states functions for mixed crystals. It is found that the theoretical calculations presented in a previous paper agree generally with experiments except for cluster states observed in system (1) at lower guest concentrations. These features are discussed semiquantitatively. As to the intermolecular interaction parameters, it is found that experimental results compare favorably with calculations based on experimental density-of-states functions but not with those based on octopole interactions or charge-transfer interactions. Previous experimental results of Sheka and the theoretical model of Broude and Rashba are also compared with present investigations.