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To further our investigations on the electronic states of heavily doped mixed $crystals1$, we have calculated the optical spectra of isotopically mixed crystals of naphthalene, using the recently acquired dispersion $relation.2$ In addition to some calculations using direct diagonalization of a $320 \times 320$ matrix, a new method, which is a hybrid of NFC (negative factor counting method)$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ and CPA (coherent potential approximation) has been devised. This method relates the optical spectra directly to the over-all density-of-states function of the mixed crystal. Results indicate that cluster absorptions, which are absent from CPA results, are retrieved here. There is a good correlation between experimental and calculated spectral structures. This theory of optical spectra of disordered systems is of particular interest to the spectroscopist because it gives special consideration to the $K=0$ component of the density-of-states function at the expense of self-consistency. Further theoretical justification of this approach is being investigated, as well as relationships with other methods, such as the moment method.