Fluorescence Spectra of Naphthacene Molecules in Solid Solution of Anthracene with the Variation of Wave-lengths

Abstract

IN the crystalline state, pure naphthacene scarcely fluoresces, but it fluoresces with characteristic yellow-green light when mixed with anthracene or chrysene. Anthracene containing traces of naphthacene is quite suitable for studying the fluorescence of the latter. By exciting such a crystal by light of various wavelengths, we have obtained the following results. (1) The positions and the number of the fluorescence bands of naphthacene remain unchanged with the change of wave-length of the exciting radiation. (2) Naphthacene fluoresces so long as the exciting radiation is not of longer wave-length than the longest wave absorption band of naphthacene. Solid anthracene has an absorption band lying at wavelengths shorter than 400 mμ and fluorescence bands at 403, 422, 438, 445 mμ. Solid naphthacene has absorption bands at 425, 453, 485 mμ. In solid solution of anthracene, there is a red shift of these bands, and in the above crystal we find the absorption bands of naphthacene at 435, 460, 491 mμ. The fluorescence bands of naphthacene are at 498, 533, 574 mμ. They are due to naphthacene, for pure anthracene has no fluorescence bands in this region.