STRUCTURE VIBRATIONNELLE DES SPECTRES D'ABSORPTION DANS L'ULTRAVIOLET DE QUELQUES DÉRIVÉS HALOGÉNÉS DU BENZÈNE

Abstract

Ultraviolet absorption spectra have been recorded, at low temperatures, for pure crystals of the following compounds: hexachlorobenzene, o, m, and p-dichlorobenzenes, o, m, and p-dibromobenzenes, 1,2,3-trichlorobenzene, and 1,2,4,5-tetrachlorobenzene. In all cases, the first electronic transition corresponding to the 1B2u−1A1g transition of benzene has been studied. For six of these compounds the spectra were sufficiently well resolved to permit complete analyses of the vibrational fine structure of the electronic bands. The results indicate that only totally symmetrical vibrations appear in conjunction with the observed electronic transitions. Several changes in published vibrational assignments are proposed, in the light of present results.