1. The observed valence transitions of trans- and cis-hexatrienes have been assigned as the traditional Bmu (B1) N-greater than V1 and the traditional Ag+(A1+) """"""""cis"""""""" valence transitions. 2. The lower Rydberg transitions of trans-hexatriene have been studied in detail. 3p(Ag), 3p(Bg), 3d(Amu), and 3d prime (4s) transitions have been observed. The 3p(Ag)-transition has been shown to be vibronically induced by an a-mu vibration with a fundamental frequency of equal 90 cm-1 in the ground electronic state. 3. The intensities of the two valence transitions observed in each of the cyclic dienes cyclopentadiene, cyclohexadiene, and cycloheptadiene, have been shown to be reciprocally related in each molecule. This relation was shown to be satisfactorily described by exciton interaction theory. From this the second allowed valence transition was deduced to be to the """"""""traditional"""""""" A1+ state.
