Raman excitation profile of diphenylamine

Vibrational analyses have been done on the basis of Raman and FTIR spectra of diphenylamine (DPA) and contributions of the two rings to different normal modes of vibration have been discussed. From the analyses of Raman excitation profiles (REPs) of several vibrational modes, useful information about the geometries of the molecule in different excited states have been obtained. Also vibronic coupling has been found to be important in the case of some Raman bands. Besides an interesting Molecular Orbital (MO) calculation, exploring the structure of DPA in the allowed singlet electronic state (L-I(a)), has been presented. Moreover, possible orientations of the two rings with respect to the amine nitrogen atom in the ground and in the L-I(a) states have been discussed. (C) 2002 Published by Elsevier Science B.V.