Franck–Condon spectra and electron-libration coupling in para-polyphenyls

摘要: Proceeding from quantum-chemical potential energy surfaces, we compute the absorption and fluorescence spectra of conventional ladder-type para-phenylene oligomers (OPP OLPP) with up to 7 benzene rings. Electronically excited states are addressed by means extended configuration interaction within a standard molecular all-valence-electron semiempirical Hamiltonian. Adiabatic excitation energies, interstate distortions normal modes used Franck–Condon band shapes rigorous consideration vibrational structure. Theoretical agree experiment rationalize striking disparities in linear optical response OPP OLPP. Whereas electron–phonon coupling OLPP is essentially restricted carbon–carbon bond-stretching modes, photoexcitation, emission processes followed significant relaxations ring-torsional degrees freedom. The broadening OPP, especially pronounced absorption, large Stokes shift be...