Electron-phonon interactions in poly(para-phenylene) oligomers

The influence of molecular vibrations on the low-lying electronic levels of short oligomers of poly(para-phenylene) is studied. Within an interacting molecular orbital basis, the complete electron-phonon Hamiltonian is diagon alized numerically. Energy shifts and equilibrium phonon displacements are calculated for the totally symmetric vibrational modes. For the 1 (1)A(g)()-1 B-1(u)- transition, Huang-Rhys and Franck-Condon factors, as well as th e change of equilibrium geometry, are computed. The importance of vibration s with a frequency of about 0.2 eV is confirmed. The intrinsic Stokes shift is found to be zero, in agreement with experimental data. (C) 1999 America n Institute of Physics. [S0021-9606(99)50348-6].