Electron-phonon coupling in crystalline Pentacene films

The electron-phonon(e-p) interaction in Pentacene (Pn) films grown on Bi(001) was investigated using photoemission spectroscopy. The spectra reveal thermal broadening from which we determine an e-p mass enhancement factor of lambda = 0.36 +/- 0.05 and an effective Einstein energy of omega_E = 11 +/- 4 meV. From omega_E it is inferred that dominant contributions to the e-p effects observed in ARPES come from intermolecular vibrations. Based on the experimental data for lambda we extract an effective Peierls coupling value of g_eff = 0.55. The e-p coupling narrows the HOMO band width by 15 +/- 8% between 75K and 300K.