Electron Energy Loss of Terrylene Deposited on Au(111): Vibrational and Electronic Spectroscopy

We have investigated the vibrational and electronic properties of terrylene by high-resolution electron energy-loss spectroscopy (HREELS), Fourier-transform infrared spectroscopy, and low-temperature single-molecule fluorescence spectroscopy. Terrylene thin films were sublimated in an ultrahigh vacuum on the Au(111) surface in order to record the HREEL spectra. Polycrystalline p-dichlorobenzene was used as a matrix to isolate a single terrylene molecule at 1.5 K and record its fluorescence spectrum. The infrared spectrum, the vibrational components from the fluorescence spectrum, and density functional theory calculations were used for the assignment and identification of the active modes found in HREELS. Finally, we report a loss signal around 17 000 cm(-1) (2.1 eV) for the first singlet electronic excited state in agreement with optical spectroscopy. The HREEL spectra show both IR- and Raman-active vibration modes because of specific surface selection rules. Energy-loss spectroscopy could be used as a complementary technique to explore some other degrees of freedom that are not accessible by optical means.