Chemical imaging of single 4,7,12,15-tetrakis[2.2]paracyclophane by spatially resolved vibrational spectroscopy

Single 4,7,12,15-tetrakis[2.2]paracyclophane were deposited on NiAl(110) surface at 11 K. Two adsorbed species with large and small conductivities were detected by the scanning tunneling microscope (STM). Their vibrational properties were investigated by inelastic electron tunneling spectroscopy (IETS) with the STM. Five vibrational modes were observed for the species with the larger conductivity. The spatially resolved vibrational images for the modes show striking differences, depending on the coupling of the vibrations localized on different functional groups within the molecule to the electronic states of the molecule. The vibrational modes are assigned on the basis of ab initio calculations. No IETS signal is resolved from the species with the small conductivity.