Molecular Vibrations in a Polymethine Dye Layer Studied by Inelastic Electron Tunneling Spectroscopy

Abstract
Inelastic electron tunneling spectroscopy (IETS) at liquid He temperature is used to study the vibrational spectrum of the polymethine dye NH‐rhodanine merocyanine (NH‐RMc). The dye interlayers are prepared by in situ sublimation of the molecules onto the Al2O3layer of (AlAl2O3Pb) tunneling sandwiches. An interpretation of the most prominent vibration bands is given. By comparison with infrared data it is concluded that the dye molecules are arranged in the film with their polymethine chain parallel to the substrate.