Inelastic electron tunneling process for alkanethiol self-assembled monolayers

► Inelastic Electron Tunneling Spectroscopy (IETS) for alkanethiol SAMs are experimentally and theoretically investigated. ► Many vibrational modes are detected in IETS and its peaks are precisely assigned using the technique of isotope labeling. ► IETS active modes accompany a substantial amount of C-C displacement. ► Experimentally observed propensity rules are theoretically interpreted by Fermi's golden rule. ► IETS are quantitatively well reproduced by the calculation based on the density functional theory and nonequilibrium Green's function.