Role of Molecular Orbitals Near the Fermi Level in the Excitation of Vibrational Modes of a Single Molecule at a Scanning Tunneling Microscope Junction

Abstract

Inelastically tunneled electrons from the tip of a scanning tunneling microscope were used to induce S-S bond dissociation of a (CH(3)S)(2) and lateral hopping of a CH(3)S on Cu(111) at 4.7 K. Both experimental results and theoretical calculations confirm that the excitation mechanism of the vibrationally induced chemistry reflects the projected density of states of molecular orbitals that appear near the Fermi level as a result of the rehybridization of the orbitals between the adsorbed molecules and the substrate metal atoms.

Role of molecular electronic structure in inelastic electron tunneling spectroscopy:O2on Ag(110)

“…5 The characterization and control of single-molecule reactivity through the excitation of a specific vibrational mode is a challenging area for the STM-based IETS technique. 6,7 Within this context, the interaction of O 2 with metals, which plays a central role in many technological processes, has served as a model system to explore and control the fundamentals of gas/surface reactivity.…”

Lateral Hopping of CO on Ag(110) by Multiple Overtone Excitation

“…The orientation change of cis-2-butene on Pd(110) [4,7] is a multiple-mode excitation, where the excitations of the following four vibrational modes can independently contribute to the change of adsorption configuration among equivalent molecular orientations: metal-carbon stretching vðM-CÞ and C-C stretching vðC-CÞ, modes for low-barrier motion, and bending modes in CH 3 , δðCH 3 Þ, and vðC-HÞ for high-barrier motion. S-S bond dissociation in dimethyl disulfide ðCH 3 SÞ 2 on Cu(111) [21] provides a combination-mode excitation action spectrum, in which the threshold bias voltage corresponding to the excitation of the combined vðC-HÞ and S-S stretching vðS-SÞ modes was observed in addition to vðC-HÞ excitation. The single-overtone-mode excitation STM-AS has been reported for the desorption of NH 3 on Cu(100) [12], in which the excitation of the first overtone of the N-H 3 umbrella mode overcame the desorption barrier, and was clarified as a single-electron process.…”

“…To date, the reported action spectra can be classified into four types according to their spectral shapes: single-mode excitation [8][9][10][11][12][13][14], multiple-mode excitation [4,[15][16][17][18][19][20][21], combination-mode excitation [19,21,22], and single-overtonemodeexcitation [12], as shownin Figs. 1(a)-1(d), respectively.…”

Principles and Techniques

“…This resonant tunneling model was experimentally examined by Kawai and her co-workers at RIKEN, Japan. They showed that the vibrational excitation depends on the spatial distribution of the molecular orbitals formed near the Fermi level of metal [27,28].…”