Dissociation pathways of a single dimethyl disulfide on Cu(111): reaction induced by simultaneous excitation of two vibrational modes.
We present a novel reaction mechanism for a single adsorbed molecule that proceeds via simultaneous excitation of two different vibrational modes excited by inelastic tunneling electrons from a scanning tunneling microscope. Specifically, we analyze the dissociation of a single dimethyl disulfide (DMDS, (CH3S)2) molecule on Cu(111) by using a versatile theoretical method, which permits us to simulate reaction rates as a function of sample bias voltage. The reaction is induced by the excitation of C-H stretch and S-S stretch modes by a two-electron process at low positive bias voltages. However, at increased voltages, the dissociation becomes a single-electron process that excites a combination mode of these stretches, where excitation of the C-H stretch is the energy source and excitation of the S-S stretch mode enhances the anharmonic coupling rate. A much smaller dissociation yield (few orders of magnitude) at negative bias voltages is understood in terms of the projected density of states of a single DMDS on Cu(111), which reflects resonant excitation through the molecular orbitals.
Catalysis Research Center, Hokkaido University, Sapporo 001-0021, Japan.
Kenta
K
Motobayashi
Surface and Interface Science Laboratory, RIKEN, Wako 351-0198, Japan.
Yousoo
Y
Kim
International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba 305-0044, Japan.
Ryuichi
R
Arafune
Department of Advanced Materials Science, The University of Tokyo, Kashiwa 277-8561, Japan.
Michiaki
M
Ohara
Department of Advanced Materials Science, The University of Tokyo, Kashiwa 277-8561, Japan.
Hiromu
H
Ueba
Department of Advanced Materials Science, The University of Tokyo, Kashiwa 277-8561, Japan.
Maki
M
Kawai