Dissociation of disulfides on metal surface by tunneling electrons

COLL 270

Michiaki Ohara, Yousoo Kim, and Maki Kawai. Surface Chemistry Laboratory, RIKEN (The Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan
Electrons tunneling from the tip of a scanning tunneling microscope (STM) to individual dimethyl disulfide ((CH3S)2)on Cu(111) surface can cause the dissociation of S-S bond in the molecule, resulting that two methyl thiolate (CH3S) are produced from a (CH3S)2. This phenomenon shows a clear threshold in the bias voltage, and the threshold voltage (~ 360 mV) corresponds to the excitation energy of C-H symmetric stretching mode in (CH3S)2. We consider that the vibrational excitation of C-H stretching mode by inelastically tunneled electron is responsible for the dissociation.