AVS 49th International Symposium
    Surface Science Wednesday Sessions
       Session SS-WeM

Paper SS-WeM7
Single Molecular Motion and Reaction Induced by STM Inelastic Tunneling

Wednesday, November 6, 2002, 10:20 am, Room C-112C

Session: New Opportunities and Technique Innovations
Presenter: M. Kawai, RIKEN, Japan
Authors: Y. Sainoo, RIKEN and Tsukuba University, Japan
Y. Kim, RIKEN, Japan
T. Komeda, RIKEN, Japan
M. Kawai, RIKEN, Japan
Correspondent: Click to Email
Inelastically tunneled electrons using STM device enable vibration excitation of individual molecules applicable to vibration spectroscopy, mode selective reaction and so on. Here we present that the selective excitation is ruled reflecting the symmetry of adsorbed molecules and that the vibrationally excited molecules may react along the reaction coordinate through their multiple excitation state. Examples for selective excitation are given for trans-2-butene on Pd(110) surface where methyl groups are lifted towards vacuum and butadiene with flat-laying geometry. The C-H stretching vibration is clearly observed for trans-2-butene and not for butadiene. Symmetry of the adsorbed states for both adsorbates is determined by XAS and HREELS. Motions of isolated cis-2-butene molecule on the Pd(110) surface at 4.7 K between four equivalent positions were induced and monitored with tunneling electrons of scanning tunneling microscope (STM). These motions were consisted with two different flip-flop motions, and clear threshold energy indicated the existence of different potential barriers for the corresponding motions. The strong dependences of these motions rate on the tunneling current support multiple vibrational excitation mechanism via inelastic tunneling process.