Calculation of the inelastic scanning tunneling image of acetylene on Cu(100)

A Green function linear combination of atomic orbitals technique is used to theoretically calculate the "inelastic" scanning tunneling microscope imag e of a C2H2 molecule adsorbed on Cu(100) and explain previous experimental results. Our analysis of the inelastic scattering process in terms of the o rbitals shows that a destructive interference occurs in the inelastic scatt ering by the C-H bending modes. This results in a much smaller inelastic fr action due to the bending modes as compared to the stretching ones, and exp lains why the former cannot be observed experimentally.