Multiple-scattering theory of intensities in inelastic-electron-tunneling spectroscopy

A short-range multiple-scattering theory of the observed intensities in inelastic-electron-tunneling spectroscopy (IETS) is developed and compared with previous long-range theories. The scattering molecular potential is calculated using the $X\alpha$ approximation to the exchange-correlation potential and the Bardeen transfer-Hamiltonian approach is taken to calculate inelastic-tunneling cross sections. Predicted short-range cross sections are strongly energy dependent and could be quite large for tunneling electrons at a molecular bound-state energy. However, comparison of the predictions of the two theories for higher-harmonic amplitudes and opposite-bias-voltage asymmetries indicates that the long-range interactions dominate in IETS.