Theory of intensities in inelastic-electron tunneling spectroscopy orientation of adsorbed molecules

A dipole-potential, transfer Hamiltonian theory of intensities is applied to the tunneling spectrum of CH₃SO₃^- chemisorbed on alumina. In a previous study of the vibrational energies of this molecule. Hall and Hansma proposed that it absorbed on alumina with the C-S bond oriented normal to the surface. Comparison of the predictions of the present theory with experiment supports this orientation. Dipole derivatives generated from tunneling intensities compare well with those obtained from infrared measurements for similar species.