[en] For IETS from molecules adsorbed on both the alumina and magnesia barriers large differences in the relative inelastic tunneling intensities are observed for different substituted groups on the rings. These differences can be related to changes in the surface adsorption mechanisms due to changes in the electronic structure of the molecule and fall into two main categories. For substituents that act as strong acids with proton donation to the surface intensities of ring modes are very strong and the spectra are characteristic of the free molecule except for specific modifications due to the adsorbed side group. For compounds without acid groups the ring mode intensities are strongly depressed and the basic behavior suggests a π-complex formation with the surface active sites. This reaction is always accompanied by a softening of the aromatic C-H stretching mode corresponding to a frequency downshift of approx. 150 cm^-1. Asymmetries in both the elastic and inelastic tunneling components have been studied on both MgO/sub x/ and A10/sub x/. The elastic asymmetries and nonlinear current behavior have been fitted with a computer calculated model and the results reflect large differences in the effective barrier height and shape for different dopants. The asymmetries in inelastic intensities have been analyzed in terms of the range of the molecular potential and indicate the long range potential as dominant for most dopants. Modification of IETS spectra due to substrate cooling have been studied and large changes are observed for certain types of molecules. The temperature modifications are a function of the molecular configuration on the surface and also involve changes in the active site structure on the oxide surface