DYNAMICS OF THE STABLE RADICAL DI-TERT-BUTYL NITROXIDE ON AN EPITAXIALLY GROWN AL2O3 FILM

The molecular dynamics of one monolayer adsorption species of di-tert- butyl nitroxide (DTBN) adsorbed on a thin film of gamma-Al2O3(111) gro wn on a NiAl(110) single crystal has been studied via ESR line-shape a nalysis. Below 200 K a rigid limit spectrum is found, above this tempe rature the changes in line shape are consistent with slow motions of t he molecule. Best agreement between the experimental spectra and simul ations is obtained using a ''moderate jump'' model with both Brownian diffusion and jump type contributions to the molecular dynamics. The m otional processes have an activation energy of about 9 kJ/mol.