Bulk diffusion coefficients were determined, for Ti in monocrystalline MgO (100), by using 4 types of sample: Ti evaporated onto MgO, or Ti evaporated onto MgO, and pre-bombarded with 7keV Cl+, Ar+ or Cr+. Diffusion was produced by annealing at up to 1000C, following evaporation or pre-bombardment. Diffusion profiles were measured by using secondary ion mass spectrometry depth-profiling techniques. A model which included a depth-dependent bulk diffusion coefficient was used to analyse bombardment-enhanced diffusion. The bulk diffusion coefficients were of the order of 10-20m2/s, and were enhanced due to defects which were introduced by ion pre-bombardment. Differing bombardment-enhanced diffusion effects were observed for the samples which had been pre-bombarded with Cl+, Ar+ and Cr+; in spite of their very similar ballistic parameters. The diffusion model was extended so as to include the effects of lattice deformation, maintenance of electrical neutrality and chemical effects such as volatile compound formation. The extended model satisfactorily explained the bombardment-enhanced diffusion differences which were observed for Cl+, Ar+ and Cr+ implantation. The results showed that bombardment-enhanced diffusion was markedly Bulk diffusion coefficients were determined, for Ti in monocrystalline MgO (100), by using 4 types of sample: Ti evaporated onto MgO, or Ti evaporated onto MgO, and pre-bombarded with 7keV Cl+, Ar+ or Cr+. Diffusion was produced by annealing at up to 1000C, following evaporation or pre-bombardment. Diffusion profiles were measured by using secondary ion mass spectrometry depth-profiling techniques. A model which included a depth-dependent bulk diffusion coefficient was used to analyse bombardment-enhanced diffusion. The bulk diffusion coefficients were of the order of 10-20m2/s, and were enhanced due to defects which were introduced by ion pre-bombardment. Differing bombardment-enhanced diffusion effects were observed for the samples which had been pre-bombarded with Cl+, Ar+ and Cr+; in spite of their very similar ballistic parameters. The diffusion model was extended so as to include the effects of lattice deformation, maintenance of electrical neutrality and chemical effects such as volatile compound formation. The extended model satisfactorily explained the bombardment-enhanced diffusion differences which were observed for Cl+, Ar+ and Cr+ implantation. The results showed that bombardment-enhanced diffusion was markedly