Helium was implanted into Cz <111> p-type silicon wafers at 40 keV for various doses between 1 x 10(16) He+ cm(-2) and 1 x 10(17) He+ cm(-2). Furnace Anneals were subsequently applied at temperatures ranging from 650 degreesC up to 1000 degreesC. The optical models for the as-implanted samples are based on the coupled half-Gaussian model developed by Fried et al. As point defects and cavities coexist in the as-implanted sample, the original model combining two half-Gaussian profiles was modified. Both the distributions of point defects and cavities were described by Gaussian profiles in the new model, each of them using two coupled half-Gaussians. The optical model allows the overlapping of the profiles of defects and cavities. A fitting procedure, called 'multiple random search', was applied to minimize the probability of getting in a local minimum. Using this new model, the measured spectra were well fitted, while there was no acceptable fit possible with conventional models. The annealed samples could be well described by cavity profiles only. Different models were investigated including Gaussian profiles or profiles with arbitrary distributions using independent volume fractions of cavities in the! sub-layers. The results were crosschecked by transmission electron microscopy micrographs, showing a good agreement. (C) 2004 Elsevier B.V. All rights reserved.