Photo-excitation processes were investigated in chlorophyll solutions by irradiation with UV light sources. Photo-excited bulk effects during the bleaching experiments were diagnosed. The optical diagnostic was expressed by a Beer-Lambert matrix formulation and applied to the experimental results. The chromophores evaluated optical cross-section was 10(-15) cm(2) and the optical absorption coefficient dynamic variation was fitted to a simple reaction rate model. The bleaching rates were expressed by this model and fitted to the experimental data, (c) 2005 Elsevier B.V. All rights reserved.