The UV-photolysis kinetics of matrix-isolated species are discussed with respect to LIF measurements. The consideration is based on the concept of spectral overlap between light emitters and absorbers occurring during photolysis, and it develops further the model of self-limited photolysis proposed previously. We emphasise that these effects can strongly change the emission spectra and that evolution of the LIF signal during UV photolysis and annealing should be used with great caution in quantitative analysis of photochemical processes. On the other hand, the spectral overlap of narrow absorption bands with broad emission offers a spectroscopic approach to detecting the rising absorbers.