The absorption and. emission spectroscopic behaviour of the platinum complexed porphyrin PtOEP (platinum-octaethyl-porphyrin) is studied at room temperature. Liquid solutions, doped films, and a neat film are investigated. The absorption cross-section spectra including singlet-triplet absorption, the triplet-singlet stimulated emission cross-section spectra, the phosphorescence quantum distributions, the phosphorescence quantum yields, and the phosphorescence signal decays are determined. In the neat film a red-shifted phosphorescent excimer emission is observed. In diluted solid solution (polystyrene and dicarbazole-biphenyl films) as well as in de-aerated liquid solutions (tetrahydrofuran, toluene, chloroform) high phosphorescence quantum yields are obtained. In air-saturated liquid solutions, the phosphorescence efficiency :is reduced by oxygen quenching. At intense short-pulse laser excitation the phosphorescence lifetime is shortened by triplet-triplet annihilation. No amplification of spontaneous emission was observed. (c) 2006 Elsevier B.V. All rights reserved.