The present paper deals with compounds called photosensitizers, namely, psoralen, 3,4-phenyl-4',5'-
cyclohexylpsoralen, 4'-methyl-3,4-cycloheptyl psoralen, 4',5'-dimethyl-3,4-cyclohexyl psoralen (fig. 1). The
absorption spectra from excited triplets states were investigated. The computed triplet-triplet absorption spectra of
research compounds have been determined using INDO method. The experimental triplet-triplet absorption spectra
have been obtained using the technique of laser flash photolysis in ethanol. The compare of computed and experimental
data is shows that the computed second band wavelenght throughout agree very well (0,5-6 nm) with experimental data.