Optical properties of interstellar medium

The spectra of normalized extinction of electromagnetic radiation by the interstellar medium have been analyzed in terms of a model representing the total extinction as a sum of three absorption coefficients. The first coefficient is related to optical transitions of the π-π* type and the second is related to those of the σ-σ* type in amorphous carbon. The third term represents two absorption features occurring in the region of the π-π* type transitions in the amorphous phase, which are satisfactorily described by the Gaussian contours peaked at 3.2 eV (385.6 nm) and 5.67 eV (217.5 nm). These contours are compared to published data on the absorption spectra of a copolymer composed of alternating triphenylamine and fluorene molecules. The results of this analysis confirm the hypothesis concerning the most probable chemical composition and physical state of particles of the interstellar medium.