Generalized ellipsometry and dielectric tensor of rubrene single crystals

The optical spectra of rubrene single crystals are reported and compared with those of the molecule in solution. From generalized ellipsometry and a proper biaxial model, the complex dielectric tensor is deduced in the spectral region of the excitonic transitions of the crystal between 2.2 eV band 4.4 eV, where the optical bands are assigned and rationalized on the basis of the molecular and crystal symmetries.