Determination of the Dielectric Tensor of Pyrene (C₁₆H₁₀) by Means of Electron Energy Loss Measurements

Electron energy loss spectra from 0 to 40 eV were taken on pyrene single crystals with 60 keV electrons. The energy loss functions Im (−1/ε ii ) ( i = x, y, z ) were derived from spectra recorded with different orientation of the momentum transferred to the crystal by the electrons scattered inelastically. By means of a Kramers‐Kronig transformation the main axis elements ε ii of the dielectric tensor were calculated from Im (−1/ε ii ). The results obtained are interpreted in terms of excited molecular states in relation to the results of optical absorption measurements, theoretical work and other electron energy loss experiments.