POLARIZATION-DEPENDENT OPTICAL-PROPERTIES OF C-70

It is shown that the optical absorption spectrum of C70 has strong polarization dependence depending on whether light is polarized along the long axis or the short axis of the molecule. The polarization dependence is studied with a simple tight-binding model for the electronic structure and from group theory. It is found that the absorption threshold is significantly higher (by about 0.3 eV) for light polarized along the long axis compared to the same for the short axis. This effect may be useful in studying the orientation of the molecules in solid C70 by means of optical experiments. Also presented are analytical wavefunctions for the lowest unoccupied molecular orbitals which form the conduction band states in solid C70.