EFFECT OF PRESSURE ON LATTICE MODES AND ELECTRONIC EXCITATIONS OF 9,10-DIIODOANTHRACENE CRYSTALS

We have measured Raman, optical absorption, and fluorescence spectra o f 9, 10-diiodoanthracene (DIA) crystals as a function of hydrostatic p ressure. Unlike analogous anthracene derivatives with similar quasi-on e-dimensional stacking of molecules, the ambient pressure crystal stru cture remains stable up to at least 20 GEPa. Lattice dynamics calculat ions, based on intermolecular potentials, reproduce well the structura l parameters at zero pressure and the pressure dependence of the inter molecular Raman-active phonons. An explanation is given for the unusua l stability of the one-dimensional molecular packing in DIA. (C) 1997 American Institute of Physics.