Momentum dependence of the excitons in pentacene
  We have carried out electron energy-loss investigations of the lowest singlet excitons in pentacene at 20 K. Our studies allow to determine the full exciton band structure in the a*,b* reciprocal lattice plane. The lowest singlet exciton can move coherently within this plane, and the resulting exciton dispersion is highly anisotropic. The analysis of the energetically following (satellite) features indicates a strong admixture of charge transfer excitations to the exciton wave function. 
Friedrich Roth, Roman Schuster, Andreas K\"onig, Martin Knupfer,   Helmuth Berger
cond-mat.mtrl-sci