Dispersion of electron-hole excitations in pentacene along (1Â 0Â 0)

The dispersion of the lowest lying singlet electron-hole excitation of pentacene along the reciprocal lattice vector (1 0 0) has been studied using electron energy-loss spectroscopy. This exciton shows a clear dispersion along the direction with a band width of about 100 meV. Moreover, the translational symmetry indicated by the exciton band structure does not agree with that reported from diffraction studies. This might be related to the interaction responsible for the dispersion which is of next nearest neighbor type only.