Origin of the D peak in the Raman spectrum of microcrystalline graphite

We have studied the D peak in the Raman spectrum of polycrystalline graphite as a function of excitation energy in the range from 1.16 to 4.3 eV. The D peak disperses with excitation energy (approximate to 50 cm(-1)/eV and its intensity decreases with increasing laser energy. The dispersion of the D peak is explained in terms of a novel (k) over right arrow-selective resonant Raman scattering process. The scattering cross-section is resonantly enhanced for phonons on one branch in the phonon dispersion curves which have the same (k) over right arrow-vector as the electronic transition responsible for the resonance. (C) 1998 Elsevier Science B.V. All rights reserved.