  The double-resonance (DR) Raman process is a signature of all sp2 carbon
material and provide fundamental information of the electronic structure and
phonon dispersion in graphene, carbon nanotubes and different graphite-type
materials. We have performed in this work the study of different DR Raman bands
of rhombohedral graphite using five different excitation laser energies and
obtained the dispersion of the different DR features by changing the laser
energy. Results are compared with those of Bernal graphite and shows that
rhombohedral graphite exhibit a richer DR Raman spectrum. For example, the 2D
band of rhombohedral graphite is broader and composed by several maxima that
exhibit different dispersive behavior. The occurrence of more DR conditions in
rhombohedral graphite is ascribed to the fact that the volume of its Brillouin
zone (BZ) is twice the volume of the Bernal BZ, allowing thus more channels for
the resonance condition. The spectra of the intervalley TO-LA band of
rhombohedral graphite, around 2450 cm-1, is also broader and richer in features
compared to that of Bernal graphite. Results and analysis of the spectral
region 1700-1850 cm-1, where different intravalley processes involving acoustic
and optical phonons occurs, are also presented.
