Raman modes of metallic carbon nanotubes

The anomalous resonant behavior of the tangential Raman modes of carbon nan otubes has been studied in the critical region of laser energies 1.7-2.2 eV . The special enhancement of the Raman modes is explained by a model that t akes into account the transition between the singularities in the one-dimen sional density of electronic states for the metallic nanotubes and the dist ribution of diameters in the sample. The results agree with direct measurem ents of the electronic density of states for the metallic nanotubes and est ablish their association with the specially enhanced high frequency, first- order Raman modes. [S0163-1829(98)50848-X].