The Raman D-band feature (similar to1350 cm(-1)) is examined with 2.54 eV excitation for pure bulk carbon single-wall nanotube samples before and after treatments that increase defect densities. Upon employing mass-transport-limited oxidation to introduce defects, the D-band intensity increases approximately linearly with reaction time. A relatively constant ratio of the D-band intensity and the major tangential G-band intensity (D/G) is observed for the purified samples examined at 2.54 and 1.96 eV suggesting a characteristic number of defects is introduced for given synthesis and purification processes. The D/G ratio is similar to1/190 and 1/40 for excitation at 2.54 and 1.96 eV, respectively. (C) 2004 Elsevier B.V. All rights reserved.