Research and Development, Hoge Wei 33 B, B-1930 Zaventem, Belgium Ultraviolet photon absorption has been used to heat single-and double-wall carbon nanotubes and peapods in vacuum. By increasing the laser intensity up to 500 mW, a downshift and a broadening of the optical phonons are observed corresponding to a temperature of 1000°C. The UV Raman measurements are free of blackbody radiation. We find that the linewidth changes for the G + and G − bands differ considerably in single-wall carbon nanotubes. This gives evidence that the phonon decay process is different in axial and radial tube directions. We observe the same intrinsic linewidths of graphite ͑highly oriented pyrolytic graphite͒ for the G band in single-and double-wall carbon nanotubes. With increasing temperature, the interaction between the walls is modified for double-wall carbon nanotubes. Ultraviolet photon induced transformations of peapods are found to be different on silica and diamond substrates.

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Results of UV irradiation experiments in vacuum on SWNTs and peapods, as followed by in-situ Raman spectroscopy with increasing laser power up to 300 mW are reported. UV micro-Raman measurements were used to record spectra free of black-body radiation. Photon absorption was found to induce both the shifting and broadening of the G + and G -bands. The local temperature increase (up to a temperature gain of ∼ 1000 K) was able to be reliably calculated from the band feature variation, more specifically considering the G + band. Meanwhile, a specific sensitivity to oxidation of the nanotubes from peapods was revealed, due the fullerene-catalysed dissociation of molecular oxygen traces into active species. In addition, both silica and diamond substrates were used. The different thermal conductivity of the substrates has the effect of changing the laser power levels needed to induce structural transformations. Carrying-out UV irradiation of nanotube-based material while monitoring the induced temperature via in situ Raman spectroscopy therefore appears as a new tool likely to be useful for the nano-engineering of nanotube-based devices.