Abstract Submitted to the    NANOTUBE'04 Conference:

The interior of carbon nanotubes was studied using multi-frequency Raman spectroscopy. Peapod structures transformed to double wall carbon nanotubes (DWCNT) were proven to be highly perfect reflecting the catalyst free growth conditions in the nano-clean room environment of the interior of the outer tube. The transformation was followed with a systematical thermal annealing to yield information about the inner tube growth mechanism. The (n,m) indexing of small diameter inner tubes was successfully applied to refine and extend the semi-empirical models of the radial breathing vibrational mode. The identification also allowed to track diameter selectively a range of phenomena such as nanotube closing after annealing, oxidation damage to the inner and outer tubes and many more. This demonstrates that filling with peapod and their subsequent transformation to DWCNT provides an important monitoring tool for nanotube handling procedures such as nanotube separation. DWCNT transforma tion from different carbon sources such as C₆₀, C₇₀ peapod fullerenes yield similar inner tube distribution that evidence that the fullerene behaves only as a carbon source and its geometry does not play a role in the inner tube formation. The absence of a few, mid-diameter inner tubes is discussed as an intermediate bottle-neck configuration where C₇₀ peapods can not be formed. The range of available spectroscopic methods has been extended to electron spin resonance with the encapsulation of the paramagnetic N@C₆₀ inside nanotubes. N@C₆₀ is temperature sensitive and its encapsulation in SWCNT requires a low temperature method that is described in detail. Work supported by the Marie-Curie Intra European Fellowship, MEIF-CT-2003-501099 and the FWF project No. P14893.