DMITRY STRELNIKOV AND WOLFGANG KRÄTSCHMER, Max-Planck-Institut für Kernphysik, D-69029 Heidelberg, PO Box 103980, Germany.
Along with matrix gas, we co-deposited carbon vapor from two separated carbon evaporation sources, namely a 12C-source and a 13C-source. Under the applied conditions the C3 molecules are the most abundant species in both carbon sources. We observed that in the formation process of long carbon chains the C3 units play a major role. This finding was used to establish a new species identification method based on isotopic replacement. The old technique of atomic 13C 12C substitution can be reasonably applied only for molecules with a small number of carbon atoms (n\lesssim9). Using the new method of molecular 13C3 12C3 substitution, quite simple distributions having small number of isotopomeric IR absorptions were obtained also for larger species. We present data for Cn and CnO1,2 (n\gtrsim6).