AN FT-ICR STUDY ON LASER ABLATION OF GRAPHITE AND CARBON BLACK TARGETS: COSMOCHEMICAL IMPLICATIONS

Graphite and carbon black samples were laser ablated in an FT-ICR (Fourier transform-ion cyclotron resonance spectrometer) by Nd-YAG laser under high vacuum in conditions recalling those existing in the interstellar medium. It is shown that graphite gives a regular sequence of polyyne and cyclopolyyne chains from C10 to C27 and additionally produces 2% of C60 fullerene. When carbon black is used in place of graphite under the same conditions, no C60 fullerene was produced and also the sequence of polyyne species generated was very irregular. If really carbon black structure and elemental composition approaches more closely than pure graphite the structure of the carbon dust, we can predict that C60 fullerene should not be produced from the thermal decomposition of this dust in high vacuum.