MATRIX-ISOLATION SPECTROSCOPY OF LASER-ABLATED CARBON SPECIES IN NE, D-2, AND H-2 MATRICES

The results of matrix isolation experiments on carbon atoms and cluste rs generated by pulsed laser ablation of graphite are presented. C-3 a nd other C-n clusters are observed by their infrared absorptions in Ne , ortho-D-2, and para-H-2 matrices. CH4 molecules and CH3 radicals are observed in H-2 matrices, as are CD4 molecules in D-2 matrices. The C H4:C-3 concentration ratio in the H-2 matrices is seen to increase dra matically with increasing ablation laser intensity. These results conf irm and illuminate previous work by Miki, Wakabayashi, Momose, and Shi da [J. Phys. Chem. 100, 12135 (1996)] on C-n doped cryogenic para-H-2 samples produced by combined laser ablation and gas condensation in an enclosed cell. Their nonobservation of any hydrocarbon reaction produ cts (particularly CH4) is explained by the lower intrinsic absorption strengths of the CH4 vs C-3 vibrational transitions, and by attributin g a low C-1:C-3 production ratio to the ablation process under their l aser intensity and wavelength conditions. (C) 1997 American Institute of Physics.