Angular distributions of C2 and CN formed by laser ablation of graphite in a nitrogen atmosphere

Optical time-of-flight measurements have been performed to obtain snapshots of spatial distributions of C2 and CN molecules produced by laser ablation of graphite in a nitrogen atmosphere. The propagation direction of C2 was oriented along the target surface normal regardless of the nitrogen pressure while that of CN was inclined towards the incident laser beam at low nitrogen pressures. This anomalous propagation of CN molecules is attributed to the high activation energy of the reaction C2+N2→2CN, which is facilitated in a hot region generated by laser–plume interaction.