Dynamics of laser-ablated carbon plasma: formation of C2 and CN

We report time-resolved imaging of a laser-ablated carbon plasma plume to investigate the expansion dynamics of C(2) and CN in an ambient atmosphere of nitrogen gas at various pressures. An attempt is made to locate C(2) and CN species in the carbon plasma plume and correlate them with the results of spectroscopic observations. The ablated C(2) and CN species decelerate due to collisions with nitrogen gas and are localized in the slower part (approximately 300 ns) of the expanding plume. Further expansion (<700 ns) of the plasma reveals the concentration of C(2) species on the periphery of the plume, whereas CN dominates at the core of the plume. However, at times greater than 700 ns, the collisions and recombination processes dominate in the plume and C(2) expands slower than CN. The plume dynamics is studied in terms of shock-wave and drag models.