Effect of ambient nitrogen pressure on the formation and spatio-temporal behaviour of C2 and CN

摘要

We report the effect of ambient gas on the formation as well as propagation behaviour of ablated species C2 and CN within the carbon plasma created by focussing a high-power Nd:YAG (λ = 1064 nm) laser onto the rotating graphite target in the nitrogen ambient. The formation of C2 takes place earlier as well as nearer the target compared to that of CN which forms later and far from the target, in 1.2 mbar pressure of N2 gas. Peak arrival time vs. nitrogen gas pressure plot shows a shock wave-like dependence t ∝ p n in the pressure range 1.2–120 mbar (collisional regime) which indicates plume confinement with increases in ambient pressure. At higher pressure, thermalization takes place.