Optical emission spectroscopy of laterally colliding carbon plasmas

An emission spectroscopic investigation of carbon dimer formation in laterally colliding two carbon plasma plumes is carried out in vacuum and under an ambient gas environment. Under the similar experimental conditions, emission spectra obtained with colliding carbon plasmas are compared with single plasma plume to find the optimum conditions for cluster formation. Two spatially separated laser pulses from an Nd:YAG laser are used to generate two single plasma plumes in close proximity from a solid graphite target. Emission spectra of colliding plasmas and single plasma plume reveal a significant enhancement in the yield of carbon dimer in the stagnation layer, formed due to the collision of two single plasma plumes, as compared to that observed in single plasma plume. The spatial and temporal evolution of carbon dimer emission reveals that yield of carbon dimer formation is optimum near the graphite surface, and starts decreasing with an increase in time as well as distance from the target surface. The above observations are correlated with the cooling of ejected carbon species in the collisional regime and the estimated vibrational temperature of carbon dimer. (author)