Optical emission spectroscopy of molecular species in plasma induced by laser ablation of carbon in nitrogen

The results obtained from the study of time-integrated molecular spectra emitted by a plasma induced by excimer laser XeCl, ls308 nm, ts30 ns.ablation of a graphite target in nitrogen atmospheres are presented. The dominant molecular species are found to be CN and C2. The intensities of CN and C2bands have been studied for laser fluences in the range 3–12 Jrcm2, for N2 pressure in the range 1–250 Pa, and distances along the plasma axis of 1–14 mm. The values of roto-vibrational temperatures of CN radicals were calculated by fitting the experimental spectra with computer-simulated spectra. The self-absorption effects have been considered, and the optical path of the CN radical the product between CN X. density and plasma radius, R. was also estimated from the fitting procedure. The formation and the excitation of CN radicals, which could be important in the CN materials deposition process, are discussed. It is shown that a possible x mechanism could be the surface reaction of atomic nitrogen with the carbon clusters or particles existing in the plasma plume. q1998 Elsevier Science B.V.