Evidence for CN in Spectroscopic Studies of Laser-Induced Plasma During Pulsed Irradiation of Graphite Targets in Nitrogen and Ammonia

Mass- and time-integrated optical emission spectra were recorded during direct XeCl laser ablation (308 nm, 30 ns) of graphite targets in N2 and in NH3 atmospheres at various pressures (10−2–250 Pa) and at different laser fluences (3, 6, 12 J cm−2). Spectra in vacuo (10−4 Pa) were also acquired. The optical emission spectra of the laser-induced plasma are characterized by strong molecular emission bands of C2 and CN and by lines of atomic ions (CC ;NC /. At the highest pressures the spectra are dominated by a C2 Swan system (vibrational sequences 1v D −2;−1;0;C1;C2) and a CN violet system (1v D −1;0;C1). Their intensities increase with an increase of gas pressure. Mass spectrometry was also performed on the ablated materials and various chemical species were found; the most common ones were C, CN and C2N2