Measurement and Analysis of CN Violet System in Laser-Induced Plasma

Pulsed, infrared Nd:YAG laser radiation is utilized to ablate material from carbon-containing samples in air. Time-resolved measurements of the micro-plasma show well-developed diatomic spectra of the CN violet system. Of Interest are interferences from the C$_2$ Deslandres D'Azambuja system in the CN spectra, as previously noted in experiments with CO$_2$ laser radiation focused into CO$_2$ gas expanding into air. The recombination emission spectra from diatomic species, e.g., CN or C$_2$, clearly indicate temperatures in excess of 6000 Kelvin. Studies of the CO$_2$ TEA laser-induced micro-plasmas show these highly excited, high-temperature molecular transitions several tens of microseconds after plasma generation, mixed with signatures of Stark-broadened atomic lines. Spectroscopic fitting with accurate molecular line strengths of superposed emission spectra is of current interest, including study of the C$_2$ Deslandres D'Azambuja system near the 4-4 band of the CN $\Delta$v = 0 sequence of the CN B$^2\Sigma^+ \rightarrow$ X$^2\Sigma^+$ Violet System. In addition, discussed are physics phenomena associated with laser-induced optical breakdown. Laser-induced plasma applications include characterization of carbon and nitrogen containing materials.