Laser Ablation Al And Cu Plasma Spectra

Laser-ablation technique is a powerful and available method, and has been widely used in many important fields, such as thin film preparation, nano-technique and element analysis. In the course of laser-ablation, the ejected species is normally called laser ablation plasma, and its processes of production and expansion are very complex. At the same time, optical emission spectral measurement is a suitable and convenient method for the diagnosis and analysis of laser induce metal plasma. In this thesis, we studied the emission spectra of laser ablation Al and Cu plasma.(1) The emission spectra and space-resolved-spectra of aluminum plasma were observed by pulsed Q-switched YAG laser. Within 3mm of near the Al target, there were the continuum spectra and the line emissions, the former was produced by Bresstrahlung and compound of electrons, the later came from the excited state of Al, Al+ and Al2+. In order to analyze the shape of the aluminum resonant double lines, Al 1396.15nm and Al I394.40nm, relative intensities of the double lines were acquired by integrating the area under the double lines, respectively. According to the ratio of the intensities of the double lines, the ratio of transition probability of the double lines was deduced. Compared with the theoretical value, we found they coincided with each other exactly.(2) The emission spectra of laser ablation metal copper plasma were measured. The detailed mechanism of plume emission of Cu plasma was qualitatively explained using a simple model based on excitation of atom and ion in plume arising from inelastic collision between the elemental species and electron with high kinetic energy. Under the local thermal equilibrium model, the electronic temperature of copper plasma was deduced to be in the 104 scale by its emission lines. The electronic temperature, intensities of all lines and continuous spectra gradually increased with the increment of laser energy, and they got to maximum at different laser energy. Our results of copper and aluminum show that there are possibly different thresholds of laser energy to electronic temperature and intensities of emission spectra of laser ablated plasma. At the different environmental gas pressure, spatial emission intensity distribution is explained by the competition among "heat reservoir effect", "confined effect" and "shadow effect".