Research On The Emission Line Width And Shift Of Laser Plasma

Laser-induced plasmas (LIPs) are a kind of spectral source and it has important research value in terms of spectral analysis and pulse laser deposition (PLD). The optical emission spectroscopy (OES) of laser-induced plasmas is also called laser-induced breakdown spectroscopy (LIBS), which includes various bands of electromagnetic radiation in forms of line and continuous spectrum from plasma. These lines are the carriers of changing process information of microscopic particles, so the knowledge about space-time distribution and energy level structure of plasma microscopic particles can be obtained by studying LIBS. In addition, LIBS has other important advantages: less used amount, wide-ranging of choosing research object. It allows fast contact-less analysis of most matter. The LIBS has acquired great interest as a fundamental tool for studying the interaction of laser with material in recent years. Some qualitative conclusions of plasma are obtained based on the quantitative analysis. The experimental results in intuition are line width, line shift and intensity of spectral line. The line intensity is one of parameters which can get the results of line width and shift. Therefore, it has important meaning to learn about the nature of plasma by studying line width and shift.In present paper, a time-resolved spectroscopy diagnostic technology was used in titanium and aluminum plasma, and works in two areas have been done as follows:Firstly, the width and shift of two Tiâ…¢lines are measured in the early phase of titanium plasma evolution, and variation tendency of line intensity was analyzed. A modified semiempirical (MSE) approach was used to calculate the Stark width and shift of these two lines and a comparison was hold between theoretical arithmetic and experimental values. A qualitative analysis about shift of these two lines was given by considering the quadratic Stark effect.Secondly, the line shapes of aluminium were theoretically simulated by using one-dimensional radiative transfer model. The effects of parameters to the line profile were studied. An improvement of the model parameter handling approach was made in specific operations. The revolution of spatial population density distribution of species was shown in different delay times.According to the above works, some new achievements are generalized and listed as follows: 1. The electron temperature and density were determined according to the time-resolved spectroscopy diagnostic in the early phase (60ns - 200ns) of Ti plasma. The phenomenon that the intensity of line at 237.4986 nm is always lower than that of 241.3989 nm was explained from the aspect of atomic energy level structure. The three-body recombination collision mechanism plays an important role based on the line intensity variation.2. The empiric formula of Stark width of two Tiâ…¢lines at 237.4986 nm and 241.3989 nm were given by experimental results. An agreement of experimental and MSE values was found within the error bars of the theoretical method. The shift of these two lines are both blue shift and a qualitative analysis was given from the quadratic Stark effect. Meanwhile, the relationship of shift values between two lines is consistent with the computable data.3. The line shapes of Alâ… (394.4 nm) and Alâ… (396.1 nm) were theoretically simulated based on the one-dimensional radiative transfer model. The revolution of spatial population density distribution of species at different delay times was shown in chart.4. The effects of some model parameters to line shapes were investigated. The relationship between the depth of self-reverse and the ratio of population density distribution parameters radius of lower and upper levels was given and the explanation was followed. A method to judging the line shift was experimentally verified by studying the effects of shift parameter to line profile. The Stark shift is blue shift when the left line peak is higher than the right one in self-reverse line shape and rather than visa versa.