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The Automatic Identification of Emission Lines in Laser-Induced Plasma by The Correlation of Model and Experimental Spectraтезисы доклада
- Авторы: Zaytsev S.M., Popov A.M., Labutin T.A.
- Сборник: Book of Abstracts of 7th International Conference On Laser-Induced Breakdown Spectroscopy "LIBS-2012", 29 September - 4 October, Luxor, Egypt
- Тезисы
- Год издания: 2012
- Место издания: Luxor, Egypt
- Первая страница: 116
- Последняя страница: 116
- Аннотация: The identification of lines in the emission spectra of laser-induced plasma is time-consuming task for the experimenter. It is particularly difficult to evaluate the spectra of samples containing tungsten, iron, chromium and other elements with a huge number of emission transition (e.g, there are ~20000 emission lines for iron and ~15500 lines for chromium both for neutral and ion species within the range 200 800 nm [1]). Obviously, manual identification using databases is a difficult task and can lead to incorrect results, since different transitions can be excited in LIBS plasma under various conditions. At the same time, contemporary LIBS, especially calibration-free approach, requires accurate and complete lines identification in the spectra for the measurement of temperature and quantitative analysis [2]. In this work we proposed a semi automatic identification algorithm based on the correlation of experimental and model spectra, where the temperature and electron density were varied over a range typical for ns-laser ablation. We used LabVIEW software environment for our spectra modeling program, because LabVIEW is widely used in laboratory and industry with user friendly graphical interface for the fast and easy development of virtual instruments. Our model assumed the existence of LTE in plasma. The information about the parameters of the atoms, ions, and electronic transitions in them was used for intensity calculations only. The line intensities were convoluted by Voigt profile with Stark, Doppler, impact broadening and instrumental function. The experimental spectrum was correlated with the set of model spectra within the same spectral range. The model spectrum with the best correlation with experimental one was used to assign observed line with the transition(s) having the maximum contribution to calculated intensity. Thus, the aliasing of the model and experimental spectra allows us to identify lines in experimental spectra. A possibility of our approach was demonstrated for LIBS analysis of high alloy steels (BAM, Germany). We used Nd:YAG laser for ablation of the sample and ICCD camera “Nanogate 2V” (“Nanoscan”, Russia) as a detector with spectrograph “ISA HR 320” (USA). The camera was equipped with hand-made software in LabVIEW. The spectrum for one of the samples from a single laser pulse in the range 393 403 nm was recorded. The best correlated model spectrum (R=0.94) was calculated with the use of T=0.85 eV and lg(Ne)=17.25. The identification of majority of the lines in range was made successfully. The largest deviation between the model and the experimental spectra was observed at high intensity. The reason of this may lie in the fact that the simulation does not take into account self absorption. Nevertheless, the excitation temperature of laser plasma calculated by Boltzman plot (T=0.8±0.1 eV) was equal to the parametric temperature of the best correlated model spectrum. This indicates that LTE in laser induced plasma is actually established and suggested approach is quite good for plasma diagnostics, spectra evaluation and may be used for calibration-free LIBS in the future. 1. Tognoni E., Cristoforetti G., Legnaioli S., Palleschi V. Calibration-Free Laser-Induced Breakdown Spectroscopy: State of the art // Spectrochimica Acta Part B, 2010, Vol. 65, P. 1–14. 2. http://www.cfa.harvard.edu/amp/ampdata/kurucz23/sekur.html
- Добавил в систему: Лабутин Тимур Александрович