Quantitative analysis of aluminum samples in He ambient gas at different pressures in a thick LIBS plasma

Abstract

radioactive, high temperature, toxic materials) [19][20][21][22][23][24][25], industry [26][27][28][29][30][31], architecture, medical (noninvasive study of human teeth and hair, diagnosis of cancer tissue, DNA analysis) [32][33][34][35][36][37], military and civil security (detection of explosive material and biological weapons) [38][39][40][41][42][43]. Most of these applications are investigated under the condition of earth's atmosphere (i.e., at 760 Torr in air atmosphere) in order to determine the selected material compositions. Nevertheless, interest in LIBS in other ambient gases with various circumstances has been grown because of its practical application. It should be mentioned that nowadays wide applications of gas effects in space exploration (such as utilizing LIBS for investigating specific conditions on Venus and Mars) [4,44,45] are studied. For instance, in scope of gas pressure, the high-pressure environment serves to replicate the conditions of a nuclear reactor or simulate some planet environments [46]. At the opposite, reduced gas pressures or vacuum is applied for determination of isotope ratios [47][48][49], synthesis of nanoparticles and thin films.Different research groups [50][51][52][53][54][55] have investigated the quantitative analysis of plasma parameters and spectral line properties in LIBS technique by considering the influences of gas conditions. For instance, Effenberger et al. [56] have properly presented a review of applications of different gas effects in LIBS experiment. They have comprehensively mentioned the results of various groups about the effects of atmosphere compositions and gas pressures (higher and lower than 760 Torr) on plasma parameters and spectral line characteristics. Dawood et al. [57] have investigated the effects of gas nature and its pressure on temporal distribution of aluminum plasma. They have explained that both plasma temperature and electron density grow with ambient gas pressure. In addition, they have shown that argon provides the highest temperature and plasma density, helium provides the lowest one, and nitrogen produces Abstract In this paper, the influences of He ambient gas on aluminum emissions are investigated by experimental analysis of LIBS spectrum. Plasma is produced by focusing of a Nd:YAG laser pulse at a wavelength of 1064 nm on Al standard samples. In this work, the effects of helium atmosphere at different pressures on the amount of spectral self-absorption are studied. The results are discussed by utilizing two approaches: the curve of growth and calibration curve. It is seen that by increasing the gas pressure, the self-absorption enhances. Also, a new method of applying one standard sample instead of other traditional techniques is introduced for concentration prediction. The presented method would be helpful for the situation in which supplying standard samples is not very easy. Then, the accuracy of this new method can be checked by comparison of concentration prediction of the standard samples with their real concentrations.

Emission Characteristics of Laser-Induced Plasma Using Collinear Long and Short Dual-Pulse Laser-Induced Breakdown Spectroscopy (LIBS)

“…5a in gate delay time of 200 ns. The emission lines from Al samples and the self-absorption effect of Al lines have been investigated by experimental analyses of LIBS spectra in some papers, 40,41 which demonstrate the corresponding measured spectral lines in this study. The spectral parameters of different observed lines of Al sample are listed in Table 3.…”

Optically Thick Laser-Induced Plasmas in Spectroscopic Analysis

“…Finally, it should be noted that different parameters such as laser features (its wavelength [42], double or single pulse scheme [33,43], energy [34], and pulse duration [42]), ambient gas condition (the nature and its pressure [42,44]) and measurement device circumstance (delay time [8,34], gate width, and exposure time), and the sample characteristics (metal and biological cases) could affect the amount of self-absorption as well. The details of these effects can be studied in the related references.…”

The influences of ambient humidity on laser-induced breakdown spectroscopy

“…Numerous studies have shown that ambient gas components can influence plasma evolution. 13,14 During plasma evolution, the particles at the plasma front are subjected to a pressure gradient directed towards the sample surface and move towards it. In this process, a portion of the ambient gas is entrained into the plasma and becomes part of it, accompanied by an energy exchange.…”