laser-induced plasma; plasma spectroscopy; zinc; manganese; gate delay; calibration curve; normalization;INDUCED BREAKDOWN SPECTROSCOPY; FORENSIC ANALYSIS; SELF-ABSORPTION; EMISSION; LIBS; SPECTROMETRY; ABLATION; INKS

Laser-induced plasma spectroscopy is performed to determine the elemental compositions of manganese and zinc in potassium bromide (KBr) matrix. This work has utilized Q-switched Nd: YAG laser installed in LIBS2500plus system at fundamental wavelength. The pelletized sample were ablated in air with maximum laser energy of 650 mJ for different gate delays ranging from 0-18 mu s. The spectra of samples are obtained for five different compositions containing preferred spectral lines. The intensity of spectral line is observed at its maximum at a gate-delay 0.83 mu s and subsequently decayed exponentially with the increasing of gate delay. Maximum signal-to-background ratio of Mn and Zn were found at gate delays of 7.92 and 7.50 mu s, respectively. Initial calibration curves show bad data fitting, whereas the locally normalized intensity for both spectral lines shows enhancement since it is more linearly regressed. This study will give a better understanding in studying the plasma emission and the spectra analysis.

laser-induced plasma breakdown; calcium; calibration curves; localized normalization;PLASMA-MASS SPECTROMETRY; MOLECULAR-EMISSION; LIBS; AIR; TEMPERATURE; SPECTRA

This paper focuses on localized normalization for improved calibration curves in laser-induced breakdown spectroscopy (LIBS) measurements. The calibration curves have been obtained using five samples consisting of different concentrations of calcium (Ca) in potassium bromide (KBr) matrix. The work has utilized Q-switched Nd: YAG laser installed in LIBS2500plus system with fundamental wavelength and laser energy of 650 mJ. Optimization of gate delay can be obtained from signal-to-background ratio (SBR) of Ca II 315.9 and 317.9 nm. The optimum conditions are determined in which having high spectral intensity and SBR. The highest spectral lines of ionic and emission lines of Ca at gate delay of 0.83 mu s. From SBR, the optimized gate delay is at 5.42 mu s for both Ca II spectral lines. Calibration curves consist of three parts; original intensity from LIBS experimentation, normalization and localized normalization of the spectral line intensity. The R-2 values of the calibration curves plotted using locally normalized intensities of Ca I 610.3, 612.2 and 616.2 nm spectral lines are 0.96329, 0.97042, and 0.96131, respectively. The enhancement from calibration curves using the regression coefficient allows more accurate analysis in LIBS.