Abstract:Carbon detection is usually difficult to carry out with high sensitivity and minimally destructive effect. While the conventional laser induced breakdown spectroscopy (LIBS) method operated with atmospheric ambient air is well known as a powerful and versatile analytical tool, it suffers nevertheless from the low sensitivity of C detection when measured in both atmospheric and low pressure ambient air with the more adverse effect found in the former case. This was shown to have its origin in the serious time m… Show more
“…The atomic to ionic emission intensity ratio of 404.2 is the highest of all cases, 3 mm, 5 mm, 7 mm, and 9 mm. This emission spectrum taken using the compact, ungated OMA system under such a large integration time at an optical fiber probing position of 9 mm above the sample surface is only similar to that obtained with a standard, gated OMA system and very favorable for spectrochemical analysis, as show in previous works [ 27 , 28 , 29 , 30 ]. Figure 5 (a), (b), (c), and (d) show the emission spectrum detected from plasma induced on a pure copper plate using a pulse energy of 54 mJ when the probing position of the optical fiber was set at 3 mm, 5 mm, 7 mm, and 9 mm above the sample surface, respectively.…”
Section: Resultssupporting
confidence: 81%
“…Thus, the emission spectrum detected in the early regimes is not a true representation of the plasma emission. With time, the initial plasma expands radially into a larger localized region in the ambient gas and then cools, lowering the background level and yielding to a more reliable atomic emission spectrum from the constituents of the irradiated sample and the ambient gas [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. The plasma temperature was estimated using the following Boltzmann two-line method [ 32 , 33 ], where , , , , and , are the line intensity, transition wavelength, statistical weight, transition possibility, and upper level energy of the spectral line, respectively.…”
Section: Resultsmentioning
confidence: 99%
“…The features of the emission spectrum are favorable for performing qualitative and quantitative analysis. The low energy emission spectrum of plasma under a low pressure surrounding gas using the compact OMA system operated in free running mode is just comparable to that of using the standard OMA system [ 27 , 29 ]. Figure 4 Emission spectrum taken from plasma produced from a pure copper plate under ambient air at a pressure of 10 Torr using a pulse energy of (a) 70 mJ and (b) 8 mJ, respectively.…”
Section: Resultsmentioning
confidence: 99%
“…The ablated atoms moving at supersonic speed compress the ambient gas in the same manner that a piston compresses fluid, resulting in the generation of a shock wave propagating in the ambient gas. The compression of the ambient gas by the shock front produces a high temperature and high density region, leading to strong ionization confined by the surrounding gas to a very small, localized region slightly above the sample surface [26,27,28,29,30,31]. The strong ionization causes the background emission to occur strongly during the early temporal regimes of the plasma formation process through bremsstrahlung (free-free) and recombination (free-bound) transition mechanisms in the high temperature and high density plasma [32].…”
Laser induced breakdown is a highly temporally and spatially dynamic phenomenon, normally studied using a highly temporally resolved optical detector system. In this work, a compact, low cost optical multichannel analyzer (OMA) system without a built-in temporal gating device and thus operated under a free running mode was used to investigate the characteristics of laser induced plasma. A Nd-YAG laser beam was used as the excitation source from several samples, namely, copper, zinc, and aluminum plates. The characteristics of the plasma emission produced under various experimental parameters, including the pulse energy, surrounding gas pressure, and collection fiber position, were examined. It was found that the essential features of emission spectra can be investigated even using the ungated, compact OMA system even without a highly temporally resolved gating system. The plasma emission characteristics critically depend on the experimental parameters. A quality emission spectrum, featuring a high intensity with a low background, can be obtained using the ungated, compact OMA system under optimized conditions, namely, a pulse energy of approximately 8 mJ, a surrounding gas pressure of 10 Torr, and a collection fiber position of more than 5 mm above the surface of the sample. The features of the emission spectra detected under optimized conditions are only similar to those obtained using a sophisticated, gated OMA system. The characteristics of the emission spectra are in good agreement with the previous assumption of the shockwave role in plasma excitation. Having quality emission spectra under the optimized conditions, a preliminary practical laser induced breakdown spectroscopy (LIBS) analysis using the ungated, compact OMA system was performed on several samples, such as standard brass, commercial pure gold, and natural stone samples. The aluminum emission lines are strongly detected from the standard brass sample (C1118) containing aluminum at 2.8%. The LIBS system also unequivocally revealed a qualitatively abandoned impurity presence in the purportedly pure commercial gold sample. It also effectively confirmed qualitatively a Cu presence in the blinking spots of the natural stone collected from a traditional mining site in Aceh. This result implies the effectiveness of the LIBS using the ungated, compact OMA system for quick, practical analysis.
“…The atomic to ionic emission intensity ratio of 404.2 is the highest of all cases, 3 mm, 5 mm, 7 mm, and 9 mm. This emission spectrum taken using the compact, ungated OMA system under such a large integration time at an optical fiber probing position of 9 mm above the sample surface is only similar to that obtained with a standard, gated OMA system and very favorable for spectrochemical analysis, as show in previous works [ 27 , 28 , 29 , 30 ]. Figure 5 (a), (b), (c), and (d) show the emission spectrum detected from plasma induced on a pure copper plate using a pulse energy of 54 mJ when the probing position of the optical fiber was set at 3 mm, 5 mm, 7 mm, and 9 mm above the sample surface, respectively.…”
Section: Resultssupporting
confidence: 81%
“…Thus, the emission spectrum detected in the early regimes is not a true representation of the plasma emission. With time, the initial plasma expands radially into a larger localized region in the ambient gas and then cools, lowering the background level and yielding to a more reliable atomic emission spectrum from the constituents of the irradiated sample and the ambient gas [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. The plasma temperature was estimated using the following Boltzmann two-line method [ 32 , 33 ], where , , , , and , are the line intensity, transition wavelength, statistical weight, transition possibility, and upper level energy of the spectral line, respectively.…”
Section: Resultsmentioning
confidence: 99%
“…The features of the emission spectrum are favorable for performing qualitative and quantitative analysis. The low energy emission spectrum of plasma under a low pressure surrounding gas using the compact OMA system operated in free running mode is just comparable to that of using the standard OMA system [ 27 , 29 ]. Figure 4 Emission spectrum taken from plasma produced from a pure copper plate under ambient air at a pressure of 10 Torr using a pulse energy of (a) 70 mJ and (b) 8 mJ, respectively.…”
Section: Resultsmentioning
confidence: 99%
“…The ablated atoms moving at supersonic speed compress the ambient gas in the same manner that a piston compresses fluid, resulting in the generation of a shock wave propagating in the ambient gas. The compression of the ambient gas by the shock front produces a high temperature and high density region, leading to strong ionization confined by the surrounding gas to a very small, localized region slightly above the sample surface [26,27,28,29,30,31]. The strong ionization causes the background emission to occur strongly during the early temporal regimes of the plasma formation process through bremsstrahlung (free-free) and recombination (free-bound) transition mechanisms in the high temperature and high density plasma [32].…”
Laser induced breakdown is a highly temporally and spatially dynamic phenomenon, normally studied using a highly temporally resolved optical detector system. In this work, a compact, low cost optical multichannel analyzer (OMA) system without a built-in temporal gating device and thus operated under a free running mode was used to investigate the characteristics of laser induced plasma. A Nd-YAG laser beam was used as the excitation source from several samples, namely, copper, zinc, and aluminum plates. The characteristics of the plasma emission produced under various experimental parameters, including the pulse energy, surrounding gas pressure, and collection fiber position, were examined. It was found that the essential features of emission spectra can be investigated even using the ungated, compact OMA system even without a highly temporally resolved gating system. The plasma emission characteristics critically depend on the experimental parameters. A quality emission spectrum, featuring a high intensity with a low background, can be obtained using the ungated, compact OMA system under optimized conditions, namely, a pulse energy of approximately 8 mJ, a surrounding gas pressure of 10 Torr, and a collection fiber position of more than 5 mm above the surface of the sample. The features of the emission spectra detected under optimized conditions are only similar to those obtained using a sophisticated, gated OMA system. The characteristics of the emission spectra are in good agreement with the previous assumption of the shockwave role in plasma excitation. Having quality emission spectra under the optimized conditions, a preliminary practical laser induced breakdown spectroscopy (LIBS) analysis using the ungated, compact OMA system was performed on several samples, such as standard brass, commercial pure gold, and natural stone samples. The aluminum emission lines are strongly detected from the standard brass sample (C1118) containing aluminum at 2.8%. The LIBS system also unequivocally revealed a qualitatively abandoned impurity presence in the purportedly pure commercial gold sample. It also effectively confirmed qualitatively a Cu presence in the blinking spots of the natural stone collected from a traditional mining site in Aceh. This result implies the effectiveness of the LIBS using the ungated, compact OMA system for quick, practical analysis.
“…The use of He gas at low pressure (20 Torr) is based on our previous experience where low-pressure helium provides higher emission intensities and lower background signals, thus giving a higher signal-to-noise ratio (S/N). 23 − 25 …”
Laser-induced breakdown spectroscopy
(LIBS) to detect the light
elements such as lithium (Li) and boron (B) and heavy elements such
as copper (Cu) and lead (Pb) in raw fish samples is reported in this
work. This is made possible by understanding that the soft target
absorbs recoil energy and as a result, the ablated atoms gushing from
the soft target do not acquire sufficient speed to form a shock wave.
In order to overcome this problem, we set a subtarget on the back
of the soft target so as to produce the repulsion force by which the
gushing speed of the ablated atoms is increased, yielding a sufficiently
high plasma temperature or sufficiently large thermal energy needed
for the excitation of the ablated atoms. Excellent spectral qualities
of various soft samples such as margarine, butter, peanut butter,
strawberry jam, raw tuna, raw gindara, and raw salmon are presented.
Furthermore, a linear calibration curve with a zero intercept is also
obtained for Li, Cu, and Pb. The detection limit of Li, Cu, and Pb
is found to be around 0.1 mg/L. This modification of LIBS for soft
samples by using a subtarget effect clearly promises a rapid and in
situ soft sample analysis since there is practically no sample digestion
in the analysis.
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