Prashant Kumar, Rajesh K. Kushawaha, S. B. Banerjee, K. P. Subramanian, and N. G. Rudraswami, "Quantitative estimation of elemental composition employing a synthetic generated spectrum," Appl. Opt. 57, 5443-5450 (2018)
Composition of multielement samples is estimated by using a synthetic generated spectrum utilizing a nonlinear fitting routine. By fitting simultaneously a large number of emission lines, the error in the estimation is minimized. The procedure for synthetic spectrum generation includes self-absorption of emission lines by taking into account the number density of different species in the plasma. The Stark width of different emission lines is iteratively calculated based on the observed width and the degree of self-absorption in the individual lines. This procedure is found to be successful for achieving convergence of the retrieval algorithm even for dense spectra as well as for resolving merged lines with accuracy. This scheme was applied on a stainless steel and brass sample, and the laser-induced breakdown spectroscopy results match well with the reference value obtained from the electron probe microanalyzer measurement.
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Plasma Parameters Obtained Using Fitting Routine at Different Iterations Performed for Correction of the Observed Line Widtha
Parameter
(in )
(in %)
Thin
14046
3.16
[55.91; 44.09]
Thick
13876
25.8
[55.49; 44.51]
Iter 1
13959
28.5
[55.69; 44.31]
Iter 2
13979
29.2
[55.74; 44.26]
Iter 3
13985
29.4
[55.75; 44.25]
Iter 4
13987
29.5
[55.76; 44.24]
The input values are , for thin and for thick plasma condition. The composition of brass used to generate the synthetic spectra is [Cu (56%); Zn (44%)].
Table 2.
List of Emission Lines Used for the Synthetic Spectrum Generation for Brass (Cu, Zn) Samplea
Cu I
324.31
327.39
327.98
329.05
330.79
331.72
331.96
333.78
334.92
336.53
341.4
347.6
351.18
352.42
352.74
353.38
368.74
402.26
406.26
427.51
437.81
450.93
453.08
453.97
458.69
465.11
467.48
470.45
510.55
515.32
521.82
522.01
529.25
578.21
Cu II
490.97
491.79
493.16
493.72
495.16
495.37
500.68
502.12
504.73
505.18
506.54
506.7
508.82
621.69
627.33
Zn I
328.23
330.26
334.5
468.01
472.22
481.05
636.23
The wavelength values are expressed in nm.
Table 3.
List of Emission Lines Used for the Synthetic Spectrum Generation for Steel (Fe, Cr, Mn, Ni) Samplea
Fe I
300.09
300.81
300.96
302.58
303.74
304.76
305.9
306.72
307.57
319.69
320.04
321.16
321.96
322.58
323.94
328.67
330.6
340.75
342.71
344.06
346.58
347.54
349.06
353.66
354.1
354.2
355.5
355.85
356.54
357.02
358.12
358.53
358.61
358.7
360.54
360.67
360.88
361.02
361.88
362.14
363.14
364.04
365.14
368.74
370.92
371.99
372.76
373.48
373.71
374.34
374.56
374.82
374.94
375.82
376.38
376.56
376.72
379.5
381.58
382.04
382.12
382.58
382.78
383.42
384.04
384.1
385.99
388.62
390.29
396.92
404.58
406.35
407.17
414.38
426.04
427.17
430.79
432.58
438.35
440.48
Fe II
300.26
306.22
307.72
313.54
315.42
316.78
317.75
318.31
318.67
319.29
319.38
319.6
321.04
321.34
325.9
Cr I
300.5
301.37
301.48
301.76
301.84
302.06
302.43
303.02
303.42
303.98
304.08
305.38
323.77
343.36
357.43
358.43
359.34
360.53
363.66
363.98
384.94
385.89
396.36
397.66
398.38
399.11
425.43
427.48
428.97
520.45
520.6
520.84
Cr II
302.66
305.01
312.26
312.5
312.86
313.2
313.66
314.72
315.22
318.06
320.92
321.74
333.98
334.26
334.78
336.02
337.83
337.94
337.98
338.26
339.14
339.3
340.24
Mn I
323.68
324.85
353.19
354.78
382.35
403.08
403.3
403.44
403.57
404.14
404.87
445.16
476.23
478.34
482.35
Mn II
346.03
347.4
Ni I
300.36
301.19
303.79
305.08
305.76
310.15
323.29
336.96
338.06
341.48
344.62
345.84
346.16
347.25
349.3
351.03
351.5
352.45
356.64
361.94
Ni II
308.7
347.14
351.39
The wavelength values are expressed in nm.
Table 4.
Concentration Estimates for Steel and Brass Sample Obtained Using Proposed LIBS Technique Compared to the Reference Value Obtained Using EPMAa
Sample
Element
Present Work (LIBS)
Reference (EPMA)
Steel
Cr
Fe
Mn
Ni
Brass
Cu
Zn
The range is specified based on a 95% confidence interval obtained from chi-square value of the estimated parameters (temperature and neutral number densities).
Tables (4)
Table 1.
Plasma Parameters Obtained Using Fitting Routine at Different Iterations Performed for Correction of the Observed Line Widtha
Parameter
(in )
(in %)
Thin
14046
3.16
[55.91; 44.09]
Thick
13876
25.8
[55.49; 44.51]
Iter 1
13959
28.5
[55.69; 44.31]
Iter 2
13979
29.2
[55.74; 44.26]
Iter 3
13985
29.4
[55.75; 44.25]
Iter 4
13987
29.5
[55.76; 44.24]
The input values are , for thin and for thick plasma condition. The composition of brass used to generate the synthetic spectra is [Cu (56%); Zn (44%)].
Table 2.
List of Emission Lines Used for the Synthetic Spectrum Generation for Brass (Cu, Zn) Samplea
Cu I
324.31
327.39
327.98
329.05
330.79
331.72
331.96
333.78
334.92
336.53
341.4
347.6
351.18
352.42
352.74
353.38
368.74
402.26
406.26
427.51
437.81
450.93
453.08
453.97
458.69
465.11
467.48
470.45
510.55
515.32
521.82
522.01
529.25
578.21
Cu II
490.97
491.79
493.16
493.72
495.16
495.37
500.68
502.12
504.73
505.18
506.54
506.7
508.82
621.69
627.33
Zn I
328.23
330.26
334.5
468.01
472.22
481.05
636.23
The wavelength values are expressed in nm.
Table 3.
List of Emission Lines Used for the Synthetic Spectrum Generation for Steel (Fe, Cr, Mn, Ni) Samplea
Fe I
300.09
300.81
300.96
302.58
303.74
304.76
305.9
306.72
307.57
319.69
320.04
321.16
321.96
322.58
323.94
328.67
330.6
340.75
342.71
344.06
346.58
347.54
349.06
353.66
354.1
354.2
355.5
355.85
356.54
357.02
358.12
358.53
358.61
358.7
360.54
360.67
360.88
361.02
361.88
362.14
363.14
364.04
365.14
368.74
370.92
371.99
372.76
373.48
373.71
374.34
374.56
374.82
374.94
375.82
376.38
376.56
376.72
379.5
381.58
382.04
382.12
382.58
382.78
383.42
384.04
384.1
385.99
388.62
390.29
396.92
404.58
406.35
407.17
414.38
426.04
427.17
430.79
432.58
438.35
440.48
Fe II
300.26
306.22
307.72
313.54
315.42
316.78
317.75
318.31
318.67
319.29
319.38
319.6
321.04
321.34
325.9
Cr I
300.5
301.37
301.48
301.76
301.84
302.06
302.43
303.02
303.42
303.98
304.08
305.38
323.77
343.36
357.43
358.43
359.34
360.53
363.66
363.98
384.94
385.89
396.36
397.66
398.38
399.11
425.43
427.48
428.97
520.45
520.6
520.84
Cr II
302.66
305.01
312.26
312.5
312.86
313.2
313.66
314.72
315.22
318.06
320.92
321.74
333.98
334.26
334.78
336.02
337.83
337.94
337.98
338.26
339.14
339.3
340.24
Mn I
323.68
324.85
353.19
354.78
382.35
403.08
403.3
403.44
403.57
404.14
404.87
445.16
476.23
478.34
482.35
Mn II
346.03
347.4
Ni I
300.36
301.19
303.79
305.08
305.76
310.15
323.29
336.96
338.06
341.48
344.62
345.84
346.16
347.25
349.3
351.03
351.5
352.45
356.64
361.94
Ni II
308.7
347.14
351.39
The wavelength values are expressed in nm.
Table 4.
Concentration Estimates for Steel and Brass Sample Obtained Using Proposed LIBS Technique Compared to the Reference Value Obtained Using EPMAa
Sample
Element
Present Work (LIBS)
Reference (EPMA)
Steel
Cr
Fe
Mn
Ni
Brass
Cu
Zn
The range is specified based on a 95% confidence interval obtained from chi-square value of the estimated parameters (temperature and neutral number densities).