Inter-pulse delay optimization in dual-pulse laser induced breakdown vacuum ultraviolet spectroscopy of a steel sample in ambient gases at low pressure

Double-pulse laser induced breakdown spectroscopy with ambient gas in the vacuum ultraviolet: Optimization of parameters for detection of carbon and sulfur in steel

“…The intensity not only peaks at 100 ns but also revives at a longer inter-pulse delay in between 2 and 6 μs. This intensity 'dual-peak' phenomenon in nitrogen, argon and helium has been discussed previously by the authors [18]. It is also reported by Diwakar et al [43] in the case of DP-LIBS in atmospheric air for Cu neutral lines in the visible spectral range.…”

“…Thus the reheating pulse energy was set to 665 mJ for the limit of detection (LOD) calibration as it provided the greatest signal enhancement. The typical enhancement values illustrated in Table 2 were obtained with the inter-pulse delay set at 100 ns which we have previously proven [18] to provide the optimum LIBS signal gain.…”

“…After the early works of introducing the double-pulse LIBS enhancement, e.g., Cremers et al [5], a range of double-pulse configurations were investigated in terms of the beam geometry [6][7][8][9][10], pulse energy and wavelength [7,11,12], inter-pulse delay [13][14][15][16][17][18] and the incorporation of femtosecond lasers [19][20][21][22]. The LIBS investigations generally examined multiple experimental parameters which were optimized individually for measurements with different elements or sample targets.…”

“…The influence of the ambient gas pressure is studied by increasing the pressure of the ambient gas from vacuum [18,38,39]. Instead of reducing the ambient pressure from atmospheric pressure, low pressure ambient gas is introduced to the vacuum chamber.…”

“…In a recent work [18], we have examined the applicability of the double-pulse LIBS technique combined with short wavelength vacuum ultraviolet emission line detection for sensitivity enhancement of LIBS detection of carbon in steel samples. Our results showed that there was a considerable variation in spectral line emission as a function of the inter-pulse time delay.…”