Effect of atmosphere on collinear double-pulse laser-induced breakdown spectroscopy

Abstract

Double-pulse laser-induced breakdown spectroscopy (DP-LIBS) has been shown to enhance LIBS spectra. Several researchers have reported significant increases in signal-to-noise (S/N) and/or spectral intensity compared to single-pulse (SP) LIBS. In addition to DP-LIBS, atmospheric conditions can also increase sensitivity. Thus, in this study, a collinear DP-LIBS scheme was used along with manipulation of the atmospheric conditions. The DP-LIBS scheme consisted of an initial 45 mJ pulse at 1064 nm fired into a sample contained in a controlled atmospheric/vacuum chamber. A second analytical 45 mJ pulse at 1064 nm was then fired 0 to 200 μs after and along the same path of the first pulse. Ar, He, and air at pressures ranging from atmospheric pressure to 1 Torr are introduced during DP-LIBS and SP-LIBS experiments. For a brass sample, significant increases in the spectral intensities of Cu and Zn lines were observed in DP-LIBS under Ar compared to DP-LIBS in air. It was also found that Cu and Zn lines acquired with SP-LIBS in Ar are nearly as intense as DP-LIBS in air. While collinear DP-LIBS is effective for increasing the sensitivity for some reduced atmospheres (i.e., Ar and air at 630 to 100 Torr and He at 300 Torr), the enhanced spectral intensity ultimately dropped off as the pressure was reduced below 10 Torr for all atmospheric compositions in the experimental arrangement used in this study. At all pressures of air and Ar, the plasma temperature remained rather constant with increased inter-pulse delays; however, the plasma temperature was more variable for different He gas pressures and inter-pulse delays.

Laser-Induced Breakdown Spectroscopy

“…The effect of the atmosphere surrounding the plasma in collinear DP-LIBS has been also studied for brass samples . An increase in the spectral intensities of several lines has been observed in DP-LIBS in Ar compared to DP-LIBS in air.…”

Novel Signal Enhancement Strategy for Laser-Induced Breakdown Spectroscopy via Miniaturized Atmospheric Pressure Glow Discharge

“…However, compared with other analysis techniques such as inductively coupled plasma-optical emission spectroscopy/mass spectroscopy (ICP–OES/MS), , the relatively low sensitivity and poor limits of detection (LODs) of LIBS limit its application in trace elements detection. In light of that, various techniques have been used to improve the analytical sensitivity of LIBS, mainly the addition of servicing facilities, such as the double-pulse excitation, − additional excitation source, − spatial confinement, , magnetic field, − or depositing nanoparticles on sample surface, − applying purge gases, − and so on. Although beneficial results based on the above methods have been reported, inevitable limitations still exist.…”

Practical high-resolution detection method for laser-induced breakdown spectroscopy

“…7. The optimum atmosphere conditions can vary depending on other experimental variables, such as the way the plasma is viewed and the camera gating [25,26].…”