The importance of longer wavelength reheating in dual-pulse laser-induced breakdown spectroscopy

Abstract

Dual-pulse laser-induced breakdown spectroscopy (LIBS) provides improved sensitivity compared to conventional single-pulse LIBS. We used a combination of Nd: yttrium aluminum garnet (YAG) and CO 2 lasers to improve the sensitivity of LIBS. Significant emission intensity enhancement is noticed for both excited neutral lines and ionic lines for dual-pulse LIBS compared to single-pulse LIBS. However, the enhancement factor is found to be dependend on the energy levels of the lines, and resonance lines provided maximum enhancement. Our results indicate that IR reheating will cause significant improvement in sensitivity, regardless of the conditions, even with an unfocused reheating beam. The improved sensitivity with a YAG-CO 2 laser combination is caused by the effective reheating of the preplume with a longer wavelength laser is due to efficient inverse Bremsstrahlung absorption. The role of the spot sizes, inter-pulse delay times, energies of the preheating and reheating pulses on the LIBS sensitivity improvements are discussed.

Signal enhancement in collinear double-pulse laser-induced breakdown spectroscopy applied to different soils

“…This phenomenon may be associated to a process of ablation at 1064 nm hotter than that obtained at 532 nm, although no significant differences were measured for the relative peak intensities. Thus, the better performance of IR laser for plasma re-heating confirms previous literature results [10,44].…”

Atomic and molecular emissions in laser-induced breakdown spectroscopy

“…Advantages of multi-pulse excitation include an increase of the plasma volume or plasma reheating by the second pulse, in turn, improvement of detection limits for LIBS 10-to 100-fold and/or a decrease in relative standard deviation when comparing single-with double-pulse bursts [5]. Following short-pulse excitation, a CO 2 laser may be used to enhance detection from a distance of atomic and molecular species [6][7][8]. Some applications are also designed with eye-safety in mind, required for remote and/or field-safe LIBS systems [9].…”

Double-pulse laser ablation sampling: Enhancement of analyte emission by a second laser pulse at 213 nm

“…The fifth observation further supports fluorescence over plume heating. If this was two-pulse LIBS, we would expect to see stronger signal if the wavelength of the second pulse was longer because it would heat the plasma more efficiently by inverse Bremsstrahlung [16,17]. However, as Fig.…”