Argon fluoride LA-LEAF for rapid arsenic quantitation

Coupling laser-induced fluorescence to laser ablation can reduce detection limits relative to LIBS. The wing of the broadband ∼193.3 nm emission from unmodified argon fluoride lasers can excite arsenic fluorescence via its 193.76 nm ground state transition for a simple fluorescence scheme. We present argon fluoride-excited laser-ablation laser-excited atomic fluorescence (LA-LEAF) measurements in steel and copper under argon and helium atmospheres. Because the ArF laser saturates the absorption transition and the steel samples show substantial nonspecific iron fluorescence, it is necessary to optimize the laser energy in addition to interpulse delay. LODs are slightly lower under helium (1.0 ppm in steel, 0.15 ppm in copper). These detection limits represent a modest improvement over previous LODs with LIBS, but suggest potential for improvement with line narrowing of the ArF laser. A 193 nm ArF excimer pulse reexcites arsenic atoms in a cooled laser ablation plasma, lowering detection limits over LIBS.