VACUUM-ULTRAVIOLET; INDUCED PLASMA; SPECTROMETRY; OPTIMIZATION; COAL; IMPROVEMENTS; ABSORPTION

Carbon is a key element for steel properties but (a) hard to be determined by laser-induced breakdown spectroscopy (LIBS). Utilizing the combination of carbon in analytes and nitrogen in ambient gas to generate carbon nitrogen (CN) radicals, LIBS assisted with laser-induced radical fluorescence (LIBS-LIRF) was proposed to resonantly excite radicals instead of atoms in plasmas. The CN radicals in the B-2 Sigma-A(2)II band were stimulated by a 421.60 nm laserwavelength and emitted 388.34 nm fluorescence. The results show that the spectral intensity of the CN radicals was enhanced by 2 orders of magnitude using LIBS-LIRF. Then carbon content in steels was accurately and sensitively determined without spectral interference. The limits of detection (LoDs) were 0.039 and 0.013 wt % in air and nitrogen gas, respectively. The limits of quantification (LoQs) were 0.130 and 0.043 wt % in air and nitrogen gas, respectively. This work demonstrated the feasibility of LIES to realize reliable carbon determination in steel industry.

QUANTITATIVE-ANALYSIS; INSTRUMENT; ABSORPTION; PLASMA; COBALT; LEAD; SOIL; AIR

Spatially selective excitation was proposed to improve excitation efficiency in laser-induced breakdown spectroscopy combined with laser-inducedfluorescence (LIBS-LIF). Taking chromium (Cr) and nickel (Ni) elements in steels as examples, it was discovered that the optimal excitation locations were the center of the plasmas for the matrix of the iron (Fe) element but the periphery for Cr and Ni elements. By focusing an excitation laser at the optimal locations, not only excitation efficiency but also the analytical accuracy and sensitivity of quantitative LIBS-LIF were better than those with excitation at the plasma center in conventional LIBS-LIF. This study provides an effective way to improve LIBS-LIF analytical performance. (C) 2017 Optical Society of America