Compositional Analysis of Aerosols Using Calibration-Free Laser-Induced Breakdown Spectroscopy
Andrew Bradley1
1Dept. of Chemistry, University of Kentucky
Due to the difficulty of analyzing the composition of aerosols, calibration-free laser induced was proposed. An Nd-YAG laser was used for the optical breakdown. The beam was focused on a flux of helium charged with alumina ions. Laser and plasma radiation was separated via a dichroic mirror. The optical fiber was coupled to an echelle spectrophotometer. A charge-coupled device matrix detector was used for photon detection. All spectral data were analyzed on the base of a partial local thermodynamic equilibrium; therefore, Boltzmann equilibrium distributions were assumed for the vapor atoms except for the helium atoms and ions. The results concluded that calibration-free LIBS is capable of performing compositional analyses of aerosols in a helium flux with a 10% accuracy. However, accurate composition measurements were only seen for delays between the laser pulse and the detector gate ≤ 1 μs. This is due to the electron density has to be large enough to allow collisional equilibrium for the aerosol species.
Suggested reading before the seminar: http://pubs.acs.org.ezproxy.uky.edu/doi/full/10.1021/acs.analchem.6b00329