Kinetic model of atomic and molecular emissions in laser-induced breakdown spectroscopy of organic compounds

A kinetic model previously developed to predict the relative intensities of atomic emission lines in laser-induced breakdown spectroscopy has been extended to include processes related to CN and C-2 molecular emissions. Simulations with this model were performed to predict the relative excited-state populations. The results from the simulations are compared with experimentally determined excited-state populations from 1,064 nm laser irradiation of organic residues on aluminum foil. The model reasonably predicts the relative intensity of the molecular emissions. Significantly, the model reproduces the vastly different temporal profiles of the atomic and molecular emissions. The latter are found to extend to much longer times after the laser pulse, and this appears to be due to the increasing concentration of the molecules versus time. From the simulations, the important processes affecting the CN and C-2 concentrations are identified.