PNNL

Abstract

The oxygen present in the ambient gas medium may affect both the LIBS and LIF emission through a reduction of the emission intensity and persistence. In this study, an evaluation is made on the role of oxygen in the ambient environment under atmospheric pressure conditions in the LIBS and LA-LIF emission. For generating plasmas, 1064 nm, 10 ns pulses were focused on an aluminum alloy sample. The LIF was performed by frequency scanning of a CW laser over the 396.15 nm (3s24s 2S1/2 ? 3s23p 2P°3/2) Al I transition. Time resolved emission and fluorescence signals are recorded for evaluating the emission intensity reduction caused by the presence of oxygen. The oxygen partial pressure in the atmospheric pressure N2 environment was varied from 0 – 400 Torr O2. 2D-fluorescence spectroscopy images were obtained for various oxygen concentrations for simultaneous evaluation of the emission and excitation spectral features. Results showed that the presence of oxygen in the ambient environment drastically reduces the persistence of the LIBS and LIF emission through an oxidation process that depletes the density of atomic species within the resulting laser produced plasma plume.