Studies on target-induced enhancement in pre-ablation orthogonal double-pulse laser-induced breakdown spectroscopy

To investigate the signal enhancement of pre-produced target plasma on the optical emissions of sample plasma in air under atmospheric pressure and its mechanisms, target-enhanced orthogonal double-pulse laser-induced breakdown spectroscopy (TEODP-LIBS) in pre-ablation scheme was studied. The signal enhancement factors with respect to single pulse LIBS were compared while using KHCO 3 target and aluminum target in pre-ablation TEODP-LIBS. It was demonstrated that KHCO 3 target could provide higher signal enhancement than aluminum target. Two orders signal enhancement could be observed at short inter-pulse delay from −0.4 to −0.6 μs when KHCO 3 target was used. Both plasma temperature and electron density in pre-ablation TEODP-LIBS were increased if compared with those in pre-ablation orthogonal double-pulse laser-induced breakdown spectroscopy (ODP-LIBS) without solid target. Significant improvement on the detection limits of lead and iron in brass sample caused by the target-induced signal enhancement have also been experimentally demonstrated. This technique is especially useful for in-situ sensitive elemental analysis under minimal sample ablation or high spatial resolution.