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Time-resolved laser-induced breakdown spectroscopy was applied for quantitative measurement of lead content in concrete at levels down to 10 ppm. The breakdown was formed at the sample surface by a Q-switched ND:YAG laser operating at a 1.06-μm wavelength and a repetition rate of 10 Hz. Contamination levels were inferred from the ratio of the integrated emission line of lead to a known reference line of the matrix. The lead contamination can be determined on an absolute scale down to 10 ppm at an optimum delay time of 3.0 μs. These results were derived from analysis of the temporal evolution of the calibration function within a 0.1- to 19.0-μs time range. The calibration function exhibits no dependence on the incident laser pulse energy, which was varied from 250 to 400 mJ.

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Phase explosions (PEs) have been observed at tens of microseconds delay after laser pulse arrival on carbon, aluminium, silicon, iron, copper, zinc, tin and lead targets ablated at an irradiance ∼3×1013 W cm−2, delivered by 100 ps laser pulses at 532 nm wavelength. The PEs in lead and tin were accompanied by an emission that caused a massive photoelectric effect from copper plates that were positioned 20 and 40 cm away from the targets. Initial estimations suggest emitted photon energy around 10 eV. The phenomenon was also studied by direct imaging with an intensified charge-coupled device camera. Analysis of the PE event is given in terms of thresholds, critical exposures (i.e. number of laser shots required to cease observation of PE), angular profiles of UV-emission and ejected particulate velocities. The velocity of the ejected particulates was ∼200 m s−1, which is about 100 times slower than the ion velocity. The fraction of mass removed via PE was ∼90%. The observations and data analysis reported in this paper can hardly be explained without considering the phase boundaries and/or charge transport. This poses certain challenge to current thermal models of PEs.

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