Laser-induced phase explosions in lead, tin and other elements: microsecond regime and UV-emission

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 similar to3 x 10(13) 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 similar to200 m s(-1), which is about 100 times slower than the ion velocity. The fraction of mass removed via PE was similar to90%. 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.