@article{25198,
  keywords = {model, target, measurements, measurement, usa, surface, emission, pulse, velocity, experimental, algorithm, interferometry, material, ablation, laser, laser ablation, laser-ablation, breakdown, time-resolved, time, ca, e, form, plasma, solids, number, pulses, vapor, c, metals, ionization, electron number densities, plasmas, picosecond, picosecond laser, picosecond laser ablation, density, pulsed laser, pulsed-laser, targets, electron, electron number density, number density, order, ha, metal, dynamics, results, expansion, plume, atmosphere, physics, air, air breakdown, electron emission, electron-emission, forms, heat-transfer, laser plasma, laser plasmas, pulsed laser ablation, pulsed-laser ablation, theoretical-model, vapor plume},
  author = {Samuel S Mao and Xianglei Mao and Ralph Greif and Richard E Russo},
  title = {Initiation of an early-stage plasma during picosecond laser ablation of solids},
  abstract = {<p>Picosecond time-resolved images of plasma initiation were recorded during pulsed-laser ablation of metal targets in an air atmosphere. An early-stage plasma was observed to form before the release of a material vapor plume. Close to the target surface, interferometry measurements indicate that the early-stage plasma has an electron number density on the order of 10<sup>20</sup> cm<sup>-3</sup>. The longitudinal expansion of the ionization front for this plasma has a velocity 10<sup>9</sup> cm/s, during the laser pulse. In contrast, a material-vapor plume forms approximately 200 ps after the laser pulse, and it moves away from the target at 10<sup>6</sup> cm/s. The experimental observations of the early-stage plasma were simulated by using a theoretical model based on a two-fluids description of laser plasmas. The results indicate that the initiation of the plasma is due to air breakdown assisted by electron emission from the target.</p>},
  year = {2000},
  journal = {Applied Physics Letters},
  volume = {77},
  pages = {2464-2466},
  month = {10/2000},
  doi = {10.1063/1.1318239},
  language = {eng},
}