Detection of ultrafine particles in ultrapure water by laser-induced breakdown acoustic effect

Intense acoustic emission from an ultrafine particle in liquids, induced by pulsed laser irradiation, has been observed. A novel method in which ultrafine particles are counted individually by counting the breakdown acoustic pulses is proposed, and its counting principle is verified using polystyrene ultrafine particles. As well as the favourable detectable particle size, this method has other merits; e.g. miscounts due to micro air bubbles can be avoided and particle size can be measured. The principle of the laser breakdown acoustic method and its application to counting ultrafine particles in ultrapure water are described. >