Photoacoustic study of relaxation dynamics in multibubble systems in laser-superheated water.

Microsecond relaxation dynamics in a cavitating surface layer of bulk water superheated by a TEA CO(2) laser was studied using contact broadband photoacoustic spectroscopy. Damped nanosecond and microsecond oscillatory pressure-tension cycles recorded by an acoustic transducer are related to oscillations of steam bubbles of different sizes exhibiting strong dissipative losses and collective (coalescence and percolation) phenomena. These measurements also give important insight into basic parameters, characteristic spatial and temporal scales, and the mechanism of laser ablation of absorbing liquids in the thermal confinement regime.