University of Twente, The Netherlands
Single sound driven gas bubbles in water can emit light. This remarkable phenomenon, discovered only in 1990 [D.F. Gaitan, Ph.D. thesis, The University of Mississippi, 1990], is called single bubble sonoluminescence. Its energy focusing power is 12 order of magnitude. Two questions immediately arise:\(i): When does this phenomenon occur?\(ii): What is the light emitting mechanism?
In the last years both of these questions could be resolved and the phenomenon could quantitatively be accounted for. For a review see [M.P. Brenner, S. Hilgenfeldt, and D. Lohse, Rev. Mod. Phys. 74, 425 (2002)]. On question (i): For sonoluminescence to occur, the bubble collapse has to be violent enough to ensure strong enough adiabatic heating of the gas inside the bubble. Moreover, the bubble has to be shape stable, diffusively stable, and chemical stable. From these conditions the phase diagrams of sonoluminescence can be calculated. They are found to be in excellent quantitative agreement with measured phase diagrams [R. Toegel and D. Lohse, "Phase diagrams for sonoluminescing bubbles: A comparison between experiment and theory", submitted to J. Chem. Phys. (2002)].
Question (ii) could be addressed thanks to experiments dealing with the width and the intensity of the light pulses [B. Gompf et al., Phys. Rev. Lett. 79, 1405 (1997)]: It turned out that the light emitting process is thermal bremsstrahlung [S. Hilgenfeldt, S. Grossmann, and D. Lohse, Nature 398, 402 (1999)].
In the second part of the talk we will briefly address applications of collapsing bubbles: Either by snapping shrimp [D. Lohse, B. Schmitz, and M. Versluis, Nature 413, 477 (2001); M. Versluis, A. v.d. Heydt, B. Schmitz, and D. Lohse, Science 289, 2114 (2000)] or in ultrasound diagnostics [S. Hilgenfeldt, D. Lohse, and M. Zomack, J. Acoust. Soc. Am. 107, 3530 (2000)] and local drug delivery.