Sonoluminescence: The Star in a Jar
Sonoluminescence is an amazing marker for the extraordinary degree by which ultrasonic energy can be focused by a cavitating bubble of gas. Local energy dissipation exceeds Kirkhoffs law by and the ambient acoustic energy density concentrates by 12 orders of magnitude to create picosecond flashes of broadband ultraviolet light. Sonoluminescence is primed by the supersonic collapse of a bubble that has been previously expanded by the rarefaction phase of the sound field. At the minimum bubble radius where the contents have been compressed to their van der Waals hard core the acceleration exceeds 1011g and a shock wave is emitted into the surrounding fluid with a strength that can approach 1MegaBar. Sonoluminescence is extremely robust having been observed from 8KHz to 11MHz, and in flow through a Venturi tube. Although the SL mechanism and its robust parameter space confound all theories it has already been put to use as a surgical device. At 30KHz it is used for internal lipectomy and at 1MHz it is used for externally assisted lipectomy. At 11MHz the maximum bubble radius is less than or about 1micron so that the collapsed bubble is measured in 10’s of nanometers. The unusual properties of the light –sonoluminescence is nature’s smallest blackbody-suggest that SL originates in a new state of matter.
Seth Putterman is a researcher in nonlinear fluid mechanics and acoustics who (with coworkers) has developed the theory of universal power spectra in wave turbulence, and participated in the discovery of fifth sound, superfluid two-phase sound and resonant mode conversion in 4He. He also participated in the observation of kink and envelope solitons in various elastic media. With colleagues he developed the theory of coherent intermittency in single atom fluoresence and most recently he has been involved with the discovery and development of synchronous picosecond sonoluminescence; and the development of a new imaging technique-diffusing light photography.
Putterman is a student of George E. Uhlenbech (Ph.D. Rockefeller University, 1970). He has been a faculty member of UCLA since 1970. He is a Fellow of the Acoustical Society of America and the American Physical Society and a past recipient of an Alfred P. Sloan Fellowship.
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