Sonoluminescence

Under sonoluminescence (Latin sonare " drown ", lumen " light " ) refers to a physical phenomenon in which a liquid ultrashort under strong pressure fluctuations, high-energy flashes of light emits. The sonoluminescence is therefore a special type of luminescence.

Causes

Cause of the phenomenon is cavitation ( formation and dissolution cavities in liquids), which can be produced artificially by ultrasound of suitable strength and frequency in liquids. Make it a wealth of new cavities that expand rapidly at first in order to then implode. When collapse of these cavities can be made has not been fully clarified reasons, a brief flash of light produced. On the surface of collapsing cavities temperatures were measured in excess of 10,000 ° C.

Research

Sonoluminescence was first discovered in 1934 by Frenzel and Schultes at the University of Cologne, as they worked on a sonar experiment. In the experiment, an ultrasonic generator is immersed in a developing bath to shorten the development time of the photographic film. Instead, they saw on the film after developing many small, bright points and concluded that in the developing liquid, small bubbles were formed that had to radiate light, while the ultrasonic generator was turned on. It was at that time not yet possible to examine the effect precisely because the flashes were too irregular and too short; the experiment is also ascribed to N. Marinesco and JJ Trillat in 1933. This phenomenon has since been multi -bubble sonoluminescence ( MBSL ) ( in German: More bubble sonoluminescence ) called. 1974 was published by Werner Lauterborn as a result of experimental studies an extension of the Rayleigh -Plesset equation describing the bubble radius:

With

Theories

From science to fully understand not all details of the sonoluminescence. One theory holds that the gas is heated by adiabatic compression as high imploding in a cavity that it lights up. This theory is the fact that the lamp has a continuous spectrum, indicating thermal radiation. Next was a temporal relationship between the light flashes and the collapse of the cavities are found. The flashes of light occurred always at the last moment of the interaction Falls. Higher atomic mass and thus lower thermal conductivity of the gas dissolved in the liquid affect the light intensity positive. Contrast, both very high and very low viscosity of the liquid surrounding the cavity reduce the light intensity.

Spectacular explanations are quantum field theo generic considerations that it was either an effect of the vacuum energy, or nuclear fusion as an energy source, the so-called bubble fusion. Both statements come in the specialized science on strong skepticism, especially after the experimenter Rusi P. Taleyarkhan of the alleged proof of bubbles fusion for the second time of the scientific misconduct accused ( in 2006 and 2008, both times with very similar allegations ) was found guilty and (2008), making his observations be questioned. The manner in which the investigations of Purdue University were carried out, but in the professional world is also not without controversy.

Multi -bubble sonoluminescence

With multi -bubble sonoluminescence ( MBSL short ) refers to the first discovered form of sonoluminescence. This observation of faint lights in heavy mechanical motion of fluids led to the discovery of sonoluminescence. The very short and only dim flashes, which happened to occur at the MBSL at various locations in the test vessel is difficult to perceive the human eye. Therefore, light amplifying cameras or long exposure was needed for this experiment the footage.

Single -bubble sonoluminescence -

In recent years it has attracted the interest of research, a newly discovered form of sonoluminescence, the Einzelblasensonolumineszenz (English Single Bubble sonoluminescence, SBSL ). The special feature here is that a single luminous cavitation bubble can be kept stable for a long time in one place and examined. This happens because you're making a single bubble in a standing ultrasonic field and compressed there for several cycles periodically and decompress. The SBSL is better suited for observations as the MBSL, because the faint flashes of light, which have a duration of only a few picoseconds, appear in the SBSL by their rapid succession on the same site as an ever- glowing bubble.