Sonoluminescence is a fascinating, mysterious physical phenomenon, that combines the principles of light and sound.
In the year 1934 H. Frenzel and H. Schultes discovered a luminous effect by ultrasonication of water. The defining moment that leads to sonoluminescence is the emergence of a cavitation in the liquid (figure 1). The high frequency ultrasound leads to the formation of bubbles, that are filled with gas and expand and collapse rapidly like a shock wave. Shortly after the collapse, the energy is released in form of sound and a short lightning, which is barely observable with the bare eye and reaches temperatures up to 10,000 K.[2,3]In the 1990s, the causes and impacts that lead to sonoluminescence have been intensively investigated but the real cause of this phenomenon remains unresolved even nearly 85 years after its discovery.[5,6] There are different quantum mechanical approaches, but they are highly controversial.[7,8]
Sonoluminescence is not only a physical phenomenon, it does indeed show capability for an academic application, at least in chemistry: in 1991 Grinstaff et al. were able to generate nearly pure amorphous iron by ultrasonication of an iron pentacarbonyl solution in decane. Compared to crystalline iron this compound shows enhanced catalytic activity when used in the Fischer-Tropsch process.
Sonoluminescence also occurs in wildlife: by snapping their claws, pistol shrimp create a sharp stream of water that does not only kill prey but generates a cavitation bubble and thus a short lightning. Scientists call this special phenomenon “shrimpoluminescence”.
— Tatjana Daenzer
 H. Frenzel, H. Schultes, Z. Phys. Chem. 1934, 27, 421–424.
 B. P. Barber, S. J. Putterman, Nature, 1991, 352, 318–320.
 K. Suslick, S.-B. Choe, A. A. Cichowias, M. Grinstaff, Nature, 1991, 353, 414–416.
 „Creative Commons“ from Dake CC BY-SA 3.0. (https://commons.wikimedia.org/wiki/File:Sonoluminescence.png#/media/File:Sonoluminescence.png) last access: 15.05.2018.
 B. P. Barber, C.-C. Wu, R. L?fstedt, P. H. Roberts, S. J. Puttermann, Phys. Rev. Lett. 1994, 72, 1380–1383.
 R. Hiller, K. Weninger, S. J. Puttermann, Science, 1994, 266, 248–250.
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