Read aloud After the 1989 widespread report of cold nuclear fusion in the test tube had proved to be a flop, many physicists hoped for a hot nuclear fusion in a test tube. However, Yuri Didenko and Kenneth Suslick of the University of Illinois in Urbana-Champaign consider it unlikely that the required temperatures can be reached in collapsing gas bubbles, as reported in the journal Nature (Volume 418, p. 394). Only recently, a Russian-American research team led by Rusi Pusi Taleyarkhan had reported that they had succeeded in nuclear fusion in such collapsing gas bubbles ( reported). In the relatively simple sonoluminescence method, sound waves in a liquid cause the collapse of minute gas bubbles.

A sound wave causes density fluctuations in a liquid as well as in the air. One thousandth of a millimeter sized gas bubbles that are in the liquid expand by a factor of 1000 when they enter the low pressure range of the sound wave. When the pressure rises again, they are suddenly compressed. As in a compressed air pump, the temperature increases according to previous estimates in the bubbles to 10, 000 to 20, 000 degrees Celsius.

As a result, the gas in the bubbles is transformed into a plasma, that is, the atoms lose electrons. When the electrons recombine with their atoms, light is emitted. Hence the name sonoluminescence: sound is transformed into light.

If the gas in the bubbles cools again, it may dissolve in the liquid. Didenko and Suslick now closed the chemical reactions that take place in the gas bubbles due to the gases found in the liquid. They found that most of the heat generated by the collapse of the bubble is used for these chemical reactions. Only a few thousandths of heat energy is turned into light. display

Because the chemical reactions consume a large part of the energy, Didenko and Suslick have doubts that the temperatures required for nuclear fusion as in the interior of the sun? a few million degrees Celsius? "We believe that the extraordinary conditions needed to ignite nuclear fusion are extremely difficult to produce in normal vapor pressure liquids. Only for liquids with very low vapor pressure, such as molten salts or liquid metals, can we not exclude this possibility. "

Axel Tilleman


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