73 lines
4.1 KiB
Plaintext
73 lines
4.1 KiB
Plaintext
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| File Name : SONOLUM2.ASC | Online Date : 11/24/94 |
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| Contributed by : Bert Pool | Dir Category : KEELY |
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| From : KeelyNet BBS | DataLine : (214) 324-3501 |
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| KeelyNet * PO BOX 870716 * Mesquite, Texas * USA * 75187 |
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| A FREE Alternative Sciences BBS sponsored by Vanguard Sciences |
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The sonoluminescence story is getting more interesting every month.
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From Science News, Vol. 146, October 15, 1994
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Making light of sound in solitary bubbles
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Trapped in an intense sound wave, a tiny gas bubble in water can emit a string
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of flashes bright enough to be visible in an undarkened room. Producing a
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startling sound-and-light show on an intriguingly small scale, this simple
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system serves as a remarkable laboratory for physics and chemistry.
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Now, researchers have demonstrated that slight changes in the composition of
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the gas inside such a bubble can strongly influence the intensity and
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wavelengths of the light that escapes. For example, adding a small amount of
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argon, xenon, or helium to a nitrogen bubble substantially increases the
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intensity of ultraviolet light emission.
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Physicists Robert Hiller, Keith Weninger, Seth J. Putterman, and Bradley P.
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Barber of the University of California, Los Angeles, describe their findings
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in the Oct. 14 SCIENCE.
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When an intense sound wave travels through the water it creates microscopic
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cavities that immediately fill with gas originally dissolved in the liquid.
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Such bubbles alternately expand and contract in step with regular changes in
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the sound wave's pressure.
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During the contraction phase, a bubble can collapse so violently and rapidly
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that it concentrates the sound energy sufficiently to heat the enclosed gas to
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temperatures exceeding 10,000 kelvins. The heated gas luminesces, giving off
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an extremely bright flash of visible and ultraviolet light lasting less than
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50 picoseconds.
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Although researchers have known about this effect - called sonoluminescence -
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since the 1930s, they still do not have a complete understanding of how it
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works (SN:10/23/93, p.271). The experiments of Hiller and his coworkers
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represent one attempt to elucidate the process.
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The researchers found that raising the noble gas content of a nitrogen bubble
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in water to 1 precent dramatically stabilizes the bubble's motion. It also
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increases the intensity of light emission by a factor of at least 10.
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At the same time, the spectrum of available light generated by a bubble
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depends strongly on the gas inside the cavity. A bubble containing argon
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produces ultraviolet light that peaks at a wavelength of 300 nanometers.
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However, a helium-laced bubble shows no such peak.
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"Some exciting atomic physics may be occurring within the collapsing
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cavitation bubble that gives rise to [single-bubble sonoluminescence],"
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Lawrence A. Crum and Ronald A. Roy of the University of Washington in Seattle
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comment in the same issue of SCIENCE. "However, many of the results [Hiller
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and his colleagues] present are also anomalous and defy immediate
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explanation."
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Clearly, further investigations are necessary to pin down how sonoluminescence
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occurs. At the same time, the new results suggest the possibility of using
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gas impurities for improved control of the characteristics of light emissions
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from collapsing bubbles. - I. Peterson
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I would like to point out that Norman Wootan has stated in the past that he
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believes the noble gases are one of the keys to free energy, and the new
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research on sonoluminescence and the increase of energy output by using noble
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gases in the collapsing bubble only bolster this position. It seems that
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argon, xenon, neon, and helium may not only be pivotal in plasma energy
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production, but in enhanced sonoluminescence as well! >> Bert
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