Sonoluminescence

Under sonoluminescence ( latin sonare "drown out" lumen "light") is meant a physical phenomenon in which a liquid ultrashort under strong pressure fluctuations that emits high-energy light flashes. Sonoluminescence is therefore a special type of luminescence . A very similar phenomenon that during snapping of the scissors of bang cancers occurs, based on sonoluminescence as Shrimpoluminescence designated.

causes

The trigger for the phenomenon is cavitation (formation and dissolution of cavities in liquids), which can be artificially generated in liquids with ultrasound of suitable strength and frequency. New cavities are constantly forming, which expand rapidly at first and then implode . When these cavities collapse, a brief flash of light can occur for reasons that have not yet been clarified. Temperatures of over 10,000 ° C were measured on the surface of collapsing cavities.

research

Sonoluminescence was first discovered by Frenzel and Schultes at the University of Cologne in 1934 while they were working on a sonar experiment. In the experiment, an ultrasonic generator was immersed in a developer bath in order to reduce the development time of the photographic film. Instead, they saw many small, bright spots on the film after development and concluded that small bubbles had formed in the developing liquid that had to emit light while the ultrasonic generator was switched on. At that time, however, it was not yet possible to examine the effect more closely, as the flashes were too irregular and too short; the experiment is also attributed to N. Marinesco and J. J. Trillat in 1933. Since then, this phenomenon has been called multi-bubble sonoluminescence (MBSL) (in German: multi-bubble sonoluminescence). In 1974 Werner Lauterborn published an extension of the Rayleigh-Plesset equation to describe the bubble radius as a result of experimental investigations :

${\displaystyle {\ddot {R}}+{\frac {3}{2R}}{\dot {R}}^{2}={1 \over \rho \cdot R}\left(p_{n}\left({\frac {R_{n}}{R}}\right)^{3\chi }+p_{\mathrm {d} }-{\frac {2\sigma }{R}}-{\frac {4\mu }{R}}{\dot {R}}-p_{\mathrm {stat} }-p(t)\right)}$

With

${\displaystyle p_{n}={2\sigma \over R_{n}}+p_{\mathrm {stat} }+p_{\mathrm {d} }}$

${\displaystyle R}$: instantaneous radius of the spherical bubble

${\displaystyle \rho }$: Density of the liquid

${\displaystyle R_{n}}$: Radius of rest of the bladder

${\displaystyle p_{n}}$: Gas pressure in the bladder at ${\displaystyle R=R_{n}}$

${\displaystyle \chi }$: Polytropic exponent of the gas in the bubble

${\displaystyle p_{\mathrm {d} }}$: Vapor pressure of the liquid

${\displaystyle p_{\mathrm {stat} }}$: external static pressure at the location of the bladder

${\displaystyle \sigma }$: Surface tension of the liquid

${\displaystyle \mu }$: Viscosity of the liquid

From left to right: appearance of the bubble, slow expansion, rapid sudden collapse, light emission

Theories

Not all details of sonoluminescence are fully understood. One theory is that the gas in an imploding cavity is heated so much by adiabatic compression that it lights up. This theory is supported by the fact that the glow has a continuous spectrum , which indicates thermal radiation. A temporal relationship between the flashes of light and the collapse of the cavities could also be determined. The flashes of light always occurred at the last moment of the collapse. Higher atomic mass and thus poorer thermal conductivity of the gas dissolved in the liquid have a positive effect on the light intensity. In contrast, both very high and very low viscosity of the liquid surrounding the cavity reduce the light intensity.

Spectacular attempts at explanation are quantum field theoretical considerations, it is either an effect of vacuum energy or nuclear fusion , usable as an energy source, as so-called bubble fusion . Both explanations are met with great skepticism in specialist science, especially after the investigator Rusi P. Taleyarkhan was accused of scientific misconduct for the second time (2006 and 2008, both times with very similar accusations) and was found guilty in 2008, which led to his observations to be questioned. The way in which the investigations at Purdue University were carried out are also not without controversy in the professional world.

Multi-bubble sonoluminescence

Glycerine sonicated at 0 ° C with a Branson Sonifier 450 sonotrode. Image taken at 5 min exposure time with a highly sensitive film . Position of the sonotrode indicated with a red line

Multi-bubble sonoluminescence (MBSL for short) is the name given to the form of sonoluminescence that was first discovered. This observation of weak glow in liquids with strong mechanical movement led to the discovery of sonoluminescence. The very short and only weakly glowing flashes that happen by chance at different locations in the test vessel in MBSL are difficult to perceive for the human eye. Therefore, light-intensifying cameras or long-term exposure of the film material were required for this experiment.

Single bubble sonoluminescence

Single bladder sonoluminescence image

In recent years, a newly discovered form of sonoluminescence has aroused the interest of research, the single bubble sonoluminescence (SBSL). The specialty here is that a single luminous cavitation bubble can be kept stable and examined in one place for a long time. This is done by holding a single air bubble in a stationary ultrasonic field and periodically compressing and decompressing it over several cycles. The SBSL is better suited for observations than the MBSL, because with the SBSL the weak flashes of light, which only last a few picoseconds, appear in the same place as a constantly glowing bubble due to their rapid succession.

literature

Books:

• FR Young: Sonoluminescence . CRC Press, Boca Raton 2005, ISBN 0-8493-2439-4 .
• Lawrence A. Crum: Sonochemistry and sonoluminescence . Kluwer, Dordrecht 1999, ISBN 0-7923-5549-0 .
• John D. Wrbanek, Gustave C. Gralic, Susan Y. Wrbanek, Nancy R. Hall: Investigating Sonoluminescence as a Means of Energy Harvesting. In: Marc G. Millis, Eric W. Davis: Frontiers of Propulsion Science. American Inst. Of Aeronautics & Astronautics, Reston 2009, ISBN 1-56347-956-7 , pp. 605-637 ( abstract ).

Journal Articles:

• Michael P. Brenner, Sascha Hilgenfeldt, Detlef Lohse : Single-bubble sonoluminescence . In: Reviews of Modern Physics . tape 74 , no. 2 , April 13, 2002, p. 425-484 , doi : 10.1103 / RevModPhys.74.425 .
• H. Frenzel, H. Schultes: Luminescence in ultrasound-fed water . In: magazine f. Physical Chemistry, Div. B . tape 27 , 1934, pp. 421-424 .
• YT Didenko, KS Suslick: The energy efficiency of formation of photons, radicals and ions during single-bubble cavitation . In: Nature . tape 418 , no. 6896 , 2002, pp. 394-397 , doi : 10.1038 / nature00895 .
• H. Dittmar-Ilgen: News about sonoluminescence and pyrofusion . In: Naturwissenschaftlichen Rundschau . No. 9 , 2006, p. 484 .
• Seth Putterman : Sonoluminescence: the star in a jar. In: Physics World No. 3, 1998, pp. 38-42; physics.ucla.edu (PDF) accessed June 24, 2009.
• Seth Putterman: Sonoluminescence: Sound into Light. In: Scientific American , February 1995, pp. 32-37; physics.ucla.edu (PDF) accessed August 5, 2010.
• Ryan Gutenkunst: Extracting Light from Water: Sonoluminescence. In: Caltech Undergraduate Research Journal. 2, No. 1, 2002, pp. 16–22 ( cnls.lanl.gov ( Memento of July 28, 2010 in the Internet Archive ; PDF), accessed October 10, 2009).

Articles by authors who have received a lot of scientific criticism:

• RP Taleyarkhan, JS Cho, CD West, RT Lahey Jr, RI Nigmatulin, RC Block: Additional evidence of nuclear emissions during acoustic cavitation . In: Physical Review E . tape 69 , no. 3 , 2004, p. 36109 , doi : 10.1103 / PhysRevE.69.036109 .

Web links

Commons : Sonoluminescence  - collection of images, videos and audio files

• John Wrbanek et al .: Investigating Sonoluminescence as a Source of Alternative Energy ( Memento October 18, 2011 in the Internet Archive ; PDF) Glenn Research Center 08/2009 (accessed July 26, 2010).

Individual evidence

1. ↑ Snapping shrimp make flashing bubbles . In: Nature , Volume 413, pp. 477–478, 2001 ( abstract online )
2. ^ H. Frenzel, H. Schultes: Luminescence in ultrasound-charged water . In: magazine f. Physical Chemistry, Div. B . tape 27 , 1934, pp. 421-424 .
3. ^ N. Marinesco, JJ Trillat: Action of supersonic waves upon the photographic plate . In: Proc. R. Acad. Sci . tape 196 , 1933, pp. 858-860 .
4. ↑ W. Lauterborn: Cavitation by laser light . In: Acustica . tape 31 , no. 2 , 1974, p. 51-78 .
5. ^ Claudia Eberlein: Sonoluminescence as Quantum Vacuum Radiation. In: Phys. Rev. Lett. 76, No. 20, 1996, pp. 3842-3845, doi: 10.1103 / PhysRevLett.76.3842 .
6. ^ RP Taleyarkhan, CD West, JS Cho, RT Lahey, RI Nigmatulin, RC Block: Evidence for Nuclear Emissions During Acoustic Cavitation . In: Science . tape 295 , no. 5561 , 2002, pp. 1868–1873 , doi : 10.1126 / science.1067589 .
7. ↑ D. Shapira, M. Saltmarsh: Nuclear Fusion in Collapsing Bubbles - Is It There? An Attempt to Repeat the Observation of Nuclear Emissions from Sonoluminescence . In: Physical Review Letters . tape 89 , no. 10 , 2002, p. 104302 , doi : 10.1103 / PhysRevLett.89.104302 .
8. ^ Report of the investigation Committee In the Matter of Dr. Rusi P. Taleyarkhan (PDF)