Sonoluminescence: A new electrical breakdown hypothesis

Garcı́a, N.; Levanyuk, A. P.

doi:10.1134/1.567246

Cited by 15 publications

(9 citation statements)

References 14 publications

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“…However, there was little agreement as to the details of how this worked, and many other physical mechanisms were suggested, including dielectric breakdown of the gas (Garcia and Levanyuk, 1996;Lepoint et al, 1997;Garcia and Hasmy, 1998), fracture-induced light emission (Prosperetti, 1997), bremsstrahlung (Moss, 1997;Frommhold, 1998), collision-induced emission (Frommhold and Atchley, 1994;Frommhold, 1997;Frommhold and Meyer, 1997), and even the quantum-electrodynamical Casimir effect (Eberlein, 1996a(Eberlein, , 1996b, an idea pioneered in this context by Schwinger (1992).…”

Section: Historical Overviewmentioning

confidence: 99%

Single-bubble sonoluminescence

2002

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Single-bubble sonoluminescence occurs when an acoustically trapped and periodically driven gas bubble collapses so strongly that the energy focusing at collapse leads to light emission. Detailed experiments have demonstrated the unique properties of this system: the spectrum of the emitted light tends to peak in the ultraviolet and depends strongly on the type of gas dissolved in the liquid; small amounts of trace noble gases or other impurities can dramatically change the amount of light emission, which is also affected by small changes in other operating parameters (mainly forcing pressure, dissolved gas concentration, and liquid temperature). This article reviews experimental and theoretical efforts to understand this phenomenon. The currently available information favors a description of sonoluminescence caused by adiabatic heating of the bubble at collapse, leading to partial ionization of the gas inside the bubble and to thermal emission such as bremsstrahlung. After a brief historical review, the authors survey the major areas of research: Section II describes the classical theory of bubble dynamics, as developed by Rayleigh, Plesset, Prosperetti, and others, while Sec. III describes research on the gas dynamics inside the bubble. Shock waves inside the bubble do not seem to play a prominent role in the process. Section IV discusses the hydrodynamic and chemical stability of the bubble. Stable single-bubble sonoluminescence requires that the bubble be shape stable and diffusively stable, and, together with an energy focusing condition, this fixes the parameter space where light emission occurs. Section V describes experiments and models addressing the origin of the light emission. The final section presents an overview of what is known, and outlines some directions for future research. CONTENTS

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Section: Historical Overviewmentioning

confidence: 99%

Single-bubble sonoluminescence

2002

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“…An electrical breakdown hypothesis was advanced [138]. According to that model, the large pressure gradients at the smallest bubble radii polarize the water, thus setting up strong electric elds (' exoelectric eVect' ) which lead to electrical breakdown in the water and to the emission of light [139].…”

Section: Other 'Hot-spot' Modelsmentioning

confidence: 99%

Sonoluminescence: how bubbles glow

Hammer¹,

Frommhold²

2001

J. Mod. Optics

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We review recent attempts to elucidate the phenomenon of sonoluminescence in terms of fundamental principles. We focus mainly on the processes which generate the light, but other relevant facts, such as the bubble dynamics, must also be considered for the understanding of the physics involved. Our emphasis is on single bubble sonoluminescence which in recent years has received much attention, but we also look at some of the excellent work on multiple bubble sonoluminescence and its spectral characteristics for clues. The weakly ionized gas models were recently studied most thoroughly and are remarkably successful when combined with a hydrodynamic bubble model, in terms of reproducing observed spectral shapes, intensities, optical pulse widths and the dependencies of these observables on the experimental parameters. Other radiation models, such as proton tunnelling radiation and the con ned electron model, were not combined with hydrodynamic models and/or have freely adjustable parameters so that their relevance to sonoluminescence studies is at present less critically tested.

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“…The mechanism under consideration is based on the idea put forward in Ref. [14] that SBSL occurs because of electric breakdown in strong electric fields arising near the bubble surface as a result of flexoelectric effect, that is the effect of polarization of water because of gradients of pressure [16]. Here we present a scenario and estimations that show that within the hypothesis the main features of SBSL can be explained using relatively moderate parameters, e.g., temperatures (5÷10)10 3 K for the bubble gas [6], and the natural (expected) value of the flexoelectric coefficient of water [14].…”

Section: Introductionmentioning

confidence: 99%

“…Let us mention that Ref. [14] has left many questions to answer. The origin of the optical radiation of the bubble remaines unexplained.…”

Section: Introductionmentioning

confidence: 99%

Nature of sonoluminescence: Noble gas radiation excited by hot electrons in cold water

Garcı́a

Levanyuk

2000

Phys. Rev. E

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It was proposed before that single bubble sonoluminescence (SBSL) may be caused by strong electric fields occurring in water near the surface of collapsing gas bubbles because of the flexoelectric effect involving polarization resulting from a gradient of pressure. Here we show that these fields can indeed provoke dynamic electric breakdown in a micron-size region near the bubble and consider the scenario of the SBSL. The scenario is (i) at the last stage of incomplete collapse of the bubble, the gradient of pressure in water near the bubble surface has such a value and a sign that the electric field arising from the flexoelectric effect exceeds the threshold field of the dynamic electrical breakdown of water and is directed to the bubble center; (ii) mobile electrons are generated because of thermal ionization of water molecules near the bubble surface; (iii) these electrons are accelerated in "cold" water by the strong electric fields; (iv) these hot electrons transfer noble gas atoms dissolved in water to high-energy excited states and optical transitions between these states produce SBSL UV flashes in the transparency window of water; (v) the breakdown can be repeated several times and the power and duration of the UV flash are determined by the multiplicity of the breakdowns. The SBSL spectrum is found to resemble a black-body spectrum where temperature is given by the effective temperature of the hot electrons. The pulse energy and some other characteristics of the SBSL are found to be in agreement with the experimental data when realistic estimates are made.

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Sonoluminescence: A new electrical breakdown hypothesis

Cited by 15 publications

References 14 publications

Single-bubble sonoluminescence

Single-bubble sonoluminescence

Sonoluminescence: how bubbles glow

Nature of sonoluminescence: Noble gas radiation excited by hot electrons in cold water

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