Single-bubble sonoluminescence

Abstract

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

Sonoluminescence and sonochemiluminescence from a microreactor

“…It has been modeled and experimentally confirmed for a single bubble that the strength of the bubble collapse is affected by its translational movement (accelerated due to added mass forces while the driving pressure increases), and that the strength of the bubble collapse and its sphericity (i.e., the focusing power) are key ingredients determining the SL and SCL intensity (Brenner et al, 1995;Sadighi-Bonabi et al, 2009;Hatanaka et al, 2002;Brenner et al, 2002). Indeed, in our experiments higher SL is observed for higher power.…”

“…The controlled and localized acoustic microbubble generation can be sustained for at least several hours due to dissolved gas in the liquid transported into the pit by a process similar to rectified diffusion (Brenner et al, 2002;Apfel, 1970;Crum, 1982;Fowlkes & Crum, 1988). Since temperature and gas escaping the microchamber could not be controlled in this particular case, all experiments were carried out within 5 to 10 minutes.…”

“…Sometimes, bubbles can cavitate in phase with the applied sound frequency. These bubbles behave as "individual micro-reactors", as they are often accompanied by a violent collapse that leads to high pressures and temperatures within and in the local vicinity of the bubbles (Lohse, 2005;Didenko & Suslick, 2002;Brenner et al, 2002). Among the events generated during such collapses, some can be identified as plasma formation, lysis of molecules yielding radicals (water molecule sonolysis is a well known example), strong pressure shockwaves, liquid jetting and surface erosion.…”

“…multibubble SL). For SBSL the collapse is nearly spherically symmetric and highly reproducible (Brenner et al, 2002); and for MBSL the more frequent non repeatable asymmetric collapse produces liquid jets penetrating the hot bubble contents (Crum, 1994;Flint & Suslick, 1991;Matula & Roy, 1997;W.B. McNamara III, 2000).…”

Plasma Quenching by Air during Single-Bubble Sonoluminescence

“…2,3 The vast majority of SBSL studies have been conducted in partially degassed water, and some of this previous work has shown how chemistry affects the light emission. 4,5 Results suggest that polyatomic molecules that are able to enter the bubble cause a reduction in the overall sonoluminescence (SL) intensity.…”