Energy Balance for a Sonoluminescence Bubble Yields a Measure of Ionization Potential Lowering

B. Kappus, A. Bataller, and S. J. Putterman

Phys. Rev. Lett. 111, 234301 – Published 6 December 2013

Abstract

Application of energy conservation between input sound and the microplasma which forms at the moment of sonoluminescence places bounds on the process, whereby the gas is ionized. Detailed pulsed Mie scattering measurements of the radius versus time for a xenon bubble in sulfuric acid provide a complete characterization of the hydrodynamics and minimum radius. For a range of emission intensities, the blackbody spectrum emitted during collapse matches the minimum bubble radius, implying opaque conditions are attained. This requires a degree of ionization $> 36 %$ . Analysis reveals only $2.1 \pm 0.6 eV / atom$ of energy available during light emission. In order to unbind enough charge, collective processes must therefore reduce the ionization potential by at least 75%. We interpret this as evidence that a phase transition to a highly ionized plasma is occurring during sonoluminescence.

Received 9 December 2011

DOI:https://doi.org/10.1103/PhysRevLett.111.234301

Authors & Affiliations

B. Kappus¹, A. Bataller¹, and S. J. Putterman^1,2

¹Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
²California Nano-Systems Institute, University of California, Los Angeles, California 90095, USA

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Vol. 111, Iss. 23 — 6 December 2013

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