Peak temperature and density inside a collapsing sonoluminescent bubble · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title
Peak temperature and density inside a collapsing sonoluminescent bubble
Plain
A single bubble trapped in a sound field collapses once per cycle and emits a flash of light lasting less than a billionth of a second. Nobody has measured directly how hot and how dense its center becomes.
Precise · changed · core
Revision 1: For a stably driven argon or air bubble in water (ambient radius $R_0 \sim 5e-4\,\mathrm{cm}$, drive frequency $\sim 2.5e4\,\mathrm{Hz}$, acoustic pressure amplitude $P_a \sim 1.2\ \text{to}\ 1.5\,\mathrm{bar}$), determine the spatially resolved peak temperature $T_{\max}$ and gas density at collapse. Spectral fits in water give $T$ of order $6e3\ \text{to}\ 2e4\,\mathrm{K}$, spectroscopy in concentrated sulfuric acid shows plasma signatures, and some models predict converging shocks heating a small core above $1e5\,\mathrm{K}$. An answer is a measured $T_{\max}(r)$ with error bars, or a simulation that matches spectra, absolute photon number and pulse width simultaneously without free parameters.
Revision 2: For a stably driven argon or air bubble in water (ambient radius $R_0 \sim 5 \times 10^{-4}\,\mathrm{cm}$, drive frequency $\sim 2.5 \times 10^{4}\,\mathrm{Hz}$, acoustic pressure amplitude $P_a \sim 1.2\ \text{to}\ 1.5\,\mathrm{bar}$), determine the spatially resolved peak temperature $T_{\max}$ and gas density at collapse. Spectral fits in water give $T$ of order $6 \times 10^{3}\ \text{to}\ 2 \times 10^{4}\,\mathrm{K}$, spectroscopy in concentrated sulfuric acid shows plasma signatures, and some models predict converging shocks heating a small core above $10^{5}\,\mathrm{K}$. An answer is a measured $T_{\max}(r)$ with error bars, or a simulation that matches spectra, absolute photon number and pulse width simultaneously without free parameters.
Settled by
A model-independent temperature diagnostic of the collapse core (for example time-resolved line broadening or X-ray or neutron yield limits) consistent with a parameter-free bubble-dynamics simulation.
Kind
well-posed
Answer type
value
References
(empty)
Literature status
contested
Status note
Temperature estimates in water remain model-dependent and differ by factors of several; no direct measurement of the core temperature as of 2026 (not re-verified for 2024-2026).
Posed since
(empty)

Decisions