{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"a55efd940f96d5d1a802d1c136134e441360c8672c0336342544002a45d3db1f","created":"2026-10-03T07:18:03Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"5776ed586965d93b9934bff40ce04dd3b62493c546f7a89301b7a9b1a5833a06","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"fluid.cavitation.sbsl-peak-temperature","kind":"well-posed","literature_status":"contested","n":"1","parents":[],"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.","posed_since":"","precise":"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.","problem_ref":null,"references":"","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.","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).","title":"Peak temperature and density inside a collapsing sonoluminescent bubble","topic_ref":"ce084ca85ea118983bae60657d686bf2b3a2063cc2bba0a728c0b347e11c1da4"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"7f4faf8f53f7921d5e0e2cabbde43adaca95be1e1ce584244f3c810bd93afba5","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"67157cd0115477ca767cb135ea417076f50d82ad7a999403b2b06661ea2bb97c","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"SBziwFVwHYyvYZmXb0--mgZ1X8mFDeVgfXBJVKr2y3xO3LAFIk45rHDHkvwK7TvRpGK-q7px3BFIfGVK2QwRBQ"},"schema":"pubphys.envelope/1"},"record_hash":"7f4faf8f53f7921d5e0e2cabbde43adaca95be1e1ce584244f3c810bd93afba5","leaf_index":1397}