page_title: Mechanism of sonoluminescence
section_title: Thermal processes
hierarchical_section_title: Mechanism of sonoluminescence / Light emission / Thermal processes
caption_attribution_description: English: Upon the violent collapse of a bubble during cavitation, a hot spot will be produced that lasts for a small amount of time. The hot spot contains a high temperature core, with a cooler outer shell.
context_page_description: Sonoluminescence is a phenomenon that occurs when a small gas bubble is acoustically suspended and periodically driven in a liquid solution at ultrasonic frequencies, resulting in bubble collapse, cavitation, and light emission. The thermal energy that is released from the bubble collapse is so great that it can cause weak light emission. The mechanism of the light emission remains uncertain, but some of the current theories, which are categorized under either thermal or electrical processes, are Bremsstrahlung radiation, argon rectification hypothesis, and hot spot. Some researchers are beginning to favor thermal process explanations as temperature differences have consistently been observed with different methods of spectral analysis. In order to understand the light emission mechanism, it is important to know what is happening in the bubble's interior and at the bubble's surface.
context_section_description: Because the bubble collapse occurs within microseconds, the hot spot theory states that the thermal energy results from an adiabatic bubble collapse. In 1950 it was assumed that the bubble internal temperatures were as high as 10,000 K at the collapse of a spherical symmetric bubble. In the 1990s, sonoluminescence spectra were used by Suslick to measure effective emission temperatures in bubble clouds (multibubble sonoluminescence) of 5000 K, and more recently temperatures as high as 20,000 K in single bubble cavitation.
caption: Upon the collapse of a bubble experiencing cavitation, a hot spot is produced for a small amount of time. That hot spot contains a high temperature core that is surrounded by a cooler outer shell.
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