Estimation of the Temperature of Single-Bubble Sonoluminescence in Various Liquids From Color Images

Determining the content of various substances in solutions by sonoluminescence spectroscopy is an urgent task. The temperature in the sonoluminescence bubble has a significant influence on the measurement of the concentration of substances. When measuring temperature, the method of spectral pyrometry is used. An alternative option is to estimate the temperature by the RGB components in a color image. The subject of the study is the temperature in a luminous sonoluminescence bubble. The aim of the work is to create an experimental setup, obtain glowing bubbles, fix images of the bubbles, and estimate the temperature by the RGB components. The experimental setup is based on a 250 mL round-bottomed flask with piezoceramic emitters. The temperature assessment is carried out according to the following algorithm: recording a color image of the bubble, decomposing the image into RGB components, determining the histograms and medians in each component, calculating the median contrast, and estimating the temperature by contrast. Four liquids are used in the experiment: distilled water for injection, spring water from the village of Srostki in the Altai krai, distilled water for batteries, and distilled water saturated with argon. In the bubbles of the first three liquids, the temperatures are 5984, 5340, and 5351 K. A bubble in the distilled water saturated with argon shows a temperature of 12 120 K. The created experimental setup makes it possible to obtain stable single-bubble sonoluminescence in various liquids. The developed technique for estimating the temperature inside single-bubble sonoluminescence by median contrast can be used in experimental studies.