Single-bubble Sonoluminescence In Water Doped With Different Solutes

A single stable bubble can be levitated in a liquid at the antinode of a standing ultrasound wave. The bubble will undergo a pulsating motion and emit picosecond light which is synchronized with the ultrasound wave. The spectrum of the light extends from infrared to ultraviolet. This phenomenon is called sonoluminescence (SL) which is remarkable because the energy is concentrated by twelve orders of magnitude in order to produce light.This thesis mainly focuses on the effects of different solutes on the single-bubble sonoluminescence (SBSL) and discusses the effect of alcohol on the driving parametric region, light intensity and bubble dynamics. And a series of important conclusions have been achieved.Firstly, the driving parametric region in frequency-amplitude space and the optimal parameters for SBSL in alcohol aqueous solutions are studied systematically by taking measurements of the spectrum and bubble dynamics. The experimental results show that with an increase in alcohol concentration, the region shrinks and shifts. The optimized parameters differ for alcohol solutions having different concentrations, and SBSL driven by fixed parameters dims quickly and is even destroyed immediately with the addition of a small amount of alcohol to pure water. Furthermore, it is seen that the intensity of optimized SBSL decreases as the alcohol concentration increases. Also, with the measurement of the light-pressure curves, the concentration of alcohol can be divided into three parts. At the low concentrations, the light intensity increases as alcohol added when sound pressure fixed. When the concentrations are higher, the light intensity will decrease as the concentration increases at the same sound pressure. As the alcohol is further added, the slope of the curves will decrease as the same pressure. The results of the bubble dynamic measurements can explain these phenomena above. The optimized driving amplitude acquired by direct measurement and that obtained by fitting the radius-time curves with the Rayleigh-Plesset equation both decrease. At a given driving pressure the ambient and maximum bubble sizes increased with increasing ethanol concentration. In addition, as the ethanol was increased, the sonoluminescence intensity decreased while the bubble dynamics remained largely unchanged. The translational oscillation of the levitated bubble, however, became increasingly violent with increasing ethanol concentration. The displacement of the bubble reached0.7mm at the highest concentration studied (1.3×10-3) and the maximum bubble size was found to change as the bubble jumped up and down. This bubble translation may be responsible for the decrease of the acoustic driving pressure threshold and suggests that repetitive injection of ethanol molecules into the bubble takes place. These results may be account for the different sensitivities of single bubble and multi-bubble sonoluminescence to the presence of volatile additives.We also investigated the effect of several solutes on the spectra of SBSL in water. The results show that both the line and continuous spectrum decrease in rare earth metal solutions when the sound pressure decreases. In contrast, the line emission becomes stronger than continuous spectra relatively in NaCl solution. The spectra in h-water solution indicate that the atoms with large radius will increase the line emission. But the reason is not a main aspect. Meanwhile, the emissiones of OH radical were studies, and the changes of the line emissiones were first observed under different sound pressure. These experiments will help us to understand the mechanisms of sonoluminescence.