Influence of argon content on intensity of multibubble sonoluminescence

When liquids are subjected to low pressures, microscopic nuclei can grow to macroscopic bubbles or cavities leading to the phenomenon of cavitation. Ultrasonic cavitation results from liquid samples subjected to high intensity ultrasound. One unique feature of cavitation is the possibility of runaway collapse of macroscopic bubbles or cavities once they are formed. The bubble implosion process can result in extreme conditions within the cavity like high temperatures estimated to be well in excess of thousands of degrees. These hot spots can be sites of light emission leading to a phenomenon commonly termed as sonoluminescence (SL). There is interest in studying the physical characteristics of SL since it can act as a diagnostic tool for inferring the extreme conditions reached within a collapsing bubble. We have studied the influence of composition of dissolved gas on the characteristics of multibubble SL from ethylene glycol samples subjected to high intensity ultrasound. Both overall intensity and spectra of SL have been measured. It is found that with variation of argon percentage from 0 to 100 percent in nitrogen there is a significant change in the overall SL intensity as well as the nature of spectra. These observations could have implications for choosing optimum parameters for wide ranging application of ultrasonic cavitation like synthesis of nano-particles using this route and degradation of pollutants.