Didenko Yuri T, Suslick Kenneth S
Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Nature. 2002 Jul 25;418(6896):394-7. doi: 10.1038/nature00895.
It is extremely difficult to perform a quantitative analysis of the chemistry associated with multibubble cavitation: unknown parameters include the number of active bubbles, the acoustic pressure acting on each bubble and the bubble size distribution. Single-bubble sonoluminescence (characterized by the emission of picosecond flashes of light) results from nonlinear pulsations of an isolated vapour-gas bubble in an acoustic field. Although the latter offers a much simpler environment in which to study the chemical activity of cavitation, quantitative measurements have been hindered by the tiny amount of reacting gas within a single bubble (typically <10(-13) mol). Here we demonstrate the existence of chemical reactions within a single cavitating bubble, and quantify the sources of energy dissipation during bubble collapse. We measure the yields of nitrite ions, hydroxyl radicals and photons. The energy efficiency of hydroxyl radical formation is comparable to that in multibubble cavitation, but the energy efficiency of light emission is much higher. The observed rate of nitrite formation is in good agreement with the calculated diffusion rate of nitrogen into the bubble. We note that the temperatures attained in single-bubble cavitation in liquids with significant vapour pressures will be substantially limited by the endothermic chemical reactions of the polyatomic species inside the collapsing bubble.
未知参数包括活性气泡的数量、作用于每个气泡的声压以及气泡尺寸分布。单泡声致发光（其特征是发射皮秒级的光脉冲）是由声场中孤立的蒸汽 - 气体气泡的非线性脉动产生的。尽管后者提供了一个简单得多的研究空化化学活性的环境，但定量测量受到单个气泡内反应气体量极少（通常<10^(-13)摩尔）的阻碍。在此，我们证明了单个空化气泡内化学反应的存在，并量化了气泡坍塌过程中的能量耗散源。我们测量了亚硝酸根离子、羟基自由基和光子的产率。羟基自由基形成的能量效率与多泡空化中的相当，但发光的能量效率要高得多。观察到的亚硝酸盐形成速率与计算出的氮气向气泡内的扩散速率高度吻合。我们注意到，在具有显著蒸气压的液体中，单泡空化所达到的温度将受到坍塌气泡内多原子物种吸热化学反应的显著限制。
