Mechanism of sonoluminescence from alkali-metal atoms

我们研究了声空化气泡的光发射机制(声致发光)。钠、钾等碱金属原子的声致发光，由于其发射位置受到质疑，即气泡内的气相或气泡/液体界面的液体，一直受到人们的关注。研究了不同温度、不同溶解气体和不同超声频率下的声致发光光谱。利用高速相机研究了与声致发光发生密切相关的气泡动力学。本文的研究结果有力地表明，碱金属的排放来自气泡内的气相。此外，还首次观测到了钠发射的两个成分，即能量移位加宽线和未移位的窄线。这一发现有待进一步澄清，并将为声致发光研究提供新的发展方向。

We have studied a mechanism of light emission from acoustic cavitation bubbles(sonoluminescence). Sonoluminescence from alkali-metal atoms, such as sodium and potassium, have been interested because its emission site is questioned, that is gas phase inside bubble or liquid phase at bubble/liquid interface. Sonoluminescence spectrum were investigated under the conditions of various temperatures, various dissolved gases and various ultrasonic frequencies. High-speed camera was used to study bubble dynamics which are closely related to the occurrence of sonoluminescence. The results of the present study strongly suggest the alkali-metal emission is originated from gas phase inside bubble. Furthermore, two components of Na emission, energy-shifted and broadened line and unshifted narrow line, were observed for the first time. This finding should be clarified in future and will provide a new development of sonoluminescence study.