Abstract
Numerical simulations of bubble pulsation and the light emission called sonoluminescence (SL) at the bubble collapse have been performed in mercury and water under the experimental condition of Futakawa et al. 2). The results have indicated that the SL intensity in mercury is correlated with the shock wave intensity from bubbles. On the other hand, they are not correlated in water because the amount of water vapor inside a bubble strongly influences the SL intensity in a complex way through the maximum bubble temperature and the amount of free electrons in a plasma inside a bubble. The SL intensity from Xe bubbles in water sometimes reaches as high as 200 W according to the present numerical simulations. The SL intensity is higher in water than in mercury because the amount of vapor inside a bubble is a few orders of magnitude larger due to the much higher saturated vapor pressure. Vapor is a source of free electrons and intensifies SL. The bubble expands more in water than in mercury mostly due to smaller density of water.
