Hot-spot model of single-bubble sonoluminescence

Abstract

The hot-spot model of single-bubble sonoluminescence (SBSL) is studied. The temperature is assumed to be spatially uniform inside the bubble except at the thermal boundary layer near the bubble wall even at the strong collapse based on the theoretical results by Kwak et al. [Phys. Rev. Lett. 77, 4454 (1996)]. The effect of the kinetic energy of gases inside the bubble is taken into account, which heats up the whole bubble when gases stop their motions at the end of the strong collapse. A bubble in water containing air is assumed to consist mainly of argon based on the hypothesis by D. Lohse [D. Lohse et al., Phys. Rev. Lett. 78, 1359 (1997)]. Numerical calculations under an SBSL condition reveal that the kinetic energy of gases heats up the whole bubble considerably. It is also clarified that vapor molecules (H2O) undergo chemical reactions in the heated interior of the bubble at the collapse and that chemical reactions decrease the temperature inside the bubble considerably. It is suggested that SBSL originates in quasithermal radiation from the whole bubble rather than a local point (the bubble center) heated by a converging spherical shock wave widely suggested in the previous theories of SBSL.