Variation of Liquid Temperature at Bubble Wall near the Sonoluminescence Threshold

The liquid temperature at bubble wall ( T L , i ) is numerically calculated, including effect of the thermal conduction and that of the latent heat of non-equilibrium evaporation and condensation at the bubble wall under a condition of the picosecond sonoluminescence and that of nonlight-emission. It is concluded that T L , i is almost identical to the ambient liquid temperature during bubble oscillations except at strong collapses. At strong collapses, T L , i increases to the same order of magnitude with that of the maximum temperature attained in the bubble. It is mainly due to the thermal conduction from the heated interior of the bubble. It is clarified that the energy given to the surrounding liquid by the latent heat of vapor condensation from the time of the maximum bubble radius to that of the minimum radius is comparable to or more than that by the thermal conduction, though the latent heat does not contribute much to the increase of T L , i at the final stage of the strong collapse.