Equivalent temperature of sonoluminescence at incipient and desinent thresholds of light emission

Abstract

The emission of light in air-water has been studied by the pulse technique during different stages of acoustic cavitation, in particular at the incipient and desinent thresholds of strong cavitation. It has been observed that the equivalent temperature of the light emitted at the incipient cavitation threshold is higher than that corresponding to the light emitted during the last stages of desinent cavitation. With respect to the irradiation time, the equivalent temperature of the light pulses increases in the beginning of the incipient phase, then decreases by a further increase of irradiation time. The equivalent temperature values of the light emitted during the stable cavitation present immediately before the onset of the bubble chain multiplication phase are near to the values found at the desinent emission. Both stable and transient cavitation contribute to sonoluminescence by different ratios at different development stages of the cavitation zone. Equivalent temperatures of about 4000 K for the desinent light and of about 10 000 K for the incipient light are found.