Difference in Threshold between Sono- and Sonochemical Luminescence

The difference in threshold between sonoluminescence (SL) and sonochemical luminescence (SCL) has been investigated. The intensity of both SL from distilled water and SCL from a luminol solution in a rectangular glass cell was measured while changing the driving frequency and voltage applied to the transducer. The second hamonic component of the sound-pressure waveform was also measured simultaneously. The results show that the thresholds in sound pressure become higher for cavitation, SCL and SL in this order. As the dissolved gas in a liquid decreases, the SCL intensity decreases but the SL intensity increases. For a constant quantity of dissolved gas, as the liquid temperature becomes higher, the SCL intensity increases but the SL intensity decreases. In the case of air-saturated liquids, the difference in threshold between SCL and SL becomes larger as the liquid temperature increases. The dependence of the ratio of SCL to SL on temperature is similar to that of vapor pressure.