抄録
The content of gases dissolved in liquids affects sonochemistry, since it affects the cavitation dynamics. The conventional sonochemistry is usually made to take place in saturated liquids because saturation facilitates the onset of cavitation and removes the ambiguity in one of the controllable parameters, the relative gas content. However, recent advances in single bubble sonoluminescence (SBSL) research have made it clear that the gas content influences the luminescence in stability and brightness. If there exists some kind of relationship between SBSL and the conventional sonoluminescence, or the so-called multibubble sonoluminescence (MBSL), then it is likely that effects of gas content can be observed also for the latter luminescence, which is akin to sonochemistry in many ways. We thus changed the content of dissolved air and monitored the MBSL intensity using the photon counting technique. A sonicator, that is, a horned PZT transducer, was used as a power source. In one of the experiments, a sample chamber was evacuated continuously by a vacuum pump as slowly as possible so that nonequilibrium existed between the air content and the ambient pressure within the otherwise stationary environment. Henry's law did not seem to hold during the experiment. Once the pumping started, the luminescence intensity increased until a certain pressure from which the intensity began to decrease. In another experiment, an air reservoir was connected to the chamber and the continuous pumping was avoided so that equilibrium could be established between the air content and the ambient pressure. In contrast to the previous experiment, the intensity changed little, although a slight maximum was observed about at 300 torr. The two dissimilar results are difficult to explain, and there may have been systematic errors involved in the experiments. In order to have definite results under these different conditions we have designed a better experimental setup in which the power delivered by the transducer can be kept constant during the pressure change and a fixed portion of light can always be collected.
