不同温度下的频率失谐对单泡声致发光影响的实验观察

Effect of Frequenciys Disresonance on Single Bubble Sonoluminescence at Different Temperatures

报道了驱动频率和谐振器本征频率不匹配对单泡声致发光强度的影响。实验结果表明:系统在一定的频率失谐范围内都可以实现单泡声致发光,但在不同的频率驱动下,有着不同的发光强度,并存在一个最佳频率,在该频率驱动下的发光强度达到最强。还对这种频率相关性在不同温度下的表现进行了研究,结果表明随着温度的上升,可发光的上限、下限和最佳频率升高,可发光频率宽度变宽。这些频率的随温度升高而升高,在理论上可以从声速与温度的关系上进行解释。同时,也测定了可发光的频率-声压参数域,以及它随温度的变化关系。

A cavitated bubble trapped in the antinode of a standing ultrasound field in liquid can emit light. This phenomenon is called Single Bubble Sonoluminescence (SBSL). It is well known that the frequency takes an important role in SBSL. In this paper we will report our experimental investigation of the dependences of SBSL intensity on the disresonant frequency of driving ultrasound in an air-water system. During the experiment, other parameters except frequency such as the oxygen concentration are kept constant. At a specified temperature, the ultrasound is added and a bubble is generated, when the sound pressure is strong enough the bubble will give light. We measure and record the light and the corresponding sound pressure, and then change the frequency a little, but still keep the sound pressure unchanged. At this time, the intensity of the emission light will change. If the frequency is changed from low to high gradually, we will observe the light from deem to strong and to deem again. Here there exist a strongest light, and it can be believed that the corresponding frequency is best for SBSL, so we call it optimal frequency, and at the same time we get a frequency band width in which SBSL light can be observed. The previous experiment result indicates that SBSL can be driven by a band of disresonant frequencies. At different frequency, of course, the bubble emits different intensity of SBSL. There exists an optimal frequency at which the bubble radiates the strongest light. Also we perform the same experiments at different temperatures. Similar phenomena are observed, but the optimal frequencies at different temperatures are different. At the same time, we find that with the temperature increasing, the band width of the frequency is widened and the optimal frequency is ascended which can be explained as the increasing of the ultrasound speed when the temperature increases At last, the luminescence region in frequency - pressure plate is researched. We find that it is changeable as the temperature changes, which can be used to explain the sensitivity of SBSL to temperature in some sense. In a word, experiments of SBSL's sensitivity to driving frequency are performed systematically in this paper. The results show that finding a proper frequency is of great significance and it is very important to use an optimal frequency in future SBSL experiments.