乙二醇溶液中圆锥泡声致发光的发光特性

利用一种改进后的U形管圆锥泡声致发光装置，研究了乙二醇溶液中圆锥泡声致发光的发光特性.实验结果表明，利用乙二醇溶液可以得到超强的单个发光脉冲，其脉冲宽度可以达到150 μs，其值远远高于其他方式产生的声致发光的脉冲宽度.测量得到的光谱为一从紫外到可见光波长范围的连续谱，在589 nm附近叠加有钠的3P-3S原子发射谱线.在钠的原子发射谱线两侧测量得到了Na-Ar分子激发态跃迁形成的蓝卫星带，并在声致发光实验中测得了Na-Ar的红卫星带以及钠的3S-4S原子发射谱线. 关键词： 圆锥泡声致发光 光脉冲 光谱 卫星带     

Hydrodynamic approach to multibubble sonoluminescence

The velocity profile and radiation pressure field of a bubble cluster containing several thousand micro bubbles were obtained by solving the continuity and momentum equations for the bubbly mixture. In this study, the bubbles in the cluster are assumed to be generated and collapsed synchronously with an applied ultrasound. Numerical calculations describing the behavior of a micro bubble in a cluster included the effect of the radiation pressure field from the synchronizing motion of bubbles in the cluster. The radiation pressure generated from surrounding bubbles affects the bubble’s behavior by increasing the effective mass of the bubble so that the bubble expands slowly to a smaller maximum size. The light pulse width and spectral radiance from a bubble in a cluster subjected to ultrasound were calculated by adding a radiation pressure term to the Keller–Miksis equation, and the values were compared to experimental values of the multibubble sonoluminescence condition. There was close agreement between the calculated and observed values.     

圆锥气泡声致发光光脉冲和光谱

对一种U形管圆锥气泡发光装置进行了改进，使其发光效果更好，利用光电倍增管和光谱仪 得到了水中空气圆锥气泡的发光脉冲和发光光谱图. 得到的发光脉冲在几百个ps和几个ns之 间不等；在近红外波长范围内观测到了水分子振动能级的特征谱，其连续谱发光强度随着波 长的增加而升高. 另外还得到了在水中加入NaCl溶液的气泡发光光谱图. 关键词： 声致发光 圆锥气泡 光脉冲 光谱     

Calculation of light emission in sonoluminescence

We modify a uniform model of single bubble sonoluminescence, in which heat diffusion, water vapor diffusion and chemical reactions are included to describe the bubble dynamics, and the processes of electron-atom bremsstrahlung, electron-ion bremsstrahlung and recombination radiation, radiative attachment of electrons to atoms and molecules, line emissions of OH radicals and Na atoms are taken into account to calculate the light emission. With this model, we compute the light pulse width, the photon number per flash, the continuum and line spectra and the gas species as the products of chemical reactions, and try to compare with all the experimental data available. We obtain good agreement with the observations of Ar and Xe bubbles in many cases, but fail to match the experimental data of the photon number per flash. We also find that for He bubble the computed photon number is always too small to interpret the observations. Supported by the National Natural Science Foundation of China (Grant Nos. 10674081 and 10434070)     

Optical spectra of water sonoluminescence

The sonolumiescence spectra of water saturated with noble gases were studied in a 220–500 nm interval. Total light power of sonoluminescence and the rate of hydrogen peroxide formation were measured. The number of photons emitted by OH^*-radicals was compared with the yield of OH-radicals. The intensity of the shortwave part of the spectra and the OH^*/OH ratio increased while the atomic weight of the gas increased.     

Finite-amplitude vibration of a bubble and sonoluminescence

Numerical solutions of the differential equation for a bubble performing finite-amplitude vibration are given in detail for a variety of situations. The results demonstrate that in lower acoustic pressure (maximum Mach number very low) its vibration has bounce. When acoustic pressure is in excess of 1.18atm and the instantaneous radius of the bubble approaches its equivalent Van der Waals radius, the maximum velocity and acceleration on the surface of a bubble have a huge increase in a very short period, which seems to favour the sonoluminescence. In vacuum environment (0.1atm), an intensive sonoluminescence could be generated.     

A review of the electrical hypothesis of sonoluminescence

The new electrical hypothesis proposed by Degrois and Baldo has been reviewed. The results show that the hypothesis is incompatible with the experimental observations.     

The effect of bulk viscosity on single bubble dynamics and sonoluminescence

In our previous paper, we derived a new single bubble model including the effect of bulk viscosity. To confront it to experiments, single bubble dynamics was measured here in 30% (v/v) glycerol-water mixture under different acoustic amplitudes and compared to models including or not the effect of bulk viscosity. The results showed that calculated bubble dynamics were not significantly affected by the bulk viscosity within the experimental conditions used in this study. However, there was a noticeable delay for the first rebound when bulk viscosity was considered. The corresponding sonoluminescence intensities were collected and compared with theoretical predictions. The results did not allow to discriminate between the two models (one includes the effect of bulk viscosity, the other does not), confirming the negligible effect of bulk viscosity in this condition (30% (v/v) glycerol-water mixture). Due to the instability of a single bubble in higher viscosity solutions, we could not implement experiments that can discriminate between the two models.     

有机溶液中圆锥泡声致发光

在U形管声致发光装置的基础上建立了一套新型的声致发光装置——直管圆锥泡声致发光装置. 利用此装置以有机溶液为液体介质得到了超强的发光脉冲并测量得到了其发光光谱. 结果表明发光光谱为一从紫外光至可见光波长范围的连续谱,上面叠加有C₂的d³Π_g→d³Π_u跃迁形成的五个序列谱带,分别对应于Δv=-2,Δv=-1,Δv=0,Δv< 关键词： 声致发光 光谱 斯旺带 振动温度     

Comparison of Xe single bubble sonoluminescence in water and sulfuric acid

Using the equations of fluid mechanics with proper boundary conditions and taking account of the gas properties, we can numerically simulate the process of single bubble sonoluminescence, in which electron-neutral atom bremsstrahlung, electron-ion bremsstrahlung and recombination radiation, and the radiative attachment of electrons to atoms and molecules contribute to the light emission. The calculation can quantitatively or qualitatively interpret the experimental results. We find that the accumulated heat energy inside the compressed gas bubble is mostly consumed by the chemical reaction, therefore, the maximum degree of ionization inside Xe bubble in water is much lower than that in sulfuric acid, of which the vapour pressure is very low. In addition, in sulfuric acid much larger pa and R0 are allowed which makes the bubbles in it much brighter than that in water.     

水蒸气对声致发光单气泡稳定性的影响

在考虑水蒸气凝结与水的蒸发过程的基础上，推导了球形气泡形状稳定性方程-利用这个方程以及气泡运动时的气体扩散平衡条件，分别研究了环境水温217℃时声驱动频率为206kHz（溶于水中的氩气含量是其饱和度的14％）、环境水温0℃时声驱动频率为319kHz（溶于水中的氮气分压为20kPa，其中含1％氩气），以及环境水温20℃时声驱动频率为338kHz（溶于水中的氮气分压为20kPa，其中含1％氩气）可控制条件下气泡稳定性问题-理论计算结果与前人的实验数据比较，发现考虑水蒸气以后比忽略水蒸气对单气泡稳定区域 关键词： 声致发光 水蒸气 形状不稳定性 扩散平衡     

A unique circular path of moving single bubble sonoluminescence in water

Based on a quasi-adiabatic model,the parameters of the bubble interior for a moving single bubble sonoluminescence (m-SBSL) in water are calculated.By using a complete form of the hydrodynamic force,a unique circular path for the m-SBSL in water is obtained.The effect of the ambient pressure variation on the bubble trajectory is also investigated.It is concluded that as the ambient pressure increases,the bubble moves along a circular path with a larger radius and all bubble parameters,such as gas pressure,interior temperature and light intensity,increase.A comparison is made between the parameters of the moving bubble in water and those in N-methylformamide.With fluid viscosity increasing,the circular path changes into an elliptic form and the light intensity increases.     

硫酸中多气泡声致发光光谱

非线性声波方程与气泡脉动方程联立, 可以描述声空化云中的声场以及任何一个气泡的脉动过程,为数值计算空化场问题提供了理论框架.计算的声压分布变化可以用来计算单气泡动力学,了解任何位置处气泡发光过程以及气泡内气体温度和压强变化等. 对浓硫酸中氙气泡空化云的计算定性符合实验观测, 只有钠原子线谱的计算结果相比实验观测有些出入.     

气泡的大振幅振动及其在声致发光和空化核聚变中的应用

评述了气泡大振幅振动方程，特别是R—P方程的来龙去脉，指出了该方程所存在的缺陷并对它进行了修正，将修正方程的数值解和R—P方程的数值解作了比较，在此基础上，对与气泡振动方程有关的应用(如声致发光和空化核聚变)情况作了分析。     

The effect of fluorocarbon gases on sonoluminescence: a failure of the electrical hypothesis

Ultrasonic irradiation of solutions containing volatile organometallic complexes results in intense emission from excited-state metal atoms. We have determined the effect of dissolved gases (Xe, Kr, Ar, Ne, He, CF₄, C₂F₆, CO, N₂) on the intensity of the sonoluminescence resulting from ultrasonic irradiation of silicone oil solutions of Cr(CO)₆. This provides a well-defined, spectrally resolved probe of sonoluminescence with emission resulting from a single species, the chromium atom excited states. As predicted by the hot-spot, thermal mechanisms of sonoluminescence, the intensity of excited-state Cr emission decreases with increasing thermal conductivity of the noble gases. The intensity of sonoluminescence increases with increasing γ (i.e. C_p/C_v), which is also in accord with a thermal mechanism. Sonoluminescence is substantially diminished by the addition of even small amounts (≈ 1%) of CF₄ or C₂F₆, even though they are capable of supporting electrical discharge. This is in agreement with a thermal mechanism, but is in direct conflict with electrical theories of sonoluminescence.     

稀土盐水溶液单泡声致发光中的特征光谱

在溶有稀有气体的稀土盐氯化铽水溶液中进行了单泡声致发光光谱的研究. 在固定驱动超声频率、不同驱动声压下, 观察到了一系列OH自由基从第一激发态A²∑⁺到基态X²Π 各振动能级跃迁所产生的谱线, 包括波长307 nm处的(0, 0)跃迁谱线, 335 nm处的(0, 1)跃迁谱线以及276 nm处的(1, 0) 跃迁谱线等. 实验结果表明较高的驱动声压有利于 276 nm处谱线的产生, 而较低的驱动声压则有利于 307 与 335 nm 处谱线的产生. 通过定义线状光谱与连续谱的光强比, 定量地表征了线状光谱在总光谱中的相对强度, 并给出了驱动声压对各跃迁谱线光强比的影响. 关键词： 单泡声致发光 驱动声压 线状光谱 光强比     

Computational simulation of ionization processes in single-bubble and multi-bubble sonoluminescence

The most recent spectroscopic studies of moving-single bubble sonoluminescence (MSBSL) and multi-bubble sonoluminescence (MBSL) have revealed that hydrated electrons (e$_{{rm aq}}^{-}$) are generated in MSBSL but absent in MBSL. To explore the mechanism of this phenomenon, we numerically simulate the ionization processes in single- and multi-bubble sonoluminescence in aqueous solution of terbium chloride (TbCl$_{3}$). The results show that the maximum degree of ionization of single-bubble sonoluminescence (SBSL) is approximately 10000 times greater than that of MBSL under certain special physical parameters. The hydrated electrons (e$_{{{rm aq}}}^{-}$) formed in SBSL are far more than those in MBSL provided these electrons are ejected from a bubble into a liquid. Therefore, the quenching of e$_{{{rm aq}}}^{-}$ to SBSL spectrum is stronger than that of the MBSL spectrum. This may be the reason that the trivalent terbium [Tb(III)] ion line intensities from SBSL in the TbCl$_{3}$ aqueous solutions with the acceptor of e$_{{{rm aq}}}^{-}$ are stronger than those of TbCl$_{3}$ aqueous solutions without the acceptor of e$_{{{rm aq}}}^{-}$. Whereas the Tb(III) ion line intensities from MBSL are not variational, which is significant for exploring the mechanism behind the cavitation and sonoluminescence.     

Concomitance in single bubble sonoluminescence of period doubling in emission and shape distortion

We report the first direct observation for a single stable sonoluminescing bubble of a shape instability. Furthermore we show that stable saturation of the shape distortion caused by the instability for a certain range of parameters is experimentally possible and furthermore is directly linked to the curious phenomenon of flash by flash period doubling of the sonoluminescent emission as the afterbounce instability causing the shape distortion is always period doubled whenever the emission is & vice versa.     

测量单泡声致发光中气泡R(t)曲线的前向Mie散射技术

光干涉原理和Mie理论计算结果表明,单泡声致发光中气泡前向Mie散射的振荡信号,主要是由于气泡的透射光束和表面反射光束之间光干涉产生的. 这些干涉波峰形成了测量气泡半径的空间标尺,标尺的单位长度δR由散射角θ,检测光波波长和流体光折射率确定,而每个波峰就是标尺的刻线,它们与该时刻的气泡半径大小一一对应. 在30°—50°散射角范围内,利用前向Mie散射实验测定了单泡声致发光中气泡的最大半径,R(t)曲线及平衡半径,表明前向Mie散射是一种便捷的测定气泡运动特性的有效方法. 关键词： 单泡声致发光 前向Mie散射 光干涉