Joint Institute of High Temperatures, Russian Academy of Sciences, Izhorskaya 13, Bd. 2, 125412 Moscow, Russia.
Moscow Institute of Physics and Technology, 9 Institutskiy per., Dolgoprudny, Moscow Region 141701, Russia.
Phys Rev E. 2017 Oct;96(4-1):043204. doi: 10.1103/PhysRevE.96.043204. Epub 2017 Oct 6.
Oscillation of particles in a dust crystal formed in a low-pressure radio-frequency gas discharge under microgravity conditions is studied. Analysis of experimental data obtained in our previous study shows that the oscillations are highly isotropic and nearly homogeneous in the bulk of a dust crystal; oscillations of the neighboring particles are significantly correlated. We demonstrate that the standard deviation of the particle radius vector along with the local particle number density fully define the coupling parameter of the particle subsystem. The latter proves to be of the order of 100, which is two orders of magnitude lower than the coupling parameter estimated for the Brownian diffusion of particles with the gas temperature. This means significant kinetic overheating of particles under stationary conditions. A theoretical interpretation of the large amplitude of oscillation implies the increase of particle charge fluctuations in the dust crystal. The theoretical estimates are based on the ionization equation of state for the complex plasma and the equation for the plasma perturbation evolution. They are shown to match the results of experimental data processing. Estimated order of magnitude of the coupling parameter accounts for the existence of the solid-liquid phase transition observed for similar systems in experiments.
在微重力条件下的低压射频气体放电中形成的尘埃晶体中的颗粒振动进行了研究。对我们之前研究中获得的实验数据的分析表明，振动在尘埃晶体的大部分区域内具有高度各向同性和近乎均匀性；相邻颗粒的振动存在显著相关性。我们证明，颗粒半径向量的标准偏差以及局部颗粒数密度完全定义了颗粒子系统的耦合参数。该参数约为 100，比根据气体温度下布朗扩散颗粒的耦合参数估计值低两个数量级。这意味着在静止条件下颗粒存在显著的动力学过热。对大振幅振动的理论解释意味着尘埃晶体中颗粒电荷波动的增加。理论估计基于复杂等离子体的电离状态方程和等离子体微扰演化方程。结果表明，它们与实验数据处理结果相匹配。估计的耦合参数量级解释了在实验中观察到类似系统中存在的固-液相变。
