We demonstrate experimentally that the void in capacitively-coupled RF complex plasmas can exist in two qualitatively different regimes. The ‘bright’ void is characterized by bright plasma emission associated with the void, whereas the ‘dim’ void possesses no detectable emission feature. The transition from the dim to the bright regime occurs with an increase of the discharge power and has a discontinuous character. The discontinuity is manifested by a kink in the void size power dependencies. We reproduce the bright void (mechanically stabilized due to the balance of ion drag and electrostatic forces) by a simplified time-averaged 1D fluid model. To reproduce the dim void, we artificially include the radial ion diffusion into the continuity equation for ions, which allows to mechanically stabilize the void boundary due to very weak electrostatic forces. The electric field at the void boundary occurs to be so small that it, in accordance with the experimental observation, causes no void-related emission feature.

我们通过实验证明电容耦合 RF 复合等离子体中的空隙可以存在于两种性质不同的状态。“明亮”空隙的特征是与空隙相关的明亮等离子体发射，而“暗淡”空隙则没有可检测的发射特征。从暗态到亮态的转变随着放电功率的增加而发生并且具有不连续的特征。不连续性表现为空隙大小功率依赖性的扭结。我们通过简化的时间平均一维流体模型重现了明亮的空隙（由于离子阻力和静电力的平衡而机械稳定）。为了重现昏暗的空隙，我们人为地将径向离子扩散包含在离子的连续性方程中，由于非常弱的静电力，这允许机械地稳定空隙边界。空隙边界处的电场非常小，根据实验观察，它不会引起与空隙相关的发射特征。