A novel concept of the mass ratio of negative to positive ions has been introduced to explore its effect on the sheath structure in three electronegative cold plasmas, namely, CF4, O2, and C60 plasmas, for spherical geometry with different probe radii. The magnitudes of velocity of positive ions and potential at the sheath edge are found to modify with the mass ratio, electronegativity, and probe radius. The modification in positive ions’ velocity is designated as modified Bohm criterion. Expression is obtained for the sheath thickness, which is found to increase with the higher mass ratios, whereas it reduces with the enhancement in electronegativity and probe radius. No oscillatory structure is observed for the potential profile when the negative ions are described by their fluid equations (as that of the positive ions), instead of their Boltzmann distribution assumed by the other workers. Positive ions’ density as a function of distance from the probe for the different mass ratios is also examined.

中文翻译：

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具有冷离子的带负电等离子体中的鞘结构：负离子质量的影响

引入了负离子与正离子质量比的新概念，以探讨其对三种带负电的冷等离子体（即 CF4、O2 和 C60 等离子体）鞘结构的影响，用于具有不同探针半径的球形几何形状。发现正离子的速度大小和鞘层边缘的电位会随着质量比、电负性和探针半径而改变。正离子速度的修正称为修正玻姆判据。获得了鞘厚度的表达式，发现它随着质量比的提高而增加，而随着电负性和探针半径的增加而减少。当负离子由它们的流体方程（如正离子的流体方程）描述时，没有观察到电位分布的振荡结构，而不是其他工人假设的玻尔兹曼分布。还检查了正离子密度作为不同质量比的探针距离的函数。