{'fraction_non_alphanumeric': 0.019801980198019802, 'fraction_numerical': 0.0036003600360036, 'mean_word_length': 5.143646408839779, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Sheath Structure in Electronegative Plasma Having Cold Ions: An Impact of Negative Ions’ Mass

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.