Solution pH is a significant parameter that affects the electrical characteristics of gas–liquid discharges and thus potentially produces different plasma chemistries for different plasma-engineered applications. In this study, the discharge characteristics and long-lived aqueous reactive species under different initial pH conditions were investigated. It was found that the discharge contained three phases in one pulse cycle, which occurred at the pulse rising edge, the falling edge, and between the rising and falling edges. The discharge intensity and average power at an initial solution pH of 7.0 are much lower than those obtained at an initial solution pH of 5.0 and 9.0. In contrast, the density ratio of N₂ (C³Π_u, v = 1)/N₂ (C³Π_u, v = 0) is much higher under neutral solution conditions, indicating that the relatively high vibrational energy was obtained in the gas–liquid discharge plasma. Concentrations of aqueous species H₂O₂, NO₂^–, and NO₃^– are higher at the initial pH of 9.0, indicating that different plasma intensities and chemical compositions (H⁺ and OH^–) are involved in their generation and consumption processes. This study provides insights into understanding and controlling the characteristics of the gas–liquid discharge under different solution conditions.

中文翻译：

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溶液 pH 值对大气中脉冲气液放电特性和含水活性物质的影响

溶液 pH 值是影响气液放电电特性的重要参数，因此可能会为不同的等离子体工程应用产生不同的等离子体化学物质。在本研究中，研究了不同初始 pH 条件下的放电特性和长寿命水性活性物质。发现放电在一个脉冲周期中包含三个阶段，分别发生在脉冲上升沿、下降沿和上升沿和下降沿之间。初始溶液 pH 值为 7.0 时的放电强度和平均功率远低于初始溶液 pH 值为 5.0 和 9.0 时获得的放电强度和平均功率。相比之下，N ₂ (C ³ Π _u , v  = 1)/N的密度比₂ (C ³ Π _u , v  = 0) 在中性溶液条件下要高得多，表明在气液放电等离子体中获得了相对较高的振动能量。在初始 pH 值为 9.0 时，水性物质 H ₂ O ₂、NO ₂ ^–和 NO ₃ ^–的浓度较高，表明不同的等离子体强度和化学成分（H ⁺和 OH ^–）参与了它们的生成和消耗过程。这项研究为理解和控制不同溶液条件下气液排放的特性提供了见解。