Singlet oxygen generation in a high pressure non-self-sustained electric discharge
Singlet oxygen generation in a high pressure non-self-sustained electric discharge
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DOI：
10.1088/0022-3727/38/20/007
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发表时间：
2005-09
期刊：
影响因子：
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通讯作者：
A. Hicks;Seth A. Norberg;P. Shawcross;W. Lempert;J. Rich;I. Adamovich
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文献类型：
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作者：
A. Hicks;Seth A. Norberg;P. Shawcross;W. Lempert;J. Rich;I. Adamovich
本文介绍了高压非自持交叉放电中单线态制氧的实验结果。放电包括高压、短脉冲持续时间、高重复率的脉冲放电和低压直流放电，前者在流动中产生电离，后者在脉冲之间的衰变等离子体中维持电流。维持电压可以独立变化，以最大限度地提高单线态δ氧（SDO）电子冲击激发的能量输入。结果表明，在P0 = 380 Torr的静压力下，O2-He混合物中可以实现稳定和扩散的交叉放电，在P0 = 120 Torr下可以实现至少1200 W的持续放电功率。持续放电的正柱电场减小范围为E/N = 0.3 × 10−16 ~ 0.65 × 10−16 V cm2，显著低于自持续放电的E/N，接近理论预测的O2（a 1Δ）激励的最优值。对放电余辉中可见发射光谱O2（b 1Σ→X 3Σ）的测量表明，O2（b 1Σ）浓度随持续放电功率的增大而增大，随流动中O2含量的增大而减小。从这些光谱中推断出10% O2-90% He的旋转温度为P0 = 120 Torr，质量流率为365-465 K。根据使用黑体源校准的O2（a 1Δ→X 3Σ）红外发射光谱（0,0）波段的综合强度推断，在这些条件下SDO产率为1.7%至4.4%。在放电余辉中，至少在距离放电点15厘米的范围内，其产量几乎保持不变。利用准一维非平衡脉冲保持体放电模型和等离子体电子的玻尔兹曼方程进行动力学建模计算，预测了放电过程中气体温升，与实验测量结果吻合较好。然而，该模型对O2（a 1Δ）产率的预测过高了2-2.5倍，这表明该模型对高压下非平衡O2 - he等离子体动力学的描述并不十分充分。
This paper presents results of singlet oxygen generation experiments in a high-pressure, non-self-sustained crossed discharge. The discharge consists of a high-voltage, short pulse duration, high repetition rate pulsed discharge, which produces ionization in the flow, and a low-voltage dc discharge which sustains current in a decaying plasma between the pulses. The sustainer voltage can be independently varied to maximize the energy input into electron impact excitation of singlet delta oxygen (SDO). The results demonstrate operation of a stable and diffuse crossed discharge in O2–He mixtures at static pressures of at least up to P0 = 380 Torr and sustainer discharge powers of at least up to 1200 W, achieved at P0 = 120 Torr. The reduced electric field in the positive column of the sustainer discharge varies from E/N = 0.3 × 10−16 to 0.65 × 10−16 V cm2, which is significantly lower than E/N in self-sustained discharges and close to the theoretically predicted optimum value for O2(a 1Δ) excitation. Measurements of visible emission spectra O2(b 1Σ → X 3Σ) in the discharge afterglow show the O2(b 1Σ) concentration to increase with the sustainer discharge power and to decrease as the O2 fraction in the flow is increased. Rotational temperatures inferred from these spectra in 10% O2–90% He flows at P0 = 120 Torr and mass flow rates of are 365–465 K. SDO yield at these conditions, 1.7% to 4.4%, was inferred from the integrated intensity of the (0, 0) band of the O2(a 1Δ → X 3Σ) infrared emission spectra calibrated using a blackbody source. The yield remains nearly constant in the discharge afterglow, up to at least 15 cm distance from the discharge. Kinetic modelling calculations using a quasi-one-dimensional nonequilibrium pulser–sustainer discharge model coupled with the Boltzmann equation for plasma electrons predict gas temperature rise in the discharge in satisfactory agreement with the experimental measurements. However, the model overpredicts the O2(a 1Δ) yield by a factor of 2–2.5, which suggests that the model's description of nonequilibrium O2–He plasma kinetics at high pressures is not quite adequate.