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首页> 外文期刊>Journal of Physics, D. Applied Physics: A Europhysics Journal >Singlet oxygen generation in O-2 flow excited by RF discharge: I. Homogeneous discharge mode: alpha-mode
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Singlet oxygen generation in O-2 flow excited by RF discharge: I. Homogeneous discharge mode: alpha-mode

机译：在RF放电激发下的O-2流中产生单线态氧：I.均匀放电模式：α模式

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摘要

The production and transport dynamics of O-2(a(1)Delta(g)) and O-2(b(1)Sigma(g)(+)) molecules as well as O(P-3) atoms has been studied in an O-2 flow excited by a 13.56 MHz RF discharge in a quartz tube at pressures of 1-20 Torr. It has been shown that the densities of O-2(a(1)Delta(g)) and O(P-3) are saturated with increasing energy input into the discharge. The maximum yield of singlet oxygen (SO) and the O-2 dissociation degree drops with pressure. It is demonstrated that depending on the energy input the RF discharge can exist in three modes: I-in the spatially homogeneous mode or alpha-mode; III-in the substantially inhomogeneous mode, when plasma jets are present outside the discharge; and II-in the transient mode between modes I and III. In this paper only the homogeneous mode of RF discharge in the O-2 flow is considered in detail. A self-consistent model of the a-mode is developed, that allows us to analyse elementary processes responsible for the production and loss of O-2(a(1)A(g)) and O-2(b(1)Sigma(g)(+)) molecules as well as O(P-3) atoms in detail. To verify both the kinetic scheme of the model and the conclusions, some experiments have been carried out at lower flow velocities and higher pressures (>= 10 Torr), when the stationary densities of O-2(a(1)Delta(g)), O-2(b(1)Sigma(g)(+)) and O(P-3) in the discharge area were established not by the escape of particles but by the losses due to the volumetric and surface reactions. The O-2(b(1)Sigma(g)(+)) density under these conditions is determined by the balance of O-2(b(1)Sigma(g)(+)) production by both direct electron impact and electronic excitation transfer from metastable O(D-1) atoms and deactivation by oxygen atoms and tube walls, including quenching by ozone in the afterglow. The O(P-3) density is determined by the balance between the production through O-2 dissociation by electron impact and heterogeneous loss at the wall recombination. The stationary density of O-2(a(1)Delta(g)) is provided by the processes of O-2(a(1)Delta(g)) production by direct electron impact and loss owing to quenching by the tube walls at a low pressure below 4 Torr, as well as by three-body recombination with oxygen atoms with increasing pressure above 7 Torr. The analysis of with increasing pressure above 7 Torr. The analysis of O-2(a(1)Delta(g)) three-body quenching by oxygen atoms showed that this process could actually have a high rate constant and be able to provide a fast SO deactivation at high pressures. The approximate value of the rate constant-(1-3) x 10(-32) cm(3) s(-1) has been obtained from the best agreement between the simulated and experimental data on transport dynamics of O-2(a(1)Delta(g)) molecules and O(P-3) atoms. It is shown that the RF discharge a-mode corresponds to a discharge with an effective reduced electrical field in a quasi-neutral plasma of about similar to 30 Td, which makes possible a rather high efficiency of SO production of similar to 3-5%.
机译：研究了O-2（a（1）Delta（g））和O-2（b（1）Sigma（g）（+））分子以及O（P-3）原子的产生和运输动力学在石英管中以1-20 Torr的压力通过13.56 MHz射频放电激发的O-2流中。已经表明，随着输入到放电中的能量的增加，O-2（a（1）Delta（g））和O（P-3）的密度达到饱和。单线态氧（SO）的最大产率和O-2的解离度随压力下降。已经证明，取决于能量输入，RF放电可以以三种模式存在：I-在空间同质模式或α-模式; III-在放电外部存在等离子流时，以基本上不均匀的模式;和II-在模式I和III之间的过渡模式下。在本文中，仅详细考虑O-2流中RF放电的均匀模式。建立了a模式的自洽模型，该模型使我们能够分析导致O-2（a（1）A（g））和O-2（b（1）Sigma）产生和损失的基本过程（g）（+））分子以及O（P-3）原子的详细信息。为了验证模型的动力学方案和结论，当O-2（a（1）Delta（g））的固定密度较低时，在较低的流速和较高的压力（> = 10 Torr）下进行了一些实验。 ），放电区域中的O-2（b（1）Sigma（g）（+））和O（P-3）不是通过颗粒逸出而是通过体积和表面反应引起的损失来确定的。在这些条件下，O-2（b（1）Sigma（g）（+））的密度取决于通过直接电子碰撞和电子轰击产生的O-2（b（1）Sigma（g）（+））的平衡。电子从亚稳态O（D-1）原子转移并通过氧原子和管壁失活，包括在余辉中被臭氧淬灭。 O（P-3）密度取决于通过电子撞击进行O-2解离的产物与壁重组时的异质损失之间的平衡。 O-2（a（1）Delta（g））的固定密度由O-2（a（1）Delta（g））的生产过程提供，该过程通过直接电子撞击和由于管壁淬火而造成的损失而产生在低于4托的低压下，以及在高于7托的压力下与氧原子进行三体重组。压力高于7托时的分析。通过氧原子对O-2（a（1）Delta（g））三体淬灭的分析表明，该过程实际上可能具有较高的速率常数，并且能够在高压下提供快速的SO失活。速率常数的近似值-（1-3）x 10（-32）cm（3）s（-1）已从O-2（a）传输动力学的模拟和实验数据之间的最佳一致性中获得（1）Delta（g））分子和O（P-3）原子。结果表明，RF放电的a模式对应于在准中性等离子体中具有有效减小的电场的放电，该放电约等于30 Td，这使得SO产生的效率相当高，接近3-5％。 。

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