Davies Helen L, Guerra Vasco, van der Woude Marjan, Gans Timo, O'Connell Deborah, Gibson Andrew R
York Plasma Institute, Department of Physics, University of York, Heslington, YO10 5DD, United Kingdom.
Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal.
Plasma Sources Sci Technol. 2023 Jan 1;32(1):014003. doi: 10.1088/1361-6595/aca9f4. Epub 2023 Feb 8.
Characterisation of the vibrational kinetics in nitrogen-based plasmas at atmospheric pressure is crucial for understanding the wider plasma chemistry, which is important for a variety of biomedical, agricultural and chemical processing applications. In this study, a 0-dimensional plasma chemical-kinetics model has been used to investigate vibrational kinetics in repetitively pulsed, atmospheric pressure plasmas operating in pure nitrogen, under application-relevant conditions (average plasma powers of 0.23-4.50 W, frequencies of 1-10 kHz, and peak pulse powers of 23-450 W). Simulations predict that vibrationally excited state production is dominated by electron-impact processes at lower average plasma powers. When the average plasma power increases beyond a certain limit, due to increased pulse frequency or peak pulse power, there is a switch in behaviour, and production of vibrationally excited states becomes dominated by vibrational energy transfer processes (vibration-vibration (V-V) and vibration-translation (V-T) reactions). At this point, the population of vibrational levels up to increases significantly, as a result of V-V reactions causing vibrational up-pumping. At average plasma powers close to where the switching behaviour occurs, there is potential to control the energy efficiency of vibrational state production, as small increases in energy deposition result in large increases in vibrational state densities. Subsequent pathways analysis reveals that energy in the vibrational states can also influence the wider reaction chemistry through vibrational-electronic (V-E) linking reactions (N + N N + N and N + N N + N ), which result in increased Penning ionisation and an increased average electron density. Overall, this study investigates the potential for delineating the processes by which electronically and vibrationally excited species are produced in nitrogen plasmas. Therefore, potential routes by which nitrogen-containing plasma sources could be tailored, both in terms of chemical composition and energy efficiency, are highlighted.
表征大气压下氮基等离子体中的振动动力学对于理解更广泛的等离子体化学至关重要，而这对于各种生物医学、农业和化学加工应用都很重要。在本研究中，一个零维等离子体化学动力学模型被用于研究在与应用相关的条件下（平均等离子体功率为0.23 - 4.50 W、频率为1 - 10 kHz以及峰值脉冲功率为23 - 450 W），在纯氮气中运行的重复脉冲大气压等离子体中的振动动力学。模拟预测，在较低的平均等离子体功率下，振动激发态的产生主要由电子碰撞过程主导。当平均等离子体功率超过一定限度时，由于脉冲频率或峰值脉冲功率增加，行为会发生转变，振动激发态的产生变为由振动能量转移过程（振动 - 振动（V - V）和振动 - 平动（V - T）反应）主导。此时，由于V - V反应导致振动上抽运，高达 的振动能级的粒子数显著增加。在接近发生转变行为的平均等离子体功率处，有可能控制振动态产生的能量效率，因为能量沉积的小幅增加会导致振动态密度大幅增加。随后的反应路径分析表明，振动态中的能量也可以通过振动 - 电子（V - E）连接反应（N + N N + N 和N + N N + N ）影响更广泛的反应化学，这会导致彭宁电离增加和平均电子密度增加。总体而言，本研究探讨了描绘在氮等离子体中产生电子激发态和振动激发态的过程的可能性。因此，强调了在化学成分和能量效率方面定制含氮等离子体源的潜在途径。
