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首页> 外文期刊>Journal of Physics, D. Applied Physics: A Europhysics Journal >NH3 and NHx3 radicals synthesis downstream a microwave discharge sustained in an Ar-N-2-H-2 gas mixture. Study of surface reactive processes and determination of rate constants
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NH3 and NHx3 radicals synthesis downstream a microwave discharge sustained in an Ar-N-2-H-2 gas mixture. Study of surface reactive processes and determination of rate constants

机译：NH3和NHx3自由基在Ar-N-2-H-2气体混合物中维持的微波放电下游合成。表面反应过程的研究和速率常数的确定

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NH3 and NHx<3 radicals are produced downstream a microwave discharge containing Ar-N-2-H-2 gas mixture. The chemical mechanism under investigation consists of heterogenous reactions between adsorbed species NH or NH2 (denoted NHs and NH2s) and H or H-2 flowing downstream the discharge. NHs is adsorbed on the stainless steel reactor wall and reacts with H or H-2 producing NH2s or NH3: NHs + H <(k(3))under right arrow> NH2s and NHs + H-2 <(k(2))under right arrow> NH3. Then, part of NH2s produced reacts with H atoms producing NH3: NH2s + H <(k(1))under right arrow> NH3; another part is desorbed from the tube wall: NH2s <(k(sg))under right arrow> NH2. We assume that NH3 is spontaneously and totally desorbed. From the balance equations, we determine analytical relations for NH2s, NH2 and NH3 concentrations. We then measure values of reaction rate constants and compare the numerical results to measurements performed in the afterglow by means of mass spectrometer versus the %H-2 injected in the discharge. We measure values in two different initial gas mixtures, 98.7% Ar-1.3% N-2, and 66.6% Ar-33.3% N-2. In the first gas mixture, k1, k(2)(NHs), k(3)(NHs) and k(sg) range between 1 x 10(-17) and 2 x 10(-17) m(3) s(-1), 0.035 and 0.045 m s(-1), 9 and 11 m s(-1), and 0.30 and 0.35 m(-1) s(-1), respectively. In the second gas mixture, as expected, similar values are found for k(1) and k(sg) but the other two values increase by a factor of 5. Such an increase for k(2)(NHs) and k(3)(NHs) is probably due to the increase of the (NH,) concentration on the reactor wall. The recombination coefficient gamma is deduced from the previous rate constant values. We find gamma(1) = 4.12 x 10(-4), gamma(2) = 4.91 x 10(-6) and gamma(3) = 7.93 x 10(-4), using the mean values of reaction rate constants determined for k(1), k(2) and k(3), respectively, in the first gas mixture. To our knowledge, these results have never been published before. They are in good agreement with values given in the literature for other similar mechanisms. Finally, we conclude that the loss of H atoms on the reactor wall mainly results in producing NH2s and NH3. [References: 23]
机译：在包含Ar-N-2-H-2气体混合物的微波放电下游产生NH3和NHx <3自由基。所研究的化学机理由吸附物质NH或NH2（表示为NHs和NH2s）与流向放电下游的H或H-2之间的异质反应组成。 NHs吸附在不锈钢反应器壁上并与H或H-2反应生成NH2s或NH3：NHs + H <（k（3））在右箭头> NH2s和NHs + H-2 <（k（2））在右箭头> NH3下。然后，产生的部分NH2与H原子反应生成NH3：NH2s + H <（k（1））在右箭头> NH3;另一部分从管壁解吸：NH2s <（右箭头下的（k（sg）））NH2。我们假设NH3是自发完全解吸的。从平衡方程中，我们确定NH2s，NH2和NH3浓度的分析关系。然后，我们测量反应速率常数的值，并将数值结果与在余辉中通过质谱仪对注入放电中的％H-2进行的测量结果进行比较。我们在两种不同的初始混合气体中测量值：98.7％Ar-1.3％N-2和66.6％Ar-33.3％N-2。在第一种气体混合物中，k1，k（2）（NHs），k（3）（NHs）和k（sg）的范围介于1 x 10（-17）和2 x 10（-17）m（3）s之间（-1），0.035和0.045 ms（-1），9和11 ms（-1），以及0.30和0.35 m（-1）s（-1）。在第二种气体混合物中，正如预期的那样，k（1）和k（sg）的值相似，但其他两个值增加了5倍。k（2）（NHs）和k（3 （NHs）可能是由于反应器壁上（NH，）浓度的增加所致。从先前的速率常数值推导重组系数γ。使用确定的反应速率常数的平均值，我们发现gamma（1）= 4.12 x 10（-4），gamma（2）= 4.91 x 10（-6）和gamma（3）= 7.93 x 10（-4）分别在第一混合气体中的k（1），k（2）和k（3）。据我们所知，这些结果从未公开过。它们与文献中针对其他类似机制给出的值高度吻合。最后，我们得出结论，反应器壁上H原子的损失主要导致产生NH2和NH3。 [参考：23]

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