Air Force Research Laboratory, Space Vehicle Directorate, Kirtland Air Force Base, New Mexico 87117, USA.
J Chem Phys. 2013 Nov 14;139(18):184306. doi: 10.1063/1.4829447.
Thermal electron attachment to the radical species C2F3 and C2F5 has been studied over the temperature range 300-890 K using the Variable Electron and Neutral Density Attachment Mass Spectrometry technique. Both radicals exclusively undergo dissociative attachment to yield F(-). The rate constant for C2F5 shows little dependence over the temperature range, remaining ~4 × 10(-9) cm(3) s(-1). The rate constant for C2F3 attachment rises steeply with temperature from 3 × 10(-11) cm(3) s(-1) at 300 K to 1 × 10(-9) cm(3) s(-1) at 890 K. The behaviors of both species at high temperature are in agreement with extrapolations previously made from data below 600 K using a recently developed kinetic modeling approach. Measurements were also made on C2F3Br and C2F5Br (used in this work as precursors to the radicals) over the same temperature range, and, for C2F5Br as a function of electron temperature. The attachment rate constants to both species rise with temperature following Arrhenius behavior. The attachment rate constant to C2F5Br falls with increasing electron temperature, in agreement with the kinetic modeling. The current data fall in line with past predictions of the kinetic modeling approach, again showing the utility of this simplified approach.
使用可变电子和中性密度附着质谱技术，在 300-890 K 的温度范围内研究了自由基 C2F3 和 C2F5 与热电子的附着。这两种自由基都只经历离解附着，生成 F(-)。C2F5 的速率常数在整个温度范围内几乎没有依赖性，保持在~4×10(-9) cm(3) s(-1)左右。C2F3 附着的速率常数随温度急剧上升，从 300 K 时的 3×10(-11) cm(3) s(-1)上升到 890 K 时的 1×10(-9) cm(3) s(-1)。两种物质在高温下的行为与之前使用最近开发的动力学建模方法，根据 600 K 以下的数据外推结果一致。在相同的温度范围内还对 C2F3Br 和 C2F5Br（在这项工作中用作自由基的前体）进行了测量，并在 C2F5Br 中作为电子温度的函数进行了测量。两种物质的附着速率常数随温度升高均呈阿累尼乌斯行为。C2F5Br 的附着速率常数随电子温度的升高而降低，这与动力学模型一致。当前的数据与动力学建模方法的过去预测一致，再次显示了这种简化方法的实用性。
