Mechanism for the destruction of H3+ ions by electron impact
Mechanism for the destruction of H3+ ions by electron impact
复制标题
电子撞击破坏 H3 离子的机制
作者：
V. Kokoouline;C. Greene;B. Esry
最简单的三原子离子（H3+）与低能电子复合后解离的速率已在许多实验中测量过。这个过程对于理解漫射星际云中H3+的观测特别重要。但是，尽管付出了大量的努力，还没有任何理论方法被证明能够预测低能量下解离重组的测量速率，甚至在一个数量级内。在这里，我们展示了在电子-分子碰撞的理论描述中几乎被普遍忽视的扬-泰勒对称-扭曲效应，以比任何其他已知机制都快得多的速度产生复合。我们估计的速率常数与实验所得的值范围重叠。我们将低能碰撞过程视为一个曲线交叉问题，以前认为这不适用于H3+中的低能复合。我们的计算再现了中性碎片的三体与二体分裂的测量倾向，以及H2产物分子的振动分布。
The rate at which the simplest triatomic ion (H3+) dissociates following recombination with a low-energy electron has been measured in numerous experiments. This process is particularly important for understanding observations of H3+ in diffuse interstellar clouds. But, despite extensive efforts, no theoretical treatment has yet proved capable of predicting the measured dissociative recombination rates at low energy, even to within an order of magnitude. Here we show that the Jahn–Teller symmetry-distortion effect—almost universally neglected in the theoretical description of electron–molecule collisions—generates recombination at a much faster rate than any other known mechanism. Our estimated rate constant overlaps the range of values spanned by experiments. We treat the low-energy collision process as a curve-crossing problem, which was previously thought inapplicable to low-energy recombination in H3+. Our calculation reproduces the measured propensity for three-body versus two-body breakup of the neutral fragments, as well as the vibrational distribution of the H2 product molecules.