Collision-Energy Dependence of the Ion–Molecule Charge-Exchange Reaction Ar⁺ + CO → Ar + CO⁺

Abstract

Ion–molecule charge-exchange reactions Ar+ + CO → Ar + CO+ at the center-of-mass collision energies of 4.40, 6.40, and 8.39 eV are investigated using ion velocity map imaging technique. Although multiple electronically excited states of CO+ are accessed, the population of CO+ at the A2Π state is predominant in the present collision-energy range. In contrast to our previous study for NO, but similar to the case of O2, the forward-scattered CO+ yields show a broader angular distribution at the higher collision energy. Typically, the Franck–Condon-region charge transfer, energy resonant charge transfer, and intimate collision are three different mechanisms in which the intimate collision experiences an intermediate complex, and this mechanism usually plays an essential role in the thermal-energy reactions. However, the present observations indicate that this mechanism, concerning the intermediate (Ar–CO)+, is still of utmost importance in a relatively high collision-energy range.

Progresses in the Study of Low-Energy Ion-molecule Reaction Dynamics※

“…我们研究组 [15,36] VMI 系统的设计能量分辨率是 2%, 由于离子束和分子束的能量和速度展宽, 实测的速度影 像能量分辨率约为 11%; 根据 Wester 组 [35] 在碰撞能 0.83 eV 时能量展宽为 0.14 eV 的表述, 可估算出其离子速度 影像的能量分辨率约为 16%; Farrar 组 [27] 的离子速度影 像速度分辨率为 10%, 对应的能量分辨率则是 20%. 利用此装置, 我们 [9][10][15][16][17][18][19][20] 在研究 Ar ＋ 和小分子的 CT 和 DCE 过程中发现了各种有趣的立体动力学特征, 后面 将详细介绍具体现象和相关动力学机制.…”

“…奥地利的 Wester 组从 实验和理论方面, 对负离子亲核取代(S N 2)及相关反应 过程进行了系统的研究工作 [11][12][13] , 还对部分正离子分子 反应过程开展了研究 [21][22][23][24][25][26] ; 美国的 Farrar 组 [14,[27][28][29][30][31][32] 则重 点研究了 C ＋ 、N ＋ 、O ＋ 等原子离子和各种含氢小分子的 CT 和 DCE 过程. 我们组目前已开展了 Ar ＋ 和双原子分 子和多原子分子的 CT 和 DCE 研究 [9][10][15][16][17][18][19][20] , 澄清了以 前对碰撞 CT 过程的争议, 发现了奇特的立体碰撞反应 动力学机制 [9][10] .…”

Collision-Energy Dependent Stereodynamics of Dissociative Charge Exchange Reaction between Ar+ and CO

“…Using our 3D-VMI apparatus, ,, the momentum or velocity distributions of the C + products in three-dimensional space are recorded at the collision energies E c.m. = 7.46, 8.39, 9.21, and 9.97 eV, respectively.…”

“…At last, we address a little about the difference between the charge-exchange-only and DCE reactions. In the charge-exchange only reaction, the angular distributions of the forward-scattered O 2 + (ref ) and CO + (ref ) yields become wider or more diffuse with the increase of collision energy. The present observations, as well as the previous, are unlikely to be relevant to the charge-exchange-only reaction, , although the charge exchange is their common doorway.…”

“…In the charge-exchange only reaction, the angular distributions of the forward-scattered O 2 + (ref ) and CO + (ref ) yields become wider or more diffuse with the increase of collision energy. The present observations, as well as the previous, are unlikely to be relevant to the charge-exchange-only reaction, , although the charge exchange is their common doorway. In other words, the charge exchange is accomplished in significantly different ways between DCE and the charge-exchange-only reaction, which deserves further theoretical simulations.…”