Liu Li, Martin Courtney, Farrar James M
Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
J Chem Phys. 2006 Oct 7;125(13):133117. doi: 10.1063/1.2212417.
The reactions between OH+(3Sigma-) and C2H2 have been studied using crossed ion and molecular beams and density functional theory calculations. Both charge transfer and proton transfer channels are observed. Products formed by carbon-carbon bond cleavage analogous to those formed in the isoelectronic O(3P)+C2H2 reaction, e.g., 3CH2 + HCO+, are not observed. The center of mass flux distributions of both product ions at three different energies are highly asymmetric, with maxima close to the velocity and direction of the precursor acetylene beam, characteristic of direct reactions. The internal energy distributions of the charge transfer products are independent of collision energy and are peaked at the reaction exothermicity, inconsistent with either the existence of favorable Franck-Condon factors or energy resonance. In proton transfer, almost the entire reaction exothermicity is transformed into product internal excitation, consistent with mixed energy release in which the proton is transferred with both the breaking and forming bonds extended. Most of the incremental translational energy in the two higher-energy experiments appears in product translational energy, providing an example of induced repulsive energy release.
利用交叉离子与分子束以及密度泛函理论计算研究了OH+(3Σ-)与C2H2之间的反应。观察到了电荷转移和质子转移通道。未观察到类似于等电子体O(3P)+C2H2反应中形成的通过碳-碳键断裂形成的产物，例如3CH2 + HCO+。三种不同能量下两种产物离子的质心通量分布高度不对称，最大值接近前体乙炔束的速度和方向，这是直接反应的特征。电荷转移产物的内能分布与碰撞能量无关，且在反应放热处达到峰值，这与有利的弗兰克-康登因子或能量共振的存在均不一致。在质子转移中，几乎整个反应放热都转化为产物的内部激发，这与混合能量释放一致，其中质子转移时键的断裂和形成都在延伸。在两个较高能量实验中，大部分增加的平动能量出现在产物的平动能量中，这提供了一个诱导排斥能量释放的例子。
