Probing Transition States of Chemical Reactions Utilizing Neutralization of Molecular Ions

在这个项目中，我们打算通过四种不同的方法，尽可能直接地探索化学反应的中间或过渡状态。主要目的是建立一种利用多原子离子的重组过程来临时产生中性反应中间状态的技术。在第一种方法中，我们研究了与此相反的过程，即中性受激分子形成离子对。为此，我们利用同步辐射的光激发。我们研究的体系包括，例如，CH_3X *X^-+CH_3^+，其中X是卤素原子H或D，SO_2*O_-+SO_+, O_-+S_+O。我们可以成功地获得导致离子对形成的势能表面的一系列重要信息，这些信息反过来又与正离子-负离子重组有关。在第二种方法中，流动的余辉技术被用于研究振动激发分子的碰撞失活…更多的离子和电子激发的过渡金属原子。得到了CO_+ (A^2II,v)、N_2O^+ (A^2SIGMA, v)、Ti （A^ 3F, A^ 5F）和v （A^ 4F, A^ 6D）碰撞过程的机制、中间态和相关速率常数等有价值的信息。在第三和第四种方法中，我们首先设计和构建了一个具有三种类型离子源的束室/穿着束装置，用于产生高强度正离子和负离子束。它们是双等离子体型、科隆型和普通电子冲击型离子源。我们已经成功地获得了高强度的正离子束，如N_2+，接近空间电荷极限，即<约等于>0_5 cm^<-3>，经过质量选择和减速到几个eV。此外，我们开发了一种冷却版的双等离子体型离子源来产生簇离子，并研究了簇离子的光解离和碰撞解离。用铜蒸气激光研究了（N_2） _2^+、（N_2） _3^+、（CO_2） _2_+和（N_2O） _2^+的光解作用。例如，（CO_2） _2^+光解反应得到的唯一产物是CO_2_+，这表明这里探测的二聚体离子的激发态不可能是CO_2^++CO_2*CO_3^++CO反应的中间态。少

In this project, we intended to probe intermediate or transition state of chemical reactions as directly as possible, by taking four different approaches. The main objective is to establish the technique that utilizes the recombination processes of polyatomic ions to produce temporarily the intermadiate states of neutral rections. In the first approach, we studied the reverse processes to this, that is, the ion pair formation from neutral excited molecules. For this purpose we utilized photoexcitation by synchrotron radiation. The systems we studied include, for example, CH_3X *X^-+CH_3^+, where X is either a halogen atom, H,or D,SO_2*O_-+SO_+, O_-+S_+O.We could successfully obtain a body of important information on the potential energy surfaces leading to ion pair formation, which in turn is relevant to the positive ion-negative ion recombination. In the second approach, a flowing afterglow technique has been used to investigate collisional deactivation of vibronically excited molecul … More ar ions and electronically excited transition metal atoms. Valuable information on the mechanisms, intermediate states, and the relevant rate constants have been obtained for the collisional processes of, for example, CO_+ (A^2II,v), N_2O^+ (A^2SIGMA, v), Ti (a^3F,a^5F), and V (a^4F,a^6D). In the third and fourth approarch, we started with designing and constructing a beam-chamber/cressed beams apparatus with three types of ion sources for generating high intensity positive and negative ion beams. These are duoplasmatron type, Colutron type, and ordinary electron impact type ion sources. We have succeeded in obtaining as high an intensity of positive ion beam, such as of N_2+, as that close to the space-charge limit, i.e., <approximately equal> 10_5 cm^<-3>, after mass selection and deceleration down to a few eV.In addition, we developed a cooled version of the duoplasmatron type ion source to produce cluster ions, with which we studied the photodissociation and collisional dissociation of the cluster ions. Photodissociation of cluster ions (N_2) _2^+, (N_2) _3^+, (CO_2) _2_+, and (N_2O) _2^+has been stuided using a copper vapor laser. It has been found that the only product obtained in the photodissociation of, for example, (CO_2) _2^+is CO_2_+, indicating that the excited states of the dimer ion probed here cannot be an intermediate state of the reaction CO_2^++CO_2*CO_3^++CO. Less