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Probing Transition States of Chemical Reactions Utilizing Neutralization of Molecular Ions

利用分子离子的中和作用探测化学反应的过渡态

基本信息

批准号：
03403003
负责人：
KOYANO Inosuke
金额：
$ 21.7万
依托单位：
Himeji Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (A)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1994
项目状态：
已结题

项目摘要

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

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测化学反应的中间或过渡态。主要目的是建立一种利用多原子离子的复合过程产生中性反应中间态的技术。在第一种方法中，我们研究了与此相反的过程，即中性激发分子的离子对形成。为此，我们利用同步辐射光激发。我们所研究的体系包括CH_3X *X^-+CH_3^+，其中X是卤素原子，H，或D，SO_2 *O_-+SO_+，O_-+S_+O。我们成功地获得了导致离子对形成的势能面的一系列重要信息，而这些势能面又与正离子-负离子复合有关。在第二种方法中，流动余辉技术被用来研究振动激发分子的碰撞失活， ...更多信息 Ar离子和电子激发的过渡金属原子。对于CO_+（A^2II，v）、N_2O^+（A^2SIGMA，v）、Ti（a^3F，a^5F）和V（a^4F，a^6D）等分子的碰撞过程，我们已经获得了关于碰撞机制、中间态和相关速率常数的有价值的信息。在第三、第四种方法中，我们首先设计和建造了一个束室/cressed束装置，该装置具有三种类型的离子源，用于产生高强度的正、负离子束。它们是双等离子体管型、Colutron型和普通电子碰撞型离子源。我们成功地获得了接近空间电荷极限的高强度正离子束，如N_2+，<approximately equal>此外<-3>，我们还研制了一种用于产生团簇离子的冷却型双等离子体离子源，并利用它研究了团簇离子的光解离和碰撞解离。用铜蒸气激光器研究了团簇离子（N_2）_2^+、（N_2）_3^+、（CO_2）_2_+和（N_2O）_2^+的光解。已经发现，在光解离（例如，（CO_2）_2^+）中获得的唯一产物是CO_2_+，这表明这里探测的二聚体离子的激发态不可能是反应CO_2^++CO_2*CO_3^++ CO的中间态。