• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Exit routes from the transition state: Angular momentum constraints on the formation of products
【24h】

Exit routes from the transition state: Angular momentum constraints on the formation of products

机译：从过渡状态退出的路线：角动量限制了产品的形成

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

We have analyzed experimental data from a number of exothermic processes in which molecules in well-defined initial states are deactivated by inelastic, dissociative, or reactive collisions. Further, we analyze deactivation processes that do not occur in molecules despite their containing high levels of excitation. Significant common elements are found among these forms of deactivation. The initial step consists of transition to a product state involving minimum rotation state change (Delta j) consistent with energy conservation. Frequently, this process is near-energy-resonant. More critically, it may frequently require substantial angular momentum (AM) change. Analysis of experimental data indicates that constraints act upon on the formation of products in processes that involve release of excess energy. These constraints are associated with the magnitude of AM that must be generated for the initial transition to occur and this AM "load" increases with the amount of energy to be released. In general, the probability of generating rotational AM falls rapidly as Delta j increases, and this effectively limits the size of energy gap that may be bridged by a given reactant pair and at some point the constraint is sufficient to constitute a barrier that prevents the process from taking place. The choice of reactant species strongly affects the probability of each process that increases (i) when molecules efficiently interconvert momentum and (ii) when many product states are available in the critical near-resonant region. These factors increase the proportion of initial trajectories that possess the energy and momentum necessary to open a "product" channel. Evidence is presented showing that AM load-reduction strategies lead to marked enhancement of rates of collision-induced processes, suggesting that reduction of constraints in the exit channels from the transition state may constitute a previously unrecognized form of catalysis.
机译：我们已经分析了许多放热过程的实验数据，在这些过程中，处于明确定义的初始状态的分子因无弹性，解离或反应性碰撞而失活。此外，我们分析了尽管包含高水平激发但在分子中不会发生的失活过程。在这些失活形式中发现了重要的共同元素。初始步骤包括过渡到涉及最小旋转状态变化（Δj）且符合节能要求的产品状态。通常，该过程是近能量共振的。更关键的是，它可能经常需要大量的角动量（AM）变化。对实验数据的分析表明，在涉及释放过多能量的过程中，约束条件会影响产品的形成。这些约束与为发生初始转变而必须产生的AM的大小相关，并且此AM“负载”随要释放的能量的增加而增加。通常，随着Δj的增加，产生旋转AM的可能性会迅速下降，这有效地限制了给定反应物对可以弥合的能隙大小，并且在某些时候，该约束足以构成阻止该过程的障碍从发生。反应物种类的选择极大地影响了每个过程增加的可能性（i）当分子有效地相互转换动量时，以及（ii）在临界近共振区域中有许多产物态可用时。这些因素增加了具有打开“产品”通道所需的能量和动量的初始轨迹的比例。证据表明，减少AM负荷的策略会导致碰撞诱导过程速率的显着提高，这表明减少过渡态出口通道中的约束可能构成了以前无法识别的催化形式。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号