Real-Time Clocking of Energy Redistribution in Molecules Falling Apart

分子分裂中能量重新分配的实时时钟

• 批准号: 9419397
• 负责人: Mostafa El-Sayed
• 金额: $ 27万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-03-01 至 1998-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9419397&HistoricalAwards=false
• 关键词: Real; Time; Clocking; Energy; Redistribution

In this project in the Physical Chemistry program of the Chemistry Division, Professor Mostafa El-Sayed of the Georgia Institute of Technology will pursue a series of investigations in transition state spectroscopy. Specifically, the internal vibrational energy redistribution (IVR) in photodissociating molecules will be studied in real time using a pump-probe method. Two femtosecond lasers are to be used, one to cause photodissociation and the other, suitably time delayed with respect to the first, to resonantly ionize one of the photofragments whose recoil velocity distribution is determined as function of the pump-probe time delay. The spatial distribution of the recoil velocities of the photofragments will also be determined. This distribution depends on the internal energy distribution over the various degrees of freedom of the parent and photofragment species. The experiments will be done with unsaturated organic and metal iodide molecules. One of the current problem areas in chemistry is the nature of the transition state. Inherent in the field of chemistry is the simple idea that during a chemical reaction the reactants are converted to products by breaking reactant bonds and forming new bonds. During the reaction new species are formed which are neither reactants nor products. These species are transient species and, due to their role in the transition from reactants to products, are said to occur in the `transition region`, and their specific nuclear configurations are termed `transition states`. One of the most important issues in chemical reaction dynamics is to elucidate the relation between the properties of the transition state and the characteristics of the reaction product. The duration, or life time, of a transition state, and thus the duration of a chemical reaction rocess, varies from one trillionth of one second (one picosecond) to one housandth of a trillionth of one second (one quadrillionth, or one femtosecond). Direct, detailed molecular level information about the transition state of molecular systems can only be obtained with sophisticated techniques that employ lasers with ultra short pulse duration (femtosecond lasers). The research proposed by Professor El-Sayed uses novel laser techniques to obtain needed data for the understanding of the transition state in chemical reactions.

在这个项目中的物理化学程序的化学 格鲁吉亚研究所Mostafa El-Sayed教授 技术将在过渡状态下进行一系列调查 谱 特别是内部振动能 再分配（IVR）在光解离分子将在 真实的时间使用泵浦探测方法。 两个飞秒激光器将被 一种用于引起光解离，另一种用于适当延迟时间 相对于第一种，共振地吸收其中一个光碎片， 其反冲速度分布被确定为 泵浦-探测延时 反冲速度的空间分布 也将确定光碎片的数量。 这种分布取决于 在不同自由度上的内能分布 和光碎片物种之间的关系 实验将在 与不饱和有机和金属碘化物分子。 化学中当前的问题领域之一是 过渡态 化学领域固有的一个简单概念是 在化学反应过程中反应物转化为产物 通过破坏反应物键并形成新的键。 在反应期间 形成既不是反应物也不是产物的新物质。 这些 物种是过渡物种，由于它们在过渡中的作用， 从反应物到产物，据说发生在“过渡区”， 其特定的核构型被称为“过渡态”。 化学反应动力学中最重要的问题之一是 阐明过渡态性质与 反应产物的特性。持续时间，或生命时间， 也就是化学反应的持续时间 过程，从一万亿分之一秒（一皮秒）到一 万亿分之一秒（千万亿分之一，或一 飞秒）。 直接，详细的分子水平信息， 分子系统的过渡态只能用 采用超短脉冲激光的尖端技术 持续时间（飞秒激光）。 教授提出的研究 El-Sayed使用新的激光技术来获得所需的数据， 理解化学反应中的过渡态。