Studies on Weak Intermolecular Interactions by Low-Frequency Vibrational Coherence

低频振动相干性研究弱分子间相互作用

基本信息

批准号：
10440170
负责人：
YOSHIHARA Keitaro
金额：
$ 6.4万
依托单位：
Japan Advanced Institute of Science and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

Ultrashort light pulses can coherently excite vibrations with the frequency smaller than the pulse bandwidth. This coherence can be observed by spectroscopic methods in real time as oscillations and specific knowledge can be gained about dynamics of the particular low frequency vibrational mode. Coherent spectroscopy is currently a separate spectroscopic method to study vibrational relaxation, vibrational dephasing and contribution of particular vibrations to chemical reactions, intermolecular vibrations, molecular recognition in biological systems. Electronic states having a charge-transfer character can be found in many natural molecular systems, for example, in iron porphyrin and in photosynthetic reaction center.The excited-state dynamics of several electron donor-acceptor complexes was studied by a femtosecond fluorescence up-conversion technique. The spontaneous fluorescence of the complexes exhibits an oscillatory feature superimposed with an ultrafast decay component. The oscillation is assigned to the out-of-plane vibration of the acceptors, for complexes with three different acceptors used, tetracyanoethylene, chloranil, and fluoranil. The peak-shift correlation function shows an ultrafast relaxation attributed mainly to the intramolecular vibrational energy redistribution process superimposed with the oscillatory component that demonstrates the modulation of the transition frequency during the vibration. At the same time the modulation of the mean transition moment is observed, which is an indication of the non-Condon transition. Thus, two mechanisms are observed to be responsible for the oscillations : the modulation of the transition frequency and the modulation of the mean transition moment by the vibrational motion.

Ultrashort Light脉冲可以与小于脉冲带宽的频率相干地激发振动。可以通过光谱方法实时观察到这种连贯性，因为振荡和特定知识可以在特定的低频振动模式的动力学上获得。相干光谱法当前是一种研究振动松弛，振动性的振动和特定振动对化学反应，分子间振动，生物系统分子识别的贡献的单独光谱方法。具有电荷转移特性的电子状态可以在许多天然分子系统中找到，例如在铁卟啉和光合反应中心中。通过一种fomtsecond荧光上流技术研究了几种电子供体供应器复合物的激发态动力学。复合物的自发荧光表现出与超快衰减成分叠加的振荡特征。对于使用三种不同受体的复合物，四乙烯乙烯，氯不良和氟纳米，将振荡分配给受体的平面外振动。峰值相关函数显示了一种超快松弛，主要归因于分子内振动能重新分布过程，该过程与振荡分量叠加，该过程证明了振动期间过渡频率的调节。同时，观察到平均过渡矩的调制，这是非核对转变的指示。因此，观察到两种机制是负责振荡的原因：过渡频率的调节以及通过振动运动对平均过渡力矩的调节。