Experimental exploration of structural transformation of isolated small many-body systems

孤立小型多体系统结构变换的实验探索

基本信息

批准号：
14340180
负责人：
OHSHIMA Yasuhiro
金额：
$ 9.47万
依托单位：
Institute for Molecular Science (2004)Kyoto University (2002-2003)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

This research project aims at deeper understanding on structural phase transformation, such as melting, via experimental exploration on isolated gas-phase clusters, which are typical systems with limited number of degrees of freedom. We have planned to characterize their energy-level structure of vibrations pertinent to structural transformation by utilizing laser spectroscopy, and to probe in real time the motion of molecules along with the structural transformation by femto-second time-resolved spectroscopy. We have achieved experimental data on some important systems and developed a new experimental method, as follows.1) Electronic spectra of benzene clusters have been reexamined by using mass-selective resonance-enhanced ionization. In contrast that hexamer and the smaller clusters exhibit sharp vibronic bands, the larger clusters show broad absorption. This observation implies the coexistence of many structural isomers and/or large structural fluctuation for the larger clusters. Sudden change in the morphology of potential energy surfaces pertinent to structural transformation may occur at this cluster size.2) Clusters containing aromatic molecules with protic solvents, i.e., anthracene-ammonia and benzene-water, have been studied. Weak vibronic bands pertinent to intermolecular modes have been observed with good S/N by utilizing laser double resonance. The present data will be essential to construct the intermolecular potential with high accuracy.3) A time-resolved spectroscopic method in femto-second regime has been developed for real-time probing of structural transformation motions. The versatility of the method have been demonstrated by the successful observation of vibrational and rotational wavepackets of various molecules. In particular, wavepacket of the internal-rotation of a methyl group has been observed for the first time.

该研究项目旨在通过对孤立的气相簇进行实验探索，以更深入地了解结构相变，例如融化，这些群体是典型的自由度的典型系统。我们计划通过使用激光光谱法来表征它们与结构转化相关的振动的能量水平结构，并实时探测分子的运动以及FEMTO-SECENT-SECENT-SECENT-SECENT-SECENT-SECONTARE SEPTRACROSCOPY的结构转化。我们已经在某些重要系统上实现了实验数据，并开发了一种新的实验方法，如下所示。1）通过使用质量选择性共振增强电离电离，已经重新验证了苯簇的电子光谱。相比之下，六聚体和较小的簇表现出锋利的振动带，较大的簇显示出广泛的吸收。该观察结果意味着许多结构异构体和/或较大的结构波动的共存。在此簇大小的情况下，可能发生与结构转化有关的势能表面形态的突然变化。2）含有含有原始溶剂的芳香族分子的簇，即蒽 - 氨和苯二氧化碳。通过使用激光双共振，已经观察到了与分子间模式相关的弱振动带。目前的数据对于以高精度构建分子间电位至关重要。3）已经开发了一种时间分辨的femto秒状态的光谱法，以实时探测结构转化运动的实时探测。通过成功观察各种分子的振动和旋转波袋，该方法的多功能性已证明。特别是，首次观察到甲基内部旋转的波袋。