Time resolved imaging of nanoscale dynamics of gas phase metal particles

如果宏观物质的大小缩小到接近原子的大小，它的许多性质就会发生巨大的变化。对于结构和电子特性来说尤其如此，因此可以预期，运动动力学的许多方面也将与宏观行为有很大的不同。我们打算研究分离的纳米粒子在强激发后如何变形或振荡。目前这是一个几乎未开发的领域，因为到目前为止还没有技术可以监测自由纳米颗粒随时间变化的形状。我们打算利用时间分辨x射线衍射的新技术首次直接成像纳米颗粒动力学。利用自由电子激光器应使用的超短x射线脉冲测量粒子在强激光脉冲激发后的随时间变形。这些纳米粒子动力学的“电影”不仅提供了直接接触粒子的弹性特性和潜在的原子相互作用的途径，而且还允许人们研究粒子熔化、强电子激发或高电荷如何改变这些特性。一般的原子结构、表面形貌以及电子和原子核之间的耦合都会影响动力学。我们期望观察到许多新的动力学现象，这将激发纳米物理学以外的研究领域。

If macroscopic matter is reduced in size to almost atomic dimensions, many of its properties change dramatically. This is particularly true for structural and electronic properties, and one can therefore expect that also many aspects of motional dynamics will differ substantially from macroscopic behavior. We intend to study how isolated nanoparticles deform or oscillate after a strong excitation. This is presently an almost unexplored field, as no technique was available up to now which couldmonitor the time-dependent shape of a free nanoparticle. We intend to directly image the nanoparticle dynamics for the first time with a novel technique employing time-resolved x-ray diffraction. Ultrashort X-ray pulses from a free electron laser shall be used to measure the time-dependent deformation of the particles after an excitation by a strong optical laser pulse. These „movies“ of the nanoparticle dynamics will not only offer direct access to the elastic properties of the particles and the underlying atomic interactions, but it will also allow one to study how these are changed by a melting of the particles, by a strong electronic excitation, or a high charging. The general atomic structure, the surface morphology as well as the coupling between electrons and nuclei will affect the dynamics. We expect to observe many novel dynamical phenomena which will stimulate research fields far beyond nanophysics.