Subshell Differential Photoionization Studies of Single- and Multi-Walled Fullerene Endohedrals

原子在富勒烯中的封装提供了一个独特的天然实验室来研究受限原子的行为。对这些面体内化合物的研究不仅可以在原子尺度上产生有趣的效应，还可以探索纳米区域量子效应的微妙之处。除了单壁限制外，嵌套的同心单壁富勒烯的多壁禁闭壳层--巴基洋葱，可以使中心原子与壳层的耦合具有丰富的新效应。在技术上，面内富勒烯也具有令人兴奋的应用前景：(A)正在研究将面内掺杂的富勒烯和巴基洋葱作为固体量子计算的种子材料，其中量子比特可以编码在被封装原子的电子和核自旋中。(B)最近用Ar@C60进行的实验发现，有证据表明包裹的原子显著提高了材料的超导能力。(三)建议的生物医学用途是在富勒烯笼子内屏蔽放射性示踪剂，然后将该材料注入人体血液中以监测血液流动。(D)富勒烯将金属原子隔离在体内的能力使其作为磁共振成像的对比度增强剂的潜力得以发掘。在地外环境中发现了富勒烯，并捕获了稀有气体，这表明他们的研究具有天体物理学意义。因此，了解禁闭笼对原子光谱的影响，以及反之亦然，是非常有意义的事情。由于光子与电子的耦合很弱，光子在最终的通道中消失，因此光电离是一种很好地解释原子系统分立态和连续态的多电子动力学的众所周知的方法。利用这个工具，我们将研究离域电子在面内掺杂的单壁和多壁富勒烯中的集体运动所起的作用。我们将计算原子和富勒烯亚壳层的电离截面和不对称参数，以了解决定这些纳米粒子光吸收性质的多体相互作用。此外，还将本着最近讨论的傅里叶光谱学方法，详细研究原子光致自由电子穿过禁闭墙的衍射。

The encapsulation of atoms in fullerenes offers a unique natural laboratory to examine the behavior of an atom in confinement. Studies of these endohedral compounds can not only lead to intriguing effects at the atomic scale but also can probe subtleties of quantum effects in the nanometer region. Besides the single-wall confinement, the multi-walled confining shell of nested concentric single-walled fullerenes, bucky-onions,can make the coupling of the central atom with the shell rich in novel effects.Technologically also the endohedral fullerenes hold the promise of exciting applications:(a) Research is underway to use endohedrally doped fullerenes and bucky onions as seed materials in solid state quantum computations, in which quantum bits can be encoded in the electronic and nuclear spins of the encapsulated atoms. (b) Recent experiments with Ar@C60 find evidence of encaged atoms significantly improving the superconducting ability of materials. (c) A proposed biomedical application of endohedral materials is to shield radioactive tracers inside fullerene cages, and then inject the material into human blood to monitor blood flow. (d) The ability of fullerenes to sequester metal atoms inside has led to exploring their potential as contrast-enhancing agents for magnetic resonance imaging. The discovery of endo fullerenes with trapped noble gases in extraterrestrial environments indicates the astrophysical relevance of their studies. Therefore, understanding the influence of the confining cage on thespectroscopy of the atom inside, and vice versa, are matters of significant interest.A theoretical photoionization study of these compounds is proposed. Photoionization is a well known method to obtain a fairly undistorted account of the many-electron dynamics of the discrete and continuum states of atomic systems, since the coupling of the photon with the electrons is so weak and the photon disappears in the final channel.Employing this tool we will investigate the role of the collective motion of delocalized electrons in endohedrally doped single- and multi-walled fullerenes. Cross sections and asymmetry parameters of the ionization from both atomic and fullerene sub-shells will be calculated to understand the many-body interactions that determine the photoabsorption properties of these nanoparticles.Moreover, the diffraction of atomic photo-liberated electrons in crossing the confining wall will be studied in detail in the spirit of a recently discussed Fourier photo-spectroscopy approach.