This project is aimed at an advanced theoretical study and understanding of systems known as spherical endohedral fullerenes, designated as A@Cn. These are systems where a foreign atom A is captured and held inside the hollow carbon cage consisting of n-carbon atoms, Cn, termed a fullerene (also known as a bucky-ball). These systems were discovered only relatively recently and their study is only really beginning. There are a number of possible applications of these novel systems; thus the study of their fundamental properties is of both basic and applied (technological) importance. They are regarded as new building blocks for materials with unique properties, as containers for reversible energy storage, as ideal building blocks for the qubits of a quantum computer, as unique drug delivery "vehicles" in medical imaging and cancer therapy, etc. The current knowledge of their properties is far from complete. It is only over the latest decade or so that the structure of atoms A encapsulated (confined) inside fullerene cages, as well as their interaction with electromagnetic and charged-particle radiation, have fallen under intense scrutiny by theorists. As for experiment on these formations, it is in its infancy. In this project, various important aspects of the structure and dynamics of endohedral fullerenes will be studied. Specifically, the impact of confinement-produced effects due to the fullerene cage on the structure of the encapsulated atom, as well as ionization spectra of the atom A captured inside neutral fullerenes Cn, A@Cn, positively charged fullerene ions (cations, A@Cnz+) and negatively charged fullerence ions (anions, A@Cnz-). In addition atoms inside of multiwalled, nested, fullerenes (A@Cn@Cm@...@Ck) known as bucky-onions, will be investigated. Various models representing the effects of confinement will be used to address the problem at various levels of approximation. Existing computer programs will be generalized to include the effects of confinement, electron-electron interactions and dynamical polarization of carbon cages of endohedral fullerenes by the incoming radiation on the structure and dynamics of the encapsulated atoms. The research program is expected to reveal new properties of endohedral fullerenes of fundamental and technological significance. Collaboration with experimental groups will be purposefully sought to assure quality of the theoretical study. Thus, the calculational results will be provided to experimenters on gas-phase endohedral fullerenes to identify some of the most interesting and/or useful measurements which could be performed, thereby contributing synergy to the advancement of this promising, rapidly developing area of research.
The involvement and active participation of undergraduate students in this project, with a special focus on students from underrepresented groups, will foster and strengthen integration of quality research and education at the University of North Alabama, as well as enhance the research infrastructure. The research will motivate undergraduate students to seek engagement in professional physics or other science and engineering careers. The results of research will be disseminated broadly to the scientific community. Society will benefit from the proposed activity by gaining new fundamental knowledge on natural phenomena with possibly important applications, and by the training of students who, early in their careers, will have acquired a unique professional experience. This, in turn, will significantly contribute to the benefit, health and vitality of science and engineering and the prosperity of society.
During the entire life of the award, novel aspects of the structure and spectra of free atoms as well as single-walled A@C60 and A@C240 and multi-walled A@C60@C240 endohedral fullerenes have been uncovered. Thus, to name a few, it has been found that atoms under increasing compression can behave in a counter-intuitive manner such as starting suddenly swelling rather than shrinking or alternatively shrinking and swelling with increasing pressure on them, when certain conditions are met, that inter-electron interaction in atoms changes upon their confinement inside of endohedral fullerenes thereby leading to novel resonant effects in electron-impact ionization or photoionization of the systems, that the ionization process of an atom inside endohedral fullerenes is accompanied by the change in the potential of a fullerene cage itself which, in turn, affects the final outcome of the ionization process, etc. A number of existing models and/or computer codes for studying of the structure and spectra of atoms inside fullerenes have been developed and/or improved for getting a deeper insight into properties of the systems and processes in question. Research results are of interest to atomic and molecular physics, astrophysics, nano-science and nano-technology, etc. They have been disseminated to research community via sixteen publications as well as about ten conference presentations. Society has, thus, benefited from the performed activities by gaining new fundamental knowledge on natural phenomena of interdisciplinary significance with possibly important applications. Altogether, six undergraduate students from the University of North Alabama were actively involved in research and became co-authors in about eight publications as well as co-presenters or presenters of research results at various physics conferences. Four of them are now pursuing graduate study in physics in various universities in the United States. Society has, thus, benefited from the project performance by having gained well trained students who, early in their careers, have acquired a superior undergraduate research experience and now master it to further professional heights in graduate universities in the United States to the future benefit, health and vitality of science and engineering and the prosperity of society.
