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Journal ArticleDOI

Photoionization of atomic krypton confined in the fullerene C60

TL;DR: In this article, the combined effects of interchannel coupling, relativistic interactions and endohedral confinement on the photoionization of atomic Kr are studied, and the confinement of the Kr atom placed at the centre of the C60 cage is modelled by placing the atom inside an annular spherical potential.
Abstract: The combined effects of interchannel coupling, relativistic interactions and endohedral confinement on the photoionization of atomic Kr are studied. The confinement of the Kr atom placed at the centre of the C60 cage is modelled by placing the atom inside an annular spherical potential. Cross sections for the photoionization and angular distribution of photoelectrons from the 4p, 4s, 3d and 3p subshells are reported within the framework of the relativistic-random-phase approximation.
Citations
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Journal ArticleDOI
TL;DR: Electron density analysis shows that the He-He interaction in He2@B16N16 is of closed-shell type whereas for the same in He 2@B12N12 there may have some degree of covalent character, and confinement causes some type of orbital interaction between two He atoms, which akins to some degree.
Abstract: The stability of Ngn@B12N12 and Ngn@B16N16 systems is assessed through a density functional study and ab initio simulation. Although they are found to be thermodynamically unstable with respect to the dissociation of individual Ng atoms and parent cages, ab initio simulation reveals that except Ne2@B12N12 they are kinetically stable to retain their structures intact throughout the simulation time (500 fs) at 298 K. The Ne2@B12N12 cage dissociates and the Ne atoms get separated as the simulation proceeds at this temperature but at a lower temperature (77 K) it is also found to be kinetically stable. He-He unit undergoes translation, rotation and vibration inside the cavity of B12N12 and B16N16 cages. Electron density analysis shows that the He-He interaction in He2@B16N16 is of closed-shell type whereas for the same in He2@B12N12 there may have some degree of covalent character. In few cases, especially for the heavier Ng atoms, the Ng-N/B bonds are also found to have some degree of covalent character. But the Wiberg bond indices show zero bond order in He-He bond and very low bond order in cases of Ng-N/B bonds. The energy decomposition analysis further shows that the ΔEorb term contributes 40.9% and 37.3% towards the total attraction in the He2 dimers having the same distances as in He2@B12N12 and He2@B16N16, respectively. Therefore, confinement causes some type of orbital interaction between two He atoms, which akins to some degree of covalent character.

55 citations

Journal Article
TL;DR: In this paper, the dynamical and static dipole polarizabilities of the C 60 molecule have been calculated on the basis of the experimental data on the cross section of the fullerene photoabsorption.
Abstract: Abstract The dynamical and static dipole polarizabilities of the C 60 molecule have been calculated on the basis of the experimental data on the cross section of the fullerene photoabsorption. It has been shown that the fullerene shell in the static electric field behaves most likely as a set of separate carbon atoms rather than as a conducting sphere.

38 citations

Journal ArticleDOI
TL;DR: In this paper, a review of investigations of the electronic structure and dynamics of atoms encaged in a single molecule is presented, where the major effects of confinement on the dynamical properties, e.g., confinement resonances, hybridization, Wigner time delay, are delineated.
Abstract: Confined atomic systems are of great importance owing a multitude of possible applications in various areas of science and technology. Of particular interest are atoms encaged in the $$\hbox {C}_{{60}}$$ molecule, $$\hbox {A}@\hbox {C}_{{60}}$$ , since the near-spherical symmetry of $$\hbox {C}_{{60}}$$ simplifies theoretical studies, and the stability of $$\hbox {C}_{{60}}$$ renders it amenable to experimental examination. A review of investigations of the electronic structure and dynamics of $$\hbox {A}@\hbox {C}_{{60}}$$ is presented in this manuscript focusing on developments in the last decade. Addressed mainly are how the confinement affects electronic structure properties such as ionization potentials, localization of atomic electrons, Shannon entropy, correlation effects, relativistic interactions, and others. In the area of dynamics, photoionization and e- $$\hbox {A}@\hbox {C}_{{60}}$$ scattering are reviewed and summarized, and the major effects of confinement on the dynamical properties, e.g., confinement resonances, hybridization, Wigner time delay, are delineated.

15 citations

Journal ArticleDOI
TL;DR: In this article, the static exchange method is applied to investigate photoionization of a confined system, Ar@C60, which explicitly includes the position of each carbon atom in the C60, a considerable improvement over methods to address the structure and photo dynamics of a constrained system where the carbon shell is modelled by a spherically symmetric model potential.
Abstract: The static-exchange method is applied to investigate photoionization of a confined system, Ar@C60. The realistic confinement potential employed in the present work explicitly includes the position of each carbon atom in the C60, which is a considerable improvement over methods to address the structure and photo dynamics of a confined system where the carbon shell is modelled by a spherically symmetric model potential. In the present study, photoionization from the deepest of the valence shells of C60 and Ar with ag symmetry is considered. There is a one-to-one correspondence between resonances that appear in the Ar@C60 system when the hole is in the 3s of the Ar, when the hole is in the C60 shell, or when the hole is in a free C60 system. Encapsulation of the Ar atom leads to some differences in the shapes and shifts in the energies of the resonant features in the cross-sections. However the qualitative features of the resonant state wave functions are very similar in the corresponding resonances of Ar@C60 and C60.

12 citations

Journal ArticleDOI
TL;DR: In this article, two transient phase methods have been used to directly compute the photoionization phase shift and Wigner time delay of confined atoms (A@C60) in the single-active electron (SAE) approximation.
Abstract: In contrast to the conventional finite difference methods, two transient phase methods have been effectively used in the present work to directly compute the photoionization phase shift and Wigner time delay of confined atoms (A@C60) in the single-active electron (SAE) approximation. The different phase methods: (A) employing logarithmic derivatives at shell boundaries, and (B) Born approximation are verified with the help of well-established finite difference methods in SAE approximation and sophisticated many-electron techniques. In this work, confinement oscillations on the dipole phase and photoelectron group delay following ionization from 1s subshell of H@C60, 3p subshell of Ar@C60 and 5p subshell of Xe@C60 are analyzed. The comparison with many-body calculation shows that the features in the time delay of a confined system are governed mainly by the effects of screening apart from that due to the external potential. A systematic study and comparison of the results from phase methods and many-electron techniques indicate that these techniques can be effectively used in the analysis of photoionization phase shift and time delay in confined atoms.

9 citations

References
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Journal ArticleDOI
TL;DR: In this article, the photoionization cross sections of 5 s electrons in Xe atom in the Xe@C60 endohedral complex have been calculated and the strong dependence of this effect upon the radius of the fullerene shell has been predicted.
Abstract: The photoionization cross sections of 5 s electrons in Xe atom in the Xe@C60 endohedral complex have been calculated. It is shown that within the wide frequency region, from the threshold to the giant resonance, the cross section is qualitatively modified, acquiring additional resonances due to inner reflection of the photoelectron from the surrounding carbon atoms. The strong dependence of this effect upon the radius of the fullerene shell has been predicted. PACS number~s!: 33.80.Eh, 36.40.Cg At present there are many papers devoted to the study of the properties of endohedral atoms @1#, i.e., atoms located inside the C60 fullerene cage. The number of different atoms which may be introduced into C60 continuously increases and has already reached about one-third of the Periodic Table including the rare gases @2,3#. The unusual geometrical structure of endohedrals makes them extremely attractive objects to study. The analysis of elementary processes of these particles will provide information on their very specific structure, which is affected to a large extent by the mutual influence of the C60 cage and the inner atom. To understand this

52 citations

Journal ArticleDOI
TL;DR: The synthesis of a mg amount of pure argon containing fullerene allowed the synthesis of the first endohedral superconductors with critical temperatures lower than expected, an indication of the strong influence of the argon atom on the C60 cage.

47 citations

01 Jan 2011
TL;DR: In this article, a model potential for modeling the environment of atoms and molecules inside fullerenes is proposed taking into consideration that the electrons of the guest atom or molecule are affected by an attractive short-range Gaussian shell to simulate the Cn cage.
Abstract: A novel model potential for modelling the environment of atoms and molecules inside fullerenes is proposed. The model takes into consideration that the electrons of the guest atom or molecule are affected by an attractive short-range Gaussian shell to simulate the Cn cage. As a test case, the present model is employed to study the electronic structure of an endohedrally confined hydrogen atom by C36 and C60 fullerenes. This study is performed using a new implementation of the p-version of the finite-element method by a self-consistent finite-element methodology. The results are then compared with previous ones obtained by using other short-range model potentials.

45 citations

Journal ArticleDOI
TL;DR: In this article, the dynamical and static dipole polarizabilities of the C 60 molecule have been calculated on the basis of the experimental data on the cross section of the fullerene photoabsorption.

42 citations

Journal ArticleDOI
TL;DR: In this paper, it was demonstrated that outer and inner electron shells, including those formed by collectivized electrons of the fullerene C{sub 60}, affect dramatically the cross section of the subvalent ns subshells of the noble-gas endohedral atoms A-C{sub60}.
Abstract: It is demonstrated that outer and inner electron shells, including that formed by collectivized electrons of the fullerene C{sub 60}, affects dramatically the cross section of the subvalent ns subshells of the noble-gas endohedral atoms A-C{sub 60} The calculations are performed within the framework of a very simple, so-called ''orange skin,'' model that makes it possible, in spite of its simplicity, to take into account the modification of the ns subshell due to its interaction with inner and outer atomic shells, as well as with the collectivized electrons of the C{sub 60} As a concrete example, we consider the Xe 5s electrons completely collectivized by the powerful action of the Xe close and remote multielectron neighboring shells

42 citations