Double photoionization of atoms and ions confined in charged fullerenes

Abstract

The double photoionization of a helium atom and a singly charged lithium positive ion enclosed in charged Cq60 fullerenes is studied using the time-dependent close-coupling method. Continuum raising and lowering effects are seen in the shift of the double-ionization threshold of the confined atom or ion. Confinement resonances in the double-photoionization cross section, previously observed for helium confined inside a neutral fullerene, persist for helium confined in both positively and negatively charged fullerenes and are found to be independent of the charge on the fullerene. The double photoionization of a confined singly positively charged lithium ion is found to exhibit similar behaviour to a confined neutral atom, with confinement resonances present in the double-photoionization cross section for confinement in neutral, positively and negatively charged fullerenes. In addition, the confinement resonances are shown to be sensitive to the width of the fullerene with the resonances having a smaller amplitude for larger fullerene widths.

Sensitivity of cross sections to the diffuseness of the confining potential in time-dependent close-coupling calculations of the double photoionization of He@C60

“…However, at lower energies, there is still a large deviation from the isolated He results for α = 0.2. Unlike the damping effect illustrated in [8], where the amplitude of the confinement oscillations decreased as the confining potential was made shallower and wider, here there is no phase shift in the locations of the peaks of the confinement resonances, showing that this is a distinct effect.…”

“…width in the experiment of Kilcoyne et al [2]. The sensitivity to the depth and width of the confining potential was investigated for double photoionization in [8]. It was found that as the confining potential becomes wider and shallower (while maintaining the same electron affinity), the confinement resonances are decreased in amplitude.…”

“…The time-dependent close-coupling (TDCC) method [6] has been utilized in a series of studies [7][8][9] of the photoionization of endohedral atoms. These studies made use of a square-well model potential to represent the fullerene shell.…”

On the shell‐confined atom problem

“…We use here the description of the problem [45] (see eqs. [15][16][17][18] for the case of the ks-state of the spherically symmetric one-electron system with the exact stationary wave-function Ψ = Ψ ks . In the presence of the external electric field with constant strength F and the potential −Fz one can use for the first-order correction to the wave function as an approximation by linear combination of M functions of the form f j Ψ ( j = 1/M)…”

Electronic Structure of Helium Atom in a Quantum Dot

“…A number of phenomenological potentials have been used to model atoms within cavities [3], atoms under pressure [4], impurities in quantum dots or nano crystals [5], nanopores [6,7], fullerenes [8] and foreign atoms in liquid helium environment [9] etc. The study of quantum dots (QD) has got considerable attention in recent times due to its fundamental importance in theoretical researches as well as in fabricating new functional devices.…”