Giant resonances of endohedral atoms

TL;DR

This paper demonstrates that the fullerene shell can induce giant resonances in endohedral atoms, significantly altering their photoionization cross-sections through polarization and electron reflection effects.

Contribution

It introduces the concept of Giant Endohedral Resonances (GER) caused by fullerene shells and models their effects on photoionization in endohedral atoms for the first time.

Findings

Xe@C60 exhibits a strong resonance at 17 eV with oscillator strength ~25.

Fullerene polarization and electron reflection significantly modify photoionization cross-sections.

The dipole angular anisotropy parameter is strongly affected by electron reflection.

Abstract

We demonstrate for the first time that the effect of fullerene shell upon photoionization of the "caged" atom in an endohedral can result in formation of Giant Endohedral Resonances or GER. This is illustrated by the concrete case of Xe@C60 photoionization cross-section that exhibits at 17 eV a powerful resonance with total oscillator strengths of about 25. The prominent modification of the 5p6 electron photoionization cross-section of Xe@C60 takes place due to strong fullerene shell polarization under the action of the incoming electromagnetic wave and oscillation of this cross-section due to the reflection of the photoelectron from Xe by the C60. These two factors transform the smoothly decreasing 5p6 cross-section of Xe into a rather complex curve with a powerful maximum for Xe@C60, with the oscillator strength being equal to 25! We present also the results for the dipole angular anisotropy parameter that is strongly affected by the reflection of the photoelectron waves but not modified by C60 polarization. The polarization of C60 is expressed via its total photoabsorption cross-section. The reflection of the photoelectron is taken into account in the frame of the so-called bubble potential that is a spherical delta-type potential.