Photoionization of the outer electrons in noble gas endohedral atoms
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TOMS, MOLECULES, OPTICS
Photoionization of the Outer Electrons in Noble Gas Endohedral Atoms1 M. Ya. Amusiaa,b, A. S. Baltenkovc, and L. V. Chernyshevab a
Racah Institute of Physics, the Hebrew University 91904, Jerusalem, Israel Ioffe Physicotechnical Institute, Russian Academy of Sciences, St. Petersburg, 194021 Russia c Arifov Institute of Electronics, Academy of Sciences of the Republic of Uzbekistan, Tashkent, 700125 Uzbekistan e-mail: [email protected] b
Received February 18, 2008
Abstract—We suggest a prominent modification of the outer shell photoionization cross section in noble gas (NG) endohedral atoms NG@Cn under the action of the electron shell of fullerene Cn. This shell leads to two important effects: a strong enhancement of the cross section due to fullerene shell polarization under the action of the incoming electromagnetic wave and to prominent oscillation of this cross section due to the reflection of a photoelectron from the NG by the fullerene shell. Both factors lead to powerful maxima in the outer shell ionization cross sections of NG@Cn , which we call giant endohedral resonances. The oscillator strength reaches a very large value in the atomic scale, 25. We consider atoms of all noble gases except He. The polarization of the fullerene shell is expressed in terms of the total photoabsorption cross section of the fullerene. The photoelectron reflection is taken into account in the framework of the so-called bubble potential, which is a spherical δ-type potential. It is assumed in the derivations that the NG is centrally located in the fullerene. It is also assumed, in accordance with the existing experimental data, that the fullerene radius RC is much larger than the atomic radius rA and the thickness ∆C of the fullerene shell. As was demonstrated recently, these assumptions allow us to represent the NG@Cn photoionization cross section as a product of the NG cross section and two well-defined calculated factors. PACS numbers: 31.15.V-, 32.80.-t, 32.80.Fb DOI: 10.1134/S1063776108080025 1
1. INTRODUCTION
We consider the photoionization of outer shells of noble gas (NG) endohedral atoms, formed by fullerene Cn inside which an NG atom is located, NG@Cn. We present data on all noble gases except He. In concrete calculations, we consider C60 as a fullerene [1]. Presently, much attention is concentrated on photoionization of endohedral atoms. It was demonstrated in a number of papers [2–10] that the C60 shell adds a prominent resonance structure in the photoionization cross section of an atom A that is “caged” in the fullerene shell, forming an endohedral atom. Although the experimental investigation of A@C60 photoionization seems to be currently very difficult, it will be inevitably be intensively studied in the nearest future.2 This justifies the current efforts of theorists to predict rather nontrivial effects. 1 The
text was submitted by the authors in English. 2 As first examples of such research, we mention the data on measurements of the photoionization cross section of Ce@C82 and ce
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