Calculation of the photoionization cross section of the 4d10 subshell of the La atom

The photoionization cross section of 4d¹⁰ subshell of La atom is calculated. The cross section curve near its threshold is strongly modified by rearrangement of outer shells in the process of photoionization.     

Role of a fullerene shell upon stuffed atom polarization potential

We have demonstrated that the polarization of the fullerene shell considerably alters the polarization potential of an atom, stuffed inside a fullerene. This essentially affects the electron elastic scattering phases as well as corresponding cross sections. We illustrate the general trend by particular examples of electron scattering upon endohedrals Ne@C₆₀ and Ar@C₆₀. To obtain the presented results, we have suggested a simplified approach that permits to incorporate the effect of fullerenes polarizability into the Ne@C₆₀ and Ar@C₆₀ polarization potential. By applying this approach, we obtained numeric results that show strong variations in shape and magnitudes of scattering phases and cross sections due to effect of fullerene polarization upon the endohedral polarization potential.     

Polarization bremsstrahlung in α decay

A mechanism of formation of electromagnetic radiation that accompanies α decay and is associated with the emission of photons by electrons of atomic shells due to the scattering of α particles by these atoms (polarization bremsstrahlung) is proposed. It is shown that, when the photon energy is no higher than the energy of K electrons of an atom, polarization bremsstrahlung makes a significant contribution to the bremsstrahlung in α decay.     

Application of the nuclear liquid drop model to atomic and molecular physics problems

The liquid drop model is applied to describe some basic properties of atoms, homoatomic molecules, metallic clusters of atoms and fullerene molecules. Equilibrium atomic size, energy and polarizability of the atom are calculated. Collective modes of oscillations (dipole, quadrupole and monopole, or breathing, ones) are regarded. Electromagnetic radiation by an atom, passing through a barrier is studied. Equilibrium volume of a homoatomic molecule of two atoms, axes ratio, dissociation energy and the frequencies of the dipole oscillations are calculated. Models to describe some properties of clusters and fullerene molecules are proposed. The size of the metallic cluster, its energy and the frequency of dipole oscillations are calculated. The frequencies of the dipole and breathing mode oscillations of the fullerene molecules are obtained. The calculated frequency of the dipole oscillations was found to be in a rather good accord with the experimental one.     

Back-to-back emission of the electrons in double photoionization of helium

We calculate the double differential distributions and distributions in recoil momenta for the high energy non-relativistic double photoionization of helium atom. We show that the results of recent experiments provide the pioneering experimental manifestation of the quasifree mechanism for the double photoionization which was predicted long ago in our papers. This mechanism provides a surplus in distribution over the recoil momenta at small values of the latter, corresponding to nearly ??back-to-back?? emission of the photoelectrons. Also, in agreement with previous analysis we demonstrate that this surplus is due to the quadrupole terms of the photon-electron interaction. We present the characteristic angular distribution for the back-to-back electron emission. The confirmation of the quasifree mechanism existence opens a new area for exciting experiments, which are expected to increase our understanding of the electron dynamics and of the bound states structure.     

Non-physical consequences of the muffin-tin-type intra-molecular potential

We demonstrate, using a simple model, that, in the frame of muffin-tin-like potential, non-physical peculiarities appear in molecular photoionization cross-sections that are a consequence of “jumps” in the potential and its first derivative at some radius. The magnitude of non-physical effects is of the same order as the physical oscillations in the cross-section of a diatomicmolecule. The role of the size of these “jumps” is illustrated by choosing three values for it. The results obtained are connected to the previously studied effect of non-analytic behavior as a function of r, the potential V(r) acting upon a particle on its photoionization cross-section. In reality, such potential has to be analytic in magnitude and have a first derivative function in r. The introduction of non-analytic features in model V(r) leads to non-physical features — oscillations, additional maxima, and so forth — in the corresponding cross-section.     

Giant resonances of endohedral atoms

It is demonstrated for the first time that the effect of a fullerene shell on the photoionization of a “caged” atom in an endohedral can result in the formation of giant endohedral resonances or GER. This is illustrated by the concrete case of the Xe@C₆₀ photoionization cross section that, at 17 eV, exhibits a powerful resonance with total oscillator strengths of about 25. The prominent modification of the 5p ⁶ electron photoionization cross section of Xe@C₆₀ takes place due to the strong fullerene shell polarization under the action of the incoming electromagnetic wave and the oscillation of this cross section due to the reflection of the photoelectron from Xe by the C₆₀. These two factors transform the smoothly decreasing 5p ⁶ cross section of Xe into a rather complex curve with a powerful maximum for Xe@C₆₀, with the oscillator strength of it being equal to 25. We also present 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 text was submitted by the authors in English.     

Distortion and preservation of giant resonances in endohedral atoms A@C<Subscript>60</Subscript>

It is demonstrated in this Letter that the effect of the fullerene shell upon atomic Giant resonance decisively depends upon energy of photoelectrons, by which the resonance decay. According to the earlier prediction, the Giant resonance in Xe is strongly modified in the endohedral Xe@C₆₀ being transformed from a single broad and powerful maximum in Xe into four quite narrow, but with almost the same total oscillator strength. On the contrary, here the 4d Giant resonances in ions Ce³⁺ (the electronic structure that Ce has, when stuffed into fullerene), in Ce⁴⁺, and Eu are considered. In none of them the 4d Giant resonance in endohedrals is affected essentially. This is because the decay of the Giant resonances in these endohedrals proceeds by emission of fast photoelectrons that are almost unaffected by the C₆₀ shell. The results obtained give at least qualitative explanation to the fact that relatively recent observation of 4d Giant resonance in Ce@C₈₂⁺, where the Giant resonance was observed as a maximum without noticeable structure. The article is published in the original.     

Flat Bands and Salient Experimental Features Supportingthe Fermion Condensation Theory of Strongly Correlated Fermi Systems

Physics of Atomic Nuclei - The physics of strongly correlated Fermi systems, being the mainstream topic for more than half a century, still remains elusive. Recent advancements in experimental...