Role of electronic shell in the double beta decay
We demonstrate that the limiting energy available for ejected electrons in double beta decay is diminished by about 400 eV due to inelastic processes in the electronic shell.
nucl-th↗
arXiv subjects
M. Ya. Amusia
Publications and source records attributed to M. Ya. Amusia.
The role of 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 concrete examples of electron scattering by endohedrals of Neon and Argon. To obtain the presented results, we have suggested a simplified approach that permits to incorporate the effect of fullerenes polarizability into the Neon and Argon endohedrals polarization potential. As a result, 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.
physics.atm-clus↗
Electron elastic scattering off $A$@C$_{60}$: The role of atomic polarization under confinement
The present paper explores possible features of electron elastic scattering off endohedral fullerenes $A$@C$_{60}$. It focuses on how dynamical polarization of the encapsulated atom $A$ by an incident electron might alter scattering off $A$@C$_{60}$ compared to the static-atom-$A$ case, as well as how the C$_{60}$ confinement modifies the impact of atomic polarization on electron scattering compared to the free-atom case. The aim is to provide researchers with a "relative frame of reference" for understanding which part of the scattering processes could be due to electron scattering off the encapsulated atom and which due to scattering off the C$_{60}$ cage. To meet the goal, the C$_{60}$ cage is modeled by an attractive spherical potential of a certain inner radius, thickness, and depth which is a model used frequently in a great variety of fullerene studies to date. Then, the Dyson equation for the self-energy part of the Green's function of an incident electron moving in the combined field of an encapsulated atom $A$ and C$_{60}$ is solved in order to account for the impact of dynamical polarization of the encaged atom upon $e + A@{\rm C_{60}}$ scattering. The Ba@C$_{60}$ endohedral is chosen as the case study. The impact is found to be significant, and its utterly different role compared to that in $e + Ba$ scattering is unraveled.
physics.atom-ph↗
Influence of the inner shell electrons on photoionization of outer shells
We have studied the role of virtual excitations of inner shells upon outer shell photoionization. The calculations were performed in the frames of the Random Phase Approximation and its generalized version GRPAE that take into account variation of the atomic field due to electron elimination and the inner vacancies decay. We employ both analytic approximation and numeric computations. The results are presented for 3p electrons in Ar and 4d-electrons in Pd near inner shells thresholds. The effect proved to be noticeable.
physics.atom-ph↗
Heavy fermion spin liquid in herbertsmithite
We analyze recent heat capacity measurements in herbertsmithite $\rm ZnCu_3(OH)_6Cl_2$ single crystal samples subjected to strong magnetic fields. We show that the temperature dependence of specific heat $C_{mag}$ formed by quantum spin liquid at different magnetic fields $B$ resembles the electronic heat capacity $C_{el}$ of the HF metal $\rm YbRh_2Si_2$. We demonstrate that the spinon effective mass $M^*_{mag}\propto C_{mag}/T$ exhibits a scaling behavior like that of $C_{el}/T$. We also show that the recent measurements of $C_{mag}$ are compatible with those obtained on powder samples. These observations allow us to conclude that $\rm ZnCu_3(OH)_6Cl_2$ holds a stable strongly correlated quantum spin liquid, and a possible gap in the spectra of spinon excitations is absent even under the application of very high magnetic fields of 18 T.
cond-mat.str-el↗
Comment on the shape of Hydrogen equation in spaces of arbitrary dimension
We note that presenting Hydrogen atom Schrodinger equation in the case of arbitrary dimensions require simultaneous modification of the Coulomb potential that only in three dimensions has the form Z/r . This was not done in a number of relatively recent papers [1-5]. Therefore some results obtained there seem to be doubtful. Some required considerations in the area are mentioned.
quant-ph↗
On the behavior of scattering phases in collisions of electrons with multi-atomic objects
We have studied the energy dependence of several first scattering phases with multi-atomic object. As concrete examples representing the general trends endohedrals Neon inside C60 and Argon inside C60 are considered. It appeared that the presence of an inner atom, either Ne or Ar, qualitatively affects the scattering phases, in spite of the fact that the fullerene consists of 60 carbon atoms, while the atom staffed inside is only one. Calculations are performed in the one-electron Hartree-Fock (HF) and random phase approximation with exchange (RPAE) for the inner atom while the fullerenes shell is substituted by static potential without and with the polarization potential. It appeared that the total endohedral scattering phase is simply a sum of atomic, Ne or Ar, and fullerenes C60 phases, contrary to the intuitive assumption that the total phases on C60 and Neon inside C60 or Ar inside C60 has to be the same.
physics.atm-clus↗
Comment on "Topological excitations and the dynamic structure factor of spin liquids on the kagome lattice" (Punk, M., Chowdhury, D. & Sachdev, S. Nature Physics 10, 289-293 (2014))
The authors of a recent paper evidently take the view that the whole of progress made toward a theoretical understanding of the physics of quantum spin liquids (QSL) is associated with models of the kind proposed and applied in their present work. As motivation for this work, they observe that in contrast to existing theoretical models of both gapped and gapless spin liquids, which give rise to sharp dispersive features in the dynamic structure factor, the measured dynamic structure factor reveals an excitation continuum that is remarkably flat as a function of frequency. They go on to assert that "so far, the only theoretical model for a spin liquid state on the kagome lattice which naturally gives rise to a flat excitation band at low energies consists of the $Z_2$ spin liquids". Here we point out that there already exists a different and demonstrably successful approach to the QSL problem that does naturally feature a flat band.
cond-mat.str-el↗
Electron elastic scattering off a spin-polarized Cr atom
Electron elastic scattering off a spin-polarized Cr(...$3d^{5}4s^{1}$, $^{7}S$) atom is theoretically studied in the region of electron energies up to $15$ eV using both a one-electron "spin-polarized" Hartree-Fock and multielectron "spin-polarized" random phase approximation with exchange. It is found that scattering phase shifts of oppositely spin-polarized incoming electrons and corresponding cross sections of the scattering reactions significantly differ from each other, in general, even without accounting for spin-orbit interaction. This is shown to be associated with the presence of two semifilled $3d^{5}$ and $4s^{1}$ subshells in the Cr's configuration which induce considerably different exchange in the interaction of oppositely spin-polarized incoming electrons with the atom-target. The importance of electron correlation in $e^{-}+\rm Cr$ elastic scattering process is revealed. Moreover, correlation is shown to induce strong differences between scattering of oppositely spin-polarized electrons off Cr. A physically transparent interpretation for the latter is provided.
physics.atom-ph↗
Explanation of the recent results on photoionization of endohedral atoms
We suggest an explanation of the recently observed discrepancy between the experimental and theoretical results on ionization of atoms, encapsulated into the fullerenes by photons with the energies of about 80-190eV. On the ground of previous theoretical considerations we conclude that the photoionization of the caged atom without excitation of the fullerene shell has low probability.
physics.atom-ph↗
Comment on the paper Photoionization of endohedral atoms using R-matrix methods: application to Xe@C60 by T. W. Gorczyca, M. F. Hasoglu and S. T. Manson, Phys. Rev. A86, 033204 (2012) [1]
We demonstrate serious misrepresentation of existing experimental data and important omissions in the List of references in the paper [1]. We demonstrate that what is called in [1] total photoionization cross-section is in fact a partial photoionization cross-section. We demonstrate that long before [1] and presented there experimental data for photoionization of Xe@C60+ were obtained, a theoretical prediction for Xe@C60 have been published that was in a reasonable agreement with experiment. These data are even not mentioned in [1].
physics.atom-ph↗
Featured trends in e$^{-}+$Mn electron elastic scattering
The impacts of both exchange interaction and electron correlation, as well as their combined impact, on electron elastic scattering off a semifilled shell Mn(...$3d^{5}$$4s^{2}$, $^{6}S$) atom are theoretically studied in the electron energy range of $ε= 0-25$ eV. Corresponding elastic scattering phase shifts $δ_{\ell}(ε)$ as well as partial $σ_{\ell}(ε)$ and total $σ(ε)$ cross sections are found to be subject to a strong correlation impact. The latter is shown to be drastically different for oppositely spin-polarized scattered electrons, in some cases, thereby bringing significant differences in corresponding $δ_{\ell}(ε)$s, $σ_{\ell}(ε)$s, and $σ(ε)$s between said electrons. This is proven to be an inherent features of electron scattering off a semifilled shell atom in general. Electron correlation is accounted for in the framework of the self-energy part $Σ$ of the Green function of a scattered electron concept. The latter is calculated both in the second-order perturbation theory in the Coulomb interelectron interaction as well as beyond it by solving the Dyson equation for $Σ$. The significance of the "Dyson" correlation corrections in e$^{-}+$Mn scattering is unraveled. They are shown to aggravate noticeably the inherent differences between elastic scattering phase shifts and cross sections of spin-up ($\uparrow$) and spin-down ($\downarrow$) polarized electrons scattered off a spin-polarized Mn atom, in some cases. In particular, the existence of a narrow resonant maximum in $σ^{\downarrow}(ε)$ near $ε\approx 8$ eV but the absence of such in $σ^{\uparrow}(ε)$ in e$^{-}+$Mn scattering is predicted.
physics.atom-ph↗
On the dependence of one-photon - two-electron differential cross sections on recoil momenta
We calculate the distributions in recoil momenta and their energy distributions for the high energy non-relativistic double photoionization of helium caused by the quasifree mechanism of the process. The distributions obtain local maxima at small values of the recoil momenta. This is in agreement with the earlier predictions and with recently obtained experimental data. We obtained also the angular correlations, which reach the largest value in the "back-to-back" configuration of the photoelectrons. Our analysis is valid in all high energy nonrelativistic region. Particular equations are true for the case when the wavelength of the photon exceeds strongly the size of the atom. We present numerical results for the photon energies in the region of 1 keV, employed in the recent experiments.
physics.atom-ph↗
Multielectron processes in endohedral atoms at high energies
We analyze the role of shake-off and of the final state interactions in inelastic processes in the fullerene shell which follow ionization of the caged atom. We demonstrate that in the broad interval of the photon energies the process is dominated by the final state interactions. Its contribution is calculated in a model-independent way. In the large energy intervals the cross section of the process is close to that of photoionization of isolated atom.
physics.atom-ph↗
On the interactions of the high energy photoelectrons with the fullerene shell
The probability that photoionization of the caged atom in an endohedral system is accompanied by excitation of the fullerene shell is shown to be close to unity in broad intervals of the photoelectron energies. The result is obtained by summation of the perturbative series for the interaction between the photoelectron and the fullerene shell. This result means that the interaction between the photoelectron ejected from the cage atom and the fullerene shell cannot be described by a static potential, since inelastic processes become decisively important.
physics.atom-ph↗
Polarization Bremsstrahlung in collissions of fast ions with multiatomic targets
We consider the processes of polarization bremsstrahlung in collisions of fast ions with linear chains consisting of isolated atoms. We obtained intensities and angular distributions of radiation spectra for arbitrary number of atoms in the chain. It appeared that interference in the photon radiation amplitudes lead to prominent variation of spectral angular distributions of polarization bremsstrahlung as compared to these distribuitions in collisions with an isolated atom. The mean loss of energy due to radiation or the so-called rediative friction is estimated. The results obtained permit standard generalization to the case of polarization bremsstrahlung in fast ion chanelling above surfaces an and in solid body.
physics.atom-ph↗
Comment on Zeeman-Driven Lifshitz Transition: A Model for the Experimentally Observed Fermi-Surface Reconstruction in YbRh2Si2 (A. Hackl and M. Vojta, Phys. Rev. Lett. 106, 137002 (2011))
Comment on Zeeman-Driven Lifshitz Transition: A Model for the Experimentally Observed Fermi-Surface Reconstruction in YbRh2Si2 by A. Hackl and M. Vojta, Phys. Rev. Lett. 106, 137002 (2011).
cond-mat.str-el↗
Generalized oscillator strength of endohedral molecules
We investigate here the fast electron scattering upon endohedral atoms that present a fullerene CN staffed by an atom A, A@CN. We calculate the inelastic scattering cross-section expressing it via generalized oscillator strengths (GOS) density. We take into account two major effects of CN upon ionization of the atom A. Namely, the scattering of the electron by the static potential of the fullerenes shell and modification of the interaction between the fast incoming and atomic electrons due to polarization of the fullerenes shell by the incoming electron beam. To obtain the main features of the effect, we substitute the complex fullerenes shell CN by a static zero thickness potential, express its deformation under incoming electron action via CN polarizabilities. We perform all consideration in the frame of the so-called random phase approximation with exchange (RPAE) that gave reliable results for GOSes of isolated atoms, and expressions for absolute and differential in angle cross-sections. We limit ourselves with dipole and biggest non-dipole contributions to the differential in angle cross-section. We compare fast electron scattering with photoionization as a source of information on the target electronic structure and emphasize some advantages of fast electron scattering. As concrete objects of calculations, we choose noble gas endohedrals Ar@C60 and Xe@C60. The results are presented for two transferred momentum q values: q=0.1 and 1.0. Even for small q=0.1, in the so-called optical limit, the deviation from photoionization case is prominent and instructive. As an interesting and very specific object, we study onion-type endohedrals A@CN1@CN2, in which the all construction A@CN1 is stuffed inside CN2 with N2 >> N1.
physics.atm-clus↗