arXiv subjects

E. V. Tkalya

Publications and source records attributed to E. V. Tkalya.

At least 19 recordsLinked to original sources

arXiv2026

Long Time Energy Oscillation Between Electron Shell and Nucleus in $^{229}$Th Ions and Coherent Electron Bridge for Nuclear Quantum Battery

The electron shell of the Thorium ion with the $M$1(8.4~eV) transition between levels and the doublet of the $^{229}$Th nucleus ground state with the similar transition represent two qubits spatially inserted one within the other. In the case of relative proximity of the energies of these transitions, weakly damped energy oscillations can be excited between qubits, namely, multiple coherent energy transfer from the electron shell to the nucleus and vice versa. This process in the $^{229}$Th ions does not require resonant (within the width of the levels) coincidence of the transition energies due to the relatively high interaction energy of the electron and nuclear currents. The electron shell ``breathes'', periodically decreasing and increasing in size. The effect can be observed in an ion trap by the intensity of light scattered by thorium-229 ions. This extends the energy range for the $^{229m}$Th$(3/2^+,8.4$~eV) isomer excitation via an electron bridge. Furthermore, the system under consideration is transformed into a nuclear quantum battery when exposed to coherent laser radiation. To ``charge'' the battery, i.e. to excite $^{229m}$Th, one can use developed methods for charging quantum batteries, in particular, coherent excitation of the electron shell followed by coherent transfer of excitation energy to the nucleus (the coherent electron bridge). This opens the way for the design of the $^{229}$Th nuclear quantum battery at the current level of technological development.

nucl-th↗

arXiv2026

Alternative treatment of relativistic effects in linear augmented plane wave (LAPW) method: application to Ac, Th, ThO2 and UO2

We examine the influence of the relativistic effects within the linear augmented plane wave method (LAPW) for solids and propose a few alternative ways to accurately take them into account: (1) we introduce new radial dependencies for LAPW (Bloch-type) basis functions, based on two actual radial solutions of the Dirac equation for j=l-1/2 and j=l+1/2 states. The proposed radial 6p functions receive more weight from the Dirac p-1/2 solution and, due to this, can on average correctly describe completely filled $6p$ bands even without the additional p-1/2 local atomic function, as is done in the LAPW+p-1/2 method; (2) the canonical LAPW matrix elements for the spherically symmetric component of the potential, assuming non-relativistic radial wave functions, should be corrected; (3) we argue that for a realistic spin-orbit (SO) energy splitting of the semicore 6p-states the spin-orbit interaction constant zeta(p) should be calculated with the 6p-3/2 radial component, because the value of zeta(p) obtained with the canonical mixing of the 6p-1/2 and 6p-3/2 components overestimates the SO splitting. Different ways of taking into account relativistic effects can change the equilibrium lattice constant up to 0.15 A and the elastic modulus up to 26 GPa. We find that in the full treatment of the spin-orbit coupling UO2 has a small gap of forbidden states (0.2-0.4 eV) at the Fermi level, which persists for all k-vectors and, therefore, UO2 should be classified as a semimetal. We also discuss the peculiarities of the electron band structure of actinium, which result in an overestimation of its lattice constant.

cond-mat.mtrl-sci↗

arXiv2023

Energy barriers of Be and B in passing through the C60 fullerene cage

We have studied the potential barriers for the penetration of atomic beryllium or boron inside the C60 fullerene by performing ab initio density functional theory (DFT) calculations with three variants for the exchange and correlation: B3LYP (hybrid functional), PW91 and PBE. Four principal trajectories to the inner part of C60 for the penetrating atom have been considered: through the center of six-member-carbon ring (hexagon), five-member-carbon ring (pentagon), and also through the center of the double C-C bond (D-bond) and the center of the single C-C bond (S-bond). Averaging over the three DFT variants yields the following barriers for beryllium penetrating inside a deformable fullerene: 3.2 eV (hexagon), 4.8 eV (S-bond), 5.3 eV (D-bond), 5.9~eV (pentagon). These barriers correspond to the slow and adiabatic penetration of Be, in contrast to the fast (non-adiabatic) penetration through the rigid cage of C60 resulting in 5.6 eV (hexagon), 16.3 eV (pentagon), 81.8 eV (S-bond) and 93.4 eV (D-bond). The potential barriers for the boron penetrating inside deformable/rigid C60 are: 3.7/105.4 eV (D-bond), 4.0/86.8 eV (S-bond), 4.7/7.8 eV (hexagon), 6.8/14.0 eV (pentagon). The potential barriers for Be and B escaping from the inner part of C$_{60}$ are higher by the value of 0.84 eV for Be and 0.81 eV for B. The considerable reduction of the potential barriers for the deformable fullerene is ascribed to the formation of the Be-C and B-C bonds. We discuss the difference between Be and B, compare three variants of DFT, and analyze the role of the dispersion interaction.

cond-mat.mes-hall↗

arXiv2022

Reply to Comment on "Multiple locations of boron atoms in the exohedral and endohedral C60 fullerene" by J. Xu and G.-L. Hou

In three out of five cases considered in our work, DFT calculations presented by Xu and Hou in their Comment give the same ground state confirmations. On the other hand, depending on the choice of the exchange-correlation functional, the geometry optimization within DFT results in different ground state confirmations for B@C60 and B60, Table I of the Comment. Therefore, the energy balance between nearest confirmations in these molecular complexes is subtle, and various methods can give different ground state structures. Consequently, the results of our method - the Hartree-Fock (HF) approach with the second order Møller-Plesset perturbation theory (MP2) - should be compared with the DFT results on equal ground, we cannot agree that the DFT method used in the Comment is superior to HF-MP2. In the Reply, we also present additional HF calculations with the 6-31G* basis set (used in the Comment for the geometry optimization) to show that the polarization functions do not change the ground state confirmations obtained by us earlier at the HF/6-31G level.

cond-mat.mtrl-sci↗

arXiv2022

Proposal for a Nuclear Light Source

The paper considers a principal possibility of creating a nuclear light source of the vacuum ultra violet (VUV) range based on the $^{229}$Th nucleus. This nuclear light source can help to solve two main problems -- excitation of the low-lying $^{229m}$Th isomer and precision measurement of the nuclear isomeric transition energy. The Thorium nuclear light source is based on the nuclei implanted in a thin dielectric film with a large bandgap. While passing an electric current through the sample, the $^{229}$Th nuclei are excited to the low energy isomeric state $3/2^+(8.19\pm0.12$ eV) in the process of inelastic scattering of conduction electrons. The subsequent spontaneous decay of $^{229m}$Th is followed by the emission of $γ$ quanta in the VUV range. The luminosity of the Thorium nuclear light source is approximately $10^5$~photons/s per 1~A of current and per 1~ng of $^{229}$Th. The suggested scheme to obtain $γ$ radiation from the $^{229m}$Th isomer can be considered as a kind of nuclear analogue of the optical radiation from the usual metal-insulator-semiconductor (MIS) junction.

nucl-th↗

arXiv2021

Cross section of the Coulomb excitation of $^{229m}$Th by low energy muons

The inelastic scattering cross section for muons, $μ^-$, with energies $E$=9--100~eV from the $^{229}$Th nuclei is calculated in the framework of the second order of the perturbation theory for the quantum electrodynamics. The dominant contribution to the excitation of the low energy isomer $^{229m}$Th$(3/2^+,8.19\pm0.12$~eV) comes from the $E2$ multipole. The excitation cross section reaches the value of $10^{-21}$ cm$^2$ in the range $E\approx$10~eV. This is four to five orders of magnitude larger than the electron excitation cross section and enough for efficient excitation of $^{229m}$Th on the muon beam at the next generation of muon colliders.

nucl-th↗

arXiv2020

Peculiar chemical bonding between thorium and a carbon hexagon in carbon nanomaterials

We explore an unusual nature of chemical bonding of the thorium atom with a ring of six carbon atoms (hexagon) in novel carbon materials. Our ab initio calculations of Th-based metallofullerenes (Th@C60, Th@C20) and Th bound to benzene or coronene at the Hartree-Fock level with the second order perturbation (MP2) correction accounting for the van der Waals interactions, demonstrate that the optimal position of the thorium atom is where it faces the center of a hexagon and is located at a distance of 2.01-2.07 A from the center. For Th encapsulated in C60 it is found at 2.01 A, whereas the other local energy minima are shifted to larger energies (0.22 eV and higher). Inside C60 the highest local minimum at 1.17 eV is observed when Th faces the center of the five member carbon ring (pentagon). Based on our calculations for Th with benzene and coronene where the global minimum for Th corresponds to its position at 2.05 A (benzene) or 2.02 A (coronene) from the hexagon center, we conclude that a well pronounced minimum is likely to present in graphene and in a single wall carbon nanotube. The ground state of Th is singlet, other high spin states (triplet and quintet) lie higher in energy (> 1.62 eV). We discuss a potential use of the carbon nanomaterials with the 229Th isotope having the nuclear transition of the optical range, for metrological purposes.

cond-mat.mtrl-sci↗

arXiv2020

Decay of the low-energy nuclear $^{229m}$Th isomer via atomic Rydberg states

In the paper, a unique process of the decay of the $^{229m}$Th($3/2^+,8.28\pm 0.17$ eV) low energy nuclear isomer via the internal conversion (IC) channel on Rydberg states is considered for the first time. The Rydberg atom $^{229m}$Th$^{+}+e^-_{Ry}$ is a unique object where IC is possible exclusively on the Rydberg electron $e^-_{Ry}$. It is shown that in the $^{229m}$Th$^{4+}+e^-_{Ry}$ system a) IC on the electron states with relatively small values of the principal quantum number $n$ and the orbital moment $l$ is practically completely suppressed, b) IC probability, $W_{IC}$, on the $ψ_{ns_{1/2}}({\bf{r}})$ states is proportional to $|ψ_{ns_{1/2}}(0)|^2$ and can be related with the energy of the hyperfine interaction of the Rydberg electron with the nucleus, c) $W_{IC}$ decreases rapidly with the increase of $n$ in the range from 10 to 50, and in the range $n\gtrsim 150$ $W_{IC}$ changes as ${\text{Const}}/n^3$ typical for hydrogen-like ions, d) at $n\thickapprox 10$--30, $W_{IC}$ as a function of $l$ has a characteristic "knee" between $l=3$ and $l=4$, i.e. a three order of magnitude decrease of $W_{IC}$ due to the qualitative change in the ratio between the centrifugal and shielding potentials.

nucl-th↗

arXiv2020

Internal conversion of the low energy $^{229m}$Th isomer in the Thorium anion

A process of the decay of the anomalously low lying nuclear isomer $^{229m}$Th$(3/2^+,8.28 \pm 0.17$ eV) in the Thorium anion (Th$^-$) via the internal conversion (IC) channel is studied. We show that the half life of the nuclear isomer in the $6d_{3/2}^37s_{1/2}^2$ ground state and in the $6d_{3/2}^2 7s_{1/2}^2 7p_{1/2}^1$ excited state of Th$^-$ is $\approx1.5$ and $\approx1.1$ times bigger than in the $6d_{3/2}^2 7s_{1/2}^2$ ground state of the Th atom. The IC probabilities in the anion decreases despite the decay via the additional $6d_{3/2}$ or $7p_{1/2}$ electrons. This counterintuitive result is a consequence: a) of a decrease in the amplitudes of the $6d_{3/2}$ and $7s_{1/2}$ wave functions near the nucleus due to an increase in their diffuseness of upon the addition of extra electron, b) of mutual compensation in the IC probability due to a kinematic factor, which depends on the energy of the conversion electron in the continuum as $E_c^{-1/2}$, and the $E_c^{1/4}$ growth of the amplitudes of the electron wave functions.

nucl-th↗

arXiv2020

Excitation of $^{229m}$Th at Inelastic Scattering of Low Energy Electrons

Excitation of the anomalously low lying nuclear isomer $^{229m}$Th$(3/2^+, 8.28 \pm 0.17$ eV) in the process of inelastic electron scattering is studied theoretically in the framework of the perturbation theory for the quantum electrodynamics. The calculated cross sections of $^{229m}$Th by the extremely low energy electrons in the range 9 eV--12 eV for the Th atom and Th$^{1+,4+}$ ions lie in the range $10^{-25}$--$10^{-26}$ cm$^2$. Being so large, the cross section opens up new possibilities for the effective non-resonant excitation of $^{229m}$Th in experiments with an electron beam or electron (electric) current. This can be crucial, since the energy of the isomeric state is currently known with an accuracy insufficient for the resonant excitation by photons. In addition, the cross section of the time reversed process is also large, and as a consequence, the probability of the non-radiative $^{229m}$Th decay via the conduction electrons in metal is $\approx10^{6}$ s$^{-1}$, that is, close to the internal conversion probability in the Th atom.

nucl-th↗

arXiv2019

$^7$Be and $^{22}$Na radionuclides for a new therapy of cancer

The $^{10}$B isotope has been almost exclusively used in the neutron-capture radiation therapy (NCT) of cancer for decades. We have identified two other nuclides suitable for the radiotherapy, which have ca.10 times larger cross section of absorption for neutrons and emit heavy charged particles. This would provide several key advantages for potential NCT, such as the possibility to use either a lower nuclide concentration in the target tissues, or a lower neutron irradiation flux. By detecting the characteristic $γ$ radiation from the spontaneous decay of the radionuclides, one can image and control their accumulation. These advantages could be critical for the revival of the NCT as a safer, more efficient and more widely used cancer therapy.

physics.med-ph↗

arXiv2018

Excitation of $^{229}$Th nuclei in laser plasma: the energy and half-life of the low-lying isomeric state

The results of experimental studies of the low-energy isomeric state in the $^{229}$Th nucleus are presented. The work is consisted of several stages. During the first stage $^{229}$Th nuclei were excited with the inverse internal conversion to the low-lying isomeric level in plasma that was formed by laser pulse at the $^{229}$Th-containing target surface. Then thorium ions having excited nuclei were extracted from the plasma by an external electrical field and implanted into thin SiO$_2$ film grown on a silicon substrate (that is a dielectric material with about 9 eV band-gap). Gamma decay of isomeric nuclei was registered during the second stage by the general methods of the electron spectroscopy after the photon-electron emission from the silicon substrate. Substitution of the photon registration with the electron one allowed us to increase the desired signal by several orders of magnitude and detect the $^{229}$Th nuclei decay. During the third stage the electron spectra from standard Xe VUV source was obtained that allowed determining the energy of photons. In order to prove that the detected signal is caused by isomeric $^{229}$Th nuclei decay a series of experiments was carried. The analysis of electron spectra gives the following results: the energy of the nuclear transition is $E_{\text{is}}=7.1(^{+0.1}_{-0.2})$~eV, the half-life of the isomeric level in bare nucleus in vacuum is $T_{1/2}=1880\pm170$~s, the reduced probability of the isomeric nuclear transition is $B_{\text{W.u.}}(M1;3/2^+\rightarrow 5/2^+)=(3.3\pm0.3)\times10^{-2}$.

nucl-th↗

arXiv2017

Experimental studies of thorium ions implantation from pulse laser plasma into thin silicon oxide layers

We report the results of experimental studies related to implantation of thorium ions into thin silicon dioxide by pulsed plasma fluxes expansion. Thorium ions were generated by laser ablation from a metal target, and the ionic component of the laser plasma was accelerated in an electric field created by the potential difference (5, 10 and 15 kV) between the ablated target and SiO2/Si(001) sample. Laser ablation system installed inside the vacuum chamber of the electron spectrometer was equipped with YAG:Nd3+ laser having the pulse energy of 100 mJ and time duration of 15 ns in the Q-switched regime. Depth profile of thorium atoms implanted into the 10 nm thick subsurface areas together with their chemical state as well as the band gap of the modified silicon oxide at different conditions of implantation processes were studied by means of X-ray photoelectron spectroscopy (XPS) and Reflected Electron Energy Loss Spectroscopy (REELS) methods. Analysis of chemical composition showed that the modified silicon oxide film contains complex thorium silicates. Depending on local concentration of thorium atoms, the experimentally established band gaps were located in the range of 6.0 - 9.0 eV. Theoretical studies of optical properties of the SiO2 and ThO2 crystalline systems have been performed by ab initio calculations within hybrid functional. Optical properties of the SiO2/ThO2 composite were interpreted on the basis of Bruggeman effective medium approximation. A quantitative assessment of the yield of isomeric nuclei in "hot" laser plasma at the early stages of expansion has been performed. The estimates made with experimental results demonstrated that the laser implantation of thorium ions into the SiO2 matrix can be useful for further research of low-lying isomeric transitions in 229Th isotope with energy of 7.8(0.5) eV.

cond-mat.mtrl-sci↗

arXiv2016

Anomalous Hyperfine Structure of the $^{229}$Th Ground-State Doublet in Muonic Atom

The hyperfine splitting of the ground and low-energy $3/2^+(7.8 \pm 0.5$ eV) levels in the $^{229}$Th nucleus in muonic atom ($μ^-_{1S_{1/2}}{}^{229}$Th$)^*$ has been calculated considering the distribution of the nuclear magnetization in the framework of collective nuclear model with the wave functions of the Nilsson model for the unpaired neutron. It is shown that (a) the hyperfine splitting of the $3/2^+$ isomeric state is anomalously weak, and the reduction of hyperfine structure in comparison with the model of a point nuclear magnetic dipole is close to 100\%, (b) partial inversion of levels of the $^{229}$Th ground-state doublet and spontaneous decay of the ground state with excitation of the isomeric state take place, (c) the energy of the isomeric transition lies in the range of 120--140 eV, which makes possible the direct observation of the transition, registration of conversion electrons and measurement of the nuclear matrix element.

nucl-th↗

arXiv2016

Magnetic hyperfine structure of the ground-state doublet in highly charged ions $^{229}$Th$^{89+,87+}$ and the Bohr-Weisskopf effect

The magnetic hyperfine (MHF) structure of the $5/2^+$(0.0 eV) ground state and the low-lying $3/2^+$(7.8 eV) isomeric state of the $^{229}$Th nucleus in highly charged ions Th$^{89+}$ and Th$^{87+}$ is calculated. The distribution of the nuclear magnetization (the Bohr-Weisskopf effect) is accounted for in the framework of the collective nuclear model with the wave functions of the Nilsson model for the unpaired neutron. The deviations of the MHF structure for the ground and isomeric states from their values in the model of point-like nuclear magnetic dipole are calculated. The influence of the mixing of the states with the same quantum number $F$ on the energy of sublevels is studied. Taking into account the mixing of states, the probabilities of the transitions between the components of MHF structure are found.

nucl-th↗

arXiv2015

Radiative lifetime and energy of the low-energy isomeric level in $^{229}$Th

We estimate the range of the radiative lifetime and energy of the anomalous, low-energy $3/2^+(7.8 \pm 0.5$ eV) state in the $^{229}$Th nucleus. Our phenomenological calculations are based on the available experimental data for the intensities of $M1$ and $E2$ transitions between excited levels of the $^{229}$Th nucleus in the $K^π[Nn_ZΛ]=5/2^+[633]$ and $3/2^+[631]$ rotational bands. We also discuss the influence of certain branching coefficients, which affect the currently accepted measured energy of the isomeric state. From this work, we establish a favored region where the transition lifetime and energy should lie at roughly the 90% confidence level. We also suggest new nuclear physics measurements, which would significantly reduce the ambiguity in the present data.

physics.atom-ph↗

arXiv2015

Band structure and decay channels of thorium-229 low-lying isomeric state for ensemble of thorium atoms adsorbed on calcium fluoride

The results are presented on the study of the electronic structure of thorium atoms adsorbed by the liquid atomic layer deposition from aqueous solution of thorium nitrate on the surface of CaF2. The chemical state of the atoms and the change of the band structure in the surface layers of Th/CaF2 system on CaF2 substrate were investigated by XPS and REELS techniques. It was found that REELS spectra for Th/CaF2 system include peaks in the region of low energy losses (3-7 eV) which are missing in the similar spectra for pure CaF2. It is concluded that the presence of the observed features in the REELS spectra is associated with the chemical state of thorium atoms and is caused by the presence of uncompensated chemical bonds at the Th/CaF2 interface, and, therefore, by the presence of unbound 6d- and 7s-electrons of thorium atoms. Assuming the equivalence of the electronic configuration of thorium-229 and thorium-232 atoms, an estimate was made on the time decay of the excited state of thorium-229 nuclei through the channel of the electron conversion. It was found that the relaxation time is about 40 μs for 6d-electrons, and about 1 μs for 7s-electrons.

cond-mat.mtrl-sci↗

arXiv2011

Proposal for a Nuclear Gamma-Ray Laser of Optical Range

A possibility of amplification of the 7.6 eV $γ$-radiation by the stimulated $γ$-emission of the ensemble of the $^{229m}$Th isomeric nuclei in a host dielectric crystal is proved theoretically. This amplification is a result of: 1) the excitation of a large number of the $^{229m}$Th isomers by laser radiation; 2) the creation of the inverse population of nuclear levels in a cooled sample owing to the interaction of thorium nuclei with the crystal electric field or with an external magnetic field; 3) the emissions/absorption of the optical photons by thorium nuclei in the crystal without recoil; 4) the nuclear spin relaxation through the conduction electrons of the metallic covering.

nucl-th↗