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Ткаля, Евгений Викторович

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Институт лазерных и плазменных технологий
Стратегическая цель Института ЛаПлаз – стать ведущей научной школой и ядром развития инноваций по лазерным, плазменным, радиационным и ускорительным технологиям, с уникальными образовательными программами, востребованными на российском и мировом рынке образовательных услуг.
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Ткаля
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Евгений Викторович
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Теперь показываю 1 - 10 из 17
  • Публикация
    Только метаданные
    Excitation of Th-229m at Inelastic Scattering of Low Energy Electrons
    (2020) Tkalya, E. V.; Ткаля, Евгений Викторович
    Excitation of the anomalously low lying nuclear isomer Th-229m(3/2(+), 8.28 +/- 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 Th-229m by the extremely low energy electrons in the range 9-12 eV for the Th atom and Th-1+,Th-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 nonresonant excitation of Th-229m 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 nonradiative Th-229m decay via the conduction electrons in metal is approximate to 10(6) s(-1), that is, close to the internal conversion probability in the Th atom.
  • Публикация
    Только метаданные
    A Unique System for Registering One-Photon Signals in the Ultraviolet Range from An Isomeric 229mTh Nucleus Implanted on Thin SiO2/Si Films
    (2020) Lebedinskii, Y. Y.; Borisyuk, P. V.; Chubunova, E. V.; Kolachevsky, N. N.; Vasiliev, O. S.; Tkalya, E. V.; Лебединский, Юрий Юрьевич; Борисюк, Петр Викторович; Чубунова, Елена Витальевна; Васильев, Олег Станиславович; Ткаля, Евгений Викторович
    © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimCurrently, an urgent task related to creating a nuclear frequency standard is the identification of a low-lying nuclear state in the thorium-229 isotope. Herein, a method for measuring the single-photon energy during the decay of an isomeric thorium-229 nucleus implanted in a wide-gap dielectric SiO2 (Eg = 9 eV) is developed. The proposed method utilizes thin silicon oxide layers obtained by thermal oxidization of the pure silica wafers, which allows measurement of the energy of photons in the ultraviolet (UV) range using an electronic spectrometer. The modeling study of electronic state excitation is provided via UV radiation from Kr, Xe, and D resonance discharging lamps. The obtained spectra are analyzed, and a method for determining the UV photon's energy is proposed.
  • Публикация
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    Estimation of the decay rate of Be 7 and Be2 7 encapsulated in C70
    (2019) Bibikov, A. V.; Nikolaev, A. V.; Tkalya, E. V.; Ткаля, Евгений Викторович
    © 2019 American Physical Society.Electron capture (β-decay) rates of Be7 and Be27 encapsulated in C70 have been estimated by calculating the electron density ρ(0) at the Be7 nucleus and comparing it with ρ(0) and experimental β-decay rates of Be7 inside another fullerene - C60. For that the endohedral fullerenes Be7@C70 and Be27@C70 have been examined by means of the ab initio approach using the Hartree-Fock method with the the second order Møller-Plesset perturbation theory accounting for the Van der Waals foces. Our calculations indicate that the Be27@C70 complex is stable with the binding energy of 1.3 eV and the Be7 dimer bond length 2.30 Å. It has been found that ρ(0) is practically the same in Be7@C70 and Be27@C70, but larger than in an isolated Be7 atom. The increase of ρ(0) however is smaller than in Be7@C60. We also discuss in detail the mechanism underlying the increase of ρ(0) and consequently the decrease of the decay rate in Be7@C70 in comparison with the isolated Be7 atom.
  • Публикация
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    Excitation of the low-energy Th-229m isomer Th in the electron bridge process via the continuum
    (2019) Taichenachev, A. V.; Tolstikhina, I. Yu.; Yudin, V. I.; Borisyuk, P. V.; Kolachevsky, N. N.; Tkalya, E. V.; Борисюк, Петр Викторович; Ткаля, Евгений Викторович
    The paper studies the excitation of the Th-229 nucleus to the anomalously low-lying isomeric state 3/2(+)(8.28 +/- 0.17 eV) in the electron bridge process via the continuum of the electron spectrum. Resonant excitation of the nucleus was found to be always possible in the scheme, no matter where the electron levels of an atom or ion were located. Formulas for the excitation cross section by narrow and wide laser lines are obtained. In the resonance, where the process under consideration turns into laser photoionization followed by nuclear excitation in electron capture, the cross section of the process was shown to be comparable in magnitude with that of the photoionization of the thorium atom. Experimental schemes for testing the effect were proposed, which would allow measuring the frequency of the nuclear isomeric transition 3/2(+) -> 5/2(+) to a high precision, which is the first-priority (and still unresolved) task for creating a nuclear clock.
  • Публикация
    Только метаданные
    Decay of the low-energy nuclear Th 229m isomer via atomic Rydberg states
    (2019) Tkalya, E. V.; Ткаля, Евгений Викторович
    © 2019 American Physical Society.In the paper, a unique process of the decay of the Th229m(3/2+,8.28±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 Th+229m+eRy- is a unique object where IC is possible exclusively on the Rydberg electron eRy-. It is shown that in the Th4+229m+eRy- 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, WIC, on the ψns1/2(r) states is proportional to |ψns1/2(0)|2 and can be related with the energy of the hyperfine interaction of the Rydberg electron with the nucleus, (c) WIC decreases rapidly with the increase of n in the range from 10 to 50, and in the range n 150WIC changes as const/n3 typical for hydrogen-like ions, and (d) at n≈10-30, WIC as a function of l has a characteristic "knee" between l=3 and l=4, i.e., a decrease of three orders of magnitude in WIC due to the qualitative change in the ratio between the centrifugal and shielding potentials.
  • Публикация
    Только метаданные
    Autoelectronic emission and charge relaxation of thorium ions implanted into a thin-film silicon oxide matrix
    (2021) Borisyuk, P. V.; Chubunova, E. V.; Kolachevsky, N. N.; Lebedinskii, Y. Y.; Tkalya, E. V.; Vasilyev, O. S.; Yakovlev, V. P.; Борисюк, Петр Викторович; Чубунова, Елена Витальевна; Лебединский, Юрий Юрьевич; Ткаля, Евгений Викторович; Васильев, Олег Станиславович; Яковлев, Валерий Петрович
    An ensemble of thorium-229 ions embedded by pulsed laser implantation into a matrix of a broadband dielectric-silicon oxide is studied. The results of the experimental investigation of thorium ions' lifetime as charged components of the Th+/SiO2/Si system formed immediately after laser implantation are presented. The modelled theoretical description takes into account the instantaneous charging of the surface via laser implantation followed by charge relaxation due to the effect of autoelectronic emission that leads to time dependent partial neutralization of the surface charge by tunneling electrons. It was found that the lifetime of Th+ ions on the SiO2 surface can exceed 10 s, which would be an attractive opportunity for studying the nuclear low-lying isomeric transition in the thorium-229 isotope.
  • Публикация
    Только метаданные
    Neutral and charged thorium impurity in solid argon
    (2021) Nikolaev, A. V.; Tkalya, E. V.; Николаев, Александр Васильевич; Ткаля, Евгений Викторович
    ©2021 American Physical SocietyWe study the neutral and positively charged thorium impurity (, 1, 2, 3, 4) in solid argon by exploring the nature of chemical bonding in the ThAr diatomic molecule and in clusters at the Hartree-Fock level with the second-order perturbation (MP2) correction accounting for the van der Waals forces. The chemical bonding is formed from the valence states of thorium and polarized states of argon in the clusters with (, 1, 2, 3) and solely from polarized states in the clusters with . In all cases with two or more valence electrons of Th, the ground state, influenced by the first Hund rule for the thorium impurity, is the high spin state. Allowing for the cubic to orthorhombic () symmetry lowering in , we find that the averaged Th-Ar bond length decreases whereas the binding energy increases with , accounted for by the weakening of the Th-Ar repulsion and the strengthening of polarization. For , two conformations (cubic and orthorhombic) are found. We conclude that with the Th-Ar bond lengths lying very close to the Ar-Ar bond lengths in a fcc lattice, the solid argon is a material that is well suited for the accommodation of thorium impurities.
  • Публикация
    Только метаданные
    Spectroscopic Studies of Crystalline Neon Film Grown on a Gold Surface
    (2022) Kurelchuk, U. N.; Borisyuk, P. V.; Chubunova, E. V.; Domashenko, M. S.; Kolachevsky, N. N.; Lebedinskii, Yu. Yu.; Myzin, D. A.; Nikolaev, A. V.; Tkalya, E. V.; Курельчук, Ульяна Николаевна; Борисюк, Петр Викторович; Чубунова, Елена Витальевна; Лебединский, Юрий Юрьевич; Мызин, Дмитрий Анатольевич; Николаев, Александр Васильевич; Ткаля, Евгений Викторович
  • Публикация
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    Multiple locations of boron atoms in the exohedral and endohedral C60 fullerene
    (2022) Bodrenko, I. V.; Bibikov, A. V.; Nikolaev, A. V.; Borisyuk, P. V.; Tkalya, E. V.; Николаев, Александр Васильевич; Борисюк, Петр Викторович; Ткаля, Евгений Викторович
    © 2022 American Physical Society. We study theoretically the bound states of one and two boron atoms in the exohedral and endohedral C60 fullerene. The optimal position of one boron atom is found above the midpoint of the C60 double bond in the exohedral complex, and at the center of C60 or below a carbon atom in the endohedral complex. However, the optimal position of a boron atom is often altered when the second boron atom is added to the molecular complex. For two boron atoms outside the cage the optimal arrangement is realized when the B2 molecule is attached by one boron atom to a double bond midpoint of C60 or when two boron atoms are above two double bond midpoints on opposite sides of C60. Two endohedral boron atoms can lie on the line joining either two opposite double bond midpoints or two centers of opposite pentagons. The latter case corresponds to the optimal geometry of the B2@C60 complex provided that two boron atoms are close enough to form the B2 molecule. In case one boron atom is inside while the other is outside the cage, the optimal locations of atoms are above and below two neighboring carbon atoms belonging to the same hexagon of C60. Remarkably, all these optimal arrangements have different spin states: in the exohedral complex B2C60S=1, in the endohedral B2@C60S=2 (as in the isolated B2 molecule), whereas for one boron atom inside and the other outside the cage S=0. The effective (Bader) charge of boron in these configurations varies appreciably-from 0.06e at the center of C60 to 2e in the B2C58 molecule with two boron atoms substituting for two carbon atoms in C60. We also discuss various conformations in the exohedral and endohedral molecular complexes.
  • Публикация
    Только метаданные
    Features of coherent excitation of 229mTh
    (2022) Tkalya, E. V.; Ткаля, Евгений Викторович
    © 2022 Elsevier B.V.The paper studies the effects that arise at the coherent excitation of the anomalously low-lying isomeric level 3/2+(8.19±0.12 eV) in the 229Th nucleus driven by laser radiation in wide band gap dielectrics. It is shown that in such an excitation a) the appearance of additional decay channels with a width Γ of the 229mTh isomer due to electron states in the band gap leads to an effective “freezing” of the system in the ground state (the repopulation process at relatively small Γ and the Zeno effect at large Γ), making the process of nuclear excitation practically impossible, b) the probability of the α decay of a coherent superposition of the ground and isomeric states becomes equal to the half-sum of the α widths of both levels and is increased by about a factor of two in comparison with the probability of the α decay of 229Th, c) the intensity of the main α lines oscillates with the Rabi frequency and the total α spectrum shifts towards higher energies for long time measurements, d) the inverse population of nuclear levels required for the Thorium γ ray laser is achieved relatively quickly within the π pulse duration, e) the observation of the Zeno effect according to the Cook's scheme is possible for the system of three lower levels of the 229Th nucleus.