| 1. |
- Bezbakh, A.A., et al.
(författare)
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Evidence for the First Excited State of H 7
- 2020
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 124:2
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Tidskriftsartikel (refereegranskat)abstract
- The H7 system was populated in the H2(He8,He3)H7 reaction with a 26 AMeV He8 beam. The H7 missing mass energy spectrum, the H3 energy and angular distributions in the H7 decay frame were reconstructed. The H7 missing mass spectrum shows a peak, which can be interpreted either as unresolved 5/2+ and 3/2+ doublet or one of these states at 6.5(5) MeV. The data also provide indications of the 1/2+ ground state of H7 located at 1.8(5) MeV with quite a low population cross section of ∼25 μb/sr within angular range θc.m.≃(17°-27°).
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| 2. |
- Grigorenko, L, et al.
(författare)
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Asymptotic normalization coefficient method for two-proton radiative capture
- 2020
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 811
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Tidskriftsartikel (refereegranskat)abstract
- The method of asymptotic normalization coefficients is a standard approach for studies of two-body non-resonant radiative capture processes in nuclear astrophysics. This method suggests a fully analytical description of the radiative capture cross section in the low-energy region of the astrophysical interest. We demonstrate how this method can be generalized to the case of three-body 2p radiative captures. It was found that an essential feature of this process is the highly correlated nature of the capture. This reflects the complexity of three-body Coulomb continuum problem. Radiative capture 15O+p+p→17Ne+γ is considered as an illustration.
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| 3. |
- Muzalevskii, I. A., et al.
(författare)
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Resonant states in H 7: Experimental studies of the H 2 (He 8, He 3) reaction
- 2021
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Ingår i: Physical Review C. - 2469-9985 .- 2469-9993. ; 103:4
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Tidskriftsartikel (refereegranskat)abstract
- The extremely neutron-rich system H7 was studied in the direct H2(He8,He3)H7 transfer reaction with a 26 AMeV secondary He8 beam [Bezbakh et al., Phys. Rev. Lett. 124, 022502 (2020)PRLTAO0031-900710.1103/PhysRevLett.124.022502]. The missing mass spectrum and center-of-mass angular distributions of H7, as well as the momentum distribution of the H3 fragment in the H7 frame, were constructed. In addition, we carried out another experiment with the same beam but a modified setup, which was cross-checked by the study of the H2(Be10,He3)Li9 reaction. A solid experimental evidence is provided that two resonant states of H7 are located in its spectrum at 2.2(5) and 5.5(3)MeV relative to the H3+4n decay threshold. Also, there are indications that the resonant states at 7.5(3) and 11.0(3)MeV are present in the measured H7 spectrum. Based on the energy and angular distributions, obtained for the studied H2(He8,He3)H7 reaction, the weakly populated 2.2(5)-MeV peak is ascribed to the H7 ground state. It is highly plausible that the firmly ascertained 5.5(3)-MeV state is the 5/2+ member of the H7 excitation 5/2+-3/2+ doublet, built on the 2+ configuration of valence neutrons. The supposed 7.5-MeV state can be another member of this doublet, which could not be resolved in Bezbakh et al. [Phys. Rev. Lett. 124, 022502 (2020)PRLTAO0031-900710.1103/PhysRevLett.124.022502]. Consequently, the two doublet members appeared in the spectrum of H7 in the work mentioned above as a single broad 6.5-MeV peak.
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| 4. |
- Nikolskii, E.Y., et al.
(författare)
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H 6 states studied in the H 2 (He 8, He 4) reaction and evidence of an extremely correlated character of the H 5 ground state
- 2022
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Ingår i: Physical Review C. - 2469-9993 .- 2469-9985. ; 105:6
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Tidskriftsartikel (refereegranskat)abstract
- The extremely neutron-rich system H6 was studied in the direct H2(He8,He4)H6 transfer reaction with a 26A MeV secondary He8 beam. The measured missing mass spectrum shows a broad bump at ≈4-8 MeV above the H3+3n decay threshold. This bump can be interpreted as a broad resonant state in H6 at 6.8(5) MeV. The population cross section of such a presumably p-wave state (or it may be few overlapping states) in the energy range from 4 to 8 MeV is dσ/dωc.m.≃190-80+40μb/sr in the angular range 5°<θc.m.<16°. The obtained missing mass spectrum is practically free of H6 events below 3.5 MeV (dσ/dωc.m. 5μb/sr in the same angular range). The steep rise of the H6 missing mass spectrum at ≈3 MeV allows us to derive the lower limit for the possible resonant-state energy in H6 to be 4.5(3) MeV. According to the paring energy estimates, such a 4.5(3) MeV resonance is a realistic candidate for the H6 ground state (g.s.). The obtained results confirm that the decay mechanism of the H7 g.s. (located at 2.2 MeV above the H3+4n threshold) is the "true"(or simultaneous) 4n emission. The resonance energy profiles and the momentum distributions of fragments of the sequential H6→H5(g.s.)+n→H3+3n decay were analyzed by the theoretically updated direct four-body-decay and sequential-emission mechanisms. The measured momentum distributions of the H3 fragments in the H6 rest frame indicate very strong "dineutron-type"correlations in the H5 ground state decay.
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| 5. |
- Nikolskii, E.Y., et al.
(författare)
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Study of proton and deuteron pickup reactions (d, 3 He), (d, 4 He) with 8 He and 10 Be radioactive beams at ACCULINNA-2 fragment separator
- 2023
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - 0168-583X. ; 541, s. 121-125
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Tidskriftsartikel (refereegranskat)abstract
- The extremely neutron-rich systems 7H, 6H were studied in the 2H(8He, 3He)7H and 2H(8He, 4He)6H proton and deuteron pickup reactions with a 26 AMeV secondary 8He beam produced at the new ACCULINNA-2 fragment separator. In addition, the same proton and deuteron pickup reactions were generated using the 42 AMeV 10Be beam, and the population of low-lying 9Li and 8Li states was measured in reactions 2H(10Be,3He)9Li and 2H(10Be,4He)8Li, respectively. The latter were used as reference measurements in order to check the setup calibration over the excitation energy of 7,6H and to determine the real experimental energy resolution which was compared with Monte Carlo calculations. The corresponding results obtained for the superheavy hydrogen systems 7H, 6H are presented and discussed. Typical excitation spectra of the 9Li and 8Li nuclei are also shown.
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| 6. |
- Grigorenko, L, et al.
(författare)
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High-precision studies of the soft dipole mode in two-neutron halo nuclei: The He 6 case
- 2020
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Ingår i: Physical Review C. - 2469-9985 .- 2469-9993. ; 102:1
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Tidskriftsartikel (refereegranskat)abstract
- The soft dipole E1 strength function is calculated for the transition from the He60+ ground state to the 1- continuum He4+n+n. The calculations were performed within the hyperspherical harmonics formalism. The sensitivity of the results to the He6 ground-state structure and to final-state interactions, are analyzed. The large-basis calculations show the reliably converged results for soft dipole strength function and for momentum correlations of the He6→He4+n+n dissociation products. Transition mechanisms are analyzed based on the momentum correlations. The comparison with experimental data is provided.
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| 7. |
- Grigorenko, L, et al.
(författare)
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Three-body vs. dineutron approach to two-neutron radiative capture in 6 He
- 2020
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 807
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Tidskriftsartikel (refereegranskat)abstract
- The low-energy behavior of the strength function for the 1− soft dipole excitation in 6He is studied theoretically. Use of very large basis sizes and well-grounded extrapolation procedures allows to move to energies as small as 1 keV, at which the low-energy asymptotic behavior of the E1 strength function seems to be achieved. It is found that the low-energy behavior of the strength function is well described in the effective three-body “dynamical dineutron model”. The astrophysical rate for the α+n+n→6He+γ is calculated. Comparison with the previous calculations is performed.
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| 8. |
- Ruchkin, Vladislav V., 1969-, et al.
(författare)
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Dopamine-related receptors, substance dependence, behavioral problems and personality among juvenile delinquents
- 2021
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Ingår i: Personality and Individual Differences. - : Elsevier BV. - 0191-8869 .- 1873-3549. ; 169
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Tidskriftsartikel (refereegranskat)abstract
- The objective was two-fold: to examine possible associations between dopamine-related genetic polymorphisms and (1) substance dependence; and (2) self-reported psychiatric disturbances, behavioral problems, and personality. Genotyping of single nucleotide polymorphisms (SNP: s) in COMT, DAT and DRD4 was conducted in 174 Russian male juvenile inmates (14–18 years of age) subdivided into having a diagnosis of substance dependence or not, as assessed by using K-SADS-PL. The inmates completed several self-reports assessing psychiatric symptoms (CPTS-RI, BDI), behavioral problems (YSR), and personality traits (TCI). Results revealed that juveniles meeting the criteria for substance dependence differed significantly from their counterparts in four polymorphisms, namely COMT rs737865, DAT rs6347, DRD4 C_1611535 and DRD4 exon III; and exact binary regression analysis indicated a highly significant association between the DRD4 C_1611535 GG genotype and substance dependence. One-way ANOVA tests further showed this gene polymorphism variant to be significantly associated with higher levels of posttraumatic stress, thought problems, aggressive behavior, and personality traits indicating antisocial personality disturbances, as compared with the other gene polymorphism variants. In conclusion, the results underscore the role of the DRD4 polymorphism C_1611535 GG genotype for substance dependence, and suggest its associations with different self-reported phenotype characteristics.
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| 9. |
- Sharov, P.G., et al.
(författare)
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FOUR-NEUTRON DECAY CORRELATIONS
- 2021
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Ingår i: Acta Physica Polonica B, Proceedings Supplement. - 1899-2358. ; 14:4, s. 749-753
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism of simultaneous non-sequential four-neutron emission (or “true” four-neutron decay) has been considered in the phenomenological five-body approach. It is demonstrated that four-neutron decay fragments should have specific energy and angular correlations reflecting strong spatial correlations of “valence” nucleons orbiting in their four-neutron precursors. Due to the Pauli exclusion principle, the valence neutrons are pushed to the symmetry-allowed configurations in the four-neutron precursor structure, which causes a “Pauli focusing” effect. Prospects of the observation of the Pauli focusing have been considered for the hydrogen-7 nucleus. Fingerprints of its nuclear structure or/and decay dynamics are predicted.
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| 10. |
- Sukhareva, O. M., et al.
(författare)
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Studying the Validity of the Quasi-Classical Approach to Three-Body Decays
- 2020
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Ingår i: Bulletin of the Russian Academy of Sciences: Physics. - 1062-8738 .- 1934-9432. ; 84:4, s. 461-464
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Tidskriftsartikel (refereegranskat)abstract
- The hyperspherical harmonics approach is especially suited to studies of true three-body decays. Reducing the hyperspherical equations set to a single-channel approximation provides the basis for using the standard quasi-classical expression for calculating resonance widths. It is shown that the quasi-classical approach is itself quite precise when applied to the three-body single-channel effective potentials. However, reduction to the single-channel formalism seems to be unacceptable, as it leads to considerable overestimation of decay widths.
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