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°).
The interaction of an E/A = 57.6-MeV Ne-17 beam with a Be target is used to populate levels in Ne-16 following neutron knockout reactions. The decay of 16Ne states into the three-body O-14 + p + p ...continuum is observed in the High Resolution Array (HiRA). For the first time for a 2p emitter, correlations between the momenta of the three decay products are measured with sufficient resolution and statistics to allow for an unambiguous demonstration of their dependence on the long-range nature of the Coulomb interaction. Contrary to previous measurements, our measured limit Gamma
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.
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.
Coulomb and nuclear dissociation of Ne-17 on light and heavy targets are studied theoretically. The dipole E1 strength function is determined in a broad energy range including energies of ...astrophysical interest. Dependence of the strength function on different parameters of the Ne-17 ground-state structure and continuum dynamics is analyzed in a three-body model. The discovered dependence plays an important role for studies of the strength functions for the three-body E1 dissociation and radiative capture. The constraints on the s(2)/d(2) configuration mixing in Ne-17 and on p-wave interaction in the O-15+p channel are imposed based on experimental data for Ne-17 Coulomb dissociation on heavy target.
Studies of radioactive ions (RIs) are the most thriving field of low-energy nuclear physics. In this paper, the concept and the scientific agenda of the prospective accelerator and storage ring ...facility for RI beam (RIB) research are proposed for a large-scale international project based at the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research. The motivation for the new facility is discussed and its characteristics are briefly presented and shown to be comparable to those of advanced world centers, the so-called "RIB factories". In the project, the emphasis is made on studies with short-lived RIBs in storage rings. A unique feature of the project is the possibility of studying electron-RI interactions in a collider experiment to determine the fundamental properties of nuclear matter, in particular, electromagnetic form factors of exotic nuclei.
The Be6 continuum states were populated in the charge-exchange reaction H1(Li6,Be6)n collecting very high statistics data (∼5×106 events) on the three-body α+p+p correlations. The Be6 excitation ...energy region below ∼3MeV is considered, where the data are dominated by contributions from the 0+ and 2+ states. It is demonstrated how the high-statistics few-body correlation data can be used to extract detailed information on the reaction mechanism. Such a derivation is based on the fact that highly spin-aligned states are typically populated in the direct reactions.
The proton and deuteron pickup reactions
and
were studied with the
radioactive beam produced by the new fragment separator ACCULINNA-2 at FLNR, JINR. These measurements were initially motivated as ...the test reactions intended for the elucidation of results obtained in the study of the extremely neutron-rich
H and
H systems created in the
and
reactions with the use of the same setup. In the
reaction the
Li ground-state (
) and its first excited state (2.69 MeV,
) were identified in the low-energy region of its excitation spectrum. The differential cross sections for the
population were extracted at the forward center-of-mass angles (
) and compared with the FRESCO calculations. Spectroscopic factor of
, derived by a model suggesting the
clustering was found in accord with the experimental data. The energy spectrum of
Li populated in the
reaction shows the strong peak which corresponds to the excitation of the second excited state of
Li (2.25 MeV,
). The fact that the ground and the first excited states of
Li were not observed in this reaction is consistent with the shell-model structure of the nuclei involved.
The start of operation of a new separator ACCULINNA-2 makes an important upgrade for the Radioactive-Ion Beam (RIB) research done at the Flerov Laboratory of Nuclear Reactions (FLNR, JINR). Test ...results indicate that the separator meets the project specifications. Intensities obtained for the 6,8He, 9,11Li, 12Be RIBs are 15 times higher in comparison with the results achieved at the old separator ACCULINNA. An overview of the design, construction and commissioning studies of the ACCULINNA-2 separator is presented. The separator will be equipped with some key facilities: a cryogenic tritium target, zero degree spectrometer following the physical target bombarded by the RIBs, and with a neutron detector array, and the Time Projection Chamber (TPC). This opens a wide range of experimental possibilities. Overview is presented on the two first experiments devoted to the study of d + 6He elastic scattering and search for a 7H low-lying resonance state populated in the 2H(8He,3He)7H reaction.
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