| 1. |
- Aksyutina, Y., et al.
(author)
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Structure of the unbound nucleus Be-13: One-neutron knockout reaction data from Be-14 analyzed in a holistic approach
- 2013
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 87:6
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Journal article (peer-reviewed)abstract
- At the ALADIN-LAND setup at GSI the unbound nucleus Be-13 has been produced in one-neutron knockout reactions from a 304 MeV/nucleon relativistic beam of Be-14 ions impinging on a liquid hydrogen target. An analysis of the data including all available information about Be-13, and in particular recent data from a similar experiment performed at RIKEN, has been performed. A consistent description is reached. It is found that the excitation spectrum is dominated by s-waves at low energy, which solves problems from previous seemingly contradictory interpretations. A possible interference between two s-states in Be-13 is also discussed. The results indicate that the ground-state wave function of Be-14 is dominated by valence neutrons in the s-shell contributing with 60-75% of the total neutron knockout cross section.
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| 2. |
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| 3. |
- Bedaque, P., et al.
(author)
-
Quark mass variation constraints from Big Bang nucleosynthesis
- 2011
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In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 83:4
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Journal article (peer-reviewed)abstract
- We study the impact on the primordial abundances of light elements created by a variation of the quark masses at the time of Big Bang nucleosynthesis (BBN). In order to navigate through the particle and nuclear physics required to connect quark masses to binding energies and reaction rates in a model-independent way, we use lattice QCD data and a hierarchy of effective field theories. We find that the measured 4He abundances put a bound of -1%≲δmq/mq≲0.7% on a possible variation of quark masses. The effect of quark mass variations on the deuterium abundances can be largely compensated by changes of the baryon-to-photon ratio η. Including bounds on the variation of η coming from WMAP results and adding some additional assumptions further narrows the range of allowed values of δmq/mq.
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| 4. |
- Billnert, Robert, 1981, et al.
(author)
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New prompt spectral gamma-ray data from the reaction Cf-252(sf) and its implication on present evaluated nuclear data files
- 2013
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 87:2
-
Journal article (peer-reviewed)abstract
- We present results from new spectral prompt gamma-ray measurements from the spontaneous fission of Cf-252. Apart from one recent experiment, about four decades have passed since the last dedicated experiments were reported in the literature. Hence, there was a need for a revision. We have measured prompt fission. rays with both cerium-doped LaBr3 and CeBr3 scintillation detectors, both of which exhibit excellent timing and good energy resolution. The emission yield was determined to be nu(gamma) = (8.30 +/- 0.08)/fission and nu(gamma) = (8.31 +/- 0.10)/fission, with the average energy of is an element of(gamma) = (0.80 +/- 0.01) MeV and is an element of(gamma) = (0.80 +/- 0.01) MeV and total energy of E-gamma,E-tot = (6.64 +/- 0.08) MeV and E-gamma,E-tot = (6.65 +/- 0.12) MeV, with the LaBr3 and CeBr3 detectors, respectively. Since the results from the two detectors are in excellent agreement and confirm the historical data, but not those in the present evaluated nuclear data files, we strongly recommend an update.
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| 5. |
- Burda, O., et al.
(author)
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Resonance parameters of the first 1/2+ state in 9Be and astrophysical implications
- 2010
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 82:1
-
Journal article (peer-reviewed)abstract
- Spectra of the Be-9(e, e') reaction have been measured at the Superconducting Darmstadt Electron Linear Accelerator at an electron energy of E-0 = 73 MeV and scattering angles of 93 degrees and 141 degrees with high-energy resolution up to excitation energies of E-x = 8 MeV. The astrophysically relevant resonance parameters of the first excited 1/2(+) state of Be-9 have been extracted in a one-level approximation of R-matrix theory, resulting in resonance energy E-R = 1.748(6) MeV and width Gamma(R) = 274(8) keV, which are in good agreement with the latest Be-9(gamma, n) experiment but with considerably improved uncertainties. However, the reduced B(E1) transition strength deduced from an extrapolation of the (e, e') data to the photon point is smaller by a factor of two. Implications of the new results for possible production of C-12 in neutron-rich astrophysical scenarios are discussed.
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| 6. |
- Caesar, C., et al.
(author)
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Beyond the neutron drip line: The unbound oxygen isotopes O-25 and O-26
- 2013
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993 .- 0556-2813. ; 88:3
-
Journal article (peer-reviewed)abstract
- The very neutron-rich oxygen isotopes O-25 and O-26 are investigated experimentally and theoretically. The unbound states are populated in an experiment performed at the R3B-LAND setup at GSI via proton-knockout reactions from F-26 and F-27 at relativistic energies around 442 and 414 MeV/nucleon, respectively. From the kinematically complete measurement of the decay into O-24 plus one or two neutrons, the O-25 ground-state energy and width are determined, and upper limits for the O-26 ground-state energy and lifetime are extracted. In addition, the results provide indications for an excited state in O-26 at around 4 MeV. The experimental findings are compared to theoretical shell-model calculations based on chiral two- and three-nucleon (3N) forces, including for the first time residual 3N forces, which are shown to be amplified as valence neutrons are added.
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| 7. |
- Drut, J. E., et al.
(author)
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Exact-exchange density functional theory for neutron drops
- 2011
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In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 84:1
-
Journal article (peer-reviewed)abstract
- We compute the ground-state properties of finite systems of neutrons in an external harmonic trap, interacting via the Minnesota potential, using the "exact-exchange" form of orbital-dependent density functional theory. We compare our results with Hartree-Fock calculations and find very close agreement. Within the context of the interaction studied, we conclude that this simple orbital-dependent functional brings conventional nuclear density functional theory to the level of Hartree-Fock in an ab initio fashion. Our work is a first step toward higher order ab initio nuclear functionals based on realistic nucleon-nucleon interactions.
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| 8. |
- Elvers, M., et al.
(author)
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Investigation of octupole vibrational states in 150Nd via inelastic proton scattering (p,p 'gamma)
- 2011
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 84:5
-
Journal article (peer-reviewed)abstract
- Octupole vibrational states were studied in the nucleus (150)Nd via inelastic proton scattering with 10.9-MeV protons, which are an excellent probe to excite natural parity states. For the first time in (150)Nd, both the scattered protons and the gamma rays were detected in coincidence, giving the possibility to measure branching ratios in detail. Using the coincidence technique, the B(E1) ratios of the decaying transitions for 10 octupole vibrational states and other negative-parity states to the yrast band were determined and compared to the Alaga rule. The positive and negative-parity states revealed by this experiment are compared with interacting boson approximation calculations performed in the spdf boson space. The calculations are found to be in good agreement with the experimental data, for both positive and negative-parity states.
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| 9. |
- Ershov, S. N., et al.
(author)
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Binding energy constraint on matter radius and soft dipole excitations of C-22
- 2012
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In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 86:3
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Journal article (peer-reviewed)abstract
- An unusually large value of the C-22 matter radius has recently been extracted from measured reaction cross sections. The giant size can be explained by a very loose binding that is, however, not known experimentally yet. Within the three-body cluster model we have explored the sensitivity of the s-motion-dominated C-22 geometry to the two-neutron separation energy. A low energy of a few tens of keV is required to reach the alleged experimental lower value of the matter radius, while the experimental mean radius requires an extremely tiny binding. The dependence of the C-22 charge radius on the two-neutron separation energy is also presented. The soft dipole mode in C-22 is shown to be strongly affected by the loose binding and should be studied in the process of Coulomb fragmentation.
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| 10. |
- Ershov, S. N., et al.
(author)
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Modified variable phase method for the solution of coupled radial Schrodinger equations
- 2011
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 84:6
-
Journal article (peer-reviewed)abstract
- A modified variable phase method for the numerical solution of coupled radial Schrodinger equations, which maintains linear independence for different sets of solution vectors, is suggested. The modification involves rearrangement of coupled equations to avoid the usual numerical instabilities associated with components of the wave function in their classically forbidden regions. The modified method is applied to nuclear structure calculations of halo nuclei within the hyperspherical harmonics approach.
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| 11. |
- Grigorenko, L. V., et al.
(author)
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Sensitivity of three-body decays to the reactions mechanism and the initial structure by example of Be-6
- 2012
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 86:6, s. Article Number: 061602-
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Journal article (peer-reviewed)abstract
- The influence of the initial-state structure and the reaction mechanism on three-body decays is investigated using the example of the Be-6 continuum populated in neutron-knockout reactions on Be-7. The sensitivity of the Be-6 excitation spectrum and the three-body correlations to the different components of the model is demonstrated. It is shown that the spin composition of the initial state may have an overwhelming effect on the three-body continuum. The characteristics and structure of the second 0(2)(+) and 2(2)(+) states in Be-6 are predicted and the conditions for their reliable observations are formulated. The effects of interference and the alignment of three-body states on the three-body correlations are demonstrated. DOI: 10.1103/PhysRevC.86.061602
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| 12. |
- Grigorenko, L. V., et al.
(author)
-
Two-neutron radioactivity and four-nucleon emission from exotic nuclei
- 2011
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 84:2
-
Journal article (peer-reviewed)abstract
- A theoretical method for estimates of a width of "true" four-nucleon decays is developed. Several candidate isotopes to possess this property are considered. Our lifetime estimates compare one-neutron, true two-neutron, and true four-neutron emissions at similar conditions. Prospects of experimental search for two-neutron, four-proton, and four-neutron radioactivity are discussed.
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| 13. |
- Grigorenko, L. V., et al.
(author)
-
Two-proton radioactivity and three-body decay. V. Improved momentum distributions
- 2010
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 82:1
-
Journal article (peer-reviewed)abstract
- Nowadays quantum-mechanical theory allows one to reliably calculate the processes of 2p radioactivity (true three-body decays) and the corresponding energy and angular correlations up to distances of the order of 10(3) fm. However, the precision of modern experiments has now become sufficient to indicate some deficiency of the predicted theoretical distributions. In this paper we discuss extrapolation along the classical trajectories as a method to improve the convergence of the theoretical energy and angular correlations at very large distances (of the order of atomic distances), where only long-range Coulomb forces are still operating. The precision of this approach is demonstrated using the "exactly" solvable semianalytical models with simplified three-body Hamiltonians. It is also demonstrated that for heavy 2p emitters, the 2p decay momentum distributions can be sensitive to the effect of screening by atomic electrons. We compare theoretical results with available experimental data.
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| 14. |
- Gürdal, G., et al.
(author)
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Measurements of g(41+,22+) in 70,72,74 ,76Ge: Systematics of low-lying structures in 30≤Z≤40 and 30≤N≤50 nuclei
- 2013
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 88:1
-
Journal article (peer-reviewed)abstract
- Background: The interplay between single-particle and collective excitations in the 30 ≤Z≤ 40 and 30 ≤N≤ 50 even-even isotopes has been examined in light of recent new measurements of magnetic moments of 41+, 22+, and 21+ states. Purpose: The g factors of the 41+ and 22+ states in the 72,74,76Ge isotopes have been measured for the first time and the g(21+) values have been remeasured. Methods: The transient field (TF) technique in inverse kinematics with a variety of targets has been applied, following Coulomb excitation of the relevant states. The data have been analyzed within the framework of the IBA-II model. Large-scale shell-model calculations have been performed within the p3/2,p1/2,f 5/2,g9/2 orbital space for both protons and neutrons with the JUN45 and JJ4B interactions. Results: The measured Ge g factors were compared to the g factors of the low-lying states of the neighboring Zn, Ge, Se, Kr, and Sr isotopes. The results were evaluated in the context of the systematics of g factors in the A∼80 region. Conclusions: The predictions based on the classic collective model and the interacting boson model IBA-II agree with the experimental results. No evidence for shell closure was found for neutrons at N=38 or N=40. © 2013 American Physical Society.
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| 15. |
- Hennig, A., et al.
(author)
-
Mixed-symmetry octupole and hexadecapole excitations in the N=52 isotones
- 2014
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 90:5, s. Art. no. 051302-
-
Journal article (peer-reviewed)abstract
- Background: Excitations with mixed proton-neutron symmetry have been previously observed in the N=52 isotones. Besides the well-established quadrupole mixed-symmetry states (MSS), octupole and hexadecapole MSS have been recently proposed for the nuclei Zr92 and Mo94. Purpose: The heaviest stable N=52 isotone Ru96 was investigated to study the evolution of octupole and hexadecapole MSS with increasing proton number. Methods: Two inelastic proton-scattering experiments on Ru96 were performed to extract branching ratios, multipole mixing ratios, and level lifetimes. From the combined data, absolute transition strengths were calculated. Results: Strong M1 transitions between the lowest-lying 3- and 4+ states were observed, providing evidence for a one-phonon mixed-symmetry character of the 32(-) and 42+ states. Conclusions: sdg-IBM-2 calculations were performed for Ru96. The results are in excellent agreement with the experimental data, pointing out a one-phonon hexadecapole mixed-symmetry character of the 42+ state. The 31-||M1||32(-) matrix element is found to scale with the 2s+||M1||2ms+ matrix element.
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| 16. |
- Hyldegaard, S., et al.
(author)
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R-matrix analysis of the beta decays of 12N and 12B
- 2010
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 81:2
-
Journal article (peer-reviewed)abstract
- The β decays of 12N and 12B have been studied at KVI and JYFL to resolve the composition of the broad and interfering 0+ and 2+ strengths in the triple-α continuum. For the first time a complete treatment of 3α decay is presented including all major breakup channels. A multilevel, many-channel R-matrix formalism has been developed for the complete description of the breakup in combination with the recently published separate analysis of angular correlations. We find that, in addition to the Hoyle state at 7.65 MeV, more than one 0+ and 2+ state is needed to reproduce the spectra. Broad 03+ and 22+ states are found between 10.5 and 12 MeV in this work. The presence of β strength up to the 12N Q-value window suggests the presence of additional 0+ and 2+ components in the 12C structure at energies above 12.7 MeV.
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| 17. |
- Imai, N., et al.
(author)
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Isobaric analog resonances of Mg-31 and the border of the island of inversion
- 2014
-
In: Physical Review C (Nuclear Physics). - 0556-2813 .- 2469-9985 .- 2469-9993. ; 90:1
-
Journal article (peer-reviewed)abstract
- The evolution of the nuclear shell structure in the region of the neutron-rich shell-breaking nucleus Mg-32 has been the subject of considerable interest. We present here the first determination of the overlap of the ground and two first excited states in Mg-31 with a neutron coupled to the ground state in Mg-30 based on studies of its isobaric analog resonances in Al-31. The excitation function for proton resonant elastic scattering on Mg-30 was measured close to 0 degrees in the laboratory frame by bombarding a thick polyethylene target with a Mg-30 beam at an energy of 2.92 MeV/nucleon at the REX-ISOLDE facility at CERN. Three resonances were successfully resolved, and angular momenta and total and proton resonance widths were determined by using R-matrix analysis. The deduced spectroscopic factor for the ground state in Mg-31 is consistent with the shell-model calculation, whereas those for the first and second excited states could not be reproduced. These results show that a drastic change in structure occurs between Mg-30 and Mg-31 and that the onset of structural change in this region therefore occurs between these two isotopes.
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| 18. |
- Johansen, J. G., et al.
(author)
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Experimental study of bound states in Be-12 through low-energy Be-11(d,p)-transfer reactions
- 2013
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 88:4
-
Journal article (peer-reviewed)abstract
- The bound states of Be-12 have been studied through a Be-11(d, p) Be-12 transfer reaction experiment in inverse kinematics. A 2.8 MeV/u beam of Be-11 was produced using the REX-ISOLDE facility at CERN. The outgoing protons were detected with the T-REX silicon detector array. The MINIBALL germanium array was used to detect gamma rays from the excited states in Be-12. The gamma-ray detection enabled a clear identification of the four known bound states in Be-12, and each of the states has been studied individually. Differential cross sections over a large angular range have been extracted. Spectroscopic factors for each of the states have been determined from distorted wave Born approximation (DWBA) calculations and have been compared to previous experimental and theoretical results.
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| 19. |
- Kanungo, R., et al.
(author)
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Exploring the anomaly in the interaction cross section and matter radius of 23O
- 2011
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993 .- 0556-2813 .- 1089-490X. ; 84:6, s. art. no. 061304(R)-
-
Journal article (peer-reviewed)abstract
- New measurements of the interaction cross sections of 22,23O at 900A MeV performed at the GSI, Darmstadt are reported that address the unsolved puzzle of the large cross section previously observed for 23O. The matter radii for these oxygen isotopes extracted through a Glauber model analysis are in good agreement with the new predictions of the ab initio coupled-cluster theory reported here. They are consistent with a 22O+neutron description of 23O as well.
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| 20. |
- Kanungo, R., et al.
(author)
-
Matter radii of 32-35Mg
- 2011
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993 .- 0556-2813 .- 1089-490X. ; 83:2
-
Journal article (peer-reviewed)abstract
- The interaction cross sections of Mg32-35 at 900A MeV have been measurmed using the fragment separator at GSI. The deviation from the r(0)A(1/3) trend is slightly larger for Mg-35, signaling the possible formation of a longer tail in the neutron distribution for Mg-35. The radii extracted from a Glauber model analysis with Fermi densities are consistent with models predicting the development of neutron skins.
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| 21. |
- Kirsebom, O. S., et al.
(author)
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Breakup of 12C resonances into three α particles
- 2010
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 81:6
-
Journal article (peer-reviewed)abstract
- The reaction He-3 + B-11 -> d + C-12* has been used to populate resonances in C-12 up to an excitation energy of 15 MeV. The subsequent breakup to three alpha particles has been measured in complete kinematics. Dalitz plots are used to visualize and analyze the data. The Dalitz plot intensity distribution exhibits zero points characteristic of the total spin and parity of the 3 alpha system allowing us to determine the spin and parity of a state in C-12 at 13.35 MeV whose quantum numbers were hitherto not well established. The Dalitz plot intensity distributions of the 2(-) state at 11.83 MeV and the 1(+) state at 12.71 MeV are compared with the predictions of a recent three-body calculation as well as with simpler models. All are able to reproduce the gross structures seen in the Dalitz plot, but none give an accurate description of the detailed profile of the distributions.
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| 22. |
- Kirsebom, O. S., et al.
(author)
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Precise and accurate determination of the B-8 decay spectrum
- 2011
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 83:6
-
Journal article (peer-reviewed)abstract
- Accurate measurements of the B-8 neutrino spectrum are important for the interpretation of solar neutrino data. Experimentally, the B-8 neutrino spectrum can be obtained from the measurement of the beta-delayed alpha spectrum. We report on an alpha-alpha coincidence measurement performed at the IGISOL facility in Jyvaskyla, Finland. Our measurement allows extensive cross-checks to be performed and gives a more intense neutrino spectrum at high energies compared to the present standard. The deviation reaches 4% at the end point of the spectrum. Below 11 MeV, the deviation is less than 1%.
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| 23. |
- Koldste, G. T., et al.
(author)
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Multiparticle emission in the decay of Ar-31
- 2014
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 89:6
-
Journal article (peer-reviewed)abstract
- A multihit capacity setup was used to study the decay of the dripline nucleus Ar-31, produced at the ISOLDE facility at CERN. A spectroscopic analysis of the beta-delayed three-proton decay of Ar-31 is presented for the first time together with a quantitative analysis of the beta-delayed 2p gamma decay. A new method for determination of the spin of low-lying levels in the beta p daughter 30S using proton-proton angular correlations is presented and used to determine that the spin of the 5.2-MeV level is most likely 3(+) with 4(+) also possible. The half-life of Ar-31 is found to be 15.1(3) ms. An improved analysis of the Fermi beta strength including the beta 3p-decay mode gives a total measured branching ratio of 3.60(44)%, which is lower than the theoretical value found to be 4.24(43)%. Finally, a previously unidentified. transition from the isobaric analog state in the decay of Ar-33 has been found.
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| 24. |
- Koldste, G. T., et al.
(author)
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Relative proton and gamma widths of astrophysically important states in S-30 studied in the beta-delayed decay of Ar-31
- 2013
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 87:5
-
Journal article (peer-reviewed)abstract
- Resonances just above the proton threshold in S-30 affect the P-29(p, gamma)S-30 reaction under astrophysical conditions. The (p,gamma)-reaction rate is currently determined indirectly and depends on the properties of the relevant resonances. We present here a method for finding the ratio between the proton and gamma partial widths of resonances in S-30. The widths are determined from the beta 2p- and beta p gamma-decay of Ar-31, which is produced at the ISOLDE radioactive ion beam facility at the European research organization CERN. Experimental limits on the ratio between the proton and gamma partial widths for astrophysical relevant levels in S-30 have been found for the first time. A level at 4689.2(24) keV is identified in the gamma spectrum, and an upper limit on the Gamma(p)/ Gamma gamma ratio of 0.26 (95% C.L.) is found. In the two-proton spectrum two levels at 5227(3) keV and 5847(4) keV are identified. These levels were previously seen to gamma decay and upper limits on the Gamma(gamma)/Gamma(p) ratio of 0.5 and 9, respectively, (95% C.L.) are found, where the latter differs from previous calculations.
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| 25. |
- Langer, C., et al.
(author)
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Thermonuclear reaction S-30(p,gamma)Cl-31 studied via Coulomb breakup of Cl-31
- 2014
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 89:3
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Journal article (peer-reviewed)abstract
- Coulomb breakup at high energy in inverse kinematics of proton-rich Cl-31 was used to constrain the thermonuclear S-30(p,gamma)Cl-31 capture reaction rate under typical Type I x-ray burst conditions. This reaction is a bottleneck during rapid proton-capture nucleosynthesis (rp process), where its rate depends predominantly on the nuclear structure of Cl-31. Two low-lying states just above the proton-separation threshold of S-p = 296( 50) keV in Cl-31 have been identified experimentally using the (RB)-B-3-LAND setup at the GSI Helmholtzzentrum fur Schwerionenforschung GmbH. Both states are considered to play a key role in the thermonuclear S-30( p,gamma)Cl-31 capture reaction. Excitation energies of the first J(pi) = 1/2(+), 5/2(+) states have been extracted and the reaction rate for proton capture on S-30 under typical rp-process temperatures has been investigated.
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