Tue·May 22, 2018Tuesday·May 22, 2018

1. 01*

   alpha-induced reactions on 115In: cross section measurements and statistical model analysis

   G.G.Kiss🇭🇺 · T. Szucs🇭🇺 · P.Mohr🇭🇺 · Zs.Torok · R.Huszank🇭🇺 · Gy.Gyurky🇭🇺 · Zs. Fulop🇭🇺

   [Background] Alpha-nucleus optical potentials are basic ingredients of statistical model calculations used in nucleosynthesis simulations. While the nucleon+nucleus optical potential is fairly well known, for the alpha+nucleus optical potential several different parameter sets exist and large deviations, reaching sometimes even an order of magnitude, are found between the cross section predictions calculated using different parameter sets. [Purpose] A measurement of the radiative alpha-capture and the alpha-induced reaction cross sections on the nucleus 115In at low energies allows a stringent test of statistical model predictions. Since experimental data is scarce in this mass region, this measurement can be an important input to test the global applicability of alpha+nucleus optical model potentials and further ingredients of the statistical model. [Methods] The reaction cross sections were measured by means of the activation method. The produced activities were determined by off-line detection of the gamma-rays and characteristic x-rays emitted during the electron capture decay of the produced Sb isotopes. The 115In(alpha,gamma)119Sb and 115In(alpha,n)118Sbm reaction cross sections were measured between Ec.m. = 8.83 MeV - 15.58 MeV, and the 115In(alpha,n)118Sbg reaction was studied between Ec.m. = 11.10 MeV - 15.58 MeV. The theoretical analysis was performed within the statistical model.

   nucl-exPRC(2018)·12 citations
2. 02*

   News on the nuclear structure of neutron-rich nuclei at and beyond N=28

   Alexandra Gade🇺🇸

   The nuclear potential and resulting shell structure are well established for the valley of stability, however, dramatic modifications to the familiar ordering of single-particle orbitals in rare isotopes with a large imbalance of proton and neutron numbers have been found: new shell gaps emerge and conventional magic numbers are no longer valid. This article outlines some of the recent in-beam gamma-ray spectroscopy measurements at NSCL aimed at shedding light on the evolution of nuclear structure around neutron number N = 28 in neutron-rich Ar and S isotopes.

   nucl-exJPS Conf.Proc.(2018)·0 citations
3. 03*

   Measurement of the $2^{+}\to 0^{+}$ ground-state transition in the $\beta$ decay of ${}^{20}$F

   O. S. Kirsebom · M. Hukkanen🇫🇮 · A. Kankainen🇫🇮 · W. H. Trzaska🇫🇮 · D. F. Strömberg🇩🇪 · G. Martínez-Pinedo🇩🇪 · K. Andersen · E. Bodewits · L. Canete · J. Cederkäll🇸🇪 · T. Enqvist🇫🇮 · T. Eronen and 27 other authors

   We report the first detection of the second-forbidden, non-unique, $2^{+}\to 0^{+}$, ground-state transition in the $\beta$ decay of ${}^{20}$F. A low-energy, mass-separated ${}^{20}{\mathrm{F}}^{+}$ beam produced at the IGISOL facility in Jyväskylä, Finland, was implanted in a thin carbon foil and the $\beta$ spectrum measured using a magnetic transporter and a plastic-scintillator detector. The $\beta$-decay branching ratio inferred from the measurement is $b_{\beta }=[0.41\pm 0.08\text{(stat)}\pm 0.07\text{(sys)}]\times 10^{-5}$ corresponding to $\log ft=10.89(11)$, making this one of the strongest second-forbidden, non-unique $\beta$ transitions ever measured. The experimental result is supported by shell-model calculations and has significant implications for the final evolution of stars that develop degenerate oxygen-neon cores. Using the new experimental data, we argue that the astrophysical electron-capture rate on ${}^{20}$Ne is now known to within better than 25% at the relevant temperatures and densities.

   nucl-exPRC(2019)·26 citations
4. 04*

   Backward single-pion production in the $\mathbf{pd}\to {}^3\text{He}{\mathbf{\pi }}^0$ reaction with WASA-at-COSY

   P. Adlarson🇸🇪 · W. Augustyniak🇵🇱 · W. Bardan🇵🇱 · M. Bashkanov🇬🇧 · F.S. Bergmann🇩🇪 · M. Berłowski🇵🇱 · A. Bondar🇷🇺 · M. Büscher🇩🇪 · H. Calén🇸🇪 · I. Ciepał🇵🇱 · H. Clement🇩🇪 · E. Czerwiński🇵🇱 and 80 other authors

   New data on the production of single neutral pions in the $pd\to {}^3\text{He}{\pi }^0$ reaction are presented. For fifteen proton beam momenta between $p_p=1.60\text{GeV}/c$ and $p_p=1.74\text{GeV}/c$, differential cross sections are determined over a large fraction of the backward hemisphere. Since the only previous systematic measurements of single-pion production at these energies were made in collinear kinematics, the present work constitutes a significant extension of the current knowledge on this reaction. Even this far above the production threshold, significant changes are found in the behaviour of the angular distributions over small intervals in beam momentum.

   nucl-exnucl-thEPJA(2018)·1 citation
5. 05*

   Theoretical considerations about heavy-ion fusion in potential scattering

   L. F. Canto🇧🇷 · R. Donangelo🇧🇷 · M. S. Hussein🇧🇷 · J. Lubian🇧🇷 · P. Lotti · J. Rangel

   We carefully compare the one-dimensional WKB barrier tunneling model, and the one-channel Schödinger equation with a complex optical potential calculation of heavy-ion fusion, for a light and a heavy system. It is found that the major difference between the two approaches occurs around the critical energy, above which the effective potential for the grazing angular momentum ceases to exhibit a pocket. The value of this critical energy is shown to be strongly dependent on the nuclear potential at short distances, on the inside region of the Coulomb barrier, and this dependence is much more important for heavy systems. Therefore the nuclear fusion process is expected to provide information on the nuclear potential in this inner region. We compare calculations with available data to show that the results are consistent with this expectation.

   ↳ nucl-thnucl-exPRC(2018)·15 citations
6. 06*

   Persistence of magicity in neutron rich exotic ${}^{78}$Ni in ground as well as excited states

   Mamta Aggarwal🇮🇳 · G. Saxena🇮🇳

   Recent experimental observation of magicity in ${}^{78}$Ni has infused the interest to examine the persistence of the magic character across the N$=$50 shell gap in extremely neutron rich exotic nucleus ${}^{78}$Ni in ground as well as excited states. A systematic study of Ni isotopes and N$=$50 isotones in ground state is performed within the microscopic framework of relativistic mean-field (RMF) and the triaxially deformed Nilson Strutinsky model (NSM). Ground state density distributions, charge form factors, radii, separation energies, pairing energies, single particle energies and the shell corrections show strong magicity in ${}^{78}$Ni. Excited nuclei are treated within the statistical theory of hot rotating nuclei where the variation of level density parameter and entropy shows significant magicity with a deep minima at N$=$50, which, persists up to the temperatures $\approx$ 1.5$-$2 MeV and then slowly disappear with increasing temperature. Rotational states are evaluated and effect of rotation on N$=$50 (Z$=$20$-$30) isotones are studied. Our results agree very well with the available experimental data and few other theoretical calculations.

   ↳ nucl-thnucl-exIJMPE(2018)·4 citations
7. 07*

   Stability of the linear chain structure for ${}^{12}$C in covariant density functional theory on a 3D lattice

   Z. X. Ren🇨🇳 · S. Q. Zhang🇨🇳 · P. W. Zhao🇺🇸 · N. Itagaki🇯🇵 · J. A. Maruhn🇩🇪 · J. Meng

   The stability of the linear chain structure of three $\alpha$ clusters for ${}^{12}$C against the bending and fission is investigated in the cranking covariant density functional theory, in which the equation of motion is solved on a 3D lattice with the inverse Hamiltonian and the Fourier spectral methods. Starting from a twisted three $\alpha$ initial configuration, it is found that the linear chain structure is stable when the rotational frequency is within the range of $\sim$2.0 MeV to $\sim$2.5 MeV. Beyond this range, the final states are not stable against fission. By examining the density distributions and the occupation of single-particle levels, however, these fissions are found to arise from the occupation of unphysical continuum with large angular momenta. To properly remove these unphysical continuum, a damping function for the cranking term is introduced. Eventually, the stable linear chain structure could survive up to the rotational frequency $\sim$3.5 MeV, but the fission still occurs when the rotational frequency approaches to $\sim$4.0 MeV.

   ↳ nucl-thnucl-exSCPMA(2019)·60 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.