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Employing the Argonne Fragment Mass Analyzer and the implantation-decay-decay correlation technique, a weak 0.50(21)% proton decay branch was identified in 108I for the first time. The 108I proton-decay width is consistent with a hindered l = 2 emission, suggesting a d 5 2 origin. Using the extracted 108I proton-decay Q value of 597(13) keV, and the Q α values of the 108I and 107Te isotopes, a proton-decay Q value of 510(20) keV for 104Sb was deduced. Similarly to the 112,113Cs proton-emitter pair, the Q p ( I 108 ) value is lower than that for the less-exotic neighbor 109I, possibly due to enhanced proton-neutron interactions in N ≈ Z nuclei. In contrast, the present Q p ( Sb 104 ) is higher than that of 105Sb, suggesting a weaker interaction energy. For the present Q p ( Sb 104 ) value, network calculations with the one-zone X-ray burst model Mazzocchi et al. (2007) [18] predict no significant branching into the Sn-Sb-Te cycle at 103Sn.

7 pags., 5 figs., 2 tabs., The single-particle properties of Mg29 have been investigated via a measurement of the Mg28(d,p)Mg29 reaction, in inverse kinematics, using the ISOLDE Solenoidal Spectrometer. The negative-parity intruder states from the fp shell have been identified and used to benchmark modern shell-model calculations. The systematic data on the single-particle centroids along the N=17 isotones show good agreement with shell-model predictions in describing the observed trends from stability toward O25. However, there is also evidence that the effect of the finite geometry of the nuclear potential is playing a role on the behavior of the p orbitals near the particle-emission threshold., This work wassupported by the U.K. Science and Technology Facilities Council [Grants No. ST/P004598/1, No. ST/N002563/1, No. ST/M00161X/1 (Liverpool), No. ST/P004423/1 (Manchester), No. ST/P005314/1 (Surrey), the ISOL-SRS Grant (Daresbury), No. ST/R004056/1 (Ernest Rutherford Fellowship - Gaffney), and No. ST/T004797/1 (Ernest Rutherford Fellowship - Sharp)], the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contracts No. DE-AC02-06CH11357 (ANL) and No. DE-SC-0014552 (UConn), the European Union’s Horizon 2020 Framework research and innovation program under Grant Agreement No. 654002 (ENSAR2), the Marie Skłodowska-Curie Grant Agreement No. 665779, the Research Foundation Flanders (FWO, Belgium), the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC Grant Agreement No. 617156, and the Spanish Ministry of Science and Innovation under Grants No. PGC2018-095640- B-I00“ELEGANT” and No. PID2019-104390GB-I00. This research used targets provided by the Center for Accelerator Target Science at Argonne National Laboratory. The FSU shell-model calculations were performed using the computational facility of the nuclear physics theory group, Florida State University, supported by grants from the U.S. Department of Energy, Office of Science (DE-SC-0009883 (FSU).

Spectroscopic factors to low-lying negative-parity states in $^{11}$Be extracted from the $^{12}$B($d$,$^3$He)$^{11}$Be proton-removal reaction are interpreted within the rotational model. Earlier predictions of the $p$-wave proton removal strengths in the strong coupling limit of the Nilsson model underestimated the spectroscopic factors to the $3/2^-_1$ and $5/2^-_1$ states and suggested that deviations in the $1^+$ ground state of the odd-odd $^{12}$B due to Coriolis coupling should be further explored. In this work we use the Particle Rotor Model to take into account these effects and obtain a good description of the level scheme in $^{11}$B, with a moderate $K$-mixing of the proton Nilsson levels [110]1/2 and [101]3/2. This mixing, present in the $1^+$ bandhead of $^{12}$B, is key to explaining the proton pickup data., 5 Pages, 2 Figures, to be submitted to Phys. Rev. C

The nuclei below lead but with more than 126 neutrons are crucial to an understanding of the astrophysical r process in producing nuclei heavier than A∼190. Despite their importance, the structure and properties of these nuclei remain experimentally untested as they are difficult to produce in nuclear reactions with stable beams. In a first exploration of the shell structure of this region, neutron excitations in ^{207}Hg have been probed using the neutron-adding (d,p) reaction in inverse kinematics. The radioactive beam of ^{206}Hg was delivered to the new ISOLDE Solenoidal Spectrometer at an energy above the Coulomb barrier. The spectroscopy of ^{207}Hg marks a first step in improving our understanding of the relevant structural properties of nuclei involved in a key part of the path of the r process. ispartof: Physical Review Letters vol:124 issue:6 ispartof: location:United States status: published

International audience; The 12C+12C fusion reaction is one of the most important for nuclear astrophysics since it determines the carbon ignition in stellar environments. Two experiments which make use of the gamma-particle coincidence technique to measure the 12C+12C S-factors at deep sub barrier energies are discussed. Results are presented showing a decrease of the S-factor below Ec.m. = 3 MeV.

International audience; Neutron-rich isotopes are an important source of new information on nuclear physics. Specifically, the spin-isospin components in the nucleon-nucleon (NN) interaction, e.g., the proton-neutron tensor force, are expected to modify shell structure in exotic nuclei. These potential changes in the intrinsic shell structure are of fundamental interest. The study of the excitation energy of states corresponding to specific configurations in even-even isotopes, together with the single-particle character of the first excited states of odd-A, neutron-rich Ni isotopes, probes the evolution of the neutron orbitals around the Fermi surface as a function of the neutron number a step forward in the understanding of the region and the nature of the NN interaction at large N/Z ratios. In an experiment carried out at the National Superconducting Cyclotron Laboratory [1], new spectroscopic information was obtained for 68Ni and the distribution of single-particle strengths in 67,69Ni was characterized by means of single-neutron knockout from 68,70Ni secondary beams. The spectroscopic strengths, deduced from the measured partial cross sections to the individual states tagged by their de-exciting gamma rays, is used to identify and quantify configurations that involve neutron excitations across the N = 40 harmonic oscillator shell closure. The de-excitation γ rays were measured with the GRETINA tracking array [2]. The results challenge the validity of the most current shell-model Hamiltonians and effective interactions, highlighting shortcomings that cannot yet be explained. These results suggest that our understanding of the low-energy states in such nuclei is not complete and requires further investigation.

Carbon burning plays a crucial role in stellar evolution, where this reaction is an important route for the production of heavier elements. A particle-γ coincidence technique that minimizes the backgrounds to which this reaction is subject and provides reliable cross sections has been used at the Argonne National Laboratory to measure fusion cross-sections at deep sub-barrier energies in the 12 C+12 C system. The corresponding excitation function has been extracted down to a cross section of about 6 nb. This indicates the existence of a broad S-factor maximum for this system. Experimental results are presented and discussed.

{\bf Background:} Level sequences of rotational character have been observed in several nuclei in the $A=60$ mass region. The importance of the deformation-driving $\pi f_{7/2}$ and $\nu g_{9/2}$ orbitals on the onset of nuclear deformation is stressed.\\ {\bf Purpose:} A measurement was performed in order to identify collective rotational structures in the relatively neutron-rich $^{62}$Ni isotope. \\ {\bf Method:} The $^{26}$Mg($^{48}$Ca,2$\alpha$4$n\gamma$)$^{62}$Ni complex reaction at beam energies between 275 and 320~MeV was utilized. Reaction products were identified in mass ($A$) and charge ($Z$) with the Fragment Mass Analyzer (FMA) and $\gamma$ rays were detected with the Gammasphere array. \\ {\bf Results:} Two collective bands, built upon states of single-particle character, were identified and sizable deformation was assigned to both sequences based on the measured transitional quadrupole moments, herewith quantifying the deformation at high spin. \\ {\bf Conclusions:} Based on Cranked Nilsson-Strutinsky calculations and comparisons with deformed bands in the $A=60$ mass region, the two rotational bands are understood as being associated with configurations involving multiple $f_{7/2}$ protons and $g_{9/2}$ neutrons, driving the nucleus to sizable prolate deformation.

International audience; Superheavy nuclei exist solely due to quantum shell effects,which create a pocket in the potential-energy surface of the nucleus, thusproviding a barrier against spontaneous fission. Determining the height ofthe fission barrier and its angular-momentum dependence is important toquantify the role that microscopic shell corrections play in enhancing andextending the limits of nuclear stability. In this talk, the first measurement ofa fission barrier in the very heavy nucleus 254No will be presented.

Background: Neutron-rich, even-mass chromium and iron isotopes approaching neutron number $N=40$ have been important benchmarks in the development of shell-model effective interactions incorporating the effects of shell evolution in the exotic regime. Odd-mass manganese nuclei have received less attention, but provide important and complementary sensitivity to these interactions.Purpose: We report the observation of two new $\ensuremath{\gamma}$-ray transitions in $^{63}\mathrm{Mn}$, which establish the $(9/{2}^{\ensuremath{-}})$ and $(11/{2}^{\ensuremath{-}})$ levels on top of the previously known $(7/{2}^{\ensuremath{-}})$ first-excited state. The lifetime for the $(7/{2}^{\ensuremath{-}})$ and $(9/{2}^{\ensuremath{-}})$ excited states were determined for the first time, while an upper limit could be established for the $(11/{2}^{\ensuremath{-}})$ level.Method: Excited states in $^{63}\mathrm{Mn}$ have been populated in inelastic scattering from a $^{9}\mathrm{Be}$ target and in the fragmentation of $^{65}\mathrm{Fe}$. $\ensuremath{\gamma}\ensuremath{\gamma}$ coincidence relationships were used to establish the decay level scheme. A Doppler line-shape analysis for the Doppler-broadened $(7/{2}^{\ensuremath{-}})\ensuremath{\rightarrow}5/{2}^{\ensuremath{-}}$, $(9/{2}^{\ensuremath{-}})\ensuremath{\rightarrow}(7/{2}^{\ensuremath{-}}),$ and $(11/{2}^{\ensuremath{-}})\ensuremath{\rightarrow}(9/{2}^{\ensuremath{-}})$ transitions was used to determine (limits for) the corresponding excited-state lifetimes.Results: The low-lying level scheme and the excited-state lifetimes were compared with large-scale shell-model calculations using different model spaces and effective interactions in order to isolate important aspects of shell evolution in this region of structural change.Conclusions: While the theoretical $(7/{2}^{\ensuremath{-}})$ and $(9/{2}^{\ensuremath{-}})$ excitation energies show little dependence on the model space, the calculated lifetime of the $(7/{2}^{\ensuremath{-}})$ level and calculated energy of the $(11/{2}^{\ensuremath{-}})$ level reveal the importance of including the neutron ${g}_{9/2}$ and ${d}_{5/2}$ orbitals in the model space. The LNPS effective shell-model interaction provides the best overall agreement with the new data.

International audience; Analyses of data from both deep inelastic reactions at Argonne National Laboratory and single-and multiple-particle knockout reactions at Michigan State University revealed new gamma-ray transitions in even-even Ni-66,68,70,72(38,40,42,44) and in Co-67(40) that provide strong evidence for multiple shape coexistence at N = 38 and 40 and deep prolate minima in Ni-70(42) and isotonic Cu-71(42). A new transition at 642 keV is proposed for Ni-66 as the prolate 2(+) to 0(+) transition. Two new transitions in Ni-72 at 915 and 1225 keV were identified in the knock-out reaction study and could represent de-population of prolate states. Taken together with recent theoretical work using the Monte Carlo shell model, a well defined region of shape coexistence can be seen existing precisely between 38

Physics letters / B 747, 88 - 92 (2015). doi:10.1016/j.physletb.2015.04.055, Published by North-Holland Publ., Amsterdam

Deep-inelastic collisions of a 208Pb beam on a 208Pb target were performed using the ATLAS accelerator at Argonne National Laboratory. The Gammasphere detector array was used for the detection of prompt and delayed gamma-rays of the reaction products.207Tl is one proton away from the 208Pb doubly-magic nucleus. Its low-energy level structure is dominated by the single proton-hole states πs1/2−1, πd3/2−1 and πh11/2−1. The 11/2− state is isomeric with T1/2 = 1.33(11) s. The reaction partner of 207Tl is 209Bi, which has arelatively well established level scheme compared to 207Tl. Cross-coincidences between these two nuclei were used to confirm or establish levels above the 11/2− isomeric state in 207Tl. These states are obtained via breaking of the neutron core. Angular correlation analysis was performed on known transitions in 208Pb, proving the applicability of this method for multipolarity assignment.

The gamma-ray multiplicity and total energy emitted by the heavy nucleus 254No have been measured at 2 different beam energies. From these measurements, the initial distributions of spin I and excitation energy E * of 254No were constructed. The distributions display a saturation in excitation energy, which allows a direct determination of the fission barrier. 254No is the heaviest shell-stabilized nucleus with a measured fission barrier. © Owned by the authors, published by EDP Sciences, 2014.

The low-spin level scheme of ${}^{68}$Ni was investigated following two-neutron-knockout and multinucleon-transfer reactions. The energy of the first excited state was determined to be ${E}_{x}({0}_{2}^{+})=1603.5(3)$ keV. Relative $B(E2)$ transition probabilities were deduced and compared with shell-model calculations using several modern effective interactions. Theory reproduces the data well, but indicates substantial mixing of multi-particle, multi-hole configurations for the lowest observed ${0}^{+}$ and ${2}^{+}$ states.

The single-neutron properties of N = 51 nuclei have been studied with the ( d , p )and( α , 3 He) reactions, at beam energies of 15 and 50 MeV respectively, on 88 Sr, 90 Zr, and 92 Mo targets. The light reaction products were momentum analyzed using a conventional magnetic spectrometer. Additionally, the 2 H( 86 Kr ,p ) reaction was measured at a beam energy of 10 MeV / u, where outgoing light ions were analyzed using a helical-orbit spectrometer. Absolute cross sections and angular distributions corresponding to the population of different final states in the heavy product were obtained for each reaction. Spectroscopic factors were extracted and centroids of the single-particle strength were deduced. The observations appear consistent with calculations based on an evolution of single-particle structure driven by the nucleon-nucleon forces acting between valence protons and neutrons. ispartof: Physical Review C, Nuclear Physics vol:87 issue:1 status: published

The structure of 15C, with an s1/2 neutron weakly bound to a closed-neutron shell nucleus 14C, makes it a prime candidate for a one-neutron halo nucleus. We have for the first time studied the cross section for the fusion-fission reaction 15C + 232Th at energies in the vicinity of the Coulomb barrier and compared it to the yield of the neighboring 14C + 232Th system measured in the same experiment. At sub-barrier energies, an enhancement of the fusion yield by factors of 2-5 was observed for 15C, while the cross sections for 14C match the trends measured for 12,13C., 4 pages, 2 figures, Phys. Rev. Lett. (accepted)