Science.gov

Sample records for neutron-rich argon beams

  1. Toward neutron-rich nuclei via transfer reactions with stable and radioactive beams

    NASA Astrophysics Data System (ADS)

    Mun, Myeong-Hwan; Adamian, G. G.; Antonenko, N. V.; Oh, Yongseok; Kim, Youngman

    2015-05-01

    The possibilities of production of yet-undiscovered neutron-rich isotopes of Ca, Gd, Dy, Er, Yb, Hf, W, Os, Hg, Pb, and Th are explored in various multinucleon transfer reactions with stable and radioactive beams. The probable projectile-target combinations and bombarding energies to produce these neutron-rich isotopes are suggested for future experiments.

  2. Results from the NSCL TOF Mass Measurement of Neutron-rich Isotopes of Argon through Iron

    NASA Astrophysics Data System (ADS)

    Meisel, Zachary; George, Sebastian; NSCL TOF Collaboration

    2015-04-01

    A recent experiment at the National Superconducting Cyclotron Laboratory has resulted in an extension of the nuclear mass surface for neutron-rich isotopes of argon through iron. The time-of-flight technique was employed to experimentally determine the masses of several nuclei for the first time. Results include the identification of argon as the lowest even- Z element exhibiting the N = 28 shell closure, as well the uncovering of a relatively small odd-even mass stagger between 56 Ti and 56 Sc. The latter result yields strong Urca cooling when implemented in a state-of-the-art accreted neutron star crust reaction network. A strong 56 Ti-56 Sc Urca neutrino cooling layer makes shallow neutrino cooling in the crust of accreting neutron stars a strong and robust effect due to the copious production of A = 56 material in thermonuclear burning processes that occur at the accreted neutron star surface. This project is funded by the NSF through Grants 247 No. PHY-0822648, PHY-1102511, PHY-1404442, and 248 No. PHY-1430152. S.G. acknowledges support from 249 the DFG under Contracts No. GE2183/1-1 and No. 250 GE2183/2-1.

  3. Production cross section of neutron-rich isotopes with radioactive and stable beams

    NASA Astrophysics Data System (ADS)

    Mun, Myeong-Hwan; Adamian, G. G.; Antonenko, N. V.; Oh, Yongseok; Kim, Youngman

    2014-03-01

    The production cross section of neutron-rich isotopes of Ca, Zn, Te, Xe, and Pt are predicted in the diffusive multinucleon transfer reactions with stable and radioactive beams. With these isotopes one can treat the neutron shell evolution beyond N =28, 50, 82, and 126. Because of the small cross sections, the production of nuclei near the neutron drip line requires the optimal choice of reaction partners and bombarding energies.

  4. Cluster-transfer reactions with radioactive beams: A spectroscopic tool for neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Bottoni, S.; Leoni, S.; Fornal, B.; Raabe, R.; Rusek, K.; Benzoni, G.; Bracco, A.; Crespi, F. C. L.; Morales, A. I.; Bednarczyk, P.; Cieplicka-Oryńczak, N.; Królas, W.; Maj, A.; Szpak, B.; Callens, M.; Bouma, J.; Elseviers, J.; De Witte, H.; Flavigny, F.; Orlandi, R.; Reiter, P.; Seidlitz, M.; Warr, N.; Siebeck, B.; Hellgartner, S.; Mücher, D.; Pakarinen, J.; Vermeulen, M.; Bauer, C.; Georgiev, G.; Janssens, R. V. F.; Balabanski, D.; Sferrazza, M.; Kowalska, M.; Rapisarda, E.; Voulot, D.; Lozano Benito, M.; Wenander, F.

    2015-08-01

    An exploratory experiment performed at REX-ISOLDE to investigate cluster-transfer reactions with radioactive beams in inverse kinematics is presented. The aim of the experiment was to test the potential of cluster-transfer reactions at the Coulomb barrier as a mechanism to explore the structure of exotic neutron-rich nuclei. The reactions 7Li(98Rb,α xn ) and 7Li(98Rb,t xn ) were studied through particle-γ coincidence measurements, and the results are presented in terms of the observed excitation energies and spins. Moreover, the reaction mechanism is qualitatively discussed as a transfer of a clusterlike particle within a distorted-wave Born approximation framework. The results indicate that cluster-transfer reactions can be described well as a direct process and that they can be an efficient method to investigate the structure of neutron-rich nuclei at medium-high excitation energies and spins.

  5. Production of neutron-rich Ca, Sn, and Xe isotopes in transfer-type reactions with radioactive beams

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Lacroix, D.

    2010-12-15

    The production cross sections of neutron-rich isotopes {sup 52,54,56,58,60}Ca, {sup 136,138,140,142}Sn, and {sup 146,148,150,152}Xe are predicted for future experiments in the diffusive multinucleon transfer reactions {sup 86,90,92,94}Kr, {sup 124,130,132,134}Sn, {sup 136,140,142,146}Xe, and {sup 138,144,146}Ba+{sup 48}Ca with stable and radioactive beams at incident energies close to the Coulomb barrier. Because of the small cross sections, the production of neutron-rich isotopes requires the optimal choice of projectile-target combinations and bombarding energies.

  6. Production of beams of neutron-rich nuclei between Ca and Ni using the ion-guide technique

    SciTech Connect

    Perajarvi, K.; Cerny, J.; Hager, U.; Hakala, J.; Huikari, J.; Jokinen, A.; Karvonen, P.; Kurpeta, J.; Lee, D.; Moore, I.; Penttila, H.; Popov, A.; Aysto, J.

    2004-09-28

    Since several elements between Z = 20-28 are refractory in their nature, their neutron-rich isotopes are rarely available as low energy Radioactive Ion Beams (RIB) in ordinary Isotope Separator On-Line facilities [1-4]. These low energy RIBs would be especially interesting to have available under conditions which allow high-resolution beta-decay spectroscopy, ion-trapping and laser-spectroscopy. As an example, availability of these beams would open a way for research which could produce interesting and important data on neutron-rich nuclei around the doubly magic {sup 78}Ni. One way to overcome the intrinsic difficulty of producing these beams is to rely on the chemically unselective Ion Guide Isotope Separator On-Line (IGISOL) technique [5]. Quasi- and deep-inelastic reactions, such as {sup 197}Au({sup 65}Cu,X)Y, could be used to produce these nuclei in existing IGISOL facilities, but before they can be successfully incorporated into the IGISOL concept their kinematics must be well understood. Therefore the reaction kinematics part of this study was first performed at the Lawrence Berkeley National Laboratory using its 88'' cyclotron and, based on those results, a specialized target chamber was built[6]. The target chamber shown in Fig. 1 was recently tested on-line at the Jyvaaskylaa IGISOL facility. Yields of mass-separated radioactive projectile-like species such as {sup 62,63}Co are about 0.8 ions/s/pnA, corresponding to about 0.06 % of the total IGISOL efficiency for the products that hit the Ni-degrader. (The current maximum 443 MeV {sup 65}Cu beam intensity at Jyvaaskylaa is about 20 pnA.) This total IGISOL efficiency is a product of two coupled loss factors, namely inadequate thermalization and the intrinsic IGISOL efficiency. In our now tested chamber, about 9 % of the Co recoils are thermalized in the owing He gas (p{sub He}=300 mbar) and about 0.7 % of them are converted into the mass-separated ion beams. In the future, both of these physical

  7. Near and sub-barrier fusion of neutron-rich oxygen and carbon nuclei using low-intensity beams

    NASA Astrophysics Data System (ADS)

    Steinbach, Tracy K.

    Fusion between neutron-rich light nuclei in the crust of an accreting neutron star has been proposed as a heat source that triggers an X-ray superburst. To explore the probability with which such fusion events occur and examine their decay characteristics, an experimental program using beams of neutron-rich light nuclei has been established. Evaporation residues resulting from the fusion of oxygen and 12C nuclei, are directly measured and distinguished from unreacted beam particles on the basis of their energy and time-of-flight. Using an experimental setup developed for measurements utilizing low-intensity (< 105 ions/s) radioactive beams, the fusion excitation functions for 16O + 12C and 18O + 12C have been measured. The fusion excitation function for 18O + 12C has been measured in the sub-barrier domain down to the 820 mub level, a factor of 30 lower than previous direct measurements. This measured fusion excitation function is compared to the predictions of a density constrained time-dependent Hartree-Fock model. This comparison reveals a shape difference in the fusion excitation functions, indicating a larger tunneling probability for the experimental data as compared to the theoretical calculations. In addition to the measured cross-section, the measured angular distribution of the evaporation residues provides insight into the relative importance of the different de-excitation channels. These evaporation residue angular distributions are compared to the predictions of a statistical model code, evapOR, revealing an under-prediction of the de-excitation channels associated with alpha particle emission.

  8. Extending studies of the fusion of heavy nuclei to the neutron rich region using accelerated radioactive ion beams.

    SciTech Connect

    Shapira, Dan

    2011-01-01

    One of the stated goals for proposed and existing facilities that produce and accelerate radioactive ion beams is to explore and achieve a new understanding of the reactions mechanisms leading to the synthesis of the heaviest nuclei. Nuclear synthesis of two large nuclei into a single entity is a complex multistep process. The beam intensities of radioactive ions accelerated at present day facilities are not sufficient to synthesize super heavy elements. However the study of the iso-spin dependence of nuclear synthesis and the many processes competing with it can be carried out at present day facilities. Of special interest are cases where the interacting nuclei and the synthesized product are extremely neutron-rich. The effects of neutron excess on the reaction processes leading to the formation of the synthesized nucleus that emerged in earlier studies are poorly understood and sometimes counter intuitive. Results from measurements performed at HRIBF, as well as our plans for future measurements and the equipment being prepared will be presented.

  9. Evaporation Residue Yields in Reactions of Heavy Neutron-Rich Radioactive Ion Beams with 64Ni and 96Zr Targets

    SciTech Connect

    Shapira, Dan; Liang, J Felix; Gross, Carl J; Varner Jr, Robert L; Beene, James R; Stracener, Daniel W; Mueller, Paul Edward; Kolata, Jim J; Roberts, Amy; Loveland, Walter; Vinodkumar, A. M.; Prisbrey, Landon; Sprunger, Peter H; Grzywacz-Jones, Kate L; Caraley, Anne L

    2009-01-01

    As hindrance sets in for the fusion of heavier systems, the effect of large neutron excess in the colliding nuclei on their probability to fuse is still an open question. The detection of evaporation residues (ERs), however, provides indisputable evidence for the fusion (complete and incomplete) in the reaction. We therefore devised a system with which we could measure ERs using low intensity neutron-rich radioactive ion beams with an efficiency close to 100%. We report on measurements of the production of ERs in collisions of {sup 132,134}Sn, {sup 134}Te and {sup 134}Sb ion beams with medium mass, neutron-rich targets. The data taken with {sup 132,134}Sn bombarding a {sup 64}Ni target are compared to available data (ERs and fusion) taken with stable Sn isotopes. Preliminary data on the fusion of {sup 132}Sn with {sup 96}Zr target are also presented.

  10. Evaporation residue yields in reactions of heavy neutron-rich radioactive ion beams with {sup 64}Ni and {sup 96}Zr targets

    SciTech Connect

    Shapira, D.; Liang, J. F.; Gross, C. J.; Varner, R. L.; Beene, J. R.; Stracener, D. W.; Mueller, P. E.; Kolata, J. J.; Roberts, A.; Loveland, W.; Vinodkumar, A. M.; Prisbrey, L.; Sprunger, P.; Jones, K. L.; Caraley, A. L.

    2009-03-04

    As hindrance sets in for the fusion of heavier systems, the effect of large neutron excess in the colliding nuclei on their probability to fuse is still an open question. The detection of evaporation residues (ERs), however, provides indisputable evidence for the fusion (complete and incomplete) in the reaction. We therefore devised a system with which we could measure ERs using low intensity neutron-rich radioactive ion beams with an efficiency close to 100%. We report on measurements of the production of ERs in collisions of {sup 132,134}Sn, {sup 134}Te and {sup 134}Sb ion beams with medium mass, neutron-rich targets. The data taken with {sup 132,134}Sn bombarding a {sup 64}Ni target are compared to available data (ERs and fusion) taken with stable Sn isotopes. Preliminary data on the fusion of {sup 132}Sn with {sup 96}Zr target are also presented.

  11. Characterization of uranium carbide target materials to produce neutron-rich radioactive beams

    NASA Astrophysics Data System (ADS)

    Tusseau-Nenez, Sandrine; Roussière, Brigitte; Barré-Boscher, Nicole; Gottberg, Alexander; Corradetti, Stefano; Andrighetto, Alberto; Cheikh Mhamed, Maher; Essabaa, Saïd; Franberg-Delahaye, Hanna; Grinyer, Joanna; Joanny, Loïc; Lau, Christophe; Le Lannic, Joseph; Raynaud, Marc; Saïd, Abdelhakim; Stora, Thierry; Tougait, Olivier

    2016-03-01

    In the framework of a R&D program aiming to develop uranium carbide (UCx) targets for radioactive nuclear beams, the Institut de Physique Nucléaire d'Orsay (IPNO) has developed an experimental setup to characterize the release of various fission fragments from UCx samples at high temperature. The results obtained in a previous study have demonstrated the feasibility of the method and started to correlate the structural properties of the samples and their behavior in terms of nuclear reaction product release. In the present study, seven UCx samples have been systematically characterized in order to better understand the correlation between their physicochemical characteristics and release properties. Two very different samples, the first one composed of dense UC and the second one of highly porous UCx made of multi-wall carbon nanotubes, were provided by the ActILab (ENSAR) collaboration. The others were synthesized at IPNO. The systems for irradiation and heating necessary for the release studies have been improved with respect to those used in previous studies. The results show that the open porosity is hardly the limiting factor for the fission product release. The homogeneity of the microstructure and the pore size distribution contributes significantly to the increase of the release. The use of carbon nanotubes in place of traditional micrometric graphite particles appears to be promising, even if the homogeneity of the microstructure can still be enhanced.

  12. In-Beam {gamma}-Ray Spectroscopy of the N=50 Isotones on the Neutron-Rich Side

    SciTech Connect

    Prevost, A.; Astier, A.; Deloncle, I.; Porquet, M.-G.; Lucas, R.

    2005-11-21

    High-spin states of 84Se, produced as a fission fragment in the fusion-fission reaction 18O+208Pb and studied with the EUROBALL IV array, have been identified for the first time. Their interpretation gives new insights about the evolution of the N=50 shell gap at the vicinity of 78Ni. To characterize this evolution, it would be worth using a new device devoted to the high-spin studies of neutron-rich nuclei produced by asymmetric fission modes. Such dedicated studies are reported in a second part.

  13. Production of Secondary Radioactive Beams of He and Li Neutron-Rich Isotopes in the Fragmentation Reaction {sup 15}N(47 MeV/A)+{sup 9}Be

    SciTech Connect

    Milewska, Aleksandra

    2007-11-26

    Yields of neutron-rich isotopes of He and Li produced in the reaction {sup 15}N(47 MeV/A)+{sup 9}Be have been measured. The experiment was carried out at the fragment separator COMBAS of the Flerov Laboratory of Nuclear Reactions, JINR (Dubna). Ion beams accelerated with the U-400M cyclotron and thick target were used. The products were identified according to their magnetic rigidities and time of flight (TOF) via the separator. The path length of TOF was 7,5 m. As a result of fragmentation, beams of four isotopes of Lithium and two isotopes of Helium were obtained. The inclusive velocities of reaction products were obtained and isotopes yields were calculated.

  14. Pair correlations in neutron-rich nuclei

    SciTech Connect

    Esbensen, H.

    1995-08-01

    We started a program to study the ground-state properties of heavy, neutron-rich nuclei using the Hartree-Fock-Bogolyubov (HFB) approximation. This appears at present to be the most realistic approach for heavy nuclei that contain many loosely bound valence neutrons. The two-neutron density obtained in this approach can be decomposed into two components, one associated with the mean field and one associated with the pairing field. The latter has a structure that is quite similar to the pair-density obtained by diagonalizing the Hamiltonian for a two-neutron halo, which was studied earlier. This allows comparison of the HFB solutions against numerically exact solutions for two-neutron halos. This work is in progress. We intend to apply the HFB method to predict the ground-state properties of heavier, more neutron-rich nuclei that may be produced at future radioactive beam facilities.

  15. Argon beam coagulation in foot and ankle surgery.

    PubMed

    Adams, Melissa L; Steinberg, John S

    2011-01-01

    In this brief report, we introduce the principles, indications, advantages, disadvantages, and surgical techniques involved in the use of argon beam coagulation in foot and ankle surgery. PMID:21907597

  16. Multi-Messenger Observations of Neutron Rich Matter

    SciTech Connect

    Horowitz, C. J.

    2012-01-01

    At very high densities, electrons react with protons to form neutron rich matter. This material is central to many fundamental questions in nuclear physics and astrophysics. Moreover, neutron rich matter is being studied with an extraordinary variety of new tools such as the Facility for Rare Isotope Beams (FRIB) and the Laser Interferometer Gravitational Wave Observatory (LIGO). We describe the Lead Radius Experiment (PREX) that uses parity violating electron scattering to measure the neutron radius in 208Pb. This has important implications for neutron stars and their crusts. We discuss X-ray observations of neutron star radii. These also have important implications for neutron rich matter. Gravitational waves (GW) open a new window on neutron rich matter. They come from sources such as neutron star mergers, rotating neutron star mountains, and collective r-mode oscillations. Using large scale molecular dynamics simulations, we find neutron star crust to be very strong. It can support mountains on rotating neutron stars large enough to generate detectable gravitational waves. We believe that combing astronomical observations using photons, GW, and neutrinos, with laboratory experiments on nuclei, heavy ion collisions, and radioactive beams will fundamentally advance our knowledge of compact objects in the heavens, the dense phases of QCD, the origin of the elements, and of neutron rich matter.

  17. Spectroscopy of Neutron-rich Pu Nuclei

    SciTech Connect

    Chowdhury, P.; Hota, S.; Lakshmi, S.; Tandel, S. K.; Harrington, T.; Jackson, E.; Moran, K.; Shirwadkar, U.; Ahmad, I.; Carpenter, M. P.; Greene, J.; Hoffman, C. R.; Janssens, R. V. F.; Khoo, T. L.; Kondev, F. G.; Lauritsen, T.; Lister, C. J.; McCutchan, E. A.; Seweryniak, D.; Stefanescu, I.

    2011-10-28

    Spectroscopic studies of nuclei in the A{approx}250, Z{approx}100 region provide critical input to theoretical models that attempt to describe the structure and stability of the heaviest elements. We report here on new spectroscopic studies in the N = 150,151 nuclei {sup 244,245}Pu. (Z = 94). Excitations in these nuclei on the neutron-rich side of the valley of stability, accessed via inelastic and transfer reactions, complement fusion-evaporation studies of Z{>=}100 nuclei. States in {sup 244,245}Pu were populated using {sup 47}Ti and {sup 208}Pb beams incident on a {sup 244}Pu target, with delayed and prompt gamma rays detected by the Gammasphere array. The new results are discussed in the context of emerging systematics of one- and two-quasiparticle excitations in N{>=}150 nuclei.

  18. Experimental and numerical study of high intensity argon cluster beams

    SciTech Connect

    Korobeishchikov, N. G.; Kalyada, V. V.; Shmakov, A. A.; Zarvin, A. E.; Skovorodko, P. A.

    2014-12-09

    Experimental and numerical investigations of expansion of argon with homogeneous condensation in supersonic conical nozzle and in free jet behind it were carried out. Optimal parameters (stagnation pressure, nozzle-skimmer distance) for the formation of cluster beam with maximum intensity were determined. Two available models for nonequilibrium nucleation were tested. The numerical results are in satisfactory agreement with the measured data.

  19. Studies of near-barrier fusion induced by neutron-rich nuclei at HRIBF

    SciTech Connect

    Liang, J Felix

    2011-01-01

    Fusion induced by neutron-rich radioactive beams is a topic of current interest. The findings will be useful for using radioactive beams to produce superheavy elements. Results from recent measurements performed with neutron-rich radioactive Sn and Te beams are presented. Coupled-channels calculations were carried out to study the observed sub-barrier fusion enhancement. The fusion probability in Sn on Ni were probed by comparing the evaporation residue cross sections at high excitation energies.

  20. Spectroscopy of Argon Excited in an Electron Beam Ion Trap

    SciTech Connect

    Trabert, E

    2005-04-18

    Argon is one of the gases best investigated and most widely used in plasma discharge devices for a multitude of applications that range from wavelength reference standards to controlled fusion experiments. Reviewing atomic physics and spectroscopic problems in various ionization stages of Ar, the past use and future options of employing an electron beam ion trap (EBIT) for better and more complete Ar data in the x-ray, EUV and visible spectral ranges are discussed.

  1. Thermodynamics of neutron-rich nuclear matter

    NASA Astrophysics Data System (ADS)

    López, Jorge A.; Porras, Sergio Terrazas; Gutiérrez, Araceli Rodríguez

    2016-07-01

    This manuscript presents methods to obtain properties of neutron-rich nuclear matter from classical molecular dynamics. Some of these are bulk properties of infinite nuclear matter, phase information, the Maxwell construction, spinodal lines and symmetry energy.

  2. Pulsed electron beam propagation in argon and nitrogen gas mixture

    SciTech Connect

    Kholodnaya, G. E.; Sazonov, R. V.; Ponomarev, D. V.; Remnev, G. E.; Zhirkov, I. S.

    2015-10-15

    The paper presents the results of current measurements for the electron beam, propagating inside a drift tube filled in with a gas mixture (Ar and N{sub 2}). The experiments were performed using the TEA-500 pulsed electron accelerator. The main characteristics of electron beam were as follows: 60 ns pulse duration, up to 200 J energy, and 5 cm diameter. The electron beam propagated inside the drift tube assembled of three sections. Gas pressures inside the drift tube were 760 ± 3, 300 ± 3, and 50 ± 1 Torr. The studies were performed in argon, nitrogen, and their mixtures of 33%, 50%, and 66% volume concentrations, respectively.

  3. Use of the argon aiming beam in visual function testing.

    PubMed

    Kelley, J S

    1978-12-01

    The aiming beam of the argon laser photocoagulator can be a useful tool in visual function testing. Applied with the slit lamp delivery system and fundus contact lens, it clearly documents the size of the blind spot surrounding the optic nerve head and the normal area of nonfunctional retina in the periphery. The size of pathologic field defects can be recorded on fundus photographs or retinal drawings by an observer. Safety precautions must be taken to protect all patients from excessive laser energy. PMID:736394

  4. Concerning Apparent Similarity of Structures of Fluoropolymer Surfaces Exposed to an Argon Plasma or Argon Ion Beam

    NASA Technical Reports Server (NTRS)

    Golub, Morton A.; Covington, M. Alan (Technical Monitor)

    1995-01-01

    X-ray photoelectron spectroscopy (XPS) C(sub 1s) spectra of fluoropolymers exposed to either an argon plasma or argon ion beam show remarkable similarity, implying that the surface-modification reactions for these two processes likely proceed through comparable mechanisms, revolving predominantly ion-surface interactions. The importance of working with a monochromatized x-ray source for XPS analysis of the surface-modified fluoropolymers is once again emphasized.

  5. Probing neutron rich matter with parity violation

    NASA Astrophysics Data System (ADS)

    Horowitz, Charles

    2016-03-01

    Many compact and energetic astrophysical systems are made of neutron rich matter. In contrast, most terrestrial nuclei involve approximately symmetric nuclear matter with more equal numbers of neutrons and protons. However, heavy nuclei have a surface region that contains many extra neutrons. Precision measurements of this neutron rich skin can determine properties of neutron rich matter. Parity violating electron scattering provides a uniquely clean probe of neutrons, because the weak charge of a neutron is much larger than that of a proton. We describe first results and future plans for the Jefferson Laboratory experiment PREX that measures the thickness of the neutron skin in 208Pb. Another JLAB experiment CREX will measure the neutron radius of 48Ca and test recent microscopic calculations of this neutron rich 48 nucleon system. Finally, we show how measuring parity violation at multiple momentum transfers can determine not just the neutron radius but the full radial structure of the neutron density in 48Ca. A neutron star is eighteen orders of magnitude larger than a nucleus (km vs fm) but both the star and the neutron rich nuclear skin are made of the same neutrons, with the same strong interactions, and the same equation of state. A large pressure pushes neutrons out against surface tension and gives a thick neutron skin. Therefore, PREX will constrain the equation of state of neutron rich matter and improve predictions for the structure of neutron stars. Supported in part by DOE Grants DE-FG02-87ER40365 (Indiana University) and DE-SC0008808 (NUCLEI SciDAC Collaboration).

  6. Fusion probability for neutron-rich radioactive Sn induced reactions

    SciTech Connect

    Liang, J Felix; Gross, Carl J; Kohley, Zachary W; Shapira, Dan; Varner Jr, Robert L; Allmond, James M; Caraley, Anne L; Lagergren, Karin B; Mueller, Paul Edward

    2012-01-01

    Evaporation residue cross sections for $^{124,126,127,128}$Sn+$^{64}$Ni and $^{132}$Sn+$^{58}$Ni have been measured to study the effects of neutron excess in neutron-rich radioactive nuclei on fusion. For the reactions with $^{64}$Ni, the fusion probability does not decrease with increasing neutron excess in Sn, contrary to the result of the stable beam Sn+Zr measurement. A comparison of the reduced evaporation residue cross sections for $^{126}$Sn+$^{64}$Ni and $^{132}$Sn+$^{58}$Ni, which make the same compound nucleus, shows that the fusion probability is indistinguishable for reactions involving the same atomic elements but different isotope combinations.

  7. β- decay of the neutron-rich isotope 215Pb

    NASA Astrophysics Data System (ADS)

    De Witte, H.; Eeckhaudt, S.; Andreyev, A. N.; Borzov, I. N.; Cederkäll, J.; De Smet, A.; Fedorov, D. V.; Fedoseyev, V. N.; Franchoo, S.; Górska, M.; Grawe, H.; Huber, G.; Huyse, M.; Janas, Z.; Köster, U.; Kurcewicz, W.; Kurpeta, J.; Płochocki, A.; Van de Vel, K.; Van Duppen, P.; Weissman, L.

    2013-06-01

    This Brief Report reports on the first observation of the β--delayed γ decay of 215Pb, feeding states in 215Bi. The 215Pb beam was produced using resonant laser ionization and mass separated at the ISOLDE-CERN on-line mass separator. This ensured clean identification of the γ rays as belonging to the decay of 215Pb or its β-decay daughters. A half-life of 147(12) s was measured for the 215Pb β decay and a level scheme for the daughter nucleus 215Bi is proposed, resulting in an extended systematics of the excited states of the neutron-rich Bi isotopes.

  8. Effective Interactions in Neutron-Rich Matter

    SciTech Connect

    Sammarruca, F.; Krastev, P.; Barredo, W.

    2005-10-14

    We are generally concerned with probing the behavior of the isospin-asymmetric equation of state. In particular, we will discuss the one-body potentials for protons and neutrons obtained from our Dirac-Brueckner-Hartree-Fock calculations of neutron-rich matter properties. We will also present predictions of proton-proton and neutron-neutron cross sections in the isospin-asymmetric nuclear medium.

  9. Fission and Properties of Neutron-Rich Nuclei

    NASA Astrophysics Data System (ADS)

    Hamilton, Joseph H.; Ramayya, A. V.; Carter, H. K.

    2008-08-01

    Opening session. Nuclear processes in stellar explosions / M. Wiescher. In-beam [symbol]-ray spectroscopy of neutron-rich nuclei at NSCL / A. Gade -- Nuclear structure I. Shell-model structure of neutron-rich nuclei beyond [symbol]Sn / A. Covello ... [et al.]. Shell structure and evolution of collectivity in nuclei above the [symbol]Sn core / S. Sarkar and M. S. Sarkar. Heavy-ion fusion using density-constrained TDHF / A. S. Umar and V. E. Oberacker. Towards an extended microscopic theory for upper-fp shell nuclei / K. P. Drumev. Properties of the Zr and Pb isotopes near the drip-line / V. N. Tarasov ... [et al.]. Identification of high spin states in [symbol] Cs nuclei and shell model calculations / K. Li ... [et al.]. Recent measurements of spherical and deformed isomers using the Lohengrin fission-fragment spectrometer / G. S. Simpson ... [et al.] -- Nuclear structure II. Nuclear structure investigation with rare isotope spectroscopic investigations at GSI / P. Boutachkov. Exploring the evolution of the shell structures by means of deep inelastic reactions / G. de Anaelis. Probing shell closures in neutron-rich nuclei / R. Krücken for the S277 and REX-ISOLDEMINIBALL collaborations. Structure of Fe isotopes at the limits of the pf-shell / N. Hoteling ... [et al.]. Spectroscopy of K isomers in shell-stabilized trans-fermium nuclei / S. K. Tandel ... [et al.] -- Radioactive ion beam facilities. SPIRAL2 at GANIL: a world leading ISOL facility for the next decade / S. Gales. New physics at the International Facility for Antiproton and Ion Research (FAIR) next to GSI / I. Augustin ... [et al.]. Radioactive beams from a high powered ISOL system / A. C. Shotter. RlKEN RT beam factory / T. Motobayashi. NSCL - ongoing activities and future perspectives / C. K. Gelbke. Rare isotope beams at Argonne / W. F. Henning. HRIBF: scientific highlights and future prospects / J. R. Beene. Radioactive ion beam research done in Dubna / G. M. Ter-Akopian ... [et al.] -- Fission I

  10. Lead Pipe Scale Analysis Using Broad-Beam Argon Ion Milling to Elucidate Drinking Water Corrosion

    EPA Science Inventory

    Herein, we compared the characterization of lead pipe scale removed from a drinking water distribution system using two different cross section methods (conventional polishing and argon ion beam etching). The pipe scale solids were analyzed using scanning electron microscopy (SEM...

  11. Trap-assisted studies of odd, neutron-rich isotopes from Tc to Pd

    NASA Astrophysics Data System (ADS)

    Kurpeta, J.; Jokinen, A.; Penttilä, H.; Płochocki, A.; Rissanen, J.; Urban, W.; Äystö, J.

    2014-01-01

    We review the present and future of trap-assisted structure studies of odd, neutron-rich Tc, Ru, Rh and Pd isotopes at the limits of present experimental techniques. These nuclei of refractory elements are produced in light-particle induced fission and filtered by their mass number with the IGISOL mass separator. Further mass separation with the JYFLTRAP Penning trap system provides a clean, monoisotopic beam perfectly suited for precise nuclear spectroscopy. Connecting the IGISOL and the JYFLTRAP facilities to the recently installed MCC30/15 cyclotron opens new prospects for post-trap spectroscopy of very exotic, neutron-rich nuclei.

  12. Isospin effects on fragmentation in the asymmetric reactions induced by neutron-rich targets

    NASA Astrophysics Data System (ADS)

    Sharma, Arun

    2016-05-01

    To understand the isospin effects in terms of fragment's yield in the asymmetric reactions induced by neutron-rich targets, we perform a theoretical study using isospin-dependent quantum molecular dynamics (IQMD) model. Simulations are carried out for reactions of 16O+Br80,84,92 and 16O+Ag108,113,122. We envision that fragments's yield in the asymmetric collisions induced by neutron-rich targets is better candidate to study isospin effects via symmetry energy and nucleon-nucleon (nn) cross-sections. Also, pronounced effects of symmetry energy and cross-sections can be found at lower and higher beam energies, respectively.

  13. Structure of neutron-rich nuclei

    SciTech Connect

    Nazarewicz, W. ||

    1997-11-01

    One of the frontiers of today`s nuclear science is the ``journey to the limits``: of atomic charge and nuclear mass, of neutron-to-proton ratio, and of angular momentum. The new data on exotic nuclei are expected to bring qualitatively new information about the fundamental properties of the nucleonic many-body system, the nature of the nuclear interaction, and nucleonic correlations at various energy-distance scales. In this talk, current developments in nuclear structure of neutron-rich nuclei are discussed from a theoretical perspective.

  14. ARCS 3 ionospheric artificial argon ion beam injections - Waves near the heavy ion gyrofrequencies

    NASA Technical Reports Server (NTRS)

    Erlandson, R. E.; Cahill, L. J., Jr.; Kaufmann, R. L.; Arnoldy, R. L.; Pollock, C. J.

    1989-01-01

    Low-frequency electric field data below the proton gyrofrequency are presented for the duration of the argon ion beam experiment conducted as part of the Argon Release for Controlled Studies (ARCS) program. An argon ion beam was injected from the subpayload antiparallel or perpendicular to the magnetic field at altitudes from 250 to 405 km. During the injections, the wave spectra were broadband near the subpayload and narrow-band near heavy ion gyrofrequencies at perpendicular separation distances between 42 and 254 m. It is suggested that the narrow-band waves are associated with both the perpendicular argon ion beam and an unexpected flux of low-energy ions which peaked in energy near 15 eV and pitch angle near 90 deg with respect to the magnetic field.

  15. - and -delayed neutron- decay of neutron-rich copper isotopes

    SciTech Connect

    Korgul, A.; Rykaczewski, Krzysztof Piotr; Winger, J. A.; Ilyushkin, S.; Gross, Carl J; Batchelder, J. C.; Bingham, C. R.; Borzov, Ivan N; Goodin, C.; Grzywacz, Robert Kazimierz; Hamilton, Joseph H; Krolas, W.; Liddick, S. N.; Mazzocchi, C.; Nelson, C.; Nowacki, F.; Padgett, Stephen; Piechaczek, A.; Rajabali, M. M.; Shapira, Dan; Sieja, K.; Zganjar, E. F.

    2012-01-01

    The {beta}-decay properties of neutron-rich Cu isotopes produced in proton-induced fission of {sup 238}U were studied at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The data were collected using high-resolution online mass separation, reacceleration, and digital {beta}-{gamma} spectroscopy methods. An improved decay scheme of N = 49 {sup 78}Cu and the first observation of N = 50 {sup 79}Cu {beta}-delayed neutron decay followed by a gamma transition are reported. Spin and parity (5{sup -}) are deduced for {sup 78gs}Cu. The {beta}-delayed neutron branching ratios (P{sub {beta}n}) for the {sup 77}Cu and {sup 79}Cu precursors are analyzed with the help of nuclear structure models.

  16. Neutron transfer measurements on neutron-rich N=82 nuclei

    SciTech Connect

    Pain, Steven D; Jones, K. L.; Bardayan, Daniel W; Blackmon, Jeff C; Chae, K. Y.; Chipps, K.; Cizewski, J. A.; Hatarik, Robert; Kapler, R.; Kozub, R. L.; Liang, J Felix; Moazen, Brian; Nesaraja, Caroline D; Shapira, Dan; ShrinerJr., J. F.; Smith, Michael Scott

    2009-01-01

    Calculations of r-process nucleosynthesis rely significantly on nuclear structure models as input, which are not well tested in the neutron-rich regime, due to the paucity of experimental data on the majority of these nuclei. High quality radioactive beams have recently made possible the measurement of (d,p) reactions on unstable nuclei in inverse kinematics, which can yield information on the development of single-neutron structure away from stability in close proximity to suggested r-process paths. The Oak Ridge Rutgers University Barrel Array (ORRUBA) has been developed for the measurement of such reactions. An early partial implementation of ORRUBA has been utilized to measure the {sup 132}Sn(d,p){sup 133}Sn and {sup 134}Te(d,p){sup 135}Te reactions for the first time.

  17. Clusters in neutron-rich light nuclei

    NASA Astrophysics Data System (ADS)

    Jelavić Malenica, D.; Milin, M.; Di Pietro, A.; Figuera, P.; Lattuada, M.; Miljanić, D.; Musumarra, A.; Pellegriti, M. G.; Prepolec, L.; Scuderi, V.; Skukan, N.; Soić, N.; Torresi, D.; Uroić, M.

    2016-05-01

    Due to their high selectivity, transfer and sequential decay reactions are powerful tools for studies of both single particle (nucleon) and cluster states in light nuclei. Their use is particularly simple for investigations of α-particle clustering (because α-particle has Jπ=0+, which simplifies spin and parity assignments to observed cluster states), but they are also easily applicable to other types of clustering. Recent results on clustering in neutron-rich isotopes of beryllium, boron and carbon obtained measuring the 10B+10B reactions (at 50 and 72 MeV) are presented. The highly efficient and segmented detector systems used, built from 4 Double Sided Silicon Strip Detectors (DSSSD) allowed detection of double and multiple coincidences and, in that way, studies of states populated in transfer reactions, as well as their sequential decay.

  18. Dual beam organic depth profiling using large argon cluster ion beams

    PubMed Central

    Holzweber, M; Shard, AG; Jungnickel, H; Luch, A; Unger, WES

    2014-01-01

    Argon cluster sputtering of an organic multilayer reference material consisting of two organic components, 4,4′-bis[N-(1-naphthyl-1-)-N-phenyl- amino]-biphenyl (NPB) and aluminium tris-(8-hydroxyquinolate) (Alq3), materials commonly used in organic light-emitting diodes industry, was carried out using time-of-flight SIMS in dual beam mode. The sample used in this study consists of a ∽400-nm-thick NPB matrix with 3-nm marker layers of Alq3 at depth of ∽50, 100, 200 and 300 nm. Argon cluster sputtering provides a constant sputter yield throughout the depth profiles, and the sputter yield volumes and depth resolution are presented for Ar-cluster sizes of 630, 820, 1000, 1250 and 1660 atoms at a kinetic energy of 2.5 keV. The effect of cluster size in this material and over this range is shown to be negligible. © 2014 The Authors. Surface and Interface Analysis published by John Wiley & Sons Ltd. PMID:25892830

  19. Preparation of a primary argon beam for the CERN fixed target physics

    SciTech Connect

    Küchler, D. O’Neil, M.; Scrivens, R.; Thomae, R.

    2014-02-15

    The fixed target experiment NA61 in the North Area of the Super Proton Synchrotron is studying phase transitions in strongly interacting matter. Up to now they used the primary beams available from the CERN accelerator complex (protons and lead ions) or fragmented beams created from the primary lead ion beam. To explore a wider range of energies and densities a request was made to provide primary argon and xenon beams. This paper describes the results of the setting up and 10 week test run of the Ar{sup 11+} beam from the 14.5 GHz ECR ion source and the linear accelerator (Linac3) at CERN.

  20. Relativistic mean field calculations in neutron-rich nuclei

    SciTech Connect

    Gangopadhyay, G.; Bhattacharya, Madhubrata; Roy, Subinit

    2014-08-14

    Relativistic mean field calculations have been employed to study neutron rich nuclei. The Lagrange's equations have been solved in the co-ordinate space. The effect of the continuum has been effectively taken into account through the method of resonant continuum. It is found that BCS approximation performs as well as a more involved Relativistic Continuum Hartree Bogoliubov approach. Calculations reveal the possibility of modification of magic numbers in neutron rich nuclei. Calculation for low energy proton scattering cross sections shows that the present approach reproduces the density in very light neutron rich nuclei.

  1. Structure of Light Neutron-rich Nuclei Studied with Transfer Reactions

    SciTech Connect

    Wuosmaa, A. H.

    2015-01-01

    Transfer reactions have been used for many years to understand the shell structure of nuclei. Recent studies with rare-isotope beams extend this work and make it possible to probe the evolution of shell structure far beyond the valley of stability, requiring measurements in inverse kinematics. We present a novel technical approach to measurements in inverse kinematics, and apply this method to different transfer reactions, each of which probes different properties of light, neutron-rich nuclei.

  2. γ-ray spectroscopy of neutron-rich S40

    NASA Astrophysics Data System (ADS)

    Wang, Z. M.; Chapman, R.; Liang, X.; Haas, F.; Azaiez, F.; Behera, B. R.; Burns, M.; Caurier, E.; Corradi, L.; Curien, D.; Deacon, A. N.; Dombrádi, Zs.; Farnea, E.; Fioretto, E.; Gadea, A.; Hodsdon, A.; Ibrahim, F.; Jungclaus, A.; Keyes, K.; Kumar, V.; Latina, A.; Lunardi, S.; Mărginean, N.; Montagnoli, G.; Napoli, D. R.; Nowacki, F.; Ollier, J.; O'Donnell, D.; Papenberg, A.; Pollarolo, G.; Salsac, M.-D.; Scarlassara, F.; Smith, J. F.; Spohr, K. M.; Stanoiu, M.; Stefanini, A. M.; Szilner, S.; Trotta, M.; Verney, D.

    2010-05-01

    Yrast states up to (6+) in the neutron-rich S40 nucleus have been studied using binary grazing reactions produced by the interaction of a 215 MeV beam of S36 ions with a thin Pb208 target. The novel experimental setup that combines the large acceptance magnetic spectrometer, PRISMA, and the high-efficiency γ-ray detection array, CLARA, was used. A new γ-ray transition at an energy of 1572 keV was observed and tentatively assigned to the (6+)→(4+) transition. A comparison of experimental observations and the results of large-scale 0ℏω sd-pf shell-model calculations indicates that one- and two-proton excitations from the 2s1/2 to the 1d3/2 orbitals play an important role in reproducing the S40 yrast level structure and the published B(E2;0g.s.+→21+) value. The structure of the yrast states of the even-A isotopes of sulfur is interpreted in terms of the configurations of valence protons and neutrons within the context of large-scale 0ℏω sd-pf shell-model calculations.

  3. Observation of large enhancements of charge exchange cross sections with neutron-rich carbon isotopes

    NASA Astrophysics Data System (ADS)

    Tanihata, I.; Terashima, S.; Kanungo, R.; Ameil, F.; Atkinson, J.; Ayyad, Y.; Cortina-Gil, D.; Dillmann, I.; Estradé, A.; Evdokimov, A.; Farinon, F.; Geissel, H.; Guastalla, G.; Janik, R.; Knoebel, R.; Kurcewicz, J.; Litvinov, Yu. A.; Marta, M.; Mostazo, M.; Mukha, I.; Nociforo, C.; Ong, H. J.; Pietri, S.; Prochazka, A.; Scheidenberger, C.; Sitar, B.; Strmen, P.; Takechi, M.; Tanaka, J.; Toki, H.; Vargas, J.; Winfield, J. S.; Weick, H.

    2016-04-01

    Production cross sections of nitrogen isotopes from high-energy (˜ 950 MeV per nucleon) carbon isotopes on hydrogen and carbon targets have been measured for the first time for a wide range of isotopes (A = 12 to 19). The fragment separator FRS at GSI was used to deliver C-isotope beams. The cross sections of the production of N-isotopes were determined by charge measurements of forward-going fragments. The cross sections show a rapid increase with the number of neutrons in the projectile. Since the production of nitrogen is mostly due to charge-exchange (Cex) reactions below the proton separation energies, the present data suggests a concentration of Gamow-Teller and/or Fermi transition strength at low excitation energies for neutron-rich carbon isotopes. It was also observed that the Cex cross sections were enhanced much more strongly for neutron-rich isotopes in the C-target data.

  4. Informing Neutron-Capture Rates through (d,p) Reactions on Neutron-Rich Tin Isotopes

    NASA Astrophysics Data System (ADS)

    Manning, B.; Cizewski, J. A.; Kozub, R. L.; Ahn, S.; Allmond, J. M.; Bardayan, D. W.; Chae, K. Y.; Chipps, K. A.; Howard, M. E.; Jones, K. L.; Liang, J. F.; Matos, M.; Nunes, F. M.; Nesaraja, C. D.; O'Malley, P. D.; Pain, S. D.; Peters, W. A.; Pittman, S. T.; Ratkiewicz, A.; Schmitt, K. T.; Shapira, D.; Smith, M. S.; Titus, L.

    2014-03-01

    Level energies and spectroscopic information for neutron-rich nuclei provide important input for r-process nucleosynthesis calculations; specifically, the location and strength of single-neutron l = 1 states when calculating neutron-capture rates. Surman and collaborators have performed sensitivity studies to show that varying neutron-capture rates can significantly alter final r-process abundances. However, there are many nuclei important to the r-process that cannot be studied. Extending studies to more neutron-rich nuclei will help constrain the nuclear shell-model in extrapolating to nuclei even further from stability. The (d,p) reaction has been measured with radioactive ion beams of 126Sn and 128Sn to complete the set of (d,p) studies on even mass tin isotopes from doubly-magic 132 to stable 124Sn. Work supported in part by the U.S. Department of Energy and National Science Foundation.

  5. Nuclear structure in the neutron-rich doubly magic sup 78 Ni region

    SciTech Connect

    Hill, J.C.; Wohn, F.K.; Winger, J.A.; Warburton, E.K.; Gill, R.L.; Schuhmann, R.B.; Brookhaven National Lab., Upton, NY; Clark Univ., Worcester, MA )

    1989-01-01

    The magic numbers Z=28 and N=50 imply that very neutron-rich {sup 78}Ni, which has not yet been observed, is doubly magic. The {sup 78}Ni region was investigated by studying the N=50 isotones and neutron-rich Zn isotopes. Results on the level structure of {sup 83}As, {sup 74}Zn, and {sup 76}Zn populated in the decays of {sup 83}Ge, {sup 74}Cu, and {sup 76}Cu are presented. The parent nuclides were produced and mass separated using the TRISTAN facility on-line to the High-Flux Beam Reactor at Brookhaven. The systematics of the N=50 isotones and even-A Zn isotopes are discussed and compared with shell-model calculations involving active nucleons outside of a {sup 78}Ni and {sup 66}Ni core, respectively. The extent to which the {sup 78}Ni region can be considered doubly magic is assessed. 43 refs., 7 figs.

  6. New μs isomers in the neutron-rich 210Hg nucleus

    NASA Astrophysics Data System (ADS)

    Gottardo, A.; Valiente-Dobón, J. J.; Benzoni, G.; Gadea, A.; Lunardi, S.; Boutachkov, P.; Bruce, A. M.; Górska, M.; Grebosz, J.; Pietri, S.; Podolyák, Zs.; Pfützner, M.; Regan, P. H.; Weick, H.; Alcántara Núñez, J.; Algora, A.; Al-Dahan, N.; de Angelis, G.; Ayyad, Y.; Alkhomashi, N.; Allegro, P. R. P.; Bazzacco, D.; Benlliure, J.; Bowry, M.; Bracco, A.; Bunce, M.; Camera, F.; Casarejos, E.; Cortes, M. L.; Crespi, F. C. L.; Corsi, A.; Denis Bacelar, A. M.; Deo, A. Y.; Domingo-Pardo, C.; Doncel, M.; Dombradi, Zs.; Engert, T.; Eppinger, K.; Farrelly, G. F.; Farinon, F.; Farnea, E.; Geissel, H.; Gerl, J.; Goel, N.; Gregor, E.; Habermann, T.; Hoischen, R.; Janik, R.; John, P. R.; Klupp, S.; Kojouharov, I.; Kurz, N.; Lenzi, S. M.; Leoni, S.; Mandal, S.; Menegazzo, R.; Mengoni, D.; Million, B.; Modamio, V.; Morales, A. I.; Napoli, D. R.; Naqvi, F.; Nicolini, R.; Nociforo, C.; Prochazka, A.; Prokopowicz, W.; Recchia, F.; Ribas, R. V.; Reed, M. W.; Rudolph, D.; Sahin, E.; Schaffner, H.; Sharma, A.; Sitar, B.; Siwal, D.; Steiger, K.; Strmen, P.; Swan, T. P. D.; Szarka, I.; Ur, C. A.; Walker, P. M.; Wieland, O.; Wollersheim, H.-J.

    2013-10-01

    Neutron-rich nuclei in the lead region, beyond N = 126, have been studied at the FRS-RISING setup at GSI, exploiting the fragmentation of a primary uranium beam. Two isomeric states have been identified in 210Hg: the 8+ isomer expected from the seniority scheme in the νg9/2 shell and a second one at low spin and low excitation energy. The decay strength of the 8+ isomer confirms the need of effective three-body forces in the case of neutron-rich lead isotopes. The other unexpected low-lying isomer has been tentatively assigned as a 3- state, although this is in contrast with theoretical expectations.

  7. Proceedings of the Fourth International Conference Fission and Properties of Neutron-Rich Nuclei

    SciTech Connect

    Beene, James R; Hamilton, J. H.; Ramayya, A. V.; Carter, H. K.

    2007-11-01

    These proceedings are the fourth in the series of International Conferences covering fission and properties of neutron-rich nuclei, which are at the forefront of nuclear structure research. The time interval of 5 years between each conference allows for significant new results to be achieved. Recently, world leaders in theory and experiments in research and the development of new facilities for research presented their latest results in areas such as synthesis of superheavy elements, new facilities for and recent results with radioactive ion beams, structure of neutron-rich nuclei, nuclear fission process, fission yields and nuclear astrophysics. This book is a major source of the latest research in these areas and plans for the future. The conference brought together a unique group of over 100 speakers including the directors of the major nuclear laboratories in Canada, France, Germany, Japan, Russia and the U.S. along with leading research scientists from around the world.

  8. K-isomers in Hf nuclei at and beyond the neutron-rich edge of {beta}-stability.

    SciTech Connect

    Chowdhury, P.; Alarcao, R. D.; Seabury, E. H.; Walker, P. M.; Wheldon, C.; Ahmad. I.; Carpenter, M. P.; Hackman, G.; Janssens, R. V. F.; Khoo, T. L.; Nisius, D.; Reiter, P.

    1999-03-30

    New high-K isomers are populated in {sup 180,181,182}Hf nuclei via inelastic excitation and transfer reactions, using pulsed {sup 238}U beams on Hf targets. The new data explore K-hindrances for different multipolarities and the role of residual spin-spin interactions for multi-quasiparticle (qp) configurations at the neutron-rich edge of the {beta}-stability line. The mapping of 4-qp K-isomers in the A {approx} 180 region is extended into neutron-rich territory.

  9. Modern Rutherford experiment: tunneling of the most neutron-rich nucleus.

    PubMed

    Lemasson, A; Shrivastava, A; Navin, A; Rejmund, M; Keeley, N; Zelevinsky, V; Bhattacharyya, S; Chatterjee, A; de France, G; Jacquot, B; Nanal, V; Pillay, R G; Raabe, R; Schmitt, C

    2009-12-01

    A modern variation of the Rutherford experiment to probe the tunneling of exotic nuclear matter from the measurement of the residues formed in the bombardment of (197)Au by extremely neutron-rich (8)He nuclei is presented. Using a novel off-beam technique the most precise and accurate measurements of fusion and neutron transfer involving reaccelerated unstable beams are reported. The results show unusual behavior of the tunneling of (8)He compared to that for lighter helium isotopes, highlighting the role of the intrinsic structure of composite many-body quantum systems and pairing correlations. PMID:20366144

  10. Modern Rutherford Experiment: Tunneling of the Most Neutron-Rich Nucleus

    SciTech Connect

    Lemasson, A.; Navin, A.; Rejmund, M.; France, G. de; Jacquot, B.; Raabe, R.; Schmitt, C.; Keeley, N.; Zelevinsky, V.; Bhattacharyya, S.; Nanal, V.; Pillay, R. G.

    2009-12-04

    A modern variation of the Rutherford experiment to probe the tunneling of exotic nuclear matter from the measurement of the residues formed in the bombardment of {sup 197}Au by extremely neutron-rich {sup 8}He nuclei is presented. Using a novel off-beam technique the most precise and accurate measurements of fusion and neutron transfer involving reaccelerated unstable beams are reported. The results show unusual behavior of the tunneling of {sup 8}He compared to that for lighter helium isotopes, highlighting the role of the intrinsic structure of composite many-body quantum systems and pairing correlations.

  11. Structural changes at large angular momentum in neutron-rich Cd,123121

    NASA Astrophysics Data System (ADS)

    Rejmund, M.; Navin, A.; Bhattacharyya, S.; Caamaño, M.; Clément, E.; Delaune, O.; Farget, F.; de France, G.; Jacquot, B.; Lemasson, A.

    2016-02-01

    Prompt γ rays of isotopically identified neutron-rich isotopes of Cd, produced in transfer- and fusion-fission induced by the 238U beam at 6.2 MeV/u on a 9Be target, were measured using the EXOGAM γ -ray detector array and the magnetic spectrometer VAMOS++. New results for the level scheme of Cd,123121, extending to relatively large angular momentum are reported. The energy levels above 2-MeV excitation energy, are found to differ from those observed in lighter isotopes of Cd indicating a change in structure in these more neutron-rich nuclei. These states are not explained by large-scale shell model calculations, that explain well the structure of the underlying Sn isotopes and the neighboring even-A Cd isotopes. The present data, especially for the odd-A nuclei, point to a deficiency in the matrix elements related to the p-n residual interaction and provide a new domain for testing widely used shell model interactions employed for understanding the evolution of structure in neutron-rich nuclei.

  12. Modes of decay in neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Kumar, B.; Biswal, S. K.; Singh, S. K.; Lahiri, C.; Patra, S. K.

    2016-03-01

    We calculate the ground, first intrinsic excited states and density distribution for neutron-rich thorium and uranium isotopes, within the framework of relativistic mean field (RMF) approach using axially deformed basis. The total nucleon densities are calculated, from which the cluster-structures inside the parent nuclei are determined. The possible modes of decay, like α-decay and β-decay are analyzed. We find the neutron-rich isotopes are stable against α-decay, however they are very much unstable against β-decay. The life time of these nuclei predicted to be tens of second against β-decay.

  13. Octupole strength in the neutron-rich calcium isotopes

    NASA Astrophysics Data System (ADS)

    Riley, L. A.; McPherson, D. M.; Agiorgousis, M. L.; Baugher, T. R.; Bazin, D.; Bowry, M.; Cottle, P. D.; DeVone, F. G.; Gade, A.; Glowacki, M. T.; Gregory, S. D.; Haldeman, E. B.; Kemper, K. W.; Lunderberg, E.; Noji, S.; Recchia, F.; Sadler, B. V.; Scott, M.; Weisshaar, D.; Zegers, R. G. T.

    2016-04-01

    Low-lying excited states of the neutron-rich calcium isotopes Ca-5248 have been studied via γ -ray spectroscopy following inverse-kinematics proton scattering on a liquid hydrogen target using the GRETINA γ -ray tracking array. The energies and strengths of the octupole states in these isotopes are remarkably constant, indicating that these states are dominated by proton excitations.

  14. Studies of neutron-rich nuclei far from stability at TRISTAN

    SciTech Connect

    Gill, R.L.

    1984-01-01

    The ISOL facility, TRISTAN, is a user facility located at Brookhaven National Laboratory's High Flux Beam Reactor. Short-lived, neutron-rich nuclei, far from stability, are produced by thermal neutron fission of /sup 235/U. An extensive array of experimental end stations are available for nuclear structure studies. These studies are augmented by a variety of long-lived ion sources suitable for use at a reactor facility. Some recent results at TRISTAN are presented as examples of using an ISOL facility to study series of nuclei, whereby an effective means of conducting nuclear structure investigations is available.

  15. Decay spectroscopy of neutron-rich rare-earth isotopes and collectivity around double midshell

    SciTech Connect

    Watanabe, Hiroshi

    2015-10-15

    Neutron-rich rare-earth isotopes with A ≈ 170, which locate near the middle of the major shells for both proton and neutron between the doubly magic nuclei {sup 132}Sn and {sup 208}Pb, have been investigated by means of decay spectroscopy techniques at the RIBF facility at RIKEN. The nuclei of interest were produced by in-flight fission of a high-intensity {sup 238}U beam at 345 MeV/u. In this contribution, scientific motivations, the details of experimental procedures, and some prospects of the data analysis are reported.

  16. Possibility of production of neutron-rich isotopes in transfer-type reactions at intermediate energies

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Lukyanov, S. M.; Penionzhkevich, Yu. E.

    2008-08-15

    The production cross sections of neutron-rich isotopes of Mg, Al, Si, P, S, Cl, Ar, K, Ca, Sc, and Ti in the multinucleon transfer reactions {sup 48}Ca(64 MeV/nucleon, 140 MeV/nucleon) + {sup 181}Ta and {sup 48}Ca(142 MeV/nucleon) + {sup nat}W are estimated. A good agreement of the calculated results with the available experimental data confirms the mechanism of multinucleon transfer at almost peripheral collisions at intermediate energies. The global trend of production cross section with the charge (mass) number of target in reactions with {sup 48}Ca beam is discussed for the future experiments.

  17. CAPTAIN-Minerνa. Neutrino-Argon Scattering in a Medium-Energy Neutrino Beam

    SciTech Connect

    Mauger, Christopher M.

    2015-10-29

    The NuMI facility at Fermilab is currently providing an extremely intense beam of neutrinos for the NOνA, MINERνA and MINOS+ experiments. By installing the 5-ton CAPTAIN liquid argon TPC in front of the MINERνA detector in the NuMI beamline and combining the data from the CAPTAIN, MINERνA and MINOS+ detectors, a broad program of few-GeV neutrino cross section measurements on argon can be pursued. These measurements will be extremely helpful for future oscillation experiments. By directly comparing the cross sections on argon to MINERνA’s scintillator (CH) target, a new level of precision can be achieved in the measurements of the effects of the nucleus on neutrino interactions. These effects are of interest to not only the particle physics but also the nuclear physics community. This document describes in detail the physics goals of the CAPTAIN-MINERνA experiment, in addition to a first estimate of the technical resources required to install, commission and operate the CAPTAIN detector in front of the MINERVA detector.

  18. Extreme-ultraviolet beam-foil spectroscopy of highly ionized neon and argon. Doctoral thesis

    SciTech Connect

    Demarest, J.A.

    1986-08-01

    A study of the extreme-ultraviolet radiation emitted by ion beams of highly ionized neon and argon after passage through thin foils was conducted. A grazing-incidence spectrometer was equipped with a position-sensitive microchannel plate (MCP) detector, which improved the detection efficiency by two orders of magnitude. The position information of the MCP was determined to be linear over 90% of the 50-mm-wide detector. Spectra spanning regions of over 100 A were accumulated at a resolution of less than 1 A. A wavelength calibration based on a second order equation of spectrometer position was found to result in an accuracy of - 0.1 A. Over 40 transitions of Ne VIII, Ne IX, and Ne X were observed in the wavelength region from 350 to 30 A from n=2-3,4,5; n=3-4,5,6,7,8; n=4-6,7; and n=5-9. An intensity calibration of the detection system allowed the determination of the relative populations of n=3 states of Ne VIII and Ne IX. An overpopulation of states with low orbital angular momenta support electron-capture predictions by the first-order Born approximation. The argon beam-foil data confirmed the wavelength predictions of 30 previously unobserved transitions in the wavlength region from 355 to 25 A from n=2-2; n=3-4; n=4-5,6,7; and n=6-8. Lifetime determinations were made by the simultaneous measurement of 26 argon lines in the spectral region from 295-180 A. Many of the n=2-2 transitions agreed well with theory.

  19. β-DECAY Studies around 78Ni: Investigation of Neutron-Rich ni Isotopes

    NASA Astrophysics Data System (ADS)

    Morales, A. I.; Benzoni, G.; Watanabe, H.; Sohler, D.; Sahin, E.; de Angelis, G.; Nishimura, S.; Lorusso, G.; Sumikama, T.; Doornenbal, P.; Xu, Z. Y.; Isobe, T.; Söderström, P. A.; Browne, F.; Wu, J.; Baba, H.; Patel, Z.; Rice, S.; Sinclair, L.; Yokoyama, R.; Daido, R.; Fang, Y.; Niikura, M.; Avigo, R.; Bello Garrote, F. L.; Blasi, N.; Bracco, A.; Ceruti, S.; Crespi, F. C. L.; Delattre, M.-C.; Dombradi, Zs.; Gottardo, A.; Kuti, I.; Matsui, K.; Melon, B.; Mengoni, D.; Miyazaki, T.; Modamio-Hoybjor, V.; Momiyama, S.; Napoli, D. R.; Orlandi, R.; Sakurai, H.; Taniuchi, R.; Taprogge, J.; Vajta, Zs.; Valiente-Dobòn, J. J.; Wieland, O.; Yagi, A.; Yalcinkaya, M.

    2015-06-01

    This The β- decay of 70-74Co and other species in the vicinity of 78Ni has been investigated following the relativistic fission of a 238U primary beam at the Radioactive Ion Beam Factory facility in RIKEN, as part of the EURICA campaign. Extremely neutron-rich nuclei from Mn to Cu were produced and stopped in a state-of-the-art β-decay spectroscopy setup after their in-flight identification. The unprecedented high intensity of the primary beam, I = 10 pnA, ensures the access to a broad number of low-lying excited states in their daughters. In the present contribution, specific details on the setup and the experimental techniques employed are described. As well, the preliminary results are discussed.

  20. Possibility of production of neutron-rich Zn and Ge isotopes in multinucleon transfer reactions at low energies

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Sargsyan, V. V.; Scheid, W.

    2010-02-15

    The production cross sections of new neutron-rich {sup 84,86}Zn and {sup 90,92}Ge isotopes beyond N=50 are estimated for the first time in the multinucleon transfer reactions {sup 48}Ca + {sup 238}U and {sup 48}Ca + {sup 244}Pu. The production of new isotopes in reactions with a {sup 48}Ca beam is discussed for future experiments.

  1. Production of Extremely Neutron-Rich Rare Isotopes at Texas A&M

    NASA Astrophysics Data System (ADS)

    Souliotis, G. A.; Veselsky, M.; Yennello, S. J.

    2002-03-01

    The production of extermely neutron-rich isotopes in heavy-ion collisions around and below the Fermi energy ( 30 MeV/ncleon) has been investigated using the MARS recoil separator at the Cyclotron Institute of Texas A&M University. At present, the reactions: 25 MeV/nucleon ^86Kr + ^64Ni and 21 MeV/nucleon ^124Sn+^124Sn have been investigated. The experimental results on cross sections obtained to date will be presented and compared with reaction simulations appropriate for this energy domain. The current calculations involve a deep inelastic transfer code for the primary interaction stage and a modern statistical evaporation code for the deexcitation stage. The results are also compared with higher energy projectile fragmentation data and available parametrizations. In general, we show that such reactions, near or below the Fermi energy, involving substantial nucleon exchange between the projectile and the target, can be a fruitful pathway to approach extremely neutron-rich nuclei towards the neutron drip-line. Apart from in-flight possibilities, the option of utilizing this type of reaction for rare isotope production in ISOL-based facilities will be mentioned. Finally, application of such reactions in current plans of both in-flight and ISOL-type rare beam production at Texas A&M will be discussed.

  2. One-neutron knockout from light neutron-rich nuclei at relativistic energies

    SciTech Connect

    Rodriguez-Tajes, C.; Alvarez-Pol, H.; Benjamim, E.; Benlliure, J.; Caamano, M.; Casarejos, E.; Cortina-Gil, D.; Gascon, M.; Kurtukian, T.; Perez-Loureiro, D.; Aumann, T.; Chatillon, A.; Geissel, H.; Nociforo, C.; Prochazka, A.; Simon, H.; Suemmerer, K.; Weick, H.; Winkler, M.; Borge, M. J. G.

    2010-08-15

    One-neutron knockout reactions from neutron-rich nuclei, with Z=6-13 and N=8-22, were studied at the Fragment Separator (GSI) at high beam energies, around 700 MeV/nucleon. Structural phenomena such as the formation of one-neutron halos in odd-mass carbon isotopes ({sup 15,17,19}C) will be discussed. In addition, one-neutron knockout measurements from {sup 22}N were carried out for the first time and demonstrate clearly the change from a 0d{sub 5/2} to a 1s{sub 1/2} orbital for the valence neutron, an effect that is expected above N=14 and that was also observed in {sup 23}O and {sup 24}F. The possibility of an anomalous structure of {sup 26}F, due to a significant 1s{sub 1/2} neutron admixture, will also be discussed in the light of the experimental data obtained in this work. Finally, the ground-state configuration of neutron-rich neon isotopes ({sup 24-28}Ne) was studied, providing new information in a region that is relatively close to the island of inversion.

  3. Study of shape transition in the neutron-rich Os isotopes

    NASA Astrophysics Data System (ADS)

    John, P. R.; Modamio, V.; Valiente-Dobón, J. J.; Mengoni, D.; Gottardo, A.; Bazzacco, D.; Lunardi, S.; Alexander, T.; de Angelis, G.; Ashwood, N.; Barr, M.; Bizzeti, P. G.; Bizzeti-Sona, A. M.; Bottoni, S.; Bowry, M.; Bracco, A.; Browne, F.; Bunce, M.; Gadea, A.; Camera, F.; Corradi, L.; Crespi, F. C. L.; Farnea, E.; Fioretto, E.; Kokalova, Tz.; Korten, W.; Kuşoğlu, A.; Lenzi, S.; Leoni, S.; Michelagnoli, C.; Mijatović, T.; Montagnoli, G.; Montanari, D.; Napoli, D. R.; Podolyák, Zs.; Pollarolo, G.; Recchia, F.; Roberts, O. J.; Şahin, E.; Salsac, M.-D.; Scarlassara, F.; Stefanini, A. M.; Szilner, S.; Ur, C. A.; Walshe, J.; Wheldon, C.

    2014-03-01

    The neutron-rich isotopes of tungsten, osmium and platinum have different shapes in their ground states and present also shape transitions phenomena. Spectroscopic information for these nuclei is scarce and often limited to the gamma rays from the decay of isomeric states. For the neutron-rich even-even osmium isotopes 194Os and 198Os, a shape transition between a slightly prolate deformed to an oblate deformed ground state was deduced from the observed level schemes. For the even-even nucleus lying in between, 196Os, no gamma ray transition is known. In order to elucidate the shape transition and to test the nuclear models describing it, this region was investigated through gamma-ray spectroscopy using the AGATA demonstrator and the large acceptance heavy-ion spectrometer PRISMA at LNL, Italy. A two-nucleon transfer from a 198Pt target to a stable 82Se beam was utilized to populate medium-high spin states of 196Os. The analysis method and preliminary results, including the first life-time measurement of isomeric states with AGATA, are presented.

  4. Promises and Challenges of Two-Step Targets for Production of Neutron-rich RIBs

    SciTech Connect

    Talbert, W.L.; Drake, D.M.; Hsu, H.-H.; Wilson, M.T.

    2003-08-26

    Development of a prototype two-step target to produce neutron-rich RIBs is presented, with particular emphasis on thermal analysis under high-power operation. The two-step target is an attractive concept for production of fission-product activities without interference by high-energy spallation reactions which occur in direct production targets. In this concept, a high-energy production beam interacts with a primary target of refractory metal, depositing beam energy in the primary target and producing low-energy neutrons that cause fissions in a surrounding secondary target of mixed UC2 and excess C. Thermal analysis of the composite target presents challenges in cooling the primary target while maintaining the secondary target at temperatures suitable for release of the fission products. The effects of fission energy deposition in the secondary target are discussed, along with the complexities resulting from the thermally insulating character of the secondary target material.

  5. Shell structure in neutron rich nuclei by means of binary reactions

    SciTech Connect

    Angelis, G. de

    2014-08-14

    Nuclear structure studies far from stability rely mainly on the availability of radioactive nuclear beams but can complementary be addressed by means of high intensity beams of stable ions. In such contest, deep-inelastic and multinucleon transfer reactions are a powerful tool to populate yrast and non yrast states in neutron-rich nuclei. Particularly successful is here the combination of large acceptance spectrometers with highly segmented gamma-detector arrays. Such devices can provide the necessary channel selectivity to identify very rare signals. The AGATA gamma-ray detector array coupled to the PRISMA spectrometer at the Legnaro National Laboratories (LNL) in Italy is one example. Large data sets have been collected at LNL for nuclei close to the N=20, 28, 40, 50 and 82 shell closures.

  6. New Neutron Rich Nuclei Near {sup 208}Pb

    SciTech Connect

    Aeystoe, J.; Andreyev, A.; Evensen, A.-H.; Hoff, P.; Huhta, M.; Huyse, M.; ISOLDE Collaboration; Jokinen, A.; Karny, M.; Kugler, E.; Kurpeta, J.; Lettry, J.; Nieminen, A.; Plochocki, A.; Ramdhane, M.; Ravn, H.; Rykaczewski, K.; Szerypo, J.; VanDuppen, P.; Walter, G.; Woehr, A.

    1998-11-13

    The level properties near the stable doubly-magic nuclei formed the experimental grounds for the theoretical description of nuclear structure. However with a departure from the beta-stability line, the classical well-established shell structure might be modified. In particular, it may even vanish for extremely exotic neutron-rich nuclei near the neutron-drip line. Presently, it is impossible to verify such predictions by a direct experimental studies of these exotic objects. However, one may try to observe and understand the evolution of the nuclear structure while departing in the experiment as far as possible from the stable nuclei. An extension of experimental nuclear structure studies towards the nuclei characterized by high neutron excess is crucial for such verifications as well as for the {tau}-process nucleosynthesis scenario. Heavy neutron-rich nuclei, south-east of doubly-magic {sup 208}Pb, were always very difficult to produce and investigate. The nuclei like {sup 218}Po and {sup 214}Pb or {sup 210}Tl marked the border line of known nuclei from the beginning of the radioactivity era for over ninety years. To illustrate the difficulties, one can refer to the experiments employing the on-line mass separator technique. A spallation of heavy targets like {sup 232}Th and {sup 238}U by high-energy protons was proven as a source of heavy neutron-rich nuclei. The isotopes near and beyond doubly-magic {sup 208}Pb were produced too. However, such studies often suffered from an isobaric contamination of much more strongly produced and efficiently released elements like francium or radon and their decay products. A new experimental technique, based on the pulsed release element selective method recently developed at the PS Booster-ISOLDE at CERN [7,8,9] greatly reduces the contamination of these very short-lived {alpha}-emitters (Z {ge} 84) for the isobaric mass chains A=215 to A=218.

  7. NEUTRON-RICH CHROMIUM ISOTOPE ANOMALIES IN SUPERNOVA NANOPARTICLES

    SciTech Connect

    Dauphas, N.; Remusat, L.; Papanastassiou, D. A.; Guan, Y.; Ma, C.; Eiler, J. M.; Chen, J. H.; Roskosz, M.; Stodolna, J.

    2010-09-10

    Neutron-rich isotopes with masses near that of iron are produced in Type Ia and II supernovae (SNeIa and SNeII). Traces of such nucleosynthesis are found in primitive meteorites in the form of variations in the isotopic abundance of {sup 54}Cr, the most neutron-rich stable isotope of chromium. The hosts of these isotopic anomalies must be presolar grains that condensed in the outflows of SNe, offering the opportunity to study the nucleosynthesis of iron-peak nuclei in ways that complement spectroscopic observations and can inform models of stellar evolution. However, despite almost two decades of extensive search, the carrier of {sup 54}Cr anomalies is still unknown, presumably because it is fine grained and is chemically labile. Here, we identify in the primitive meteorite Orgueil the carrier of {sup 54}Cr anomalies as nanoparticles (<100 nm), most likely spinels that show large enrichments in {sup 54}Cr relative to solar composition ({sup 54}Cr/{sup 52}Cr ratio >3.6 x solar). Such large enrichments in {sup 54}Cr can only be produced in SNe. The mineralogy of the grains supports condensation in the O/Ne-O/C zones of an SNII, although a Type Ia origin cannot be excluded. We suggest that planetary materials incorporated different amounts of these nanoparticles, possibly due to late injection by a nearby SN that also delivered {sup 26}Al and {sup 60}Fe to the solar system. This idea explains why the relative abundance of {sup 54}Cr and other neutron-rich isotopes vary between planets and meteorites. We anticipate that future isotopic studies of the grains identified here will shed new light on the birth of the solar system and the conditions in SNe.

  8. Spectroscopy of Neutron-rich Nuclei of the A{approx_equal}60 region populated through binary heavy-ion collisions

    SciTech Connect

    Lunardi, S.

    2008-11-11

    Neutron-rich nuclei of the mass A = 60 region (from V to Fe) have been studied through multi-nucleon transfer reactions by bombarding a {sup 238}U target with beams of {sup 64}Ni and {sup 70}Zn. Unambiguous identification of prompt {gamma} rays belonging to each nucleus has been achieved by using the efficient gamma-array CLARA coupled to the large-acceptance magnetic spectrometer PRISMA installed at the Legnaro National Laboratories. With the new data, the existence of the N = 32 sub-shell closure has been corroborated through the study of odd V isotopes, whereas a new region of deformation appears for neutron-rich Fe nuclei close to N = 40. The results obtained for all these nuclei are compared with shell model calculations which reproduces quite well the experimental data also for the most neutron-rich nuclei when excitations from the fp shell into the upper g{sub 9/2} orbital are allowed.

  9. Level structures of neutron-rich Xe isotopes

    SciTech Connect

    Ahmad, I.; Lister, C.J.; Morss, L.R.

    1995-08-01

    The level structures of neutron-rich Xe isotopes were determined by observing prompt gamma-ray coincidences in {sup 248}Cm fission fragments. A 5-mg {sup 248}Cm, in the form of {sup 248}Cm-KCl pellet, was placed inside Eurogam array which consisted of 45 Compton-suppressed Ge detectors and 5 Low-Energy Photon Spectrometers. Transitions in Xe isotopes were identified by the appearance of new peaks in the {gamma}-ray spectra obtained by gating on the gamma peaks of the complementary Mo fragments.

  10. Exotic modes of excitation in deformed neutron-rich nuclei

    SciTech Connect

    Yoshida, Kenichi

    2011-05-06

    Low-lying dipole excitation mode in neutron-rich Mg isotopes close to the drip line is investigated in the framework of the Hartree-Fock-Bogoliubov and the quasiparticle random-phase approximation employing the Skyrme and the pairing energy-density functionals. It is found that the low-lying dipole-strength distribution splits into the K{sup {pi}} = 0{sup -} and 1{sup -} components due to the nuclear deformation. The low-lying dipole strength increases as the neutron drip-line is approached.

  11. Unexpectedly large charge radii of neutron-rich calcium isotopes

    NASA Astrophysics Data System (ADS)

    Garcia Ruiz, R. F.; Bissell, M. L.; Blaum, K.; Ekström, A.; Frömmgen, N.; Hagen, G.; Hammen, M.; Hebeler, K.; Holt, J. D.; Jansen, G. R.; Kowalska, M.; Kreim, K.; Nazarewicz, W.; Neugart, R.; Neyens, G.; Nörtershäuser, W.; Papenbrock, T.; Papuga, J.; Schwenk, A.; Simonis, J.; Wendt, K. A.; Yordanov, D. T.

    2016-06-01

    Despite being a complex many-body system, the atomic nucleus exhibits simple structures for certain `magic’ numbers of protons and neutrons. The calcium chain in particular is both unique and puzzling: evidence of doubly magic features are known in 40,48Ca, and recently suggested in two radioactive isotopes, 52,54Ca. Although many properties of experimentally known calcium isotopes have been successfully described by nuclear theory, it is still a challenge to predict the evolution of their charge radii. Here we present the first measurements of the charge radii of 49,51,52Ca, obtained from laser spectroscopy experiments at ISOLDE, CERN. The experimental results are complemented by state-of-the-art theoretical calculations. The large and unexpected increase of the size of the neutron-rich calcium isotopes beyond N = 28 challenges the doubly magic nature of 52Ca and opens new intriguing questions on the evolution of nuclear sizes away from stability, which are of importance for our understanding of neutron-rich atomic nuclei.

  12. Formation of Heavy and Superheavy Neutron Rich Nuclei

    SciTech Connect

    Zagrebaev, Valery; Greiner, Walter

    2010-04-30

    A new way is proposed to discover and examine unknown neutron-rich heavy and superheavy nuclei at the 'north-east' part of the nuclear map. The present limits of the upper part of the nuclear map is very close to stability while the unexplored area of heavy neutron-rich nuclides to the east of the stability line (also those located along the neutron closed shell N = 126) is extremely important for nuclear astrophysics investigations and for the understanding of the r-process of astrophysical nucleo-genesis. A novel idea is proposed for the production of these nuclei via low-energy multi-nucleon transfer reactions using a gain given by the shell effects. This finding may spur new studies at heavy ion facilities and should have significant impact for future experiments. The use of the multi-nucleon transfer reactions in low-energy collisions of heavy actinide nuclei gives us also the only chance to approach the 'island of stability' of superheavy elements. A possibility for a three-body decay (heavy ternary fission) is predicted for superheavy nuclei.

  13. Irradiation effect on PET surface using low energy argon ion beam

    NASA Astrophysics Data System (ADS)

    Soliman, Barakat A.; Abdelrahman, Moustafa M.; Abdelsalam, Fatama W.; Aly, Kamal A.

    2013-01-01

    A study of various physical properties of a PET film irradiated with an Ar beam is reported. SEM images and UV-VIS and FTIR spectra were obtained for a number of ionic fluxes and three irradiation times. Small changes in the energy gap of degradated samples were found, and the SEM images indicate that the optimum homogeneity and roughness are reached after 30 min of irradiation. These results may well be of practical interest. A modified saddle field ion source was used as a preparation tool of the surface of polyethylene terephthalate PET polymer substrate to be ready for coating or thin film deposition. Argon ion beam was used for this purpose, where the scanning electron microscope (SEM) shows that, the best sample is the one which was irradiated to 30 min, where this sample is more homogenous and roughness than other irradiated samples. Also the (UV-VIS) spectrum tells us that, there is small change on energy gap and this is meaning that, the change on electric properties is small also. In this case the sample is more homogenous and of higher roughness than other irradiated samples.

  14. Fluoropolymer Films Deposited by Argon Ion-Beam Sputtering of Polytetrafluoroethylene

    NASA Technical Reports Server (NTRS)

    Golub, Morton A.; Banks, Bruce A.; Kliss, Mark (Technical Monitor)

    1998-01-01

    The FT-IR, XPS and UV spectra of fluoropolymer films (SPTFE-I) deposited by argon ion-beam sputtering of polytetrafluoroethylene (PTFE) were obtained and compared with prior corresponding spectra of fluoropolymer films (SPTFE-P) deposited by argon rf plasma sputtering of PTFE. Although the F/C ratios for SPTFE-I and -P (1.63 and 1.51) were similar, their structures were quite different in that there was a much higher concentration of CF2 groups in SPTFE-I than in SPTFE-P, ca. 61 and 33% of the total carbon contents, respectively. The FT-IR spectra reflect that difference, that for SPTFE-I showing a distinct doublet at 1210 and 1150 per centimeter while that for SPTFE-P presents a broad, featureless band at ca. 1250 per centimeter. The absorbance of the 1210-per centimeter band in SPTFE-I was proportional to the thickness of the film, in the range of 50-400 nanometers. The SPTFE-I was more transparent in the UV than SPTFE-P at comparable thickness. The mechanism for SPTFE-I formation likely involves "chopping off" of oligomeric segments of PTFE as an accompaniment to "plasma" polymerization of TFE monomer or other fluorocarbon fragments generated in situ from PTFE on impact with energetic Ar ions. Data are presented for SPTFE-I deposits and the associated Ar(+) bombarded PTFE targets where a fresh target was used for each run or a single target was used for a sequence of runs.

  15. The neutron skin in neutron-rich nuclei at Jefferson Lab

    SciTech Connect

    Dalton, Mark M.

    2013-11-01

    The Jefferson Lab program to measure the symmetry energy of neutron-rich nuclear matter, using precision electroweak methods, is progressing well. The initial measurement by the PREX experiment, leading to a 2-sigma determination of the "neutron skin" in {sup 208}Pb , has been published. Design and preparation for a further, more-precise measurement on {sup 208}Pb is progressing well and there is general acceptance of the great advantage to a further measurement on {sup 48}Ca . The surprising ancillary result that the beam-normal single-spin asymmetry for {sup 208}Pb is consistent with zero is also now in the literature. This paper will discuss the current experimental situation of the program.

  16. β -decay properties of the very neutron-rich isotopes 86Ge and 86As

    NASA Astrophysics Data System (ADS)

    Mazzocchi, C.; Rykaczewski, K. P.; Grzywacz, R.; Bączyk, P.; Bingham, C. R.; Brewer, N. T.; Gross, C. J.; Jost, C.; Karny, M.; Korgul, A.; Madurga, M.; Mendez, A. J.; Miernik, K.; Miller, D.; Padgett, S.; Paulauskas, S. V.; Sonzogni, A. A.; Stracener, D. W.; Wolińska-Cichocka, M.

    2015-11-01

    The β -decay properties of very neutron rich nuclei 86Ge and 86As were measured at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. Spectroscopic information on new excited states in 86As and in 86Se was obtained and is interpreted within an advanced shell model approach. These calculations, previously explaining well the structure of 84Ge and 85Ge , are not able to reproduce all the experimentally determined features of the measured level schemes of 86As and 86Se . The Gamow-Teller decay of 86Ge and 86As is also investigated in a shell-model framework. The fission yield for 86Ge is discussed.

  17. Collectivity of neutron-rich palladium isotopes and the valence proton symmetry

    SciTech Connect

    Dewald, A.; Hackstein, M.; Rother, W.; Jolie, J.; Melon, B.; Pissulla, T.; Starosta, K.; Amthor, A. M.; Bowen, M.; Chester, A.; Gade, A.; Glasmacher, T.; Miller, D.; Moeller, V.; Norris, R. P.; Voss, P.; Petkov, P.; Adrich, P.; Baumann, T.; Bazin, D.

    2008-11-15

    Absolute transition probabilities for the first 2{sup +} states in {sup 110,114}Pd were measured using the recoil distance Doppler shift technique following projectile Coulomb excitation at intermediate beam energy. This technique was applied for the first time to projectiles produced in a primary fragmentation reaction, which get Coulomb excited in a secondary reaction. The {sup 110}Pd data was used to check the novel experimental technique as well as the data analysis procedure, which is based on the examination of {gamma}-ray line shapes. Whereas the measured B(E2) value for {sup 110}Pd agrees very well with the literature, the value obtained for {sup 114}Pd differs considerably. The new experimental data are compared to calculations in the framework of the Interacting Boson Model. The data are also used to test the novel concept of valence proton symmetry, which allows for extrapolation of nuclear properties to very neutron-rich nuclei.

  18. New subshell closure at N = 58 emerging in neutron-rich nuclei beyond 78Ni

    SciTech Connect

    Winger, J. A.; Rykaczewski, Krzysztof Piotr; Gross, Carl J; Grzywacz, Robert Kazimierz; Batchelder, J. C.; Goodin, C.; Hamilton, J. H.; Ilyushkin, S.; Korgul, A.; Krolas, W.; Liddick, Sean; Mazzocchi, C.; Padgett, Stephen; Piechaczek, A.; Rajabali, M. M.; Shapira, Dan; Zganjar, E. F.; Dobaczewski, J.

    2010-01-01

    The structure of neutron-rich nuclei beyond 78Ni was studied using postaccelerated radioactive beams of 83,84,85Ga utilizing and -n spectroscopy. Our data, when combined with energy level systematics, suggests a possible new spherical subshell closure at N = 58 is created by the nearly degenerated 3s1/2 and 2d5/2 orbitals being well separated from other orbitals above N = 50. The near degeneracy of these states could be evidenced by isomerism in this region. The energies of the 2+1 and proposed 4+1 states observed in N = 52 84Ge are interpreted as an indication of a possible weakening of the doubly magic 78Ni core for nuclei beyond N = 50. The experimental evidence is supported by spherical HFB calculations using the SkOT functional involving the tensor term in the nucleon-nucleon interaction.

  19. g-Factors of Isomeric States in the Neutron-Rich Nuclei

    SciTech Connect

    Georgiev, G.; Neyens, G.; Hass, M.; Balabanski, Dimiter Loukanov; Bingham, Carrol R; Borcea, C.; Coulier, N.; Coussenment, R.; Daugas, J. M.; De France, Gilles M; Gorska, M.; Grawe, Hubert H; Grzywacz, Robert Kazimierz; Lewitowicz, Marek; Mach, Henryk A; Matea, I.; de Oliveira Santos, F.; Page, R. D.; Pfutzner, Marek; Penionzhkevich, Yu. E.; Podolyak, Zsolt F; Regan, Patrick H; Rykaczewski, Krzysztof Piotr; Sawicka, M.; Smirnova, N. A.; Sobolev, Yu.; Stanoiu, M.; Teughels, S.; Vyvey, K.

    2004-02-01

    We report the results from the first experiment to measure gyromagnetic factors of {micro}s isomers in neutron-rich nuclei produced by intermediate-energy projectile-fragmentation reactions. The Time Dependent Perturbed Angular Distribution (TDPAD) method was applied in combination with the heavy-ion-gamma correlation technique. The nuclides in the vicinity of {sup 68}Ni were produced and spin-oriented following the fragmentation of a {sup 76}Ge, 61.4 MeV/ u beam at GANIL. The results obtained, |g|({sup 69 m}Cu) = 0.225(25) and |g|({sup 67 m}Ni) = 0.125(6) provide another indication of the importance of proton excitation across the Z = 28 shell gap for the description of these states.

  20. β and β -n decay of the neutron-rich

    NASA Astrophysics Data System (ADS)

    Korgul, A.; Rykaczewski, K. P.; Grzywacz, R. K.; Bingham, C. R.; Brewer, N. T.; Gross, C. J.; Ciemny, A. A.; Jost, C.; Karny, M.; Madurga, M.; Mazzocchi, C.; Mendez, A. J.; Miernik, K.; Miller, D.; Padgett, S.; Paulauskas, S. V.; Piersa, M.; Stracener, D. W.; Stryjczyk, M.; Wolińska-Cichocka, M.; Zganjar, E. F.

    2016-06-01

    The β -decay properties of the very neutron-rich Beam Facility at Oak Ridge National Laboratory. Several new γ -transitions and levels were added to its decay scheme and the order of the two lowest-lying levels in the daughter

  1. Recent developments at TRISTAN: nuclear structure studies of neutron-rich nuclei

    SciTech Connect

    Gill, R.L.

    1985-01-01

    The nuclear physics program at the fission product mass separator, TRISTAN, has greatly expanded, both in the types of experiments possible and in the range of nuclei available. Surface ionization, FEBIAD, high-temperature thermal, high-temperature plasma, and negative surface ionization ion sources are routinely available. Experimental facilities developed to further expand the capabilities of TRISTAN include a superconducting magnet for g-factor and Q/sub ..beta../ measurements, a windowless Si(Li) detector for conversion electron measurements, and a colinear fast-beam dye laser system for hyperfine interaction studies. This combination of ion sources, experimental apparatus, and the long running time available at a reactor makes TRISTAN a powerful tool for nuclear structure studies of neutron-rich nuclei. The effect of these developments on the nuclear physics program at TRISTAN will be discussed and recent results from some of these facilities will be presented. 6 refs., 3 figs.

  2. Conservation of Isospin in Neutron-rich Fission Fragments

    SciTech Connect

    Jain, A.K.; Choudhury, D.; Maheshwari, B.

    2014-06-15

    On the occasion of the 75{sup th} anniversary of the fission phenomenon, we present a surprisingly simple result which highlights the important role of isospin and its conservation in neutron rich fission fragments. We have analysed the fission fragment mass distribution from two recent heavyion reactions {sup 238}U({sup 18}O,f) and {sup 208}Pb({sup 18}O,f) as well as a thermal neutron fission reaction {sup 245}Cm(n{sup th},f). We find that the conservation of the total isospin explains the overall trend in the observed relative yields of fragment masses in each fission pair partition. The isospin values involved are very large making the effect dramatic. The findings open the way for more precise calculations of fission fragment distributions in heavy nuclei and may have far reaching consequences for the drip line nuclei, HI fusion reactions, and calculation of decay heat in the fission phenomenon.

  3. Beta decay rates of neutron-rich nuclei

    SciTech Connect

    Marketin, Tomislav; Huther, Lutz; Martínez-Pinedo, Gabriel

    2015-10-15

    Heavy element nucleosynthesis models involve various properties of thousands of nuclei in order to simulate the intricate details of the process. By necessity, as most of these nuclei cannot be studied in a controlled environment, these models must rely on the nuclear structure models for input. Of all the properties, the beta-decay half-lives are one of the most important ones due to their direct impact on the resulting abundance distributions. Currently, a single large-scale calculation is available based on a QRPA calculation with a schematic interaction on top of the Finite Range Droplet Model. In this study we present the results of a large-scale calculation based on the relativistic nuclear energy density functional, where both the allowed and the first-forbidden transitions are studied in more than 5000 neutron-rich nuclei.

  4. Beta decay rates of neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Marketin, Tomislav; Huther, Lutz; Petković, Jelena; Paar, Nils; Martínez-Pinedo, Gabriel

    2016-06-01

    Heavy element nucleosynthesis models involve various properties of thousands of nuclei in order to simulate the intricate details of the process. By necessity, as most of these nuclei cannot be studied in a controlled environment, these models must rely on the nuclear structure models for input. Of all the properties, the beta-decay half-lives are one of the most important ones due to their direct impact on the resulting abundance distributions. In this study we present the results of a large-scale calculation based on the relativistic nuclear energy density functional, where both the allowed and the first-forbidden transitions are studied in more than 5000 neutron-rich nuclei. Aside from the astrophysical applications, the results of this calculation can also be employed in the modeling of the electron and antineutrino spectra from nuclear reactors.

  5. Conservation of Isospin in Neutron-rich Fission Fragments

    NASA Astrophysics Data System (ADS)

    Jain, A. K.; Choudhury, D.; Maheshwari, B.

    2014-06-01

    On the occasion of the 75th anniversary of the fission phenomenon, we present a surprisingly simple result which highlights the important role of isospin and its conservation in neutron rich fission fragments. We have analysed the fission fragment mass distribution from two recent heavyion reactions 238U(18O,f) and 208Pb(18O,f) as well as a thermal neutron fission reaction 245Cm(nth,f). We find that the conservation of the total isospin explains the overall trend in the observed relative yields of fragment masses in each fission pair partition. The isospin values involved are very large making the effect dramatic. The findings open the way for more precise calculations of fission fragment distributions in heavy nuclei and may have far reaching consequences for the drip line nuclei, HI fusion reactions, and calculation of decay heat in the fission phenomenon.

  6. The pygmy dipole resonance in neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Quang Hung, Nguyen; Kiet, Hoang Anh Tuan; Duc, Huynh Ngoc; Thi Chuong, Nguyen

    2016-06-01

    The pygmy dipole resonance (PDR), which has been observed via the enhancement of the electric dipole strength E1 of atomic nuclei, is studied within a microscopic collective model. The latter employs the Hartree-Fock (HF) method with effective nucleon-nucleon interactions of the Skyrme types plus the random-phase approximation (RPA). The results of the calculations obtained for various even-even nuclei such as 16-28O, 40-58Ca, 100-120Sn, and 182-218Pb show that the PDR is significantly enhanced when the number of neutrons outside the stable core of the nucleus is increased, that is, in the neutron-rich nuclei. As the result, the relative ratio between the energy weighted sum of the strength of the PDR and that of the GDR (giant dipole resonance) does not exceed 4%. The collectivity of the PDR and GDR states will be also discussed.

  7. Characterization and literature review of bowel perforation injuring using argon beam coagulation

    NASA Astrophysics Data System (ADS)

    Barnes, Kelli S.; Merchel, Renée. A.; Taylor, Kenneth D.

    2015-03-01

    INTRODUCTION: Argon Beam Coagulation (ABC®) technology is used in conjunction with the ConMed ABCFlex® Probe to provide non-contact hemostasis, coagulation, and tissue devitalization during endoscopic procedures. ABC provides a superficial tissue effect; however, there is a risk of bowel perforation. To better understand the settings that lead to perforation, this study reviews the literature and provides an ex vivo characterization of the ABCFlex Probe tissue effect at different settings when used at small distances. METHODS: Depth of thermal tissue effect was characterized to determine the effect of three parameters: power (W), distance from probe tip to tissue (mm) and application duration (s). 3 ABCFlex Probes were used to create 15 samples on ex vivo porcine small intestine for each combination of parameters. The depth of tissue effect for each sample was measured using a light microscope. RESULTS: Depth of tissue effect increases as power and application time increases. An increase of distance from the probe tip to the tissue results in a decrease in depth of tissue effect from a near contact to 1mm distance. Depth of tissue effect doesn't significantly change from 1mm to 3mm distance. CONCLUSION: ABCFlex Probe can be used to achieve hemostasis in endoscopic procedures. Increasing power and application time increases the depth of thermal effect while increasing distance from the probe time to the surface of the tissue decreases the depth of tissue effect.

  8. Room temperature GaN-GaAs direct bonding by argon-beam surface activation

    NASA Astrophysics Data System (ADS)

    Higurashi, Eiji; Tokuda, Yuichiro; Akaike, Masatake; Suga, Tadatomo

    2007-10-01

    A room temperature direct bonding using surface activation by argon (Ar)-beam sputtering was applied to the bonding between gallium nitride (GaN) and gallium arsenide (GaAs). The silicon doped n-type GaN films used in this experiment were grown by metal organic chemical vapor deposition on (0001) sapphire substrates. The GaN film thickness is 3 μm with a surface roughness of approximately 0.22 nm (R a) as measured by atomic force microscopy. The silicon doped n-type GaAs (100) wafers with a surface roughness of approximately 0.34 nm (R a) were used as GaAs substrates. The GaN and GaAs samples were cleaned by sputtering with a 1.5 keV Ar-fast atom beam with 15 mA in the vacuum chamber (background pressure: 1.3×10 -5~4.0×10 -4 Pa). Then, the samples were brought into contact as quickly as possible with a load of 735 N at room temperature. After this process, GaN films were successfully bonded to GaAs substrates without any heat treatment. Cross-sectional scanning electron microscopy showed that most of the interface area was well bonded. The bonding strength was evaluated by die-shear tests. Although all samples were visibly separated from the interface rather than in the bulk region after die-shear tests, the estimated die-shear strength of GaN/GaAs structures was 1.5 -7 MPa. The advantage of our process is free from the various problems caused by the large thermal expansion mismatch during heat treatment in the conventional fusion bonding.

  9. Performance of a liquid argon time projection chamber exposed to the CERN West Area Neutrino Facility neutrino beam

    SciTech Connect

    Arneodo, F.; Cavanna, F.; Mitri, I. De; Mortari, G. Piano; Benetti, P.; Borio di Tigliole, A.; Calligarich, E.; Cesana, E.; Dolfini, R.; Mauri, F.; Montanari, C.; Rappoldi, A.; Raselli, G. L.; Rubbia, C.; Terrani, M.; Vignoli, C.; Bonesini, M.; Boschetti, B.; Cavalli, D.; Curioni, A.

    2006-12-01

    We present the results of the first exposure of a Liquid Argon TPC to a multi-GeV neutrino beam. The data have been collected with a 50 liters ICARUS-like chamber located between the CHORUS and NOMAD experiments at the CERN West Area Neutrino Facility (WANF). We discuss both the instrumental performance of the detector and its capability to identify and reconstruct low-multiplicity neutrino interactions.

  10. Production and identification of new, neutron-rich nuclei in the {sup 208}Pb region

    SciTech Connect

    Rykaczewski, K. ||; Kurpeta, J.; Plochocki, A.

    1998-11-01

    The recently developed methods allowing the experimental studies on new neutron-rich nuclei beyond doubly-magic {sup 208}Pb are briefly described. An identification of new neutron-rich isotopes {sup 215}Pb and {sup 217}Bi, and new decay properties of {sup 216}Bi studied by means of a pulsed release element selective technique at PS Booster-ISOLDE are reported.

  11. Measuring the electron density, temperature, and electronegativity in electron beam-generated plasmas produced in argon/SF6 mixtures

    NASA Astrophysics Data System (ADS)

    Boris, D. R.; Fernsler, R. F.; Walton, S. G.

    2015-04-01

    This paper presents measurements of electron density (ne0), electron temperature (Te), and electronegativity (α) in electron beam-generated plasmas produced in mixtures of argon and SF6 using Langmuir probes and plasma resonance spectroscopy. Langmuir probe measurements are analyzed using a model capable of handling multi-component plasmas with both positive and negative ions. Verification of the model is provided through plasma frequency resonance measurements of ne0. The results suggest a simple approach to ascertaining α in negative-ion-containing plasmas using Langmuir probes alone. In addition, modest amounts of SF6 are shown to produce sharp increases in both Te and α in electron beam generated plasmas.

  12. β-Decay of Neutron-Rich Nuclei around 158Nd and the Origin of Rare-Earth Elements

    NASA Astrophysics Data System (ADS)

    Wu, J.; Nishimura, S.; Lorusso, G.; Xu, Z. Y.; Ideguchi, E.; Simpson, G. S.; Baba, H.; Browne, F.; Daido, R.; Doornenbal, P.; Fang, Y. F.; Isobe, T.; Li, Z.; Patel, Z.; Rice, S.; Sinclair, L.; Söderström, P.-A.; Sumikama, T.; Watanabe, H.; Yagi, A.; Yokoyama, R.; Aoi, N.; Bello Garrote, F. L.; Benzoni, G.; Gey, G.; Gottardo, A.; Nishibata, H.; Odahara, A.; Sakurai, H.; Tanaka, M.; Taprogge, J.; Yamamoto, T.

    A large fraction of the rare-earth elements around mass number A = 160 observed in the solar system are produced in the astrophysical rapid (r-) neutron capture process. However, current stellar models cannot completely explain the relative abundance of these elements partially because of nuclear physics uncertainties. To address this problem, a β-decay spectroscopy experiment was performed at the RI Beam Factory (RIBF), aimed at studying a wide region of very neutron-rich nuclei around 158Nd. The data from this experiment provides a test of nuclear models as well as experimental inputs for r-process calculations.

  13. Shape evolution in the neutron-rich osmium isotopes: Prompt γ-ray spectroscopy of Os196

    NASA Astrophysics Data System (ADS)

    John, P. R.; Modamio, V.; Valiente-Dobón, J. J.; Mengoni, D.; Lunardi, S.; Rodríguez, T. R.; Bazzacco, D.; Gadea, A.; Wheldon, C.; Alexander, T.; de Angelis, G.; Ashwood, N.; Barr, M.; Benzoni, G.; Birkenbach, B.; Bizzeti, P. G.; Bizzeti-Sona, A. M.; Bottoni, S.; Bowry, M.; Bracco, A.; Browne, F.; Bunce, M.; Camera, F.; Cederwall, B.; Corradi, L.; Crespi, F. C. L.; Désesquelles, P.; Eberth, J.; Farnea, E.; Fioretto, E.; Görgen, A.; Gottardo, A.; Grebosz, J.; Grente, L.; Hess, H.; Jungclaus, A.; Kokalova, Tz.; Korichi, A.; Korten, W.; Kuşoǧlu, A.; Lenzi, S.; Leoni, S.; Ljungvall, J.; Maron, G.; Meczynski, W.; Melon, B.; Menegazzo, R.; Michelagnoli, C.; Mijatović, T.; Million, B.; Molini, P.; Montagnoli, G.; Montanari, D.; Napoli, D. R.; Nolan, P.; Oziol, Ch.; Podolyák, Zs.; Pollarolo, G.; Pullia, A.; Quintana, B.; Recchia, F.; Reiter, P.; Roberts, O. J.; Rosso, D.; Şahin, E.; Salsac, M.-D.; Scarlassara, F.; Sferrazza, M.; Simpson, J.; Söderström, P.-A.; Stefanini, A. M.; Stezowski, O.; Szilner, S.; Theisen, Ch.; Ur, C. A.; Walshe, J.

    2014-08-01

    The shape transition in the neutron-rich Os isotopes is studied by investigating the neutron-rich 196Os nucleus through in-beam γ-ray spectroscopy using a two-proton transfer reaction from a 198Pt target to a 82Se beam. The beam-like recoils were detected and identified with the large-acceptance magnetic spectrometer PRISMA, and the coincident γ rays were measured with the advanced gamma tracking array (AGATA) demonstrator. The de-excitation of the low-lying levels of the yrast-band of 196Os were identified for the first time. The results are compared with state-of-the-art beyond-mean-field calculations, performed for the even-even 188-198Os isotopes. The new results suggest a smooth transition in the Os isotopes from a more axial rotational behavior towards predominately vibrational nuclei through triaxial configurations. An almost perfect γ-unstable/triaxial rotor yrast band is predicted for 196Os which is in agreement with the experimentally measured excited states.

  14. The change in optical and electrical characteristics of tin oxide films under the action of argon ion beam

    NASA Astrophysics Data System (ADS)

    Asainov, O.; Umnov, S.; Temenkov, V.

    2016-01-01

    Thin films of tin oxide (TO) were deposited on the glass substrates at room temperature using reactive magnetron sputtering at various oxygen partial pressures. After the deposition the filmswere irradiated with argon ions beam. The change of the optical and electrical properties of the films depending on the irradiation time was studied. Films optical properties in the range of 300-1100 nm were investigated by photometry as well as their structural properties were studied using X-ray diffraction. Diffractometric research showed that the films, deposited on a substrate, have a crystal structure, and after argon ions irradiation they become quasi-crystalline (amorphous). It was found that the transmission increases proportionally with the irradiation time, but the surface resistance -disproportionally.

  15. Intruder configurations in neutron-rich {sup 34}P

    SciTech Connect

    Ollier, J.; Chapman, R.; Liang, X.; Labiche, M.; Spohr, K.-M.; Davison, M.; De Angelis, G.; Axiotis, M.; Kroell, T.; Napoli, D.R.; Martinez, T.; Bazzacco, D.; Farnea, E.; Lunardi, S.; Smith, A.G.; Haas, F.

    2005-03-01

    Extensions to the yrast and near-yrast decay sequences of the neutron-rich nucleus {sub 15}{sup 34}P{sub 19} have been established through an analysis of the {gamma} deexcitation of fragments produced in deep-inelastic processes which occur when 230-MeV {sup 36}S ions interact with a thick target of {sup 176}Yb. The highly sensitive GASP array of escape-suppressed Ge detectors was used to measure the resulting {gamma}-ray deexcitations of both projectilelike and targetlike fragments. Previously unobserved excited states in {sup 34}P were observed at 3351, 6236, 2320, and (4723) keV. Several states above an excitation energy of 2.3 MeV involve intruder configurations from the f{sub 7/2} shell. The investigation of negative parity intruder states on the periphery of the 'island of inversion' has an important role to play in our understanding of the evolution of nuclear structure as the island of inversion is approached.

  16. Transition probabilities in neutron-rich Se,8684

    NASA Astrophysics Data System (ADS)

    Litzinger, J.; Blazhev, A.; Dewald, A.; Didierjean, F.; Duchêne, G.; Fransen, C.; Lozeva, R.; Sieja, K.; Verney, D.; de Angelis, G.; Bazzacco, D.; Birkenbach, B.; Bottoni, S.; Bracco, A.; Braunroth, T.; Cederwall, B.; Corradi, L.; Crespi, F. C. L.; Désesquelles, P.; Eberth, J.; Ellinger, E.; Farnea, E.; Fioretto, E.; Gernhäuser, R.; Goasduff, A.; Görgen, A.; Gottardo, A.; Grebosz, J.; Hackstein, M.; Hess, H.; Ibrahim, F.; Jolie, J.; Jungclaus, A.; Kolos, K.; Korten, W.; Leoni, S.; Lunardi, S.; Maj, A.; Menegazzo, R.; Mengoni, D.; Michelagnoli, C.; Mijatovic, T.; Million, B.; Möller, O.; Modamio, V.; Montagnoli, G.; Montanari, D.; Morales, A. I.; Napoli, D. R.; Niikura, M.; Pollarolo, G.; Pullia, A.; Quintana, B.; Recchia, F.; Reiter, P.; Rosso, D.; Sahin, E.; Salsac, M. D.; Scarlassara, F.; Söderström, P.-A.; Stefanini, A. M.; Stezowski, O.; Szilner, S.; Theisen, Ch.; Valiente Dobón, J. J.; Vandone, V.; Vogt, A.

    2015-12-01

    Reduced quadrupole transition probabilities for low-lying transitions in neutron-rich Se,8684 are investigated with a recoil distance Doppler shift (RDDS) experiment. The experiment was performed at the Istituto Nazionale di Fisica Nucleare (INFN) Laboratori Nazionali di Legnaro using the Cologne Plunger device for the RDDS technique and the AGATA Demonstrator array for the γ -ray detection coupled to the PRISMA magnetic spectrometer for an event-by-event particle identification. In 86Se the level lifetime of the yrast 21+ state and an upper limit for the lifetime of the 41+ state are determined for the first time. The results of 86Se are in agreement with previously reported predictions of large-scale shell-model calculations using Ni78-I and Ni78-II effective interactions. In addition, intrinsic shape parameters of lowest yrast states in 86Se are calculated. In semimagic 84Se level lifetimes of the yrast 41+ and 61+ states are determined for the first time. Large-scale shell-model calculations using effective interactions Ni78-II, JUN45, jj4b, and jj4pna are performed. The calculations describe B (E 2 ;21+→01+) and B (E 2 ;61+→41+) fairly well and point out problems in reproducing the experimental B (E 2 ;41+→21+) .

  17. Mass measurements of neutron-rich Rb and Sr isotopes

    NASA Astrophysics Data System (ADS)

    Klawitter, R.; Bader, A.; Brodeur, M.; Chowdhury, U.; Chaudhuri, A.; Fallis, J.; Gallant, A. T.; Grossheim, A.; Kwiatkowski, A. A.; Lascar, D.; Leach, K. G.; Lennarz, A.; Macdonald, T. D.; Pearkes, J.; Seeraji, S.; Simon, M. C.; Simon, V. V.; Schultz, B. E.; Dilling, J.

    2016-04-01

    We report on the mass measurements of several neutron-rich Rb and Sr isotopes in the A ≈100 region with the TITAN Penning-trap mass spectrometer. By using highly charged ions in the charge state q =10 + , the masses of Rb,9998 and Sr-10098 have been determined with a precision of 6-12 keV, making their uncertainty negligible for r -process nucleosynthesis network calculations. The mass of 101Sr has been determined directly for the first time with a precision eight times higher than the previous indirect measurement and a deviation of 3 σ when compared to the Atomic Mass Evaluation. We also confirm the mass of 100Rb from a previous measurement. Furthermore, our data indicate the existence of a low-lying isomer with 80 keV excitation energy in 98Rb. We show that our updated mass values lead to minor changes in the r process by calculating fractional abundances in the A ≈100 region of the nuclear chart.

  18. Radiative neutron captures by neutron-rich nuclei and the r-process nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Goriely, S.

    1998-09-01

    The radiative neutron capture by neutron-rich nuclei is estimated with an improved description of the electric giant dipole resonance. In addition, 3 major effects affecting the capture rates by exotic neutron-rich nuclei are studied. These concern the existence of a low-energy E1 pygmy resonance, the overestimate of the statistical predictions for resonance-deficient nuclei and the direct capture mechanism. The total (n,γ) reaction rates including these 3 effects are evaluated for 3100 neutron-rich nuclei and used in parametric r-process calculations to analyze their impact on the r-abundance distribution.

  19. Gamma-ray spectroscopy of neutron-rich products of heavy-ion collisions

    SciTech Connect

    Carpenter, M.P.; Janssens, R.V.F.; Ahmad, I.

    1995-08-01

    Thick-target {gamma}{gamma} coincidence techniques are being used to explore the spectroscopy of otherwise hard-to-reach neutron-rich products of deep-inelastic heavy ion reactions. Extensive {gamma}{gamma} coincidence measurements were performed at ATLAS using pulsed beams of {sup 80}Se, {sup 136}Xe, and {sup 238}U on lead-backed {sup 122,124}Sn targets with energies 10-15% above the Coulomb barrier. Gamma-ray coincidence intensities were used to map out yield distributions with A and Z for even-even product nuclei around the target and around the projectile. The main features of the yield patterns are understandable in terms of N/Z equilibration. We had the most success in studying the decays of yrast isomers. Thus far, more than thirty new {mu}s isomers in the Z = 50 region were found and characterized. Making isotopic assignments for previously unknown {gamma}-ray cascades proves to be one of the biggest problems. Our assignments were based (a) on rare overlaps with radioactivity data, (b) on the relative yields with different beams, and (c) on observed cross-coincidences between {gamma} rays from light and heavy reaction partners. However, the primary products of deep inelastic collisions often are sufficiently excited for subsequent neutron evaporation, so {gamma}{gamma} cross-coincidence results require careful interpretation.

  20. Shape of Ar44: Onset of deformation in neutron-rich nuclei near Ca48

    NASA Astrophysics Data System (ADS)

    Zielińska, M.; Görgen, A.; Clément, E.; Delaroche, J.-P.; Girod, M.; Korten, W.; Bürger, A.; Catford, W.; Dossat, C.; Iwanicki, J.; Libert, J.; Ljungvall, J.; Napiorkowski, P. J.; Obertelli, A.; Piętak, D.; Rodríguez-Guzmán, R.; Sletten, G.; Srebrny, J.; Theisen, Ch.; Wrzosek, K.

    2009-07-01

    The development of deformation and shape coexistence in the vicinity of doubly magic Ca48, related to the weakening of the N=28 shell closure, was addressed in a low-energy Coulomb excitation experiment using a radioactive Ar44 beam from the SPIRAL facility at GANIL. The 21+ and 22+ states in Ar44 were excited on Pb208 and Ag109 targets at two different beam energies. B(E2) values between all observed states and the spectroscopic quadrupole moment of the 21+ state were extracted from the differential Coulomb excitation cross sections, indicating a prolate shape of the Ar44 nucleus and giving evidence of an onset of deformation already two protons and two neutrons away from doubly magic Ca48. New Hartree-Fock-Bogoliubov based configuration mixing calculations have been performed with the Gogny D1S interaction for Ar44 and neighboring nuclei using two different approaches: the angular momentum projected generator coordinate method considering axial quadrupole deformations and a five-dimensional approach including the triaxial degree of freedom. The experimental values and new calculations are furthermore compared to shell-model calculations and to relativistic mean-field calculations. The new results give insight into the weakening of the N=28 shell closure and the development of deformation in this neutron-rich region of the nuclear chart.

  1. Enhancing ion yields in time-of-flight-secondary ion mass spectrometry: a comparative study of argon and water cluster primary beams.

    PubMed

    Sheraz née Rabbani, Sadia; Razo, Irma Berrueta; Kohn, Taylor; Lockyer, Nicholas P; Vickerman, John C

    2015-02-17

    Following from our previous Letter on this topic, this Article reports a detailed study of time-of-flight-secondary ion mass spectrometry (TOF-SIMS) positive ion spectra generated from a set of model biocompounds (arginine, trehalose, DPPC, and angiotensin II) by water cluster primary ion beams in comparison to argon cluster beams over a range of cluster sizes and energies. Sputter yield studies using argon and water beams on arginine and Irganox 1010 have confirmed that the sputter yields using water cluster beams lie on the same universal sputtering curve derived by Seah for argon cluster beams. Thus, increased ion yield using water cluster beams must arise from increased ionization. The spectra and positive ion signals observed using cluster beams in the size range from 1,000 to 10,000 and the energy range 5-20 keV are reported. It is confirmed that water cluster beams enhance proton related ionization over against argon beams to a significant degree such that enhanced detection sensitivities from 1 μm(2) in the region of 100 to 1,000 times relative to static SIMS analysis with Ar2000 cluster beams appear to be accessible. These new studies show that there is an unexpected complexity in the ionization enhancement phenomenon. Whereas optimum ion yields under argon cluster bombardment occur in the region of E/n ≥ 10 eV (where E is the beam energy and n the number of argon atoms in the cluster) and fall rapidly when E/n < 10 eV; for water cluster beams, ion yields increase significantly in this E/n regime (where n is the number of water molecules in the cluster) and peak for 20 keV beams at a cluster size of 7,000 or E/n ∼3 eV. This important result is explored further using D2O cluster beams that confirm that in this low E/n regime protonation does originate to a large extent from the water molecules. The results, encouraging in themselves, suggest that for both argon and water cluster beams, higher energy beams, e.g., 40 and 80 keV, would enable larger

  2. Measurement of the response of the ATLAS liquid argon barrel calorimeter to electrons at the 2004 combined test-beam

    SciTech Connect

    Aharrouche, M.; Ma, H.; Adam-Bourdarios, C.; Aleksa, M.; Banfi, D.; Benchekroun, D.; Benslama, K.; Boonekamp, M.; Carli, T.; Carminati, L.; Chen, H.; Citterio, M.; Dannheim, D.; Delmastro, M.; Derue, F.; Di Girolamo, B.; El Kacimi, M.; Fanti, M.; Froeschl, R.; Fournier, D.; Grahn, K.-J.; Kado, M.; Kerschen, N.; Lafaye, R.; Laforge, B.; Lampl, W.; Laplace, S.; Lechowski, M.; Lelas, D.; Liang, Z.; Loureiro, K.; Lund-Jensen, B.; Mandelli, L.; Mazzanti, M.; McPherson, R.; Meng, Z.; Paganis, S.; Prieur, D.; Puzo, P.; Ridel, M.; Riu, I.; Rousseau, D.; Sauvage, G.; Schwemling, P.; Simon, S.; Spano, F.; Straessner, A.; Tarrade, F.; Tartarelli, F.; Thioye, M.; Unal, G.; Wilkens, H.; Wingerter-Seez, I. and Zhang, H.

    2010-03-11

    During summer and fall 2004, the response of a full slice of the ATLAS barrel detector to different particles was studied in controlled beam. One module of the ATLAS liquid argon barrel calorimeter - identical to the production modules and read out by the final front-end and back-end electronics - was used for electromagnetic calorimetry. This paper presents and discusses the electron performance of the LAr barrel calorimeter, including linearity, uniformity, and resolution with different amounts of material upstream the calorimeter and energies ranging from 1 to 250 GeV.

  3. New Isomers in the Neutron-Rich Region Beyond 208Pb

    NASA Astrophysics Data System (ADS)

    Gottardo, A.; Valiente-Dobón, J. J.; Benzoni, G.; Gadea, A.; Lunardi, S.; Boutachkov, P.; Bruce, A. M.; Górska, M.; Grebosz, J.; Pietri, S.; Podolyák, Zs.; Pfützner, M.; Regan, P. H.; Weick, H.; Alcántara Núñez, J.; Algora, A.; Al-Dahan, N.; de Angelis, G.; Ayyad, Y.; Alkhomashi, N.; Allegro, P. R. P.; Bazzacco, D.; Benlliure, J.; Bowry, M.; Bracco, A.; Bunce, M.; Camera, F.; Casarejos, E.; Cortes, M. L.; Crespi, F. C. L.; Corsi, A.; Bacelar, A. M. Denis; Deo, A. Y.; Domingo-Pardo, C.; Doncel, M.; Dombradi, Zs.; Engert, T.; Eppinger, K.; Farrelly, G. F.; Farinon, F.; Farnea, E.; Geissel, H.; Gerl, J.; Goel, N.; Gregor, E.; Habermann, T.; Hoischen, R.; Janik, R.; John, P. R.; Klupp, S.; Kojouharov, I.; Kurz, N.; Lenzi, S. M.; Leoni, S.; Mandal, S.; Menegazzo, R.; Mengoni, D.; Million, B.; Modamio, V.; Morales, A. I.; Napoli, D. R.; Naqvi, F.; Nicolini, R.; Nociforo, C.; Prochazka, A.; Prokopowicz, W.; Recchia, F.; Ribas, R. V.; Reed, M. W.; Rudolph, D.; Sahin, E.; Schaffner, H.; Sharma, A.; Sitar, B.; Siwal, D.; Steiger, K.; Strmen, P.; Swan, T. P. D.; Szarka, I.; Ur, C. A.; Walker, P. M.; Wieland, O.; Wollersheim, H.-J.

    2014-03-01

    The region of neutron-rich nuclei beyond 208Pb has been very difficult to explore due to its high mass and exoticity. However, recent experimental improvements allowed one to perform a quite extended isomer decay spectroscopy of these nuclei.

  4. Study of dipole excitations and the single particle structure of neutron rich Ni isotopes

    NASA Astrophysics Data System (ADS)

    Mahata, K.; Paschalis, S.; Adrich, P.; Aksouh, F.; Aumann, T.; Babilon, M.; Behr, K.-H.; Benlliure, J.; Berg, T.; Boehmer, M.; Boretzky, K.; Brünle, A.; Casarejos, E.; Chartier, M.; Chatillon, A.; Cortina-Gil, D.; Pramanik, U. Datta; Deveaux, L.; Elvers, M.; Emling, H.; Fernandez-Dominguez, B.; Gorska, M.; Hüller, W.; Ickert, G.; Johansson, H.; Junghans, A.; Karagiannis, C.; Kern, L.; Kiselev, O.; Klimkiewicz, A.; Kurz, N.; Labiche, M.; Le Bleis, T.; Lemmon, R.; Lindenberg, K.; Litvinov, Y.; Maierbeck, P.; Müller, S.; Nilsson, T.; Nociforo, C.; Palit, R.; Prokopowicz, W.; Rossi, D.; Simon, H.; Sümmerer, K.; Wagner, A.; Walus, W.; Weick, H.; Winkler, M.

    2008-05-01

    An experiment was performed using the FRS-LAND setup at GSI to study the dipole strength distributions above neutron separation threshold for neutron-rich Ni isotopes. Measurements, using the same experimental setup, were also carried out to extract single particle occupancies via knockout reactions to investigate the structure and magicity of the neutron-rich Ni isotopes. The status of the data analysis and preliminary results are presented.

  5. The Spectroscopy of Neutron-Rich sdf-Shell Nuclei Using the CLARA-PRISMA Setup

    SciTech Connect

    Liang, X.; Hodsdon, A.; Chapman, R.; Burns, M.; Keyes, K.; Ollier, J.; Papenberg, A.; Spohr, K.; Azaiez, F.; Ibrahim, F.; Stanoiu, M.; Haas, F.; Caurier, E.; Curien, D.; Nowacki, F.; Salsac, M.-D.; Bazzacco, D.; Beghini, S.; Farnea, E.; Menegazzo, R.

    2006-08-14

    Since the discovery of the breakdown of shell effects in very neutron-rich N=20 and 28 nuclei, studies of the properties of nuclei far from stability have been of intense interest since they provide a unique opportunity to increase our understanding of nuclear interactions in extreme conditions and often challenge our theoretical models.Deep-inelastic processes can be used to populated high spin states of neutron-rich nuclei. In the deep-inelastic processes, an equilibration in N/Z between the target and projectile nuclei is achieved. For most heavy neutron-rich target nuclei, the N/Z ratio is 1.5 - 1.6, while for the possible neutron-rich sdf-shell projectile it is about 1.2. Thus by using deep-inelastic processes one can populate neutron-rich nuclei around N=20 and N=28.New results for the spectroscopy of neutron-rich N=22 36Si and 37P are presented here.

  6. Application of argon laser beam diffraction for determination of the properties of photoinduced processes in dyed PVA foils

    NASA Astrophysics Data System (ADS)

    Planner, Alfons; Runka, Tomasz; Skrzypczak, A.; Hara, M.; Miyake, J.

    2000-11-01

    It is shown that far field patterns of argon laser beam interacting with dyed foil of polyvinyl alcohol (PVA) provide information on the mechanism of local foil discoloration or at least on a few properties of this process. In particular far field patterns observations allow discernment if the process is reversible (or a superposition of reversible and irreversible processes), photothermal, photochemical or produce a stretching in sample (photoizomerisation). The effect was studied in PVA foil containing methyl red, photosynthetic bacteria, their fragments and pigments. Apart from indicating the possibility of using the far field patterns for discernment of the foil discoloration mechanisms, the results reported point to the perspectives of using the foil for laser beam modification, shift or modulation, as well as elements of optical memory.

  7. High-spin structures in the neutron-rich isotopes {sup 57-60}Mn.

    SciTech Connect

    Steppenbeck, D.; Deacon, A. N.; Freeman, S. J.; Janssens, R. V. F.; Zhu, S.; Carpenter, M. P.; Chowdhury, P.; Honma, M.; Lauritsen, T.; Lister, C. J.; Seweryniak, D.; Smith, J. F.; Tabor, S. L.; Varley, B. J.; Physics; Schuster Lab.; Univ. of Massachusetts; Univ. of Aizu; Florida State Univ.

    2010-01-01

    Excited states in the neutron-rich isotopes {sup 57-60}Mn have been studied with fusion-evaporation reactions induced by {sup 48}Ca beams at 130 MeV on {sup 13,14}C targets. Level schemes have been deduced reaching spins of {approx}16{h_bar} and {approx}27{h_bar}/2 in the odd-odd and odd-even isotopes, respectively. States with natural parity within an fp model space are compared to the predictions of large-scale shell-model calculations using the recently developed GXPF1A effective interaction. Quasirotational structures are evident in all of the isotopes and are discussed in terms of the deformation-driving potential of the ?1g{sub 9/2} intruder orbital. It is apparent that an enlarged model space, incorporating at least the 1g{sub 9/2} intruder state, is necessary to reproduce the observed experimental systematics in a more satisfactory manner.

  8. Direct evidence of octupole deformation in neutron-rich 144Ba

    DOE PAGESBeta

    Bucher, B.; Zhu, S.; Wu, C. Y.; Janssens, R. V. F.; Cline, D.; Hayes, A. B.; Albers, M.; Ayangeakaa, A. D.; Butler, P. A.; Campbell, C. M.; et al

    2016-03-17

    Here, the neutron-rich nucleus 144Ba (t1/2 = 11.5 s) is expected to exhibit some of the strongest octupole correlations among nuclei with mass numbers A less than 200. Until now, indirect evidence for such strong correlations has been inferred from observations such as enhanced E1 transitions and interleaving positive- and negative-parity levels in the ground-state band. In this experiment, the octupole strength was measured directly by sub-barrier, multistep Coulomb excitation of a post-accelerated 650-MeV 144Ba beam on a 1.0–mg/cm2 208Pb target. The measured value of the matrix element, < 31–∥M(E3)∥01+ >= 0.65(+17–23) eb3/2, corresponds to a reduced B(E3) transition probabilitymore » of 48(+25–34) W.u. This result represents an unambiguous determination of the octupole collectivity, is larger than any available theoretical prediction, and is consistent with octupole deformation.« less

  9. Fusion of neutron-rich systems using time-dependent density-constrained DFT

    NASA Astrophysics Data System (ADS)

    Oberacker, Volker; Umar, A. S.

    2013-04-01

    In connection with experiments at Radioactive Ion Beam Facilities, we study fusion reactions with a new approach [1] which is based on a time-dependent density-constrained density functional theory (DFT). The only input is the Skyrme NN interaction, there are no adjustable parameters. We calculate heavy-ion interaction potentials V(R), mass parameters M(R), and total fusion cross sections. Some of the effects naturally included in these calculations are: neck formation, mass exchange, internal excitations, deformation effects, as well as nuclear alignment for deformed systems. Results will be presented for low-energy fusion reactions of ^12C+^16,24O and for ^16,24O+^16,24,28O which occur in the crust of neutron stars [2]. Finally, we will discuss fusion with neutron-rich halo nuclei, in particular ^11Li+^208Pb.[4pt] [1] Umar and Oberacker, PRC 74, 021601(R) (2006)[0pt] [2] Umar, Oberacker, and Horowitz, PRC 85, 055801 (2012)

  10. Direct Evidence of Octupole Deformation in Neutron-Rich ^{144}Ba.

    PubMed

    Bucher, B; Zhu, S; Wu, C Y; Janssens, R V F; Cline, D; Hayes, A B; Albers, M; Ayangeakaa, A D; Butler, P A; Campbell, C M; Carpenter, M P; Chiara, C J; Clark, J A; Crawford, H L; Cromaz, M; David, H M; Dickerson, C; Gregor, E T; Harker, J; Hoffman, C R; Kay, B P; Kondev, F G; Korichi, A; Lauritsen, T; Macchiavelli, A O; Pardo, R C; Richard, A; Riley, M A; Savard, G; Scheck, M; Seweryniak, D; Smith, M K; Vondrasek, R; Wiens, A

    2016-03-18

    The neutron-rich nucleus ^{144}Ba (t_{1/2}=11.5  s) is expected to exhibit some of the strongest octupole correlations among nuclei with mass numbers A less than 200. Until now, indirect evidence for such strong correlations has been inferred from observations such as enhanced E1 transitions and interleaving positive- and negative-parity levels in the ground-state band. In this experiment, the octupole strength was measured directly by sub-barrier, multistep Coulomb excitation of a post-accelerated 650-MeV ^{144}Ba beam on a 1.0-mg/cm^{2} ^{208}Pb target. The measured value of the matrix element, ⟨3_{1}^{-}∥M(E3)∥0_{1}^{+}⟩=0.65(+17/-23) eb^{3/2}, corresponds to a reduced B(E3) transition probability of 48(+25/-34)  W.u. This result represents an unambiguous determination of the octupole collectivity, is larger than any available theoretical prediction, and is consistent with octupole deformation. PMID:27035298

  11. Direct Evidence of Octupole Deformation in Neutron-Rich 144Ba

    NASA Astrophysics Data System (ADS)

    Bucher, B.; Zhu, S.; Wu, C. Y.; Janssens, R. V. F.; Cline, D.; Hayes, A. B.; Albers, M.; Ayangeakaa, A. D.; Butler, P. A.; Campbell, C. M.; Carpenter, M. P.; Chiara, C. J.; Clark, J. A.; Crawford, H. L.; Cromaz, M.; David, H. M.; Dickerson, C.; Gregor, E. T.; Harker, J.; Hoffman, C. R.; Kay, B. P.; Kondev, F. G.; Korichi, A.; Lauritsen, T.; Macchiavelli, A. O.; Pardo, R. C.; Richard, A.; Riley, M. A.; Savard, G.; Scheck, M.; Seweryniak, D.; Smith, M. K.; Vondrasek, R.; Wiens, A.

    2016-03-01

    The neutron-rich nucleus 144Ba (t1 /2=11.5 s ) is expected to exhibit some of the strongest octupole correlations among nuclei with mass numbers A less than 200. Until now, indirect evidence for such strong correlations has been inferred from observations such as enhanced E 1 transitions and interleaving positive- and negative-parity levels in the ground-state band. In this experiment, the octupole strength was measured directly by sub-barrier, multistep Coulomb excitation of a post-accelerated 650-MeV 144Ba beam on a 1.0 -mg /cm2 208Pb target. The measured value of the matrix element, ⟨31 -∥M (E 3 )∥01 +⟩=0.65 (+17/-23) e b3 /2, corresponds to a reduced B (E 3 ) transition probability of 48 (+25/-34) W .u . This result represents an unambiguous determination of the octupole collectivity, is larger than any available theoretical prediction, and is consistent with octupole deformation.

  12. gamma-ray spectroscopy of neutron-rich {sup 40}S

    SciTech Connect

    Wang, Z. M.; Chapman, R.; Liang, X.; Burns, M.; Hodsdon, A.; Keyes, K.; Kumar, V.; Papenberg, A.; Smith, J. F.; Spohr, K. M.; Haas, F.; Caurier, E.; Curien, D.; Nowacki, F.; Azaiez, F.; Ibrahim, F.; Verney, D.; Behera, B. R.; Corradi, L.; Fioretto, E.

    2010-05-15

    Yrast states up to (6{sup +}) in the neutron-rich {sup 40}S nucleus have been studied using binary grazing reactions produced by the interaction of a 215 MeV beam of {sup 36}S ions with a thin {sup 208}Pb target. The novel experimental setup that combines the large acceptance magnetic spectrometer, PRISMA, and the high-efficiency gamma-ray detection array, CLARA, was used. A new gamma-ray transition at an energy of 1572 keV was observed and tentatively assigned to the (6{sup +})->(4{sup +}) transition. A comparison of experimental observations and the results of large-scale 0(Planck constant/2pi)omega sd-pf shell-model calculations indicates that one- and two-proton excitations from the 2s{sub 1/2} to the 1d{sub 3/2} orbitals play an important role in reproducing the {sup 40}S yrast level structure and the published B(E2;0{sub g.s.}{sup +}->2{sub 1}{sup +}) value. The structure of the yrast states of the even-A isotopes of sulfur is interpreted in terms of the configurations of valence protons and neutrons within the context of large-scale 0(Planck constant/2pi)omega sd-pf shell-model calculations.

  13. Isomeric states in neutron-rich 129In and the πg-19/2 vh-111/2 multiplet

    NASA Astrophysics Data System (ADS)

    Taprogge, J.; Jungclaus, A.; Simpson, G.

    2014-09-01

    Within the RISING stopped beam campaign the neutron-rich indium isotopes with masses A=125-130 have been studied using the method of isomer spectroscopy. The decays of several isomeric states have been observed and here we compare our results for 129In to previous measurements for this nucleus. The isomeric states were populated in the fragmentation of a 136Xe beam at 750 MeV/u and in the relativistic fission of a 238U beam at 650 MeV/u at the accelerator facility GSI (Darmstadt, Germany).

  14. Comparisons of cross-section predictions for relativistic iron and argon beams with semiempirical fragmentation models

    NASA Technical Reports Server (NTRS)

    Townsend, Lawrence W.; Tripathi, Ram K.; Khan, Ferdous

    1993-01-01

    Cross-section predictions with semi-empirical nuclear fragmentation models from the Langley Research Center and the Naval Research Laboratory are compared with experimental data for the breakup of relativistic iron and argon projectile nuclei in various targets. Both these models are commonly used to provide fragmentation cross-section inputs into galactic cosmic ray transport codes for shielding and exposure analyses. Overall, the Langley model appears to yield better agreement with the experimental data.

  15. Beta Decay Spectroscopy of Neutron-Rich Nuclei at RIBF

    NASA Astrophysics Data System (ADS)

    Lorusso, G.; Nishimura, S.; Baba, H.; Doornenbal, P.; Isobe, T.; Söderström, P.-A.; Browne, F.; Daido, R.; Yifan, F.; Nishibata, H.; Yagi, A.; Gey, G.; Li, Z.; Wu, J.; Lubos, D.; Moschner, K.; Patel, Z.; Rice, S.; Sinclair, L.; Sumikama, T.; Taprogge, J.; Vajta, Zs.; Watanabe, H.; Xu, Z. Y.; Yoshinaga, K.

    2015-11-01

    The development of a high intensity 238U beam at the Radioactive Isotope Beam Factory (RIBF) has opened a new opportunity to explore exotic regions of the nuclear chart that were not accessible before. Along with beam development, the installation of the high efficiency γ-detector EURICA has made β-decay spectroscopy measurements of these regions possible, and a large international effort named the EURICA project has been launched to take advantage of this new opportunity.

  16. Two-Beam multiplexed laser-induced fluorescence measurements of an argon arcjet plume

    NASA Technical Reports Server (NTRS)

    Ruyten, Wilhelmus M.; Keefer, Dennis

    1993-01-01

    We describe a multiplexed, laser-induced fluorescence (LIF) technique with which radial and axial profiles of vector velocities of excited propellant species were obtained in the exhaust plume from a 300-W argon arcjet. Although the arcjet is a prototype, and although argon is not an interesting propellant from a propulsion perspective, the technique clearly demonstrates how a narrowband, frequency-stabilized ring-dye laser can be used to obtain simultaneous measurements of two velocity components in an arcjet plume and how a third signal from an optogalvanic cell can be used as a frequency reference. We also show that much information on the flow can be obtained by analyzing the Doppler widths and fluorescence intensities of the LIF data. Specifically, the data identify a boundary layer in the radial direction of the plume and a shock in the downstream region of the flow. Also, some flow anisotropy is observed, consistent with the assumption that the magnitude of the mean flow velocity fluctuates. The peak velocity on centerline remains roughly constant at 3 km/s throughout the expansion.

  17. β-decay of neutron-rich Z∼60 nuclei and the origin of rare earth elements

    SciTech Connect

    Wu, J.; Nishimura, S.; Lorusso, G.; Baba, H.; Doornenbal, P.; Isobe, T.; Söderström, P. A.; Sakurai, H.; Xu, Z. Y.; Browne, F.; Daido, R.; Fang, Y. F.; Yagi, A.; Nishibata, H.; Odahara, A.; Yamamoto, T.; Ideguchi, E.; Aoi, N.; Tanaka, M.; Collaboration: EURICA Collaboration; and others

    2014-05-02

    A large fraction of the rare-earth elements observed in the solar system is produced in the astrophysical rapid neutron capture process (r-process). However, current stellar models cannot completely explain the relative abundance of these elements partially because of nuclear physics uncertainties. To address this problem, a β-decay spectroscopy experiment was performed at RI Beam Factory (RIBF) at RIKEN, aimed at studying a wide range of very neutron-rich nuclei with Z∼60 that are progenitors of the rare-earth elements with mass number A∼460. The experiment provides a test of nuclear models as well as experimental inputs for r-process calculations. This contribution presents the experimental setup and some preliminary results of the experiment.

  18. Use of Neutron Transfer Reactions to Indirectly Determine Neutron Capture Cross Sections on Neutron-Rich Nuclei

    SciTech Connect

    McCleskey, M.; Mukhamedzhanov, A. M.; Tribble, R. E.; Simmons, E.; Spiridon, A.; Banu, A.; Roeder, B.; Goldberg, V.; Trache, L.; Chen, X. F.; Lui, Y.-W.

    2010-03-01

    {sup 14}C(n,gamma){sup 15}C is being used as a test case in the development of an indirect method to determine neutron capture cross sections on neutron-rich unstable nuclei at astrophysical energies. Our approach makes use of two reactions: one peripheral used to find the asymptotic normalization coefficient (ANC) and a second non-peripheral reaction to determine the spectroscopic factor. The ANC for {sup 15}C has been determined using a HI neutron transfer reaction with a 12 MeV/nucleon {sup 14}C beam on a {sup 13}C target. The spectroscopic factor will be determined using {sup 14}C(d,p) in forward kinematics with an incident deuteron energy of 60 MeV. Both experiments were performed using the MDM high-resolution spectrometer at Texas A and M University.

  19. Spectroscopic Quadrupole Moments in Sr,9896 : Evidence for Shape Coexistence in Neutron-Rich Strontium Isotopes at N =60

    NASA Astrophysics Data System (ADS)

    Clément, E.; Zielińska, M.; Görgen, A.; Korten, W.; Péru, S.; Libert, J.; Goutte, H.; Hilaire, S.; Bastin, B.; Bauer, C.; Blazhev, A.; Bree, N.; Bruyneel, B.; Butler, P. A.; Butterworth, J.; Delahaye, P.; Dijon, A.; Doherty, D. T.; Ekström, A.; Fitzpatrick, C.; Fransen, C.; Georgiev, G.; Gernhäuser, R.; Hess, H.; Iwanicki, J.; Jenkins, D. G.; Larsen, A. C.; Ljungvall, J.; Lutter, R.; Marley, P.; Moschner, K.; Napiorkowski, P. J.; Pakarinen, J.; Petts, A.; Reiter, P.; Renstrøm, T.; Seidlitz, M.; Siebeck, B.; Siem, S.; Sotty, C.; Srebrny, J.; Stefanescu, I.; Tveten, G. M.; Van de Walle, J.; Vermeulen, M.; Voulot, D.; Warr, N.; Wenander, F.; Wiens, A.; De Witte, H.; Wrzosek-Lipska, K.

    2016-01-01

    Neutron-rich Sr,9896 isotopes have been investigated by safe Coulomb excitation of radioactive beams at the REX-ISOLDE facility. Reduced transition probabilities and spectroscopic quadrupole moments have been extracted from the differential Coulomb excitation cross sections. These results allow, for the first time, the drawing of definite conclusions about the shape coexistence of highly deformed prolate and spherical configurations. In particular, a very small mixing between the coexisting states is observed, contrary to other mass regions where strong mixing is present. Experimental results have been compared to beyond-mean-field calculations using the Gogny D1S interaction in a five-dimensional collective Hamiltonian formalism, which reproduce the shape change at N =60 .

  20. Experimental study of β and β -n decay of the neutron-rich N =54 isotone 87As

    NASA Astrophysics Data System (ADS)

    Korgul, A.; Rykaczewski, K. P.; Grzywacz, R.; Bingham, C. R.; Brewer, N. T.; Ciemny, A. A.; Gross, C. J.; Jost, C.; Karny, M.; Madurga, M.; Mazzocchi, C.; Mendez, A. J.; Miernik, K.; Miller, D.; Padgett, S.; Paulauskas, S. V.; Stracener, D. W.; Wolińska-Cichocka, M.

    2015-11-01

    The β -decay properties of neutron-rich 87As produced in the proton-induced fission of 238U were studied at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The low-energy excited states in N =53 87Se and N =52 86Se were identified through β -γ and β -delayed neutron-γ decay of 87As, respectively. The experimental systematics of low-energy levels of N =53 isotones, Z =34 Se87, and Z =32 85Ge, and along with an analysis of shell-model calculations, allow us to discuss the main features of excited states expected for the next N =53 isotone, 83Zn.

  1. β-decay of neutron-rich Zâ¼60 nuclei and the origin of rare earth elements

    NASA Astrophysics Data System (ADS)

    Wu, J.; Nishimura, S.; Lorusso, G.; Xu, Z. Y.; Baba, H.; Browne, F.; Daido, R.; Doornenbal, P.; Fang, Y. F.; Ideguchi, E.; Isobe, T.; Li, Z.; Patel, Z.; Rice, S.; Simpson, G.; Sinclair, L.; Söderström, P. A.; Sumikama, T.; Watanabe, H.; Yagi, A.; Yokoyama, R.; Aoi, N.; Garrote, F. L. Bello; Benzoni, G.; Gey, G.; Gottardo, A.; Nishibata, H.; Odahara, A.; Sakurai, H.; Tanaka, M.; Taprogge, J.; Yamamoto, T.; Eurica Collaboration

    2014-05-01

    A large fraction of the rare-earth elements observed in the solar system is produced in the astrophysical rapid neutron capture process (r-process). However, current stellar models cannot completely explain the relative abundance of these elements partially because of nuclear physics uncertainties. To address this problem, a β-decay spectroscopy experiment was performed at RI Beam Factory (RIBF) at RIKEN, aimed at studying a wide range of very neutron-rich nuclei with Z˜60 that are progenitors of the rare-earth elements with mass number A˜460. The experiment provides a test of nuclear models as well as experimental inputs for r-process calculations. This contribution presents the experimental setup and some preliminary results of the experiment.

  2. -decay measurements for N > 40 Mn nuclei and inference of collectivity for neutron-rich Fe isotopes

    SciTech Connect

    Daugas, J; Delaroche, J. P.; Pfutzner, M.; Sawicka, M.; Becker, F.; Belier, G.; Bingham, C. R.; Borcea, C.; Bouchez, E.; Buta, A.; Dragulescu, E.; Georgiev, G.; Giovinazzo, J.; Grawe, H.; Grzywacz, R.; Hammache, F.; Libert, J.; Meot, V.; Negoita, F.; de Oliveira Santos, F.; Perru, O.; Roig, O.; Rykaczewski, Krzysztof Piotr; Saint-Laurent, M. G.; Sauvestre, J. E.; Sorlin, O.; Stanoiu, M.; Stefan, I.; Theisen, Ch.

    2011-01-01

    A decay spectroscopic study of the neutron-rich isotopes has been performed using fragmentation of a 86Kr primary beam. Fragments from this reaction have been selected by the LISE2000 spectrometer at the Grand Acc el erateur National d Ions Lourds (GANIL). Half-lives of 29 isotopes, including the first ones identified for 61Ti (15 4 ms), 64V (19 8 ms), and 71Fe (28 5 ms), have been determined and compared with model predictions. 67,68Mn -delayed rays were observed for the first time. The branching for the -delayed neutron emission was measured to be greater than 10(5)% in the 67Mn decay. The 67Fe isomeric level is firmly determined at higher energy than assigned in previous works. The excitation energies of the first (2+) and (4+) states of 68Fe are suggested to lie at 522(1) and 1389(1) keV, respectively, thus bringing confirmation of assignments based on in-beam -ray spectroscopy. Beyond-mean-field calculations with the Gogny D1S force have been performed for even-mass nuclei through the Fe isotopic chain. Not only 68Fe but most of the neutron-rich Fe isotopes with neutron numbers below N = 50 are interpreted as soft rotors. The calculated mean occupancy of the neutron g9/2 and d5/2 orbitals in correlated ground states is steadily growing with increasing neutron number throughout the isotopic chain. Interpretation of 67Fe data is based upon the present calculations for the 66Fe and 68Fe even cores.

  3. Nucleosynthesis of neutron-rich heavy nuclei during explosive helium burning in massive stars

    NASA Technical Reports Server (NTRS)

    Blake, J. B.; Woosley, S. E.; Weaver, T. A.; Schramm, D. N.

    1981-01-01

    The production of heavy nuclei during explosive helium burning has been calculated using a hydrodynamical model of a 15-solar mass (Type II) supernova and an n-process nuclear reaction network. It is found that the resulting neutron-rich heavy nuclei are not produced in the relative abundances of solar-system r-process material, especially in the vicinity of Pt, nor are any actinides produced. These deficiencies reflect an inadequate supply of neutrons. However, some neutron-rich isotopes, normally associated with the r-process, are produced which may be significant for the production of isotopic anomalies in meteorites.

  4. From laser particle acceleration to the synthesis of extremely neutron rich isotopes via the novel fission-fusion mechanism

    NASA Astrophysics Data System (ADS)

    Thirolf, P. G.

    2015-02-01

    High-power, short pulse lasers have emerged in the last decade as attractive tools for accelerating charged particles (electrons, ions) to high energies over mm-scale acceleration lengths, thus promising to rival conventional acceleration techniques in the years ahead. In the first part of the article, the principles of laser-plasma interaction as well as the techniques and the current status of the acceleration of electron and ion beams will be briefly introduced. In particular with the upcoming next generation of multi-PW class laser systems, such as the one under construction for the ELI-Nuclear Physics project in Bucharest (ELI-NP), very efficient acceleration mechanisms for brilliant ion beams like radiation pressure acceleration (RPA) come into reach. Here, ultra-dense ion beams reaching solid-state density can be accelerated from thin target foils, exceeding the density of conventionally accelerated ion beams by about 14 orders of magnitude. This unique property of laser-accelerated ion beams can be exploited to explore the scenario of a new reaction mechanism called `fission-fusion', which will be introduced in the second part of the article. Accelerating fissile species (e.g. 232Th ) towards a second layer of the same material will lead to fission both of the beam-like and target-like particles. Due to the close to solid-state density of the accelerated ion bunches, fusion may occur between neutron-rich (light) fission products. This may open an access path towards extremely neutron-rich nuclides in the vicinity of the N=126 waiting point of the astrophysical r process. `Waiting points' at closed nucleon shells play a crucial role in controlling the reaction rates. However, since most of the pathway of heavy-element formation via the rapid-neutron capture process (r-process) runs in `terra incognita' of the nuclear landscape, in particular the waiting point at N=126 is yet unexplored and will remain largely inaccessible to conventional nuclear reaction

  5. From laser particle acceleration to the synthesis of extremely neutron rich isotopes via the novel fission-fusion mechanism

    SciTech Connect

    Thirolf, P. G.

    2015-02-24

    High-power, short pulse lasers have emerged in the last decade as attractive tools for accelerating charged particles (electrons, ions) to high energies over mm-scale acceleration lengths, thus promising to rival conventional acceleration techniques in the years ahead. In the first part of the article, the principles of laser-plasma interaction as well as the techniques and the current status of the acceleration of electron and ion beams will be briefly introduced. In particular with the upcoming next generation of multi-PW class laser systems, such as the one under construction for the ELI-Nuclear Physics project in Bucharest (ELI-NP), very efficient acceleration mechanisms for brilliant ion beams like radiation pressure acceleration (RPA) come into reach. Here, ultra-dense ion beams reaching solid-state density can be accelerated from thin target foils, exceeding the density of conventionally accelerated ion beams by about 14 orders of magnitude. This unique property of laser-accelerated ion beams can be exploited to explore the scenario of a new reaction mechanism called ‘fission-fusion’, which will be introduced in the second part of the article. Accelerating fissile species (e.g. {sup 232}Th) towards a second layer of the same material will lead to fission both of the beam-like and target-like particles. Due to the close to solid-state density of the accelerated ion bunches, fusion may occur between neutron-rich (light) fission products. This may open an access path towards extremely neutron-rich nuclides in the vicinity of the N=126 waiting point of the astrophysical r process. ‘Waiting points’ at closed nucleon shells play a crucial role in controlling the reaction rates. However, since most of the pathway of heavy-element formation via the rapid-neutron capture process (r-process) runs in ‘terra incognita’ of the nuclear landscape, in particular the waiting point at N=126 is yet unexplored and will remain largely inaccessible to conventional

  6. Calibrations for studies of neutron-rich precursor fragments

    NASA Astrophysics Data System (ADS)

    Mazza, Maria; Parkhurst, Rachel; Wilensky, Samuel; Mosby, Michelle; Stephenson, Sharon; Rogers, Warren; MoNA Collaboration Collaboration

    2015-10-01

    Heavy ion collisions at relativistic energies produce the radioactive beams used at nuclear structure facilities worldwide. However, there are still unanswered questions about the reaction mechanism of projectile fragmentation and the specific roles that ablation, evaporation, and abrasion play. Using the projectile fragmentation of a 32Mg beam at 86 MeV/u on a natural Beryllium target at the National Superconducting Cyclotron Laboratory (NSCL), our experimental goal is to better understand the excitation energy and the momentum distribution of the precursors of the observed final fragments (neon, sodium, and fluorine). A suite of charged particle detectors in conjunction with the Modular Neutron Array (MoNA) allows us to analyze both the charged final fragments as well as the coincident neutrons. Detector calibration results and preliminary results will be presented. This material is based upon work supported by the National Science Foundation under Grants PHY-1205537.

  7. Shell And Halo Structure In Neutron-Rich Light Nuclei

    SciTech Connect

    Nociforo, C.

    2010-06-01

    Spectroscopic investigations performed at the neutron drip line in case of sd shell nuclei have recently shown the existence of the new magic numbers Z = 8 and N = 14,16. Predictions within the nuclear shell model calculations for the {sup 23,24}O ground state have been confirmed measuring their neutron occupancy in breakup reactions performed by using the inflight radioactive ion beams produced at the Fragment Separator FRS of GSI. Some perspectives of studying the evolution of magic numbers in this region of light exotic nuclei are given.

  8. Improved mass resolution and mass accuracy in TOF-SIMS spectra and images using argon gas cluster ion beams.

    PubMed

    Shon, Hyun Kyong; Yoon, Sohee; Moon, Jeong Hee; Lee, Tae Geol

    2016-06-01

    The popularity of argon gas cluster ion beams (Ar-GCIB) as primary ion beams in time-of-flight secondary ion mass spectrometry (TOF-SIMS) has increased because the molecular ions of large organic- and biomolecules can be detected with less damage to the sample surfaces. However, Ar-GCIB is limited by poor mass resolution as well as poor mass accuracy. The inferior quality of the mass resolution in a TOF-SIMS spectrum obtained by using Ar-GCIB compared to the one obtained by a bismuth liquid metal cluster ion beam and others makes it difficult to identify unknown peaks because of the mass interference from the neighboring peaks. However, in this study, the authors demonstrate improved mass resolution in TOF-SIMS using Ar-GCIB through the delayed extraction of secondary ions, a method typically used in TOF mass spectrometry to increase mass resolution. As for poor mass accuracy, although mass calibration using internal peaks with low mass such as hydrogen and carbon is a common approach in TOF-SIMS, it is unsuited to the present study because of the disappearance of the low-mass peaks in the delayed extraction mode. To resolve this issue, external mass calibration, another regularly used method in TOF-MS, was adapted to enhance mass accuracy in the spectrum and image generated by TOF-SIMS using Ar-GCIB in the delayed extraction mode. By producing spectra analyses of a peptide mixture and bovine serum albumin protein digested with trypsin, along with image analyses of rat brain samples, the authors demonstrate for the first time the enhancement of mass resolution and mass accuracy for the purpose of analyzing large biomolecules in TOF-SIMS using Ar-GCIB through the use of delayed extraction and external mass calibration. PMID:26861497

  9. Theoretical study of triaxial shapes of neutron-rich Mo and Ru nuclei

    NASA Astrophysics Data System (ADS)

    Zhang, C. L.; Bhat, G. H.; Nazarewicz, W.; Sheikh, J. A.; Shi, Yue

    2015-09-01

    Background: Whether atomic nuclei can possess triaxial shapes at their ground states is still a subject of ongoing debate. According to theory, good prospects for low-spin triaxiality are in the neutron-rich Mo-Ru region. Recently, transition quadrupole moments in rotational bands of even-mass neutron-rich isotopes of molybdenum and ruthenium nuclei have been measured. The new data have provided a challenge for theoretical descriptions invoking stable triaxial deformations. Purpose: To understand experimental data on rotational bands in the neutron-rich Mo-Ru region, we carried out theoretical analysis of moments of inertia, shapes, and transition quadrupole moments of neutron-rich even-even nuclei around 110Ru using self-consistent mean-field and shell model techniques. Methods: To describe yrast structures in Mo and Ru isotopes, we use nuclear density functional theory (DFT) with the optimized energy density functional UNEDF0. We also apply triaxial projected shell model (TPSM) to describe yrast and positive-parity, near-yrast band structures. Results: Our self-consistent DFT calculations predict triaxial ground-state deformations in Mo,108106 and 108,110,112Ru and reproduce the observed low-frequency behavior of moments of inertia. As the rotational frequency increases, a negative-γ structure, associated with the aligned ν (h11/2) 2 pair, becomes energetically favored. The computed transition quadrupole moments vary with angular momentum, which reflects deformation changes with rotation; those variations are consistent with experiment. The TPSM calculations explain the observed band structures assuming stable triaxial shapes. Conclusions: The structure of neutron-rich even-even nuclei around 110Ru is consistent with triaxial shape deformations. Our DFT and TPSM frameworks provide a consistent and complementary description of experimental data.

  10. Strong enhancement of dynamical emission of heavy fragments in the neutron-rich {sup 124}Sn+{sup 64}Ni reaction at 35A MeV

    SciTech Connect

    Russotto, P.; Amorini, F.; Cavallaro, S.; Di Toro, M.; Giustolisi, F.; Porto, F.; Rizzo, F.; De Filippo, E.; Pagano, A.; Cardella, G.; Lanzano, G.; Papa, M.; Pirrone, S.; Piasecki, E.; Auditore, L.; Trifiro, A.; Trimarchi, M.

    2010-06-15

    A quantitative comparison is made between the absolute cross sections associated with statistical and dynamical emission of heavy fragments in the {sup 124}Sn+{sup 64}Ni and {sup 112}Sn+{sup 58}Ni collisions experimentally investigated at 35A MeV beam energy using the multidetector CHIMERA. The result shows that the dynamical process is about twice as probable in the neutron-rich {sup 124}Sn+{sup 64}Ni system as in the {sup 112}Sn+{sup 58}Ni neutron-poor one. This unexpected and significant difference indicates that the reaction mechanism is strongly dependent on the entrance-channel isospin (N/Z) content.

  11. Beta Decay Study of Neutron-rich Magnesium

    NASA Astrophysics Data System (ADS)

    Ash, John; Rajabali, Mustafa; Griffin Collaboration

    2015-10-01

    Within the ``island of inversion'' around the N = 20 shell gap, isotopes of magnesium, and aluminum deviate from the expected closed-shell structure. Particles promoted across the N = 20 shell gap result in a lower energy deformed ground state configuration rather than the expected spherical configuration. An experiment was conducted at TRIUMF laboratory in the summer of 2015 to study the decay of ``island of inversion'' isotopes 33 , 34 , 35Mg and the structure of the respective daughter nuclei. The isotopes of interest were produced by a proton beam from TRIUMF's 500 MeV cyclotron impacting on a UCx target. The magnesium decays populated states along the decay chain in Al, Si, P, and S isotopes. The new GRIFFIN spectrometer in the ISAC-I facility was used to detect the gamma rays. Two sets of scintillators, one for detecting the beta particles (SCEPTAR) and the other for detecting beta-delayed neutrons (DESCANT), were also used in conjunction with GRIFFIN. The GRIFFIN data were energy calibrated and partially analyzed for this project. New algorithms were developed for the analysis. Preliminary results for new transitions detected in 34Mg as well as the half lives obtained will be presented in their current form. This research was supported by the Tennessee Tech research office.

  12. Production of heavy neutron-rich nuclei in transfer reactions within the dinuclear system model

    NASA Astrophysics Data System (ADS)

    Zhu, Long; Feng, Zhao-Qing; Zhang, Feng-Shou

    2015-08-01

    The dynamics of nucleon transfer processes in heavy-ion collisions is investigated within the dinuclear system model. The production cross sections of nuclei in the reactions 136Xe+208Pb and 238U+248Cm are calculated, and the calculations are in good agreement with the experimental data. The transfer cross sections for the 58Ni+208Pb reaction are calculated and compared with the experimental data. We predict the production cross sections of neutron-rich nuclei 165-168 Eu, 169-173 Tb, 173-178 Ho, and 181-185Yb based on the reaction 176Yb+238U. It can be seen that the production cross sections of the neutron-rich nuclei 165Eu, 169Tb, 173Ho, and 181Yb are 2.84 μb, 6.90 μb, 46.24 μb, and 53.61 μb, respectively, which could be synthesized in experiment.

  13. Three-body force effect on the properties of neutron-rich nuclear matter

    NASA Astrophysics Data System (ADS)

    Zuo, Wei; Bombarci, Ignazio; Lombardo, Umberto

    2016-05-01

    We review our research work in recent years on the properties of neutron-rich nuclear matter within the framework of the Brueckner theory extended to include a microscopic three-body force (TBF). We discuss specially the TBF effect on the equation of state and the singleparticle (s.p.) potentials. The TBF turns out to be crucial for describing the saturation properties of nuclear matter in nonrelativistic microscopic framework. The TBF effect on the EOS of neutron-rich nuclear matter is to result in a significant stiffening of its isovector part at supra-saturation densities. Within the Brueckner approach, the TBF may lead to a rearrangement contribution to the s.p. potentials, which enhances strongly the repulsion and momentum-dependence of the s.p. potentials at high densities and high momenta. Our results are also compared with the predictions by other ab initio approaches.

  14. Production of heavy and superheavy neutron-rich nuclei in transfer reactions

    SciTech Connect

    Zagrebaev, V. I.; Greiner, Walter

    2011-04-15

    The problem of production and study of heavy neutron-rich nuclei has been intensively discussed during recent years. Many reasons arouse a great interest in this problem. The present limits of the upper part of the nuclear map are very close to the {beta} stability line while the unexplored area of heavy neutron-rich nuclides (also those located along the neutron closed shell N=126 to the right-hand side of the stability line) is extremely important for nuclear astrophysic investigations and, in particular, for the understanding of the r process of astrophysical nucleogenesis. For elements with Z>100 only neutron deficient isotopes (located to the left of the stability line) have been synthesized so far. The 'northeast' area of the nuclear map can be reached neither in fusion-fission reactions nor in fragmentation processes widely used nowadays for the production of new nuclei. Multinucleon transfer processes in near barrier collisions of heavy (and very heavy, U-like) ions seem to be the only reaction mechanism allowing us to produce and explore neutron-rich heavy nuclei including those located at the superheavy island of stability. In this paper several transfer reactions for different projectile-target combinations are studied in detail. Besides the predictions for the cross sections of such processes, we also analyze the angular and energy distributions of primary and survived reaction products in the laboratory frame. These results, as well as predicted excitation functions for the yields of neutron-rich superheavy isotopes, might be useful for the design of appropriate experimental equipment and for carrying out experiments of such kind.

  15. Reflection Asymmetric Shapes in the Neutron-Rich 140,143Ba Isotopes

    NASA Astrophysics Data System (ADS)

    Zhu Sheng-jiang (S, J. Zhu; Wang, Mu-ge; J, H. Hamilton; A, V. Ramayya; B, R. S. Babu; W, C. Ma; Long, Gui-lu; Deng, Jing-kang; Zhu, Ling-yan; Li, Ming; T, N. Ginter; J, Komicki; J, D. Cole; R, Aryaeinejad; Y, K. Dardenne; M, W. Drigert; J, O. Rasmussen; Ts, Yu Oganessian; M, A. Stoyer; S, Y. Chu; K, E. Gregorich; M, F. Mohar; S, G. Prussin; I, Y. Lee; N, R. Johnson; F, K. McGowan

    1997-08-01

    Level schemes for the neutron-rich 140,143Ba nuclei have been determined by study of prompt γ-rays in spontaneous fission of 252Cf. The level pattern and enhanced E1 transitions between π = + and π = - bands show reflection asymmetric shapes with simplex quantum number s = +1 in 140Ba and s = ±i in 143Ba, respectively. The octupole deformation stability with spin variation has been discussed.

  16. Medium-spin states of the neutron-rich 87,89Br isotopes: configurations and shapes

    NASA Astrophysics Data System (ADS)

    Nyakó, B. M.; Timár, J.; Csatlós, M.; Dombrádi, Zs; Krasznahorkay, A.; Kuti, I.; Sohler, D.; Tornyi, T. G.; Czerwiński, M.; Rząca-Urban, T.; Urban, W.; Bączyk, P.; Atanasova, L.; Balabanski, D. L.; Sieja, K.; Blanc, A.; Jentschel, M.; Köster, U.; Mutti, P.; Soldner, T.; de France, G.; Simpson, G. S.; Ur, C. A.

    2016-06-01

    Medium-spin excited states of the neutron-rich 87Br and 89Br nuclei were observed and studied for the first time. They were populated in fission of 235U induced by the cold-neutron beam of the PF1B facility of the Institut Laue-Langevin, Grenoble. The measurement of γ radiation following fission has been performed using the EXILL array of Ge detectors. The observed level schemes were compared with results of large valence space shell model calculations. Both medium-spin level schemes consist of band-like structures, which can be understood as bands built on the πf 5/2, πp 3/2 and πg 9/2 configurations. Both nuclei have 5/2‑ ground state spin-parity contrary to the odd-mass Br isotopes containing fewer neutrons, which have 3/2‑ ground state spin-parity. On the basis of the properties of the πg 9/2 decoupled bands the deformations of the 87Br and 89Br fit to the systematics of nuclei in the region. 87Br is close to the vibrational limit, while 89Br is more rotational.

  17. New results from isochronous mass measurements of neutron-rich uranium fission fragments with the FRS-ESR-facility at GSI

    NASA Astrophysics Data System (ADS)

    Knöbel, R.; Diwisch, M.; Geissel, H.; Litvinov, Yu. A.; Patyk, Z.; Plaß, W. R.; Scheidenberger, C.; Sun, B.; Weick, H.; Bosch, F.; Boutin, D.; Chen, L.; Dimopoulou, C.; Dolinskii, A.; Franczak, B.; Franzke, B.; Hausmann, M.; Kozhuharov, C.; Kurcewicz, J.; Litvinov, S. A.; Matoš, M.; Mazzocco, M.; Münzenberg, G.; Nakajima, S.; Nociforo, C.; Nolden, F.; Ohtsubo, T.; Ozawa, A.; Stadlmann, J.; Steck, M.; Suzuki, T.; Walker, P. M.; Winkler, M.; Yamaguchi, T.

    2016-05-01

    Masses of uranium fission fragments have been measured with the FRagment Separator (FRS) combined with the Experimental Storage Ring (ESR) at GSI. A 410-415 MeV/u 238U projectile beam was fast extracted from the synchrotron SIS-18 with an average intensity of 109/spill. The projectiles were focused on a 1g/cm2 beryllium target at the entrance of the FRS to create neutron-rich isotopes via abrasion-fission. The fission fragments were spatially separated with the FRS and injected into the isochronous storage ring ESR for fast mass measurements without applying cooling. The Isochronous Mass Spectrometry (IMS) was performed under two different experimental conditions, with and without B ρ-tagging at the high-resolution dispersive central focal plane of the FRS. The evaluation has been done for the combined data sets from both experiments with a new method of data analysis. The use of a correlation matrix has provided experimental mass values for 23 different neutron-rich isotopes for the first time and 6 masses with improved values. The new masses were obtained for nuclides in the element range from Se to Ce. The applied analysis has given access even to rare isotopes detected with an intensity of a few atoms per week. The novel data analysis and systematic error determination are described and the results are compared with extrapolations of experimental values and theoretical models.

  18. The study of neutron-rich nuclei production in the region of the closed shell N=126 in the multi-nucleon transfer reaction 136Xe+208Pb

    NASA Astrophysics Data System (ADS)

    Novikov, K.; Harca, I. M.; Kozulin, E. M.; Dmitriev, S.; Itkis, J.; Knyazheva, G.; Loktev, T.; Corradi, L.; Valiente-Dobon, J.; Fioretto, E.; Montanari, D.; Stefanini, A. M.; Vardaci, E.; Quero, D.; Montagnoli, G.; Scarlassara, F.; Strano, E.; Pollarolo, G.; Piot, J.; Mijatović, T.; Szilner, S.; Ackermann, D.; Chubarian, G.; Trzaska, W. H.

    2016-04-01

    The unexplored area of heavy neutron rich nuclei is extremely important for nuclear astrophysics investigations and, in particular, for the understanding of the r-process of astrophysical nucleogenesis. For the production of heavy neutron rich nuclei located along the neutron closed shell N=126 (probably the last "waiting point" in the r-process of nucleosynthesis) the low-energy multi-nucleon transfer reaction 136Xe+208Pb at Elab=870MeV was explored. Due to the stabilizing effect of the closed neutron shells in both nuclei, N=82 and N=126, and the rather favorable proton transfer from lead to xenon, the light fragments formed in this process are well bound and the Q-value of the reaction is nearly zero. Measurements were performed with the PRISMA spectrometer in coincidence with an additional time-of-flight (ToF) arm on the +20 beam line of the PIAVE-ALPI accelerator in Legnaro, Italy. The PRISMA spectrometer allows identification of the A, Z and velocity of the projectile-like fragments (PLF), while the second arm gives access to the target-like fragments (TLF). Details on the experimental setup and preliminary results are reported.

  19. On-line experimental results of an argon gas cell-based laser ion source (KEK Isotope Separation System)

    NASA Astrophysics Data System (ADS)

    Hirayama, Y.; Watanabe, Y. X.; Imai, N.; Ishiyama, H.; Jeong, S. C.; Jung, H. S.; Miyatake, H.; Oyaizu, M.; Kimura, S.; Mukai, M.; Kim, Y. H.; Sonoda, T.; Wada, M.; Huyse, M.; Kudryavtsev, Yu.; Van Duppen, P.

    2016-06-01

    KEK Isotope Separation System (KISS) has been developed at RIKEN to produce neutron rich isotopes with N = 126 to study the β -decay properties for application to astrophysics. The KISS is an element-selective mass-separation system which consists of an argon gas cell-based on laser ion source for atomic number selection and an ISOL mass-separation system. The argon gas cell of KISS is a key component to stop and collect the unstable nuclei produced in a multi-nucleon transfer reaction, where the isotopes of interest will be selectively ionized using laser resonance ionization. We have performed off- and on-line experiments to study the basic properties of the gas cell as well as of the KISS. We successfully extracted the laser-ionized stable 56Fe (direct implantation of a 56Fe beam into the gas cell) atoms and 198Pt (emitted from the 198Pt target by elastic scattering with a 136Xe beam) atoms from the KISS during the commissioning on-line experiments. We furthermore extracted laser-ionized unstable 199Pt atoms and confirmed that the measured half-life was in good agreement with the reported value.

  20. Production of unknown neutron-rich isotopes in 238U collisions at near-barrier energy

    NASA Astrophysics Data System (ADS)

    Zhao, Kai; Li, Zhuxia; Zhang, Yingxun; Wang, Ning; Li, Qingfeng; Shen, Caiwan; Wang, Yongjia; Wu, Xizhen

    2016-08-01

    The production cross sections for primary and residual fragments with charge number from Z =70 to 120 produced in the collision of 238U at 7.0 MeV/nucleon are calculated by the improved quantum molecular dynamics (ImQMD) model incorporated with the statistical evaporation model (hivap code). The calculation results predict that about 60 unknown neutron-rich isotopes from elements Ra (Z =88 ) to Db (Z =105 ) can be produced with the production cross sections above the lower bound of 10-8 mb in this reaction. And almost all of the unknown neutron-rich isotopes are emitted at the laboratory angles θlab≤60°. Two cases, i.e., the production of the unknown uranium isotopes with A ≥244 and that of rutherfordium with A ≥269 , are investigated to understand the production mechanism of unknown neutron-rich isotopes. It is found that for the former case the collision time between two uranium nuclei is shorter and the primary fragments producing the residues have smaller excitation energies of ≤30 MeV and the outgoing angles of those residues cover a range of 30°-60°. For the latter case, a longer collision time is needed for a large number of nucleons being transferred and thus it results in higher excitation energies and smaller outgoing angles of primary fragments, and eventually results in a very small production cross section for the residues of Rf with A ≥269 which have a small interval of outgoing angles of θlab=40°-50°.

  1. β-decay properties of neutron-rich Zr and Mo isotopes

    NASA Astrophysics Data System (ADS)

    Sarriguren, P.; Pereira, J.

    2010-06-01

    Gamow-Teller strength distributions, β-decay half-lives, and β-delayed neutron emission are investigated in neutron-rich Zr and Mo isotopes within a deformed quasiparticle random-phase approximation. The approach is based on a self-consistent Skyrme Hartree-Fock mean field with pairing correlations and residual separable particle-hole and particle-particle forces. Comparison with recent measurements of half-lives stresses the important role that nuclear deformation plays in the description of β-decay properties in this mass region.

  2. High-accuracy mass measurements of neutron-rich Kr isotopes

    SciTech Connect

    Delahaye, P.; Kellerbauer, A.; Audi, G.; Lunney, D.; Blaum, K.; George, S.; Carrel, F.; Herfurth, F.; Yazidjian, C.; Herlert, A.; Schweikhard, L.; Kluge, H.-J.

    2006-09-15

    The atomic masses of the neutron-rich krypton isotopes {sup 84,86-95}Kr have been determined with the tandem Penning trap mass spectrometer ISOLTRAP with uncertainties ranging from 20 to 220 ppb. The masses of the short-lived isotopes {sup 94}Kr and {sup 95}Kr were measured for the first time. The masses of the radioactive nuclides {sup 89}Kr and {sup 91}Kr disagree by 4 and 6 standard deviations, respectively, from the present Atomic-Mass Evaluation database. The resulting modification of the mass surface with respect to the two-neutron separation energies as well as implications for mass models and stellar nucleosynthesis are discussed.

  3. One-phonon isovector 2(1,MS)(+) state in neutron-rich nucleus (132)Te

    SciTech Connect

    Danchev, M.; Rainovski, G.; Gladnishki, K. A.; Pietralla, N.; Ponomarev, V. Yu; Scheck, M.; Wambach, J.; Pietralla, N.; Gargano, A.; Covello, A.; Baktash, Cyrus; Beene, James R; Galindo-Uribarri, Alfredo {nmn}; Gross, Carl J; Radford, David C; Yu, Chang-Hong; Bingham, C. R.; Riedinger, L. L.; Stuchbery, Andrew E; Zamfir, Nicolae Victor

    2011-01-01

    The 2{sub 2}{sup +} state in {sup 132}Te is identified as the one-phonon mixed-symmetry state in a projectile Coulomb excitation experiment presenting a firm example of a mixed-symmetry state in unstable, neutron-rich nuclei. The results of shell-model calculations based on the low-momentum interaction V{sub low-k} are in good agreement with experiment demonstrating the ability of the effective shell-model interaction to produce states of mixed-symmetry character.

  4. Thermal effects on the Fission Barrier of neutron-rich nuclei

    SciTech Connect

    Minato, Futoshi; Hagino, Kouichi

    2008-11-11

    We discuss the fission barrier height of neutron-rich nuclei in a r-process site at highly excited state, which is resulted from the beta-decay or the neutron-capture processes. We particularly investigate the sensitivity of the fission barrier height to the temperature, including the effect of pairing phase transition from superfluid to normal fluid phases. To this end, we use the finite-temperature Skyrme-Hartree-Fock-Bogolubov method with a zero-range pairing interaction. We also discuss the temperature dependence of the fission decay rate.

  5. Neutron Rich Nuclei in a New Binding Energy Formula and the Astrophysical r-PROCESS

    NASA Astrophysics Data System (ADS)

    Lahiri, Chirashree; Gangopadhyay, G.

    Neutron rich nuclei has been studied with a new phenomenological mass formula. Predictions of different mass formulas for the location of the neutron drip line are compared with those from the present calculation. The implications of the new mass formula for r-process nucleosynthesis are discussed. It is found that though the neutron drip line obtained from this formula differs substantially from other formulas, the r-process abundance upto mass 200 are unlikely to be significantly different. The errors inherent in the mass formula are found to play an insignificant role beyond mass A = 80.

  6. Decay of the neutron-rich isotope 171Ho and the identification of 169Dy

    NASA Astrophysics Data System (ADS)

    Chasteler, R. M.; Nitschke, J. M.; Firestone, R. B.; Vierinen, K. S.; Wilmarth, P. A.

    1990-10-01

    Neutron-rich rare-earth isotopes were produced in multinucleon transfer reactions between 170Er ions and natW targets. On-line mass separation was used together with β- and γ-ray spectroscopy in these studies. At mass A=169, the heaviest known dysprosium isotope, 39(8) s,169Dy, was identified. It was observed to β- decay to the ground state of 169Ho or through a level at 1578 keV. In the A=171 mass chain, a partial decay scheme for 55(3)-s 171Ho was determined.

  7. Shell-model study for neutron-rich sd-shell nuclei

    SciTech Connect

    Kaneko, Kazunari; Sun Yang; Mizusaki, Takahiro; Hasegawa, Munetake

    2011-01-15

    The microscopic structure of neutron-rich sd-shell nuclei is investigated by using the spherical-shell model in the sd-pf valence space with the extended pairing plus quadrupole-quadrupole forces accompanied by the monopole interaction (EPQQM). The calculation reproduces systematically the known energy levels for even-even and odd-mass nuclei including the recent data for {sup 43}S, {sup 46}S, and {sup 47}Ar. In particular, the erosion of the N=28 shell closure in {sup 42}Si can be explained. Our EPQQM results are compared with other shell-model calculations with the SDPF-NR and SDPF-U effective interactions.

  8. Structure of Light Neutron-Rich Nuclei around N = 14 Using Quasi-Free Scattering

    NASA Astrophysics Data System (ADS)

    Alvarez-Pol, Héctor; Díaz-Fernández, Paloma; Cortina-Gil, Dolores; Caamaño, Manuel; Fernández-Domínguez, Beatriz; Mostazo, Magdalena; Pietras, Ben; Beceiro-Novo, Saul; Benlliure, José; Casarejos, Enrique; Alcántara, Juan

    Light neutron-rich nuclei around N = 14 (23O, 22O and 21N) have been for the first time investigated using quasi-free scattering (p,2p) and (p,pn) reactions at the LAND/R3B setup at GSI (Darmstadt, Germany). The inclusive cross sections and the momentum distributions have been measured in inverse kinematics at relativistic energies, supporting previous observations of the existence of a change of the structure of these nuclei when we move from N = 14 to 15 (from 0d5/2 shell to the 1s1/2).

  9. Ground-state configuration of neutron-rich Aluminum isotopes through Coulomb Breakup

    NASA Astrophysics Data System (ADS)

    Chakraborty, S.; Datta Pramanik, U.; Aumann, T.; Beceiro, S.; Boretzky, K.; Caesar, C.; Carlson, B. V.; Catford, W. N.; Chatterjee, S.; Chartier, M.; Cortina-Gil, D.; De Angelis, G.; Gonzalez-Diaz, D.; Emling, H.; Diaz Fernandez, P.; Fraile, L. M.; Ershova, O.; Geissel, H.; Heil, M.; Jonson, B.; Kelic, A.; Johansson, H.; Kruecken, R.; Kroll, T.; Kurcewicz, J.; Langer, C.; Le Bleis, T.; Leifels, Y.; Munzenberg, G.; Marganiec, J.; Nociforo, C.; Najafi, A.; Panin, V.; Paschalis, S.; Pietri, S.; Plag, R.; Rahaman, A.; Reifarth, R.; Ricciardi, V.; Rossi, D.; Ray, J.; Simon, H.; Scheidenberger, C.; Typel, S.; Taylor, J.; Togano, Y.; Volkov, V.; Weick, H.; Wagner, A.; Wamers, F.; Weigand, M.; Winfield, J. S.; Yakorev, D.; Zoric, M.

    2014-03-01

    Neutron-rich 34,35Al isotopes have been studied through Coulomb excitation using LAND-FRS setup at GSI, Darmstadt. The method of invariant mass analysis has been used to reconstruct the excitation energy of the nucleus prior to decay. Comparison of experimental CD cross-section with direct breakup model calculation with neutron in p3/2 orbital favours 34Al(g.s)⊗νp3/2 as ground state configuration of 35Al. But ground state configuration of 34Al is complicated as evident from γ-ray spectra of 33Al after Coulomb breakup of 34Al.

  10. Collective properties of neutron-rich Ru, Pd, and Cd isotopes

    NASA Astrophysics Data System (ADS)

    Wang, Y. B.; Rissanen, J.

    2014-01-01

    Collective properties of neutron-rich Ru, Pd, and Cd isotopes are reviewed, combining the original results from the IGISOL β-decay experiments with recent experimental and theoretical progress. The transitional nature of Ru and Pd nuclei is discussed via the low-lying level systematics, including the low-lying 0 + states. Although the role of an anharmonic quadrupole vibrator in Cd nuclei was recently questioned, level systematics for the three-phonon quintuplet in 116,118,120Cd are presented, and an outlook of the spectroscopic methods for the level lifetime or B( E2) values is given.

  11. Gamow-Teller strength distributions for neutron-rich nitrogen, oxygen and fluorine isotopes

    NASA Astrophysics Data System (ADS)

    Zhang, Yu-Mei

    2016-08-01

    Gamow-Teller transition properties for neutron-rich nitrogen, oxygen and fluorine isotopes are studied in integrated energy. The structures of these nuclei are described by means of nuclear shell model with the WBT interaction in the p-sd shell space. Calculations of the Gamow-Teller strength distribution reproduce the experimental data reasonably in the low-energy region. For the dripline nucleus 24O, a super Gamow-Teller transition to a single state at excitation energy of 14.72 MeV in 24F is predicted. β-decay half-lives for these nuclei are calculated and compared with the available experimental data.

  12. Monopole Modes of Excitation in Deformed Neutron-rich Mg Isotopes

    SciTech Connect

    Yoshida, Kenichi

    2009-08-26

    The giant monopole resonance (GMR) and the low-frequency mode of monopole excitation in neutron-rich magnesium isotopes close to the drip line are investigated by means of the deformed Hartree-Fock-Bogoliubov and quasiparticle random-phase approximations. It is found that the GMR has a two-peak structure due to the deformation. The lower-energy resonance is generated associated with the coupling to the K{sup p}i = 0{sup +} component of the giant quadrupole resonance. Besides the GMR, we obtain the soft K{sup p}i = 0{sup +} mode below the neutron emission threshold energy.

  13. β-decay studies of neutron-rich Tl, Pb, and Bi isotopes

    NASA Astrophysics Data System (ADS)

    Morales, A. I.; Benzoni, G.; Gottardo, A.; Valiente-Dobón, J. J.; Blasi, N.; Bracco, A.; Camera, F.; Crespi, F. C. L.; Corsi, A.; Leoni, S.; Million, B.; Nicolini, R.; Wieland, O.; Gadea, A.; Lunardi, S.; Górska, M.; Regan, P. H.; Podolyák, Zs.; Pfützner, M.; Pietri, S.; Boutachkov, P.; Weick, H.; Grebosz, J.; Bruce, A. M.; Núñez, J. Alcántara; Algora, A.; Al-Dahan, N.; Ayyad, Y.; Alkhomashi, N.; Allegro, P. R. P.; Bazzacco, D.; Benlliure, J.; Bowry, M.; Bunce, M.; Casarejos, E.; Cortes, M. L.; Bacelar, A. M. Denis; Deo, A. Y.; de Angelis, G.; Domingo-Pardo, C.; Doncel, M.; Dombradi, Zs.; Engert, T.; Eppinger, K.; Farrelly, G. F.; Farinon, F.; Farnea, E.; Geissel, H.; Gerl, J.; Goel, N.; Gregor, E.; Habermann, T.; Hoischen, R.; Janik, R.; Klupp, S.; Kojouharov, I.; Kurz, N.; Mandal, S.; Menegazzo, R.; Mengoni, D.; Napoli, D. R.; Naqvi, F.; Nociforo, C.; Prochazka, A.; Prokopowicz, W.; Recchia, F.; Ribas, R. V.; Reed, M. W.; Rudolph, D.; Sahin, E.; Schaffner, H.; Sharma, A.; Sitar, B.; Siwal, D.; Steiger, K.; Strmen, P.; Swan, T. P. D.; Szarka, I.; Ur, C. A.; Walker, P. M.; Wollersheim, H.-J.

    2014-01-01

    The fragmentation of relativistic uranium projectiles has been exploited at the Gesellschaft für Schwerionenforschung laboratory to investigate the β decay of neutron-rich nuclei just beyond 208Pb. This paper reports on β-delayed γ decays of 211-213Tl, 215Pb, and 215-219Bi de-exciting states in the daughters 211-213Pb, 215Bi, and 215-219Po. The resulting partial level schemes, proposed with the help of systematics and shell-model calculations, are presented. The role of allowed Gamow-Teller and first-forbidden β transitions in this mass region is discussed.

  14. Structure of neutron-rich nuclei around the N = 50 shell-gap closure

    SciTech Connect

    Faul, T.; Duchene, G.; Nowacki, F.; Thomas, J.-C.; Huyse, M.; Van Duppen, P.

    2010-04-26

    The structure of neutron-rich nuclei in the vicinity of {sup 78}Ni have been investigated via the beta-decay of {sup 71,73,75}Cu isotopes (ISOLDE, CERN). Experimental results have been compared with shell-model calculations performed with the ANTOINE code using a large (2p{sub 3/2}1 f{sub 5/2}2 p{sub 1/2}1 g{sub 9/2}) valence space and a (56/28)Ni{sub 28} core.

  15. Two-Neutron Separation Energies Of Even-Even Rare-Earth Neutron-Rich Nuclei

    SciTech Connect

    Benhamouda, N.; Oudih, M. R.; Allal, N. H.; Fellah, M.

    2007-04-23

    The variation of the two-neutron separation energy (S2N), as a function of N, is studied using a microscopic model that includes the pairing effects rigorously within the Fixed-Sharp-BCS method. The model has been tested for ''ordinary'' nuclei and has correctly reproduced the experimental data. The study has then been extended to the neutron-rich nuclei and has shown a relatively important variation of S2N when N= 100 which may be attributed to the existence of a new magic number.

  16. Collective Band Structures in the Neutron-Rich 107,109Ru Nuclei

    NASA Astrophysics Data System (ADS)

    Zhu, Sheng-jiang; Gan, Cui-yun; J, Hamilton H.; A, Ramayya V.; B, Babu R. S.; M, Sakhaee; W, Ma C.; Long, Gui-lu; Deng, Jing-kang; Zhu, Ling-yan; Li, Ming; Yang, Li-ming; J, Komicki; J, Cole D.; R, Aryaeinejad; Y, Dardenne K.; M, Drigert W.; J, Rasmussen O.; M, Stoyer A.; S, Chu Y.; K, Gregorich E.; M, Mohar F.; S, Prussin G.; I, Lee Y.; N, Johnson R.; F, McGowan K.

    1998-11-01

    The levels in neutron-rich odd-A 107,109Ru nuclei have been investigated by using γ-γ- and γ-γ-γ-coincidence studies of the prompt γ-rays from the spontaneous fission of 252Cf. The ground state bands and the negative parity bands are identified and expanded in both nuclei. Triaxial rotor plus particle model calculations indicate the ground state bands originate from ν(d5/2 + g7/2) quasiparticle configurations and the negative parity bands are from νh11/2 orbital.

  17. Shell model study of the neutron-rich nuclei around N=28

    SciTech Connect

    Retamosa, J.; Caurier, E.; Poves, A.

    1997-03-01

    We describe the properties of the neutron-rich nuclei around N=28 in the shell mode framework. The valence space includes the sd shell for protons and the pf shell for neutrons without any restriction. Good agreement is found with the available experimental data. The N=28 shell closure persists, even if eroded by the large neutron excess. The calculations predict that {sup 40}S and {sup 42}S are deformed with {beta}=0.29 and {beta}=0.32 respectively. {copyright} {ital 1997} {ital The American Physical Society}

  18. Nucleon effective E-mass in neutron-rich matter from the Migdal-Luttinger jump

    NASA Astrophysics Data System (ADS)

    Cai, Bao-Jun; Li, Bao-An

    2016-06-01

    The well-known Migdal-Luttinger theorem states that the jump of the single-nucleon momentum distribution at the Fermi surface is equal to the inverse of the nucleon effective E-mass. Recent experiments studying short-range correlations (SRC) in nuclei using electron-nucleus scatterings at the Jefferson National Laboratory (JLAB) together with model calculations constrained significantly the Migdal-Luttinger jump at saturation density of nuclear matter. We show that the corresponding nucleon effective E-mass is consequently constrained to M0*,E / M ≈ 2.22 ± 0.35 in symmetric nuclear matter (SNM) and the E-mass of neutrons is smaller than that of protons in neutron-rich matter. Moreover, the average depletion of the nucleon Fermi sea increases (decreases) approximately linearly with the isospin asymmetry δ according to κp/n ≈ 0.21 ± 0.06 ± (0.19 ± 0.08) δ for protons (neutrons). These results will help improve our knowledge about the space-time non-locality of the single-nucleon potential in neutron-rich nucleonic matter useful in both nuclear physics and astrophysics.

  19. Probing the Equation of State of Neutron-Rich Matter with Heavy-Ion Collisions

    NASA Astrophysics Data System (ADS)

    Li, Bao-An

    2006-06-01

    The equation of state (EOS) of neutron-rich matter plays many important roles in both nuclear physics and astrophysics. However, it is still very poorly known, especially its isospin dependent part, namely the symmetry energy. Nuclear reactions with neutron-rich nuclei, stable and/or radioactive, provide a great opportunity to pin down the EOS of isospin asymmetric nuclear matter. In this talk, we report some recent theoretical progress in this field within an isospin and momentum dependent transport model (IBUU04). Using in-medium nucleon-nucleon cross sections consistent with the nuclear mean field used in the transport model, a symmetry energy of Esym(ρ) ≈ 31.6(ρ/ρ0)0.69 was found most acceptable compared with both the MSU isospin diffusion data and the presently acceptable neutron-skin thickness in 208Pb. The isospin dependent part Kasy(ρ0) of isobaric nuclear incompressibility was further narrowed down to -500 ± 50 MeV. Predictions on several observables sensitive to the density dependence of the symmetry energy at supranormal densities accessible at GSI and the planned Rare Isotope Accelerator (RIA) are also made.

  20. Isospin quartic term in the kinetic energy of neutron-rich nucleonic matter

    NASA Astrophysics Data System (ADS)

    Cai, Bao-Jun; Li, Bao-An

    2015-07-01

    The energy of a free gas of neutrons and protons is well known to be approximately isospin parabolic with a negligibly small quartic term of only 0.45 MeV at the saturation density of nuclear matter ρ0=0.16 fm-3 . Using an isospin-dependent single-nucleon momentum distribution including a high (low) momentum tail (depletion) with its shape parameters constrained by recent high-energy electron scattering and medium-energy nuclear photodisintegration experiments as well as the state-of-the-art calculations of the deuteron wave function and the equation of state of pure neutron matter near the unitary limit within several modern microscopic many-body theories, we show for the first time that the kinetic energy of interacting nucleons in neutron-rich nucleonic matter has a significant quartic term of 7.18 ±2.52 MeV. Such a large quartic term has broad ramifications in determining the equation of state of neutron-rich nucleonic matter using observables of nuclear reactions and neutron stars.

  1. New neutron-rich isotope production in 154Sm+160Gd

    NASA Astrophysics Data System (ADS)

    Wang, Ning; Guo, Lu

    2016-09-01

    Deep inelastic scattering in 154Sm+160Gd at energies above the Bass barrier is for the first time investigated with two different microscopic dynamics approaches: improved quantum molecular dynamics (ImQMD) model and time dependent Hartree-Fock (TDHF) theory. No fusion is observed from both models. The capture pocket disappears for this reaction due to strong Coulomb repulsion and the contact time of the di-nuclear system formed in head-on collisions is about 700 fm/c at an incident energy of 440 MeV. The isotope distribution of fragments in the deep inelastic scattering process is predicted with the simulations of the latest ImQMD-v2.2 model together with a statistical code (GEMINI) for describing the secondary decay of fragments. More than 40 extremely neutron-rich unmeasured nuclei with 58 ≤ Z ≤ 76 are observed and the production cross sections are at the order of μb to mb. The multi-nucleon transfer reaction of Sm+Gd could be an alternative way to synthesize new neutron-rich lanthanides which are difficult to be produced with traditional fusion reactions or fission of actinides.

  2. Residue Coulomb Interaction Among Isobars and Its Influence in Symmetry Energy of Neutron-Rich Fragment

    NASA Astrophysics Data System (ADS)

    Ma, Chun-Wang; Wang, Shan-Shan; Zhang, Yan-Li; Zhao, Yi-Long; Wei, Hui-Ling

    2015-09-01

    The residue Coulomb interaction (RCI), which affects the result of symmetry-energy coefficient of neutron-rich nucleus in isobaric yield ratio (IYR) method, is difficult to be determined. Four RCI approximations are investigated: (i) The M1-RCI adopting the ac/T (the ratio of Coulomb energy coefficient to temperature) determined from the IYR of mirror-nucleus fragments; (ii) The M2-RCI by fitting the difference between IYRs; (iii) The M3-RCI adopting the standard Coulomb energy at a temperature T = 2 MeV; and (iv) Neglecting the RCI among isobars. The M1-, M2- and M3-RCI are no larger than 0.4. In particular, the M2-RCI is very close to zero. The effects of RCI in asym/T of fragment are also studied. The M1- and M4-asym/T are found to be the lower and upper limitations of asym/T, respectively. The M2-asym/T overlaps the M4-asym/T, which indicates that the M2-RCI is negligible in the IYR method, and the RCI among the three isobars can be neglected. The relative consistent low values of M3-asym/T (7.5 ± 2.5) are found in very neutron-rich isobars. Supported by the Program for Science & Technology Innovation Talents in Universities of Henan Province (13HASTIT046), and Young Teacher Project in Henan Normal University (HNU), China

  3. ToF-SIMS and laser-SNMS analysis of Madin-Darby canine kidney II cells with silver nanoparticles using an argon cluster ion beam.

    PubMed

    Nees, Ricarda; Pelster, Andreas; Körsgen, Martin; Jungnickel, Harald; Luch, Andreas; Galla, Hans-Joachim; Arlinghaus, Heinrich F

    2016-06-01

    The use of nanoparticles is one of the fastest expanding fields in industrial as well as in medical applications, owing to their remarkable characteristics. Silver nanoparticles (AgNPs) are among the most-commercialized nanoparticles because of their antibacterial effects. Laser postionization secondary neutral mass spectrometry (laser-SNMS) and time-of-flight secondary ion mass spectrometry in combination with argon cluster ion sputtering was used for the first time to investigate the effects of AgNPs on Madin-Darby canine kidney (MDCK) II cells. Depth profiles and high-resolution three dimensional (3D) images of nanoparticles and organic compounds from cells were obtained using an Ar cluster ion beam for sputtering and Bi3 (+) primary ions for the analysis. The 3D distribution of AgNPs and other organic compounds in MDCK II cells could be readily detected with very high efficiency, sensitivity, and submicron lateral resolution. The argon cluster ion beam is well suited for the sputtering of biological samples. It enables a high sample removal rate along with low molecular degradation. The outer membrane, the cytoplasm, and the nuclei of the cells could be clearly visualized using the signals PO(+) and C3H8N(+) or CN(+) and C3H8N(+). The laser-SNMS images showed unambiguously that AgNPs are incorporated by MDCK II cells and often form silver aggregates with a diameter of a few micrometers, mainly close to the outside of the cell nuclei. PMID:26671480

  4. Introduction of argon beam coagulation functionality to robotic procedures using the ABC D-Flex probe: equivalency to an existing laparoscopic instrument

    NASA Astrophysics Data System (ADS)

    Merchel, Renée. A.; Barnes, Kelli S.; Taylor, Kenneth D.

    2015-03-01

    INTRODUCTION: The ABC® D-Flex Probe utilizes argon beam coagulation (ABC) technology to achieve hemostasis during minimally invasive surgery. A handle on the probe allows for integration with robotic surgical systems and introduces ABC to the robotic toolbox. To better understand the utility of D-Flex, this study compares the performance of the D-Flex probe to an existing ABC laparoscopic probe through ex vivo tissue analysis. METHODS: Comparisons were performed to determine the effect of four parameters: ABC device, tissue type, activation duration, and distance from tissue. Ten ABC D-Flex probes were used to create 30 burn samples for each comparison. Ex vivo bovine liver and porcine muscle were used as tissue models. The area and depth of each burn was measured using a light microscope. The resulting dimensional data was used to correlate tissue effect with each variable. RESULTS: D-Flex created burns which were smaller in surface area than the laparoscopic probe at all power levels. Additionally, D-Flex achieved thermal penetration levels equivalent to the laparoscopic probe. CONCLUSION: D-Flex implements a small 7F geometry which creates a more focused beam. When used with robotic precision, quick localized superficial hemostasis can be achieved with minimal collateral damage. Additionally, D-Flex achieved equivalent thermal penetration levels at lower power and argon flow-rate settings than the laparoscopic probe.

  5. Neutron Transfer Reactions with Exotic Neutron-Rich Beams: Surrogates for Neutron-Capture Reactions

    SciTech Connect

    Cizewski, Jolie; Grzywacz-Jones, Kate L; Pain, Steven D; Thomas, Jeffrey S; Bardayan, Daniel W; Blackmon, Jeff C; Smith, Michael Scott; KOZUB, RAYMOND L; Johnson, Micah

    2006-03-01

    A new program to measure (d,p) reactions on rare isotopes of fission fragments has been established at Oak Ridge National Laboratory. Initial measurements on N=50 isotones and prospects for Z=50 experiments are reported.

  6. Spectroscopic Quadrupole Moments in {96,98}Sr: Evidence for Shape Coexistence in Neutron-Rich Strontium Isotopes at N=60.

    PubMed

    Clément, E; Zielińska, M; Görgen, A; Korten, W; Péru, S; Libert, J; Goutte, H; Hilaire, S; Bastin, B; Bauer, C; Blazhev, A; Bree, N; Bruyneel, B; Butler, P A; Butterworth, J; Delahaye, P; Dijon, A; Doherty, D T; Ekström, A; Fitzpatrick, C; Fransen, C; Georgiev, G; Gernhäuser, R; Hess, H; Iwanicki, J; Jenkins, D G; Larsen, A C; Ljungvall, J; Lutter, R; Marley, P; Moschner, K; Napiorkowski, P J; Pakarinen, J; Petts, A; Reiter, P; Renstrøm, T; Seidlitz, M; Siebeck, B; Siem, S; Sotty, C; Srebrny, J; Stefanescu, I; Tveten, G M; Van de Walle, J; Vermeulen, M; Voulot, D; Warr, N; Wenander, F; Wiens, A; De Witte, H; Wrzosek-Lipska, K

    2016-01-15

    Neutron-rich {96,98}Sr isotopes have been investigated by safe Coulomb excitation of radioactive beams at the REX-ISOLDE facility. Reduced transition probabilities and spectroscopic quadrupole moments have been extracted from the differential Coulomb excitation cross sections. These results allow, for the first time, the drawing of definite conclusions about the shape coexistence of highly deformed prolate and spherical configurations. In particular, a very small mixing between the coexisting states is observed, contrary to other mass regions where strong mixing is present. Experimental results have been compared to beyond-mean-field calculations using the Gogny D1S interaction in a five-dimensional collective Hamiltonian formalism, which reproduce the shape change at N=60. PMID:26824536

  7. Production of the neutron-rich hypernucleus 10LambdaLi in the (pi-,K+) double charge-exchange reaction.

    PubMed

    Saha, P K; Fukuda, T; Imoto, W; Ahn, J K; Ajimura, S; Aoki, K; Bhang, H C; Fujioka, H; Hotchi, H; Hwang, J I; Itabashi, T; Kang, B H; Kim, H D; Kim, M J; Kishimoto, T; Krutenkova, A; Maruta, T; Miura, Y; Miwa, K; Nagae, T; Noumi, H; Outa, H; Ohtaki, T; Sakaguchi, A; Sato, Y; Sekimoto, M; Shimizu, Y; Tamura, H; Tanida, K; Toyoda, A; Ukai, M; Yim, H J

    2005-02-11

    In order to produce a neutron-rich Lambda hypernucleus for the first time, we carried out an experiment by utilizing the (pi-,K+) double charge-exchange reaction on a 10B target. We observed the production of a 10LambdaLi hypernucleus. The cross section for the Lambda bound region was found to be 11.3+/-1.9 nb/sr with the 1.2 GeV/c incident momentum, which is compared with the 10LambdaB hypernucleus production cross section, 7.8+/-0.3 microb/sr, in the (pi+,K+) reaction with a 1.05 GeV/c incident momentum beam. PMID:15783631

  8. Spectroscopy of neutron-rich {sup 168,170}Dy: Yrast band evolution close to the N{sub p}N{sub n} valence maximum

    SciTech Connect

    Soederstroem, P.-A.; Nyberg, J.; Regan, P. H.; Ashley, S. F.; Catford, W. N.; Gelletly, W.; Jones, G. A.; Liu, Z.; Pietri, S.; Podolyak, Zs.; Steer, S. J.; Thompson, N. J.; Williams, S. J.; Algora, A.; Angelis, G. de; Corradi, L.; Fioretto, E.; Gottardo, A.; Grodner, E.; He, C. Y.

    2010-03-15

    The yrast sequence of the neutron-rich dysprosium isotope {sup 168}Dy has been studied using multinucleon transfer reactions following collisions between a 460-MeV {sup 82}Se beam and an {sup 170}Er target. The reaction products were identified using the PRISMA magnetic spectrometer and the gamma rays detected using the CLARA HPGe-detector array. The 2{sup +} and 4{sup +} members of the previously measured ground-state rotational band of {sup 168}Dy have been confirmed and the yrast band extended up to 10{sup +}. A tentative candidate for the 4{sup +}->2{sup +} transition in {sup 170}Dy was also identified. The data on these nuclei and on the lighter even-even dysprosium isotopes are interpreted in terms of total Routhian surface calculations and the evolution of collectivity in the vicinity of the proton-neutron valence product maximum is discussed.

  9. Half-life systematics across the N=126 shell closure: role of first-forbidden transitions in the β decay of heavy neutron-rich nuclei.

    PubMed

    Morales, A I; Benlliure, J; Kurtukián-Nieto, T; Schmidt, K-H; Verma, S; Regan, P H; Podolyák, Z; Górska, M; Pietri, S; Kumar, R; Casarejos, E; Al-Dahan, N; Algora, A; Alkhomashi, N; Álvarez-Pol, H; Benzoni, G; Blazhev, A; Boutachkov, P; Bruce, A M; Cáceres, L S; Cullen, I J; Denis Bacelar, A M; Doornenbal, P; Estévez-Aguado, M E; Farrelly, G; Fujita, Y; Garnsworthy, A B; Gelletly, W; Gerl, J; Grebosz, J; Hoischen, R; Kojouharov, I; Kurz, N; Lalkovski, S; Liu, Z; Mihai, C; Molina, F; Mücher, D; Rubio, B; Shaffner, H; Steer, S J; Tamii, A; Tashenov, S; Valiente-Dobón, J J; Walker, P M; Wollersheim, H J; Woods, P J

    2014-07-11

    This Letter reports on a systematic study of β-decay half-lives of neutron-rich nuclei around doubly magic (208)Pb. The lifetimes of the 126-neutron shell isotone (204)Pt and the neighboring (200-202)Ir, (203)Pt, (204)Au are presented together with other 19 half-lives measured during the "stopped beam" campaign of the rare isotope investigations at GSI collaboration. The results constrain the main nuclear theories used in calculations of r-process nucleosynthesis. Predictions based on a statistical macroscopic description of the first-forbidden β strength reveal significant deviations for most of the nuclei with N<126. In contrast, theories including a fully microscopic treatment of allowed and first-forbidden transitions reproduce more satisfactorily the trend in the measured half-lives for the nuclei in this region, where the r-process pathway passes through during β decay back to stability. PMID:25062171

  10. Beta-decay studies of nickel-78 and other neutron-rich nuclei in the astrophysical r-process

    NASA Astrophysics Data System (ADS)

    Hosmer, Paul Thomas

    The β-decay properties of several neutron-rich nuclei including the doubly-magic 78Ni were studied. A low-energy neutron detector NERO was designed and calibrated for use in these measurements. β-decay measurements, especially those that combine both half-life and neutron-emission probability measurements, can offer first tests of nuclear theories of neutron-rich nuclei. In addition, 78Ni is an important waiting-point in the astrophysical r-process. The results of the measurements are compared to several nuclear models, and the astrophysical implications are explored.

  11. Sensitivity of elements of the symmetry energy of nuclear matter to the properties of neutron-rich systems

    NASA Astrophysics Data System (ADS)

    Mondal, C.; Agrawal, B. K.; De, J. N.; Samaddar, S. K.

    2016-04-01

    The sensitivity of nuclear symmetry energy elements at the saturation density to the binding energies of ultra-neutron-rich nuclei (neutron-to-proton ratio ˜2 ) and the maximum mass of a neutron star is explored within a relativistic mean field model. Values of the interaction parameters governing the isovector strengths and the symmetry elements are determined in tighter bounds. Assessments based on the sensitivity matrix reveal that the properties of extreme neutron-rich systems play a predominant role in narrowing down the uncertainties in the various symmetry energy parameters. The calculations are extended over a wide range of nuclear matter density, and the results are discussed.

  12. A large liquid argon time projection chamber for long-baseline, off-axis neutrino oscillation physics with the NuMI beam

    SciTech Connect

    Finley, D.; Jensen, D.; Jostlein, H.; Marchionni, A.; Pordes, S.; Rapidis, P.A.; Bromberg, C.; Lu, C.; McDonald, T.; Gallagher, H.; Mann, A.; Schneps, J.; Cline, D.; Sergiampietri, F.; Wang, H.; Curioni, A.; Fleming, B.T.; Menary, S.; /York U., Canada

    2005-09-01

    Results from neutrino oscillation experiments in the last ten years have revolutionized the field of neutrino physics. While the overall oscillation picture for three neutrinos is now well established and precision measurements of the oscillation parameters are underway, crucial issues remain. In particular, the hierarchy of the neutrino masses, the structure of the neutrino mixing matrix, and, above all, CP violation in the neutrino sector are the primary experimental challenges in upcoming years. A program that utilizes the newly commissioned NuMI neutrino beamline, and its planned upgrades, together with a high-performance, large-mass detector will be in an excellent position to provide decisive answers to these key neutrino physics questions. A Liquid Argon time projection chamber (LArTPC) [2], which combines fine-grained tracking, total absorption calorimetry, and scalability, is well matched for this physics program. The few-millimeter-scale spatial granularity of a LArTPC combined with dE/dx measurements make it a powerful detector for neutrino oscillation physics. Scans of simulated event samples, both directed and blind, have shown that electron identification in {nu}{sub e} charged current interactions can be maintained at an efficiency of 80%. Backgrounds for {nu}{sub e} appearance searches from neutral current events with a {pi}{sup 0} are reduced well below the {approx} 0.5-1.0% {nu}{sub e} contamination of the {nu}{sub {mu}} beam [3]. While the ICARUS collaboration has pioneered this technology and shown its feasibility with successful operation of the T600 (600-ton) LArTPC [4], a detector for off-axis, long-baseline neutrino physics must be many times more massive to compensate for the low event rates. We have a baseline concept [5] based on the ICARUS wire plane structure and commercial methods of argon purification and housed in an industrial liquefied-natural-gas tank. Fifteen to fifty kton liquid argon capacity tanks have been considered. A very

  13. Limiting temperatures of neutron rich nuclei: A possible interpretation of data from isotope yield ratios

    SciTech Connect

    Natowitz, J.B.; Hagel, K.; Wada, R.; Majka, Z.; Gonthier, P.; Li, J.; Mdeiwayeh, N.; Xiao, B.; Zhao, Y.

    1995-11-01

    The recent ALADIN report of limiting temperatures for nuclear disassembly, derived from measurements of isotopic ratios for He and Li nuclei, is discussed. It is suggested that the entire excitation energy dependence which is observed may result from the fact that limiting temperatures for the onset of Coulomb instability are being measured for progressively lighter neutron rich nuclei as the excitation energy per nucleon increases. While the basic observation of plateauing in the intermediate excitation energy range remains valid, the higher excitation results may not signal entry into the vapor phase. The ALADIN result for {ital A}{approx}125, when combined with lower energy data, indicates a plateau temperature near 6.5 MeV over the range of 3--11 MeV/nucleon initial excitation energy.

  14. Structure of the Neutron Rich ga and ge Isotopes Observed at Alto

    NASA Astrophysics Data System (ADS)

    Verney, D.; Lebois, M.; Ibrahim, F.; Essabaa, S.; Azaiez, F.; Cheikh Mhamed, M.; Cottereau, E.; Cuong, P. V.; Ferraton, M.; Flanagan, K.; Franchoo, S.; Guilleamud-Mueller, D.; Hammache, F.; Lau, C.; Le Blanc, F.; Le Du, J.-F.; Mouginot, B.; Petrache, C.; Roussiere, B.; Sagui, L.; de Sereville, N.; Stefan, I.; Tastet, B.

    During test runs dedicated to the commissioning of ALTO (Accélérateur Linéaire et Tandem à Orsay), β and β-n decay of the very neutron rich 3184 {Ga}53 could be observed at the tape station installed on-line with the PARRNe mass-separator. γ-lines observed in the resulting spectra and a careful analysis of the balance of their relative intensities point toward the existence of two β-decaying states in 84Ga. The decay of these long-lived states appear to feed the 21^ + and 41^ + excited states of 3284 {Ge}52 and the 1/21^ + state in 3283 {Ge}51 allowing a significant improvement of the knowledge on nuclear structure in the immediate vicinity of 78Ni.

  15. Charge-exchange modes of excitation in deformed neutron-rich nuclei

    SciTech Connect

    Yoshida, Kenichi

    2015-10-15

    Gamow-Teller (GT) mode of excitation and β-decay properties of deformed neutron-rich even-N Zr isotopes are investigated in a self-consistent Skyrme energy-density-functional approach, in which the Hartree-Fock-Bogoliubov equation is solved in the coordinate space and the proton-neutron Quasiparticle-RPA equation is solved in the quasiparticle basis. It is found that a stronger collectivity is generated for the GT giant resonance as an increase in the neutron number. Furthermore, we find that the T = 0 pairing enhances the low-lying GT strengths cooperatively with the T = 1 pairing correlation depending on the microscopic structure of the low-lying mode and the shell structure around the Fermi levels, and that the enhanced strength shortens the β-decay half-lives by at most an order of magnitude.

  16. Neutron density distributions of neutron-rich nuclei studied with the isobaric yield ratio difference

    NASA Astrophysics Data System (ADS)

    Ma, Chun-Wang; Bai, Xiao-Man; Yu, Jiao; Wei, Hui-Ling

    2014-09-01

    The isobaric yield ratio difference (IBD) between two reactions of similar experimental setups is found to be sensitive to nuclear density differences between projectiles. In this article, the IBD probe is used to study the density variation in neutron-rich 48Ca . By adjusting diffuseness in the neutron density distribution, three different neutron density distributions of 48Ca are obtained. The yields of fragments in the 80 A MeV 40, 48Ca + 12C reactions are calculated by using a modified statistical abrasion-ablation model. It is found that the IBD results obtained from the prefragments are sensitive to the density distribution of the projectile, while the IBD results from the final fragments are less sensitive to the density distribution of the projectile.

  17. Shell structure in neutron-rich Ca and Ni nuclei under semi-realistic mean fields

    SciTech Connect

    Nakada, H.

    2010-05-15

    Shell structure in the neutron-rich Ca and Ni nuclei is investigated by the spherical Hartree-Fock calculations with semi-realistic NN interactions. Specific ingredients of the effective interaction, particularly the tensor force, often play a key role in the Z dependence of the neutron shell structure. Such examples are found in N=32 and N=40; N=32 becomes magic or submagic in {sup 52}Ca while its magicity is broken in {sup 60}Ni, and N=40 is submagic (though not magic) in {sup 68}Ni but not in {sup 60}Ca. Comments are given on the doubly magic nature of {sup 78}Ni. We point out that the loose binding can lead to a submagic number N=58 in {sup 86}Ni, assisted by the weak pair coupling.

  18. Gamow-Teller response in deformed even and odd neutron-rich Zr and Mo isotopes

    NASA Astrophysics Data System (ADS)

    Sarriguren, P.; Algora, A.; Pereira, J.

    2014-03-01

    β-decay properties of neutron-rich Zr and Mo isotopes are investigated within a microscopic theoretical approach based on the proton-neutron quasiparticle random-phase approximation. The underlying mean field is described self-consistently from deformed Skyrme Hartree-Fock calculations with pairing correlations. Residual separable particle-hole and particle-particle forces are also included in the formalism. The structural evolution in these isotopic chains including both even and odd isotopes is analyzed in terms of the equilibrium deformed shapes. Gamow-Teller strength distributions, β-decay half-lives, and β-delayed neutron-emission probabilities are studied, stressing their relevance to describe the path of the nucleosynthesis rapid neutron capture process.

  19. Splitting of the isovector giant dipole resonance in neutron-rich spherical nuclei

    SciTech Connect

    Kolomietz, V.M.; Magner, A.G.; Shlomo, S.

    2006-02-15

    The well-known splitting of the isovector giant dipole resonance is traditionally explained as a phenomenon of the nuclear isospin asymmetry (isospin splitting model) or the nuclear deformation. We suggest a new mechanism of the splitting of the giant multipole resonances in spherical neutron-rich nuclei resulting from the interplay of the isovector and isoscalar sounds with different velocities. Our approach is based on the collisional Landau kinetic theory and can be used for description of the splitting phenomena for both the isoscalar and the isovector modes in a wide region of nuclear masses A{approx}40-240. For the isovector dipole modes, the evaluated values of the splitting energy, the relative strength of the main and satellite resonance peaks, and the contribution to the energy-weighted sum rule are in agreement with experimental data.

  20. Beta-decay properties of neutron-rich medium-mass nuclei

    NASA Astrophysics Data System (ADS)

    Sarriguren, Pedro

    2016-06-01

    β-decay properties of even-even and odd-A neutron-rich Ge, Se, Kr, Sr, Zr, Mo, Ru, and Pd isotopes involved in the astrophysical rapid neutron capture process are studied within a microscopic proton-neutron quasiparticle random-phase approximation. The underlying mean field is based on a self-consistent Skyrme Hartree-Fock + BCS calculation that includes deformation as a key ingredient. The isotopic evolution of the various nuclear equilibrium shapes and the corresponding charge radii are investigated in all the isotopic chains. The energy distributions of the Gamow-Teller strength, as well as the β-decay half-lives are discussed and compared with the available experimental information. It is shown that nuclear deformation plays a significant role in the description of the decay properties in this mass region. Reliable predictions of the strength distributions are essential to evaluate decay rates in astrophysical scenarios.

  1. Magicity of neutron-rich nuclei within relativistic self-consistent approaches

    NASA Astrophysics Data System (ADS)

    Li, Jia Jie; Margueron, Jérôme; Long, Wen Hui; Van Giai, Nguyen

    2016-02-01

    The formation of new shell gaps in intermediate mass neutron-rich nuclei is investigated within the relativistic Hartree-Fock-Bogoliubov theory, and the role of the Lorentz pseudo-vector and tensor interactions is analyzed. Based on the Foldy-Wouthuysen transformation, we discuss in detail the role played by the different terms of the Lorentz pseudo-vector and tensor interactions in the appearing of the N = 16, 32 and 34 shell gaps. The nuclei 24O, 48Si and 52,54Ca are predicted with a large shell gap and zero (24O, 52Ca) or almost zero (48Si, 54Ca) pairing gap, making them candidates for new magic numbers in exotic nuclei. We find from our analysis that the Lorentz pseudo-vector and tensor interactions induce very specific evolutions of single-particle energies, which could clearly sign their presence and reveal the need for relativistic approaches with exchange interactions.

  2. Measurement of the dipole polarizability of the unstable neutron-rich nucleus 68Ni.

    PubMed

    Rossi, D M; Adrich, P; Aksouh, F; Alvarez-Pol, H; Aumann, T; Benlliure, J; Böhmer, M; Boretzky, K; Casarejos, E; Chartier, M; Chatillon, A; Cortina-Gil, D; Datta Pramanik, U; Emling, H; Ershova, O; Fernandez-Dominguez, B; Geissel, H; Gorska, M; Heil, M; Johansson, H T; Junghans, A; Kelic-Heil, A; Kiselev, O; Klimkiewicz, A; Kratz, J V; Krücken, R; Kurz, N; Labiche, M; Le Bleis, T; Lemmon, R; Litvinov, Yu A; Mahata, K; Maierbeck, P; Movsesyan, A; Nilsson, T; Nociforo, C; Palit, R; Paschalis, S; Plag, R; Reifarth, R; Savran, D; Scheit, H; Simon, H; Sümmerer, K; Wagner, A; Waluś, W; Weick, H; Winkler, M

    2013-12-13

    The E1 strength distribution in 68Ni has been investigated using Coulomb excitation in inverse kinematics at the R3B-LAND setup and by measuring the invariant mass in the one- and two-neutron decay channels. The giant dipole resonance and a low-lying peak (pygmy dipole resonance) have been observed at 17.1(2) and 9.55(17) MeV, respectively. The measured dipole polarizability is compared to relativistic random phase approximation calculations yielding a neutron-skin thickness of 0.17(2) fm. A method and analysis applicable to neutron-rich nuclei has been developed, allowing for a precise determination of neutron skins in nuclei as a function of neutron excess. PMID:24483648

  3. High Spin States and Octupole Deformation in Neutron-Rich ^145,147La Nuclei

    NASA Astrophysics Data System (ADS)

    Zhu, S. J.; Hamilton, J. H.; Ramayya, A. V.; Babu, B. R. S.; Jones, E. F.; Kormicki, J.; Daniel, A. V.; Hwang, J. K.; Beyer, C. J.; Wang, M. G.; Long, G. L.; Li, M.; Zhu, L. Y.; Gan, C. Y.; Ma, W. C.; Cole, J. D.; Aryaeinejad, R.; Dardenne, Y. X.; Drigert, M. W.; Rasmussen, J. O.; Asztalos, S.; Lee, I. Y.; Macchiavelli, A. O.; Chu, S. Y.; Gregorich, K. E.; Mohar, M. F.; Stoyer, M. A.; Lougheed, R. W.; Moody, K. J.; Wild, J. F.; Prussin, S. G.

    1998-04-01

    High spin states in neutron-rich odd-Z nuclei ^145,147La have been investigated from the study of prompt γ- rays in spontaneous fission of ^252Cf by using γ-γ- and γ-γ-γ- coincidence techniques. Alternating parity bands are extended up to spins I=(41/2) and I=(43/2) in ^145La and ^147La, respectively. Strong E1 transitions between the negative and positive parity bands give evidence for stable octupole deformation. The new higher spin levels give evidence for rotational enhancement of the stability of the octupole deformation. These collective bands show competition and co-existence between symmetric and asymmetric shapes in ^145La. Band crossing was found around hbarω≈ 0.26 ~0.30 MeV in both nuclei and these backbends are related to the alignment of two i_13/2 neutron from cranked shell model calculations.

  4. Increased rigidly triaxial deformations in neutron-rich Mo, Ru isotopes

    NASA Astrophysics Data System (ADS)

    Liang, WuYang; Jiao, ChangFeng; Xu, FuRong; Fu, XiMing

    2016-09-01

    Pairing-deformation-frequency self-consistent crankingWoods-Saxon model is employed to investigate the triaxiality in the ground states of the neutron-rich even-even Mo, Ru isotopes. Deformation evolutions and transition probabilities have been studied, giving the triaxial shapes in their ground states. The kinematic moments of inertia have been calculated to illustrate the gradually rigid deformation. To understand the origin of the asymmetry shape in this region, we analyze the evolution of single-particle orbits with changing γ deformation. The present calculations reveal the importance of the triaxial deformation in describing not only static property, but also rotational behaviors in this mass region, providing significant probes into the shell structure around.

  5. High spin structure of the neutron-rich nuclei {sup 137}I and {sup 139}Cs

    SciTech Connect

    Liu, S. H.; Hamilton, J. H.; Ramayya, A. V.; Hwang, J. K.; Covello, A.; Itaco, N.; Gargano, A.; Luo, Y. X.; Rasmussen, J. O.; Daniel, A. V.; Ter-Akopian, G. M.; Zhu, S. J.; Ma, W. C.

    2009-10-15

    High spin excited states in the neutron-rich nuclei {sup 137}I and {sup 139}Cs were investigated from a study of the prompt {gamma} rays emitted in the spontaneous fission of {sup 252}Cf with the Gammasphere detector array. Ten new excited levels with 18 new deexciting transitions were observed in {sup 139}Cs and the level scheme of {sup 139}Cs was extended up to 4670 keV. Spins and parities of levels in {sup 139}Cs were firmly assigned up to 25/2{sup +}. Three new levels were found in {sup 137}I. Shell model calculations were performed to interpret the experimental results. A good agreement between theory and experiment in both nuclei was found.

  6. Measurement of the Dipole Polarizability of the Unstable Neutron-Rich Nucleus Ni68

    NASA Astrophysics Data System (ADS)

    Rossi, D. M.; Adrich, P.; Aksouh, F.; Alvarez-Pol, H.; Aumann, T.; Benlliure, J.; Böhmer, M.; Boretzky, K.; Casarejos, E.; Chartier, M.; Chatillon, A.; Cortina-Gil, D.; Datta Pramanik, U.; Emling, H.; Ershova, O.; Fernandez-Dominguez, B.; Geissel, H.; Gorska, M.; Heil, M.; Johansson, H. T.; Junghans, A.; Kelic-Heil, A.; Kiselev, O.; Klimkiewicz, A.; Kratz, J. V.; Krücken, R.; Kurz, N.; Labiche, M.; Le Bleis, T.; Lemmon, R.; Litvinov, Yu. A.; Mahata, K.; Maierbeck, P.; Movsesyan, A.; Nilsson, T.; Nociforo, C.; Palit, R.; Paschalis, S.; Plag, R.; Reifarth, R.; Savran, D.; Scheit, H.; Simon, H.; Sümmerer, K.; Wagner, A.; Waluś, W.; Weick, H.; Winkler, M.

    2013-12-01

    The E1 strength distribution in Ni68 has been investigated using Coulomb excitation in inverse kinematics at the RB3-LAND setup and by measuring the invariant mass in the one- and two-neutron decay channels. The giant dipole resonance and a low-lying peak (pygmy dipole resonance) have been observed at 17.1(2) and 9.55(17) MeV, respectively. The measured dipole polarizability is compared to relativistic random phase approximation calculations yielding a neutron-skin thickness of 0.17(2) fm. A method and analysis applicable to neutron-rich nuclei has been developed, allowing for a precise determination of neutron skins in nuclei as a function of neutron excess.

  7. Beta-decay study of neutron rich isotopes of Bromine and Krypton

    SciTech Connect

    Miernik, Krzysztof A; Gross, Carl J; Grzywacz, Robert Kazimierz; Madurga, M; Mendez, II, Anthony J; Miller, D.; Padgett, S; Paulauskas, Stanley V; Rykaczewski, Krzysztof Piotr; Stracener, Daniel W; Wolinska-Cichocka, Marzena; Zganjar, E. F.; Batchelder, J. C.; Brewer, N.T.; Cartegni, L.; Fijalkowska, Aleksandra G; Hamilton, J. H.; Hwang, J. K.; Ilyushkin, S.; Jost, Carola U; Karny, M.; Korgul, A.; Krolas, W.; Liu, S.H.; Ramayya, A. V.; Surman, Rebecca; Winger, J. A.; Wolinska-Cichocka, M

    2013-01-01

    Short lived neutron rich nuclei including 93 Br, 93 Kr and 94 Kr were produced in proton induced fission of 238 U at the HRIBF in Oak Ridge. Their beta decay was studied by means of a high resolution on line mass separator and beta gamma spectroscopy methods. The half life of 93Br T1/2 = 152(8) ms and delayed branching ratio of Pn = 53-8+11 may be compared to the previously reported values of T1/2 = 102(10) ms and Pn = 68(7)%. At the same time the half life of 94Kr T1/2 = 227(14) ms and B delayed branching ratio of Pn = 1.9+0.6 0.2 % of 93Kr are in very good agreement with literature values. The decay properties of 93Br include four new gamma transitions following beta delayed neutron emission.

  8. {beta}-decay half-lives of new neutron-rich lanthanide isotopes

    SciTech Connect

    Ichikawa, S.; Tsukada, K.; Asai, M.; Nishinaka, I.; Nagame, Y.; Osa, A.; Sakama, M.; Oura, Y.; Kojima, Y.; Shibata, M.; Kawade, K.

    1998-12-21

    New neutron-rich lanthanide isotopes produced in the proton-induced fission of {sup 238}U have been identified using the JAERI on-line isotope separator (JAERI-ISOL) coupled to a gas-jet transport system. The observed K x-rays following the {beta}{sup -}decay of products in the mass separated fraction provided direct isotopic identifications. New isotopes observed, with values of their half-lives given in parentheses, are {sup 159}Pm(2{+-}1 s), {sup 161}Sm(4.8{+-}0.8 s), {sup 165}Gd(10.3{+-}1.6 s), {sup 166}Tb(21{+-}6 s), {sup 167}Tb(19.4{+-}2.7 s) and {sup 168}Tb(8.2{+-}1.3 s). The half-life values are compared to the results of theoretical predictions.

  9. Nuclear shape transitions in neutron-rich medium-mass nuclei

    SciTech Connect

    Sarriguren, P.; Rodriguez-Guzman, R.; Robledo, L. M.

    2012-10-20

    We study the isotopic evolution of the ground-state nuclear shapes in neutron-rich Kr, Rb, Sr, Y, Zr, Nb, and Mo isotopic chains. Both even-even and odd-A nuclei are included in the analysis. For the latter we also study the systematics of their one-quasiparticle low-lying configurations. The theoretical approach is based on a selfconsistent Hartree-Fock-Bogoliubov formalism with finite range Gogny energy density functionals. Neutron separation energies, charge radii, and the spin-parity of the ground states are calculated and compared with available data. Shape-transition signatures are identified around N= 60 isotones as discontinuities in both charge radii isotopic shifts and spin-parities of the ground states. The nuclear deformation including triaxiality is shown to play a relevant role in the understanding of the bulk and spectroscopic features of the ground and low-lying one-quasiparticle states.

  10. Continuum Effects and Three-Nucleon Forces in Neutron-Rich Oxygen Isotopes

    SciTech Connect

    Hagen, Gaute; Hjorth-Jensen, M.; Jansen, G R; Machleidt, R; Papenbrock, T.

    2012-01-01

    We employ interactions from chiral effective field theory and compute binding energies, excited states, and radii for isotopes of oxygen with the coupled-cluster method. Our calculation includes the effects of three-nucleon forces and of the particle continuum, both of which are important for the description of neutron-rich isotopes in the vicinity of the nucleus 24O. Our main results are the placement of the neutron drip-line at 24O, the assignment of spins, parities and resonance widths for several low-lying states of the drip-line nucleus, and an efficient approximation that incorporates the effects of three-body interactions.

  11. Nuclear Structure Studies of Some Neutron Rich Nuclei Produced in 252Cf Spontaneous Fission

    NASA Astrophysics Data System (ADS)

    Ramayya, A. V.; Hamilton, J. H.; Hwang, J. K.

    2015-02-01

    High spin states of neutron-rich nuclei such as 133,134Te, 93Sr, 105Nb have been studied by measuring γ- γ- γ coincidences (cube), γ- γ- γ- γ coincidences (hypercube) and angular correlations from the spontaneous fission of 252Cf with the LBNL Gammasphere detector array. Four types of particle-hole bands built on the known 334.3 keV isomer in 133Te were identified. The level structure of 93Sr is interpreted, in part, as arising from the weak coupling of the 1d5/2 neutron hole to the yrast states of the 94Sr core. The g-factor of the 4+ state in 134Te was measured, for the first time, by using a new technique developed for measuring angular correlations with Gammasphere. A new level scheme of 105Nb was established. Three new collective bands were identified with a total of 14 new levels and 36 new γ transitions. In 117-122Cd, a shift to more slightly deformed structures was found where the excited levels do not fit the long held picture of one, two and three phonon bands.

  12. E2 transition probabilities for decays of isomers observed in neutron-rich odd Sn isotopes

    DOE PAGESBeta

    Iskra, Ł. W.; Broda, R.; Janssens, R. V.F.; Wrzesiński, J.; Chiara, C. J.; Carpenter, M. P.; Fornal, B.; Hoteling, N.; Kondev, F. G.; Królas, W.; et al

    2015-01-01

    High-spin states were investigated with gamma coincidence techniques in neutron-rich Sn isotopes produced in fission processes following ⁴⁸Ca + ²⁰⁸Pb, ⁴⁸Ca + ²³⁸U, and ⁶⁴Ni + ²³⁸U reactions. By exploiting delayed and cross-coincidence techniques, level schemes have been delineated in odd ¹¹⁹⁻¹²⁵Sn isotopes. Particular attention was paid to the occurrence of 19/2⁺ and 23/2⁺ isomeric states for which the available information has now been significantly extended. Reduced transition probabilities, B(E2), extracted from the measured half-lives and the established details of the isomeric decays exhibit a striking regularity. This behavior was compared with the previously observed regularity of the B(E2) amplitudesmore » for the seniority ν = 2 and 3, 10⁺ and 27/2⁻ isomers in even- and odd-Sn isotopes, respectively.« less

  13. Empirical pairing gaps, shell effects, and di-neutron spatial correlation in neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Changizi, S. A.; Qi, Chong; Wyss, R.

    2015-08-01

    The empirical pairing gaps derived from four different odd-even mass staggering formulas are compared. By performing single-j shell and multi-shell seniority model calculations as well as by using the standard HFB approach with Skyrme force we show that the simplest three-point formula ΔC(3) (N) =1/2 [ B (N, Z) + B (N - 2, Z) - 2 B (N - 1, Z) ] can provide a good measure of the neutron pairing gap in even-N nuclei. It removes to a large extent the contribution from the nuclear mean field as well as contributions from shell structure details. It is also less contaminated by the Wigner effect for nuclei around N = Z. We also show that the strength of ΔC(3) (N) can serve as a good indication of the two-particle spatial correlation in the nucleus of concern and that the weakening of ΔC(3) (N) in some neutron-rich nuclei indicates that the di-neutron correlation itself is weak in these nuclei.

  14. Searching for isovector signatures in the neutron-rich oxygen and calcium isotopes

    NASA Astrophysics Data System (ADS)

    Chen, Wei-Chia; Piekarewicz, J.

    2015-09-01

    We search for potential isovector signatures in the neutron-rich oxygen and calcium isotopes within the framework of a relativistic mean-field theory with an exact treatment of pairing correlations. To probe the isovector sector we calibrate a few relativistic density functionals using the same isoscalar constraints but with one differing isovector assumption. It is found that under certain conditions, the isotopic chain in oxygen can be made to terminate at the experimentally observed 24O isotope and in the case of the calcium isotopes at 60Ca. To produce such behavior, the resulting symmetry energy must be soft, with predicted values for the symmetry energy and its slope at saturation density being J = (30.92 ± 0.47) MeV and L = (51.0 ± 1.5) MeV, respectively. As a consequence, the neutron-skin thickness of 208Pb is rather small: Rskin208 = (0.161 ± 0.011) fm. This same model-labeled "FSUGarnet"-predicts R1.4 = (13.0 ± 0.1) km for the radius of a "canonical" 1.4M⊙ neutron star, yet is also able to support a two-solar-mass neutron star.

  15. Isomers in Neutron-Rich A ?? 190 NNuclides from 208Pb Fragmentation

    SciTech Connect

    Caamano, M.; Walker, P. M.; Regan, P. H.; Pfutzner, M.; Podolyak, Zs.; Gerl, J.; Hellstrom, M.; Mayet, P.; Mineva, M. N.; Aprahamian, A.; Benlliure, J.; Bruce, A. M.; Butler, P. A.; Cortina Gil, D.; Cullen, D. M.; Doring, J.; Enqvist, T.; Fox, C.; Garces Narro, J.; Geissel, H.; Gelletly, W.; Giovinazzo, J.; Grawe, H.; Grzywacz, R.; Kleinbohl, A.; Korten, W.; Lewitowicz, M.; Lucas, R.; Mach, H.; O'Leary, C. D.; De Oliveira, F.; Pearson, C. J.; Rejmund, F.; Rejmund, M.; Sawicka, M.; Schaffner, H.; Schlegel, C.; Schmidt, K.; Schmidt, K.-H.; Stevenson, P. D.; Theisen, Ch.; Vives, F.; Warner, D. D.; Wheldon, C.; Wollersheim, H. J.; Wooding, S.; Xu, F.; Yordanov, O.

    2005-01-01

    Relativistic projectile fragmentation of {sup 208}Pb has been used to produce isomers in neutron-rich, A {approx} 190 nuclides. A forward-focusing spectrometer provided ion-by-ion mass and charge identification. The detection of gamma-rays emitted by stopped ions has led to the assignment of isomers in {sup 188}Ta, {sup 190}W, {sup 192}Re, {sup 193}Re, {sup 195}Os, {sup 197}Ir, {sup 198}Ir, {sup 200}Pt, {sup 201}Pt, {sup 202}Pt and {sup 203}Au, with half-lives ranging from approximately 10 ns to 1 ms. Tentative isomer information has been found also for {sup 174}Er, {sup 175}Er, {sup 185}Hf, {sup 191}Re, {sup 194}Re and {sup 199}Ir. In most cases, time-correlated, singles gamma-ray events provided the first spectroscopic data on excited states for each nuclide. In {sup 200}Pt and {sup 201}Pt, the assignments are supported by gamma-gamma coincidences. Isomeric ratios provide additional information, such as half-life and transition energy constraints in particular cases. The level structures of the platinum isotopes are discussed, and comparisons are made with isomer systematics.

  16. Interplay between collective and single particle excitations around neutron-rich doubly-magic nuclei

    NASA Astrophysics Data System (ADS)

    Leoni, S.

    2016-05-01

    The excitation spectra of nuclei with one or two particles outside a doubly-magic core are expected to be dominated, at low energy, by the couplings between phonon excitations of the core and valence particles. A survey of the experimental situation is given for some nuclei lying in close proximity of neutron-rich doubly-magic systems, such as 47,49Ca, 133Sb and 210Bi. Data are obtained with various types of reactions (multinucleon transfer with heavy ions, cold neutron capture and neutron induced fission of 235U and 241Pu targets), with the employment of complex detection systems based on HPGe arrays. A comparison with theoretical calculations is also presented, in terms of large shell model calculations and of a phenomenological particle-phonon model. In the case of 133Sb, a new microscopic "hybrid" model is introduced: it is based on the coupling between core excitations (both collective and non-collective) of the doubly-magic core and the valence nucleon, using the Skyrme effective interaction in a consistent way.

  17. Measurement of the isoscalar monopole response in the neutron-rich nucleus 68Ni.

    PubMed

    Vandebrouck, M; Gibelin, J; Khan, E; Achouri, N L; Baba, H; Beaumel, D; Blumenfeld, Y; Caamaño, M; Càceres, L; Colò, G; Delaunay, F; Fernandez-Dominguez, B; Garg, U; Grinyer, G F; Harakeh, M N; Kalantar-Nayestanaki, N; Keeley, N; Mittig, W; Pancin, J; Raabe, R; Roger, T; Roussel-Chomaz, P; Savajols, H; Sorlin, O; Stodel, C; Suzuki, D; Thomas, J C

    2014-07-18

    The isoscalar monopole response has been measured in the unstable nucleus (68)Ni using inelastic alpha scattering at 50A  MeV in inverse kinematics with the active target MAYA at GANIL. The isoscalar giant monopole resonance (ISGMR) centroid was determined to be 21.1 ± 1.9 MeV and indications for a soft monopole mode are provided for the first time at 12.9 ± 1.0 MeV. Analysis of the corresponding angular distributions using distorted-wave-born approximation with random-phase approximation transition densities indicates that the L = 0 multipolarity dominates the cross section for the ISGMR and significantly contributes to the low-energy mode. The L=0 part of this low-energy mode, the soft monopole mode, is dominated by neutron excitations. This demonstrates the relevance of inelastic alpha scattering in inverse kinematics in order to probe both the ISGMR and isoscalar soft modes in neutron-rich nuclei. PMID:25083638

  18. Pygmy dipole mode in deformed neutron-rich Mg isotopes close to the drip line

    SciTech Connect

    Yoshida, Kenichi

    2009-10-15

    We investigate the microscopic structure of the low-lying isovector-dipole excitation mode in neutron-rich {sup 36,38,40}Mg close to the drip line by means of the deformed quasiparticle random-phase approximation employing the Skyrme and the local pairing energy-density functionals. It is found that the low-lying bump structure above the neutron emission-threshold energy develops when the drip line is approached, and that the isovector dipole strength at E{sub x}<10 MeV exhausts about 6.0% of the classical Thomas-Reiche-Kuhn dipole sum rule in {sup 40}Mg. We obtained the collective dipole modes at around 8-10 MeV in Mg isotopes, that consist of many two-quasiparticle excitations of the neutron. The transition density clearly shows an oscillation of the neutron skin against the isoscalar core. We found significant coupling effects between the dipole and octupole excitation modes due to the nuclear deformation. It is also found that the responses for the compressional dipole and isoscalar octupole excitations are much enhanced in the lower energy region.

  19. Microscopic description of fission in neutron-rich radium isotopes with the Gogny energy density functional

    NASA Astrophysics Data System (ADS)

    Rodrıguez-Guzmán, R.; Robledo, L. M.

    2016-01-01

    Mean-field calculations, based on the D1S, D1N and D1M parametrizations of the Gogny energy density functional, have been carried out to obtain the potential energy surfaces relevant to fission in several Ra isotopes with the neutron number 144≤ N≤ 176. Inner and outer barrier heights as well as first and second isomer excitation energies are given. The existence of a well-developed third minimum along the fission paths of Ra nuclei is analyzed in terms of the energetics of the "fragments" defining such elongated configuration. The masses and charges of the fission fragments are studied as functions of the neutron number in the parent Ra isotope. The comparison between fission and α -decay half-lives, reveals that the former becomes faster for increasing neutron numbers. Though there exists a strong variance of the results with respect to the parameters used in the computation of the spontaneous fission rate, a change in tendency is observed at N=164 with a steady increase that makes heavier neutron-rich Ra isotopes stable against fission, diminishing the importance of fission recycling in the r-process.

  20. Symmetry energy and surface properties of neutron-rich exotic nuclei

    SciTech Connect

    Gaidarov, M. K.; Antonov, A. N.; Sarriguren, P.; Moya de Guerra, E.

    2014-07-23

    The symmetry energy, the neutron pressure and the asymmetric compressibility of spherical Ni, Sn, and Pb and deformed Kr and Sm neutron-rich even-even nuclei are calculated within the coherent density fluctuation model using the symmetry energy as a function of density within the Brueckner energy-density functional. The correlation between the thickness of the neutron skin and the characteristics related with the density dependence of the nuclear symmetry energy is investigated for isotopic chains of these nuclei in the framework of the deformed self-consistent mean-field Skyrme HF+BCS method. The mass dependence of the nuclear symmetry energy and the neutron skin thickness are also studied together with the role of the neutron-proton asymmetry. The studied correlations reveal a smoother behavior in the case of spherical nuclei than for deformed ones. We also notice that the neutron skin thickness obtained for {sup 208}Pb with SLy4 force is found to be in a good agreement with the recent data. In addition to the interest that this study may have by itself, we give some numerical arguments in proof of the existence of peculiarities of the studied quantities in Ni and Sn isotopic chains that are not present in the Pb chain.

  1. Measurement of the Isoscalar Monopole Response in the Neutron-Rich Nucleus Ni68

    NASA Astrophysics Data System (ADS)

    Vandebrouck, M.; Gibelin, J.; Khan, E.; Achouri, N. L.; Baba, H.; Beaumel, D.; Blumenfeld, Y.; Caamaño, M.; Càceres, L.; Colò, G.; Delaunay, F.; Fernandez-Dominguez, B.; Garg, U.; Grinyer, G. F.; Harakeh, M. N.; Kalantar-Nayestanaki, N.; Keeley, N.; Mittig, W.; Pancin, J.; Raabe, R.; Roger, T.; Roussel-Chomaz, P.; Savajols, H.; Sorlin, O.; Stodel, C.; Suzuki, D.; Thomas, J. C.

    2014-07-01

    The isoscalar monopole response has been measured in the unstable nucleus Ni68 using inelastic alpha scattering at 50A MeV in inverse kinematics with the active target MAYA at GANIL. The isoscalar giant monopole resonance (ISGMR) centroid was determined to be 21.1±1.9 MeV and indications for a soft monopole mode are provided for the first time at 12.9±1.0 MeV. Analysis of the corresponding angular distributions using distorted-wave-born approximation with random-phase approximation transition densities indicates that the L =0 multipolarity dominates the cross section for the ISGMR and significantly contributes to the low-energy mode. The L=0 part of this low-energy mode, the soft monopole mode, is dominated by neutron excitations. This demonstrates the relevance of inelastic alpha scattering in inverse kinematics in order to probe both the ISGMR and isoscalar soft modes in neutron-rich nuclei.

  2. High-spin structure and multiphonon {gamma} vibrations in very neutron-rich {sup 114}Ru

    SciTech Connect

    Yeoh, E. Y.; Wang, J. G.; Ding, H. B.; Gu, L.; Xu, Q.; Xiao, Z. G.; Zhu, S. J.; Hamilton, J. H.; Li, K.; Ramayya, A. V.; Hwang, J. K.; Liu, Y. X.; Liu, S. H.; Sheikh, J. A.; Bhat, G. H.; Luo, Y. X.; Rasmussen, J. O.; Lee, I. Y.; Ma, W. C.

    2011-05-15

    High-spin levels of the neutron-rich {sup 114}Ru have been investigated by measuring the prompt {gamma} rays in the spontaneous fission of {sup 252}Cf. The ground-state band and one-phonon {gamma}-vibrational band have been extended up to 14{sup +} and 9{sup +}, respectively. Two levels are proposed as the members of a two-phonon {gamma}-vibrational band. A back bending (band crossing) has been observed in the ground-state band at ({h_bar}/2{pi}){omega}{approx_equal} 0.40 MeV. Using the triaxial deformation parameters, the cranked shell model calculations indicate that this back bending in {sup 114}Ru should originate from the alignment of a pair of h{sub 11/2} neutrons. Triaxial projected shell model calculations for the {gamma}-vibrational band structures of {sup 114}Ru are in good agreement with the experimental data. However, when using the oblate deformation parameters, both of the above-calculated results are not in agreement with the experimental data.

  3. Rotational bands in neutron-rich {sup 169,171,172}Er

    SciTech Connect

    Wu, C.Y.; Cline, D.; Simon, M.W.; Teng, R.; Vetter, K.; Carpenter, M.P.; Janssens, R.V.F.; Wiedenhoever, I.

    2004-07-01

    The neutron-rich {sup 169,171,172}Er nuclei were populated by few-neutron transfer reactions between {sup 170}Er and {sup 238}U at a near barrier energy. The spectroscopy of these Er isotopes was studied using prompt {gamma} rays correlated with delayed transitions or events involving at least three prompt transitions. The ground-state band of {sup 172}Er was populated up to spin 22{sup +} at an excitation energy of 5528 keV. Rotational bands built on the 1/2{sup -}[521], 5/2{sup -}[512], and 7/2{sup +}[633] neutron configurations in {sup 169,171}Er were extended to substantially higher spins than previously known. The signature splitting observed in these rotational bands is addressed within the framework of the particle-rotor model in terms of triaxiality and Coriolis attenuation. The signature inversion observed in the 5/2{sup -}[512] band is well reproduced by including the triaxial degree of freedom in the calculation. Attenuating the Coriolis interaction in the calculation is found to be necessary to reproduce the signature splitting observed in the 7/2{sup +}[633] band. A similar Coriolis attenuation also is needed to account for the signature splitting as well as the B(M1)/B(E2) ratios in the 7/2{sup +}[633] ground-state band in the neighboring N=99 isotones, {sup 167}Er and {sup 169}Yb.

  4. Resonant states of the neutron-rich Λ hypernucleus He7Λ

    NASA Astrophysics Data System (ADS)

    Hiyama, E.; Isaka, M.; Kamimura, M.; Myo, T.; Motoba, T.

    2015-05-01

    The structure of the neutron-rich Λ hypernucleus, He7Λ is studied within the framework of an α +Λ +n +n four-body cluster model. We predict second 3 /2+ and 5 /2+ states, corresponding to a 0 s Λ coupled to the second 2+ state of 6He, as narrow resonant states with widths of Γ ˜1 MeV to be at 0.03 and 0.07 MeV with respect to the α +Λ +n +n threshold. From a separate estimate of the differential cross section for the 7Li (γ ,K+) He7Λ reaction, we suggest a possibility to observe these states at the Thomas Jefferson National Accelerator Facility (JLab) in the future. We also calculate the second 2+ state of 6He as a resonant state within the framework of an α +n +n three-body cluster model. Our result is 2.81 MeV with Γ =4.63 MeV with respect to the α +n +n threshold. This energy position is ˜1 MeV higher, and with a much broader decay width, than the recent SPIRAL data. We suggest that an experiment at JLab to search for the second 3 /2+ and 5 /2+ states of He7Λ would provide an opportunity to confirm the second 2+ state of the core nucleus 6He.

  5. E2 transition probabilities for decays of isomers observed in neutron-rich odd Sn isotopes

    SciTech Connect

    Iskra, Ł. W.; Broda, R.; Janssens, R. V.F.; Wrzesiński, J.; Chiara, C. J.; Carpenter, M. P.; Fornal, B.; Hoteling, N.; Kondev, F. G.; Królas, W.; Lauritsen, T.; Pawłat, T.; Seweryniak, D.; Stefanescu, I.; Walters, W. B.; Zhu, S.

    2015-01-01

    High-spin states were investigated with gamma coincidence techniques in neutron-rich Sn isotopes produced in fission processes following ⁴⁸Ca + ²⁰⁸Pb, ⁴⁸Ca + ²³⁸U, and ⁶⁴Ni + ²³⁸U reactions. By exploiting delayed and cross-coincidence techniques, level schemes have been delineated in odd ¹¹⁹⁻¹²⁵Sn isotopes. Particular attention was paid to the occurrence of 19/2⁺ and 23/2⁺ isomeric states for which the available information has now been significantly extended. Reduced transition probabilities, B(E2), extracted from the measured half-lives and the established details of the isomeric decays exhibit a striking regularity. This behavior was compared with the previously observed regularity of the B(E2) amplitudes for the seniority ν = 2 and 3, 10⁺ and 27/2⁻ isomers in even- and odd-Sn isotopes, respectively.

  6. High-spin states in neutron-rich Z ≈ 30 nuclei studied following fusion-evaporation

    NASA Astrophysics Data System (ADS)

    Devlin, M.; Lafosse, D. R.; Lerma, F.; Sarantites, D. G.; Rudolph, D.; Thirolf, P. G.; Clark, R. M.; Lee, I. Y.; Macchiavelli, A. O.

    1997-10-01

    High-spin states in neutron rich nuclei near the closed shell at Z = 28 and N = 40 were studied with the fusion-evaporation reaction 157 MeV ^48Ca + ^26Mg. This region of the Segrè chart is of particular interest, since it is near the beginning of the astrophysical r-process, and little detailed knowledge of the relevant orbitals is available. The experiment was conducted using the Gammasphere Ge detector array in conjunction with the Microball charged-particle detector array, in order to exploit the sensitivity of this combination for multiple-charged particle evaporation channels. High spin states in heavy isotopes of Ge, Ga, Zn, Cu and Ni will be discussed. The sensitivity and usefulness of heavy-ion fusion reactions in the study of neutron-rich nuclei will also be addressed.

  7. New Precision Mass Measurements of Neutron-Rich Calcium and Potassium Isotopes and Three-Nucleon Forces

    SciTech Connect

    Gallant, A. T.; Bale, J. C.; Chowdhury, U.; Lennarz, A.; Simon, V. V.; Holt, J. D.; Mané, E.; Menéndez, J.; Simon, M. C.; Andreoiu, C.; Delheij, P.; Pearson, M.; Savajols, H.; Schwenk, A.

    2012-01-01

    We present precision Penning trap mass measurements of neutron-rich calcium and potassium isotopes in the vicinity of neutron number N=32. Using the TITAN system, the mass of 51K was measured for the first time, and the precision of the 51,52Ca mass values were improved significantly. The new mass values show a dramatic increase of the binding energy compared to those reported in the atomic mass evaluation. In particular, 52Ca is more bound by 1.74 MeV, and the behavior with neutron number deviates substantially from the tabulated values. An increased binding was predicted recently based on calculations that include three-nucleon (3N) forces. We present a comparison to improved calculations, which agree remarkably with the evolution of masses with neutron number, making neutron-rich calcium isotopes an exciting region to probe 3N forces.

  8. Nucleosynthesis of neutron-rich heavy nuclei during explosive helium burning in a 15 solar-mass supernova

    NASA Technical Reports Server (NTRS)

    Blake, J. B.; Woosley, S. E.; Weaver, T. A.; Schramm, D. N.

    1980-01-01

    The production of heavy nuclei during explosive helium burning has been calculated using the Weaver and Woosley self-consistent model of a complete 15 solar-mass star and the n-process code of Blake and Schramm. It was found that the resulting neutron-rich heavy nuclei are not produced in the relative abundances of solar-system r-process material (such as a Pt peak) nor are any actinides produced. Basically insufficient neutrons are available.

  9. Discovery of Highly Excited Long-Lived Isomers in Neutron-Rich Hafnium and Tantalum Isotopes through Direct Mass Measurements

    SciTech Connect

    Reed, M. W.; Cullen, I. J.; Walker, P. M.; Deo, A. Y.; Kempley, R. S.; Swan, T. P. D.; Litvinov, Yu. A.; Winckler, N.; Blaum, K.; Bosch, F.; Dimopoulou, C.; Farinon, F.; Heil, M.; Knoebel, R.; Kozhuharov, C.; Kurcewicz, J.; Kuzminchuk, N.; Litvinov, S.; Nociforo, C.; Nolden, F.

    2010-10-22

    A study of cooled {sup 197}Au projectile-fragmentation products has been performed with a storage ring. This has enabled metastable nuclear excitations with energies up to 3 MeV, and half-lives extending to minutes or longer, to be identified in the neutron-rich nuclides {sup 183,184,186}Hf and {sup 186,187}Ta. The results support the prediction of a strongly favored isomer region near neutron number 116.

  10. Setup with Laser Ionization in Gas Cell for Production and Study of Neutron-Rich Heavy Nuclei

    NASA Astrophysics Data System (ADS)

    Zagrebaev, V. I.; Zemlyanoy, S. G.; Kozulin, E. M.; Kudryavtsev, Yu.; Fedosseev, V.; Bark, R.; Janas, Z.; Othman, H. A.

    2015-11-01

    The present limits of the upper part of the nuclear map are very close to stability while the unexplored area of heavy neutron-rich nuclides along the neutron closed shell N=126 is extremely important for nuclear astrophysics investigations and, in particular, for the understanding of the r-process of astrophysical nucleosynthesis. This area of the nuclear map can be reached neither in fusion-fission reactions nor in fragmentation processes widely used nowadays for the production of exotic nuclei. A new way was recently proposed for the production of these nuclei via low-energy multi-nucleon transfer reactions. The estimated yields of neutron-rich nuclei are found to be significantly high in such reactions and several tens of new nuclides can be produced, for example, in the near-barrier collision of 136Xe with 208Pb. A new setup is proposed to produce and study heavy neutron-rich nuclei located along the neutron closed shell N=126.

  11. Lifetimes in neutron-rich Nd isotopes measured by Doppler profile method

    SciTech Connect

    Ahmad, I.; Lister, C.J.; Morss, L.R.

    1995-08-01

    Lifetimes of the rotational levels in neutron-rich even-even Nd isotopes were deduced from the analysis of the Doppler broadened line shapes. The experiment was performed at Daresbury with the Eurogam array, which at that time consisted of 45 Compton-suppressed Ge detectors and 5 Low-Energy Photon Spectrometers. The source was in the form of a 7-mm pellet which was prepared by mixing 5-mg; {sup 248}Cm and 65-mg KCl and pressing it under high pressure. Events for which three or more detectors fired were used to construct a cubic data array whose axes represented the {gamma}-ray energies and the contents of each channel the number of events with that particular combination of {gamma}-ray energies. From this cubic array, one-dimensional spectra were generated by placing gates on peaks on the other two axes. Gamma-ray spectra of even-even Nd isotopes were obtained by gating on the transitions in the complimentary Kr fragments. The gamma peaks de-exciting states with I {>=} 12 h were found to be broader than the instrumental line width due to the Doppler effect. The line shapes of they-ray peaks were fitted separately with a simple model for the feeding of the states and assuming a rotational band with constant intrinsic quadruple moment and these are shown in Fig. I-27. The quadrupole moments thus determined were found to be in good agreement with the quadrupole moments measured previously for lower spin states. Because of the success of this technique for the Nd isotopes, we intend to apply this technique to the new larger data set collected with the Eurogam II array. The results of this study were published.

  12. Nuclear shape and structure in neutron-rich 110,111Tc

    SciTech Connect

    Luo, Y.X.; Hamilton, J.H.; Rasmussen, J.O.; Ramayya, A.V.; Stefanescu, I.; Hwang, J.K.; Zhu, S.J.; Gore, P.M.; Jones, E.F.; Fong,D.; Wu, S.C.; Lee, I.Y.; Ginter, T.N.; Ter-Akopian, G.M.; Daniel, A.V.; Stoyer, M.A.; Donangelo, R.; Gelberg, A.

    2006-02-02

    The structure of Tc nuclei is extended to the moreneutron-rich regions based on measurements of prompt gamma rays from thespontaneous fission of 252Cf at Gammasphere. The level scheme of N=67neutron-rich (Z=43) 110Tc is established for the first time and that of111Tc is expanded. The ground-state band of 111Tc reaches theband-crossing region and the new observation of the weakly populatedalpha = -1/2 member of the band provides important information ofsignature splitting. The systematics of band crossings in the isotopicand isotonic chains and a CSM calculation suggest that the band crossingof the gs band of 111Tc is due to alignment of a pair of h11/2 neutrons.The best fit to signature splitting, branching ratios, and excitations ofthe ground-state band of 111Tc by RTRP model calculations result in ashape of epsilon2 = 0.32 and gamma = -26 deg. for this nucleus. Itstriaxiality is larger than that of 107Tc, to indicate increasingtriaxiality with increasing neutron number. The identification of theweakly-populated "K+2 satellite" band provides strong evidence for thelarge triaxiality of 111Tc. In 110Tc the four lowest-lying levelsobserved are very similar to those in 108Tc. At an excitation of 478.9keV above the lowest state observed, ten states of a delta I = 1 band areobserved. This band is very analogous to the delta I = 1 bands in106,108Tc, but it has greater signature splitting at higherspins.

  13. Shape Coexistence in Neutron-Rich Nickel Isotopes around N = 40

    NASA Astrophysics Data System (ADS)

    Prokop, C. J.; e14039 Collaboration; e14057 Collaboration

    2015-10-01

    Shape coexistence is a fascinating phenomenon in atomic nuclei characterized by multiple states with different intrinsic shapes coexisting at similar excitation energies. In even-even nuclei, a hallmark of shape coexistence is low-energy 0+ states. In 68Ni, the Monte-Carlo Shell Model (MCSM) employing the A3DA interaction, utilizing the fpg9/2d5 / 2 model space for protons and neutrons, predicts triple shape coexistence with three 0+ states below 3 MeV. Transitioning to 70Ni, the energy of the prolate-deformed 0+ state is predicted to drop precipitously from 2511 to 1525 keV. This is due to strengthening of the attractive νg9 / 2 - πf5 / 2 and repulsive νg9 / 2 - πf7 / 2 monopole interactions of the tensor force altering the effective single-particle energies of the πf7 / 2 and πf5 / 2 single-particle states, thereby reducing the spherical Z = 28 shell gap. Recent beta-decay spectroscopy experiments at the National Superconducting Cyclotron Laboratory (NSCL) have discovered a new excited 0+ state at 1567 keV in 70Ni. This result supports MCSM predictions extending the picture of shape coexistence to 70Ni and demonstrates the importance of the tensor force for describing the nuclear structure of neutron-rich nuclei. Results of the latest NSCL experiments will be presented. Supported by NSF Contract No. PHY-1102511, by the DOE NNSA Award Nos. DE-NA0000979 and DE-FG52-08NA28552, the U.S DOE SC NP Contract No. DE-AC-06CH11357 and Grant Nos. DE-FG02-94ER40834 and DE-FG02-96ER40983, and U.S. ARL Coop. Agreement W911NF-12-2-0019.

  14. Nuclear-decay studies of neutron-rich rare-earth nuclides

    SciTech Connect

    Chasteler, R.M. . Dept. of Chemistry Lawrence Berkeley Lab., CA )

    1990-04-26

    Neutron-rich rare-earth nuclei were produced in multinucleon transfer reactions of {sup 170}Er and {sup 176}Yb projectiles on {sup nat}W targets at the Lawrence Berkeley Laboratory SuperHILAC and their radioactive decays properties studied at the on-line mass separation facility OASIS. Two unknown isotopes, {sup 169}Dy (t {sub 1/2} {equals} 39 {plus minus} 8 s) and {sup 174}Er(t{sub 1/2} {equals} 3.3 {plus minus} 0.2 m) were discovered and their decay characteristics determined. The decay schemes for two previously identified isotopes, {sup 168}Dy (t{sub 1/2} {equals} 8.8 {plus minus} 0.3 m) and {sup 171}Ho (t{sub 1/2} {equals} 55 {plus minus} 3 s), were characterized. Evidence for a new isomer of 3.0 m {sup 168}Ho{sup g}, {sup 168}Ho{sup m} (t{sub 1/2} {equals} 132 {plus minus} 4 s) which decays by isomeric transition (IT) is presented. Beta particle endpoint energies were determined for the decay of {sup 168}Ho{sup g}, {sup 169}Dy, {sup 171}Ho, and {sup 174}Er, the resulting Q{beta}-values are: 2.93 {plus minus} 0.03, 3.2 {plus minus} 0.3, 3.2 {plus minus} 0.6, and 1.8 {plus minus} 0.2 MeV, respectively. These values were compared with values calculated using recent atomic mass formulae. Comparisons of various target/ion source geometries used in the OASIS mass separator facility for these multinucleon transfer reactions were performed. 73 refs., 40 figs., 11 tabs.

  15. Modification of the cylindrical products outer surface influenced by radial beam of argon ions at automatic mode

    NASA Astrophysics Data System (ADS)

    Valikov, R. A.; Yashin, A. S.; Yakutkina, T. V.; Kalin, B. A.; Volkov, N. V.; Krivobokov, V. P.; Yanin, S. N.; Asainov, O. Kh; Yurev, Yu N.

    2015-11-01

    Obtaining surface with high purity and good roughness is important for increasing the corrosion resistance and wear resistance of products working in corrosion-active environment. Installation ILUR-03 with the coaxial ion beam wide energy spectrum source for cleaning, polishing and surface doping of long cylindrical items has been developed. Upgraded installation ILUR-03 provides effective technological defects cleaning (abrasives after mechanical polishing, acid residues after chemical etching, adsorbed gases), surface polishing, film deposition by using magnetrons and surface doping by ion mixing method in one technological cycle.

  16. Analysis of a Partial Male-Sterile Mutant of Arabidopsis thaliana Isolated from a Low-Energy Argon Ion Beam Mutagenized Pool

    NASA Astrophysics Data System (ADS)

    Xu, Min; Bian, Po; Wu, Yuejin; Yu, Zengliang

    2008-04-01

    A screen for Arabidopsis fertility mutants, mutagenized by low-energy argon ion beam, yielded two partial male-sterile mutants tc243-1 and tc243-2 which have similar phenotypes. tc243-2 was investigated in detail. The segregation ratio of the mutant phenotypes in the M2 pools suggested that mutation behaved as single Mendelian recessive mutations. tc243 showed a series of mutant phenotypes, among which partial male-sterile was its striking mutant characteristic. Phenotype analysis indicates that there are four factors leading to male sterility. a. Floral organs normally develop inside the closed bud, but the anther filaments do not elongate sufficiently to position the locules above the stigma at anthesis. b. The anther locules do not dehisce at the time of flower opening (although limited dehiscence occurs later). c. Pollens of mutant plants develop into several types of pollens at the trinucleated stage, as determined by staining with DAPI (4',6-diamidino-2-phenylindole), which shows a variable size, shape and number of nucleus. d. The viability of pollens is lower than that of the wild type on the germination test in vivo and vitro.

  17. Fabrication and characterization of tunnel barriers in a multi-walled carbon nanotube formed by argon atom beam irradiation

    NASA Astrophysics Data System (ADS)

    Tomizawa, H.; Yamaguchi, T.; Akita, S.; Ishibashi, K.

    2015-07-01

    We have evaluated tunnel barriers formed in multi-walled carbon nanotubes (MWNTs) by an Ar atom beam irradiation method and applied the technique to fabricate coupled double quantum dots. The two-terminal resistance of the individual MWNTs was increased owing to local damage caused by the Ar beam irradiation. The temperature dependence of the current through a single barrier suggested two different contributions to its Arrhenius plot, i.e., formed by direct tunneling through the barrier and by thermal activation over the barrier. The height of the formed barriers was estimated. The fabrication technique was used to produce coupled double quantum dots with serially formed triple barriers on a MWNT. The current measured at 1.5 K as a function of two side-gate voltages resulted in a honeycomb-like charge stability diagram, which confirmed the formation of the double dots. The characteristic parameters of the double quantum dots were calculated, and the feasibility of the technique is discussed.

  18. Fabrication and characterization of tunnel barriers in a multi-walled carbon nanotube formed by argon atom beam irradiation

    SciTech Connect

    Tomizawa, H.; Yamaguchi, T.; Akita, S.; Ishibashi, K.

    2015-07-28

    We have evaluated tunnel barriers formed in multi-walled carbon nanotubes (MWNTs) by an Ar atom beam irradiation method and applied the technique to fabricate coupled double quantum dots. The two-terminal resistance of the individual MWNTs was increased owing to local damage caused by the Ar beam irradiation. The temperature dependence of the current through a single barrier suggested two different contributions to its Arrhenius plot, i.e., formed by direct tunneling through the barrier and by thermal activation over the barrier. The height of the formed barriers was estimated. The fabrication technique was used to produce coupled double quantum dots with serially formed triple barriers on a MWNT. The current measured at 1.5 K as a function of two side-gate voltages resulted in a honeycomb-like charge stability diagram, which confirmed the formation of the double dots. The characteristic parameters of the double quantum dots were calculated, and the feasibility of the technique is discussed.

  19. Future developments of INFN-LNL nuclear beam facilities

    NASA Astrophysics Data System (ADS)

    Bisoffi, G.

    2007-11-01

    The accelerator group at INFN-LNL has been mostly engaged, recently, in completing and commissioning the higher current injector of the linac booster ALPI (named PIAVE) and in constructing and assembling the front-end part of a high current driver linac for the RNB facility SPES. PIAVE, designed to accelerate ions with A/Q = < 8.5 up to 1.2 MeV/u, is now completed. The injector has been commissioned with O, Ar, Ne and Xe beams. Neon and argon beams have been delivered to experiments for a total of about 400 hours. A consolidation program of PIAVE and ALPI is planned, so as to deliver a larger variety of beams with a current range 10 div 100 pnA and with an energy exceeding the Coulomb barrier in relevant nuclear reaction cases. The RNB facility SPES, allowing a frontier program in RNB physics, is being designed and prototyped: beams of neutron rich medium-to-heavy mass nuclei will be produced inducing 238U fission with a 40 MeV 200μA proton beam impinging onto a multi-slice direct target. A further development of ALPI will make it best suitable for the re-acceleration of radioactive nuclear species, after charge breeding and isotope selection.

  20. Shell-model states with seniority ν =3 , 5, and 7 in odd-A neutron-rich Sn isotopes

    NASA Astrophysics Data System (ADS)

    Iskra, Ł. W.; Broda, R.; Janssens, R. V. F.; Chiara, C. J.; Carpenter, M. P.; Fornal, B.; Hoteling, N.; Kondev, F. G.; Królas, W.; Lauritsen, T.; Pawłat, T.; Seweryniak, D.; Stefanescu, I.; Walters, W. B.; Wrzesiński, J.; Zhu, S.

    2016-01-01

    Excited states with seniority ν =3 , 5, and 7 have been investigated in odd neutron-rich 119,121,123,125Sn isotopes produced by fusion-fission of 6.9-MeV/A 48Ca beams with 208Pb and 238U targets and by fission of a 238U target bombarded with 6.7-MeV/A 64Ni beams. Level schemes have been established up to high spin and excitation energies in excess of 6 MeV, based on multifold gamma-ray coincidence relationships measured with the Gammasphere array. In the analysis, the presence of isomers was exploited to identify gamma rays and propose transition placements using prompt and delayed coincidence techniques. Gamma decays of the known 27 /2- isomers were expanded by identifying new deexcitation paths feeding 23 /2+ long-lived states and 21 /2+ levels. Competing branches in the decay of 23 /2- states toward two 19 /2- levels were delineated as well. In 119Sn, a new 23 /2+ isomer was identified, while a similar 23 /2+ long-lived state, proposed earlier in 121Sn, has now been confirmed. In both cases, isomeric half-lives were determined with good precision. In the range of ν =3 excitations, the observed transitions linking the various states enabled one to propose with confidence spin-parity assignments for all the observed states. Above the 27 /2- isomers, an elaborate structure of negative-parity levels was established reaching the (39 /2- ), ν =7 states, with tentative spin-parity assignments based on the observed deexcitation paths as well as on general yrast population arguments. In all the isotopes under investigation, strongly populated sequences of positive-parity (35 /2+ ), (31 /2+ ), and (27 /2+ ) states were established, feeding the 23 /2+ isomers via cascades of three transitions. In the ,123Sn121 isotopes, these sequences also enabled the delineation of higher-lying levels, up to (43 /2+ ) states. In 123Sn, a short half-life was determined for the (35 /2+ ) state. Shell-model calculations were carried out for all the odd Sn isotopes, from 129Sn down to 119

  1. β -Decay Half-Lives of 110 Neutron-Rich Nuclei across the N =82 Shell Gap: Implications for the Mechanism and Universality of the Astrophysical r Process

    NASA Astrophysics Data System (ADS)

    Lorusso, G.; Nishimura, S.; Xu, Z. Y.; Jungclaus, A.; Shimizu, Y.; Simpson, G. S.; Söderström, P.-A.; Watanabe, H.; Browne, F.; Doornenbal, P.; Gey, G.; Jung, H. S.; Meyer, B.; Sumikama, T.; Taprogge, J.; Vajta, Zs.; Wu, J.; Baba, H.; Benzoni, G.; Chae, K. Y.; Crespi, F. C. L.; Fukuda, N.; Gernhäuser, R.; Inabe, N.; Isobe, T.; Kajino, T.; Kameda, D.; Kim, G. D.; Kim, Y.-K.; Kojouharov, I.; Kondev, F. G.; Kubo, T.; Kurz, N.; Kwon, Y. K.; Lane, G. J.; Li, Z.; Montaner-Pizá, A.; Moschner, K.; Naqvi, F.; Niikura, M.; Nishibata, H.; Odahara, A.; Orlandi, R.; Patel, Z.; Podolyák, Zs.; Sakurai, H.; Schaffner, H.; Schury, P.; Shibagaki, S.; Steiger, K.; Suzuki, H.; Takeda, H.; Wendt, A.; Yagi, A.; Yoshinaga, K.

    2015-05-01

    The β -decay half-lives of 110 neutron-rich isotopes of the elements from Rb 37 to Sn 50 were measured at the Radioactive Isotope Beam Factory. The 40 new half-lives follow robust systematics and highlight the persistence of shell effects. The new data have direct implications for r -process calculations and reinforce the notion that the second (A ≈130 ) and the rare-earth-element (A ≈160 ) abundance peaks may result from the freeze-out of an (n ,γ )⇄(γ ,n ) equilibrium. In such an equilibrium, the new half-lives are important factors determining the abundance of rare-earth elements, and allow for a more reliable discussion of the r process universality. It is anticipated that universality may not extend to the elements Sn, Sb, I, and Cs, making the detection of these elements in metal-poor stars of the utmost importance to determine the exact conditions of individual r -process events.

  2. IDENTIFICATION OF HIGH-SPIN STATES IN NEUTRON-RICH 88,90,92Kr AND 86Se

    SciTech Connect

    J. D. Cole

    2011-08-01

    Level schemes of even-even neutron-rich {sup 88-92}Kr and {sup 86}Se have been investigated by measuring triple-{gamma} coincidence data from the spontaneous fission of {sup 252}Cf with the Gammasphere detector array. The level scheme of {sup 88}Kr has been extended up to 7169 keV state. Several new excited states with new transitions have been identified in {sup 90,92}Kr and {sup 86}Se. Spins and parities have been assigned to levels in these nuclei by following regional systematics and angular correlation measurements. The level structures of the N = 52, 54, Se, Kr, and Sr isotones are discussed.

  3. Decay of the neutron-rich isotope sup 171 Ho and the identification of sup 169 Dy

    SciTech Connect

    Chasteler, R.M.; Nitschke, J.M.; Firestone, R.B.; Vierinen, K.S.; Wilmarth, P.A. )

    1990-10-01

    Neutron-rich rare-earth isotopes were produced in multinucleon transfer reactions between {sup 170}Er ions and {sup nat}W targets. On-line mass separation was used together with {beta}- and {gamma}-ray spectroscopy in these studies. At mass {ital A}=169, the heaviest known dysprosium isotope, 39(8) s,{sup 169}Dy, was identified. It was observed to {beta}{sup {minus}} decay to the ground state of {sup 169}Ho or through a level at 1578 keV. In the {ital A}=171 mass chain, a partial decay scheme for 55(3)-s {sup 171}Ho was determined.

  4. Octupole Deformation Bands of πh11/2 in Neutron-Rich 145,147La Nuclei

    NASA Astrophysics Data System (ADS)

    Zhu, Sheng-jiang; S, Zhu J.; Wang, Mu-ge; J, Hamilton H.; A, Ramayya V.; B, Babu R. S.; W, Ma C.; Long, Gui-lu; Zhu, Ling-yan; Li, Ming; A, Sakhaee; Gan, Cui-yun; Yang, Li-ming; J, Komicki; J, Cole D.; R, Aryaeinejad; M, Drigert W.; J, Rasmussen O.; M, Stoyer A.; S, Chu Y.; K, Gregorich E.; M, Mohar F.; S, Prussin G.; I, Lee Y.; Yu, Oganessian Ts; G, Ter-Akopian M.; A, Daniel V.

    1999-03-01

    Octupole deformation bands built on πh11/2 orbital in neutron-rich odd-Z 145,147La nuclei have been investigated by measuring the prompt γ-rays emitted from the 252Cf source. The alternating parity band structures and strong E1 transitions observed between negative- and positive-parity bands in both nuclei indicate the octupole deformation enhanced by the h11/2 single proton coupling. According to observed energy displacements the octupole deformation becomes stable at the intermediate spin states.

  5. Bustling argon: biological effect

    PubMed Central

    2013-01-01

    Argon is a noble gas in group 18 of the periodic table. Certificated to exist in air atmosphere merely one century ago, discovery of argon shows interesting stories of researching and exploring. It was assumed to have no chemical activity. However, argon indeed present its biological effect on mammals. Narcotic effect of argon in diving operation and neur-protective function of argon in cerebral injury demonstrate that argon has crucial effect and be concentrated on is necessary. Furthermore, consider to be harmless to human, argon clinical application in therapy would be another option. PMID:24088583

  6. Status of radioactive ion beams at the HRIBF

    NASA Astrophysics Data System (ADS)

    Stracener, D. W.

    2003-05-01

    Radioactive Ion Beams (RIBs) at the Holifield Radioactive Ion Beam Facility (HRIBF) are produced using the isotope separation on-line technique and are subsequently accelerated up to a few MeV per nucleon for use in nuclear physics experiments. The first RIB experiments at the HRIBF were completed at the end of 1998 using 17F beams. Since then other proton-rich ion beams have been developed and a large number of neutron-rich ion beams are now available. The neutron-rich radioactive nuclei are produced via proton-induced fission of uranium in a low-density matrix of uranium carbide. Recently developed RIBs include 25Al from a silicon carbide target and isobarically pure beams of neutron-rich Ge, Sn, Br and I isotopes from a uranium carbide target.

  7. Stellar (n ,γ ) cross sections of neutron-rich nuclei: Completing the isotope chains of Yb, Os, Pt, and Hg

    NASA Astrophysics Data System (ADS)

    Marganiec, J.; Dillmann, I.; Domingo-Pardo, C.; Käppeler, F.

    2014-12-01

    The (n ,γ ) cross sections of the most neutron-rich stable isotopes of Yb, Os, Pt, and Hg have been determined in a series of activation measurements at the Karlsruhe 3.7 MV Van de Graaff accelerator, using the quasistellar neutron spectrum for k T =25 keV that can be produced with the 7Li(p ,n ) 7Be reaction. In this way, Maxwellian averaged cross sections could be directly obtained with only minor corrections. After irradiation the induced activities were counted with a HPGe detector via the strongest γ -ray lines. The stellar neutron capture cross sections of Yb,176174, Os,192190, Pt,198196, and Hg,204202, extrapolated to k T =30 keV, were found to be 157 ±6 mb, 114 ±8 mb, 278 ±11 mb, 160 ±7 mb, 171 ±19 mb, 94 ±4 mb, 62 ±2 mb, and 32 ±15 mb, respectively. In the case of 196Pt the partial cross section to the isomeric state at 399.5 keV could be determined as well. With these results the cross section data for long isotopic chains could be completed for a discussion of the predictive power of statistical model calculations towards the neutron-rich and proton-rich sides of the stability valley.

  8. Novel triaxial structure in low-lying states of neutron-rich nuclei around A ≈100

    NASA Astrophysics Data System (ADS)

    Xiang, J.; Yao, J. M.; Fu, Y.; Wang, Z. H.; Li, Z. P.; Long, W. H.

    2016-05-01

    Background: In recent years, the study of triaxiality in the low-lying states of atomic nuclei with transition character or shape coexistence has been of great interest. Previous studies indicate that the neutron-rich nuclei in the A ˜100 mass region with Z ˜40 ,N ˜60 serve as good grounds for examining the role of triaxiality in nuclear low-lying states. Purpose: The aim of this work is to provide a microscopic study of low-lying states for nuclei in the A ˜100 mass regions and to examine in detail the role of triaxiality in the shape-coexistence phenomena and the variation of shape with the isospin and spin values at the beyond mean-field level. Method: The starting point of our method is a set of relativistic mean-field plus BCS wave functions generated with a constraint on triaxial deformations (β ,γ ) . The excitation energies and electric multipole transition strengths of low-lying states are calculated by solving a five-dimensional collective Hamiltonian (5DCH) with parameters determined by the mean-field wave functions. Results: The low-lying states of Mo isotopes and of N =60 isotones in the A ˜100 mass region are calculated. The results indicate that triaxiality is essential to reproduce the data of excitation energies and electric quadrupole transition strengths in low-lying states and plays an important role in the shape evolution as a function of nucleon number. However, the decrease of nuclear collectivity with the increase of angular momentum in neutron-rich Mo isotopes has not been reproduced. Conclusions: The evolution of nuclear collectivity in the low-lying states of neutron-rich nuclei in the A ˜100 mass region as a function of nucleon number is governed by the novel triaxial structure. However, the mechanism that governs the variation of nuclear shape with spin in Mo isotopes remains unclear and deserves further investigation by taking into account the effects other than the collective motions.

  9. Observation of new K isomers among neutron-rich rare earth nuclei produced by in-flight fission of 345 MeV/nucleon 238U

    NASA Astrophysics Data System (ADS)

    Kameda, Daisuke; Kubo, Toshiyuki; BigRIPS new isotope Collaboration

    2014-09-01

    We have performed search for new K isomers for a wide range of neutron-rich rare earth nuclei using the BigRIPS separator at RIKEN RIBF. The rare earth nuclei were produced by in-flight fission of a 238U beam at 345 MeV/nucleon, and isomeric gamma rays were detected using four clover-type germanium detectors. As a result, we have observed a total of 25 new microsecond isomers: 158 m , 159 m , 160 mNd, 158 m , 159 m , 161 mPm, 160 m , 161 m , 162 mSm, 163 m , 164 mEu, 162 m , 164 m , 165 m , 166 mGd, 164 m , 165 m , 166 m , 167 m , 168 mTb, 167 m , 168 m , 169 m , 170 mDy, and 171mHo, and obtained a wealth of spectroscopic information on these nuclei. The nuclei in this region are predicted to be well deformed with a prolate shape, and Kisomers are expected to appear due to the K hindrance. In the present measurement, as anticipated, many of the observed new isomers have been interpreted as a K isomer, because we could identify some gamma rays which belong to the grand-state rotational band being fed by isomeric transitions. The systematics of known K isomers, such as those in neighboring higher- Zisotones, also help and support the interpretation of isomerism. Here we will report on the details of the experimental results and discuss the possible configurations of deformed orbits for the observed new K isomers.

  10. Decay Studies of Very Neutron Rich Nuclei near 78Ni

    SciTech Connect

    Winger, J. A.; Ilyushkin, S.; Korgul, A.; Gross, Carl J; Rykaczewski, Krzysztof Piotr; Batchelder, J. C.; Goodin, C.; Grzywacz, R.; Hamilton, J. H.; Krolas, W.; Liddick, Sean; Mazzocchi, C.; Nelson, C.; Padgett, Stephen; Piechaczek, A.; Rajabali, M. M.; Shapira, Dan; Zganjar, E. F.

    2008-01-01

    The properties of beta-gamma and beta-delayed neutron emission from 76-79Cu and 83-85Ga were measured at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. Selected results on the decay properties of copper isotopes are briefly presented and discussed.

  11. Direct Mass Measurements in the Light Neutron-Rich Region Using a Combined Energy and Time-of-Flight Technique

    NASA Astrophysics Data System (ADS)

    Pillai, C.; Swenson, L. W.; Vieira, D. J.; Butler, G. W.; Wouters, J. M.; Rokni, S. H.; Vaziri, K.; Remsberg, L. P.

    This experiment has demonstrated that direct mass measurements can be performed (albeit of low precision in this first attempt) using the M proportional to ET(2) method. This technique has the advantage that many particle-bound nuclei, produced in fragmentation reactions can be measured simultaneously, independent of their N or Z. The main disadvantage of this approach is that both energy and time-of-flight must be measured precisely on an absolute scale. Although some mass walk with N and Z was observed in this experiment, these uncertainties were largely removed by extrapolating the smooth dependence observed for known nuclei which lie closer to the valley of (BETA)-stability. Mass measurements for several neutron-rich light nuclei ranging from C-17 to NE-26 have been performed. In all cases these measurements agree with the latest mass compilation of Wapstra and Audi. The masses of N-20 N and F-24 have been determined for the first time.

  12. Structure of neutron-rich Isotopes {sup 8}Li and {sup 9}Li and allowance for it in elastic scattering

    SciTech Connect

    Ibraeva, E. T.; Zhusupov, M. A.; Imambekov, O.; Sagindykov, Sh. Sh.

    2008-07-15

    The differential cross sections for elastic proton scattering on the unstable neutron-rich nuclei {sup 8}Li and {sup 9}Li at E = 700 and 60 MeV per nucleon were considered. The {sup 8}Li nucleus was treated on the basis of the three-body {alpha}-t-n model, while the {sup 9}Li nucleus was considered within the {alpha}-t-n and {sup 7}Li-n-n models. The cross sections in question were calculated within Glauber diffraction theory. A comparison of the results with available experimental data made it possible to draw conclusions on the quality of the wave functions and potential used in the calculations.

  13. Beta decay of neutron-rich Co: Probing single-particle states at and above the N=40 subshell closure

    SciTech Connect

    Mueller, W. F.; Bruyneel, B.; Franchoo, S.; Huyse, M.; Kruglov, K.; Kudryavtsev, Y.; Raabe, R.; Reusen, I.; Duppen, P. van; Roosbroeck, J. van; Vermeeren, L.; Weissman, L.; Woehr, A.; Koester, U.; Kratz, K.-L.; Pfeiffer, B.; Thirolf, P.; Walters, W. B.

    1999-09-02

    Neutron-rich Co nuclei with A=66-70 were produced by the laser-ionization isotope-separation on-line method. The {beta} decay from these nuclei has been studied. A case example is given by reporting on the observed decay scheme of {sup 68}Co. The half life of the ground-state decay of this nucleus was measured to be 0.21(3) seconds. In addition, a new {beta} decaying isomer half life of 1.16(25) seconds was discovered. The level scheme of {sup 68}Ni has been significantly extended, and an interpretation of the observed levels is made by assuming that the N=40 gap has the characteristics of a shell closure.

  14. Observation of a vh{sub 11/2} pair alignment in neutron-rich {sup 118}Pd

    SciTech Connect

    Zhang, X. Q.; Hamilton, J. H.; Ramayya, A. V.; Zhu, S. J.; Hwang, J. K.; Beyer, C. J.; Kormicki, J.; Jones, E. F.; Gore, P. M.; Babu, B. R. S.

    2001-02-01

    The yrast band was significantly extended to 14{sup +} and the {gamma} band to 5{sup +} in neutron-rich {sup 118}Pd by measuring the {gamma}-{gamma}-{gamma} coincidences emitted from the spontaneous fission of {sup 252}Cf with Gammasphere. The first band crossing was observed in the yrast band in {sup 118}Pd at a frequency of {Dirac_h}{omega}{approx}0.36 MeV at the starting point of the backbending, which is similar to that found in {sup 112-116}Pd. The first bandbending in the yrast cascade in {sup 118}Pd is interpreted to be built on a two h{sub 11/2} neutron configuration based on its similarity to the yrast bands in even-even {sup 112-116}Pd. Our result indicates {sup 118}Pd still maintains a prolate shape. The quasineutron Routhian calculations indicate a lower crossing frequency for the h{sub 11/2} level.

  15. {beta}-decay half-lives of new neutron-rich isotopes of elements from Pm to Tb

    SciTech Connect

    Ichikawa, S.; Asai, M.; Tsukada, K.; Nishinaka, I.; Nagame, Y.; Osa, A.; Sakama, M.; Oura, Y.; Kojima, Y.; Shibata, M.; Kawade, K.

    1999-11-16

    Eight new neutron-rich lanthanide isotopes produced in the proton-induced fission of {sup 238}U have been identified using the JAERI on-line isotope separator (JAERI-ISOL) coupled to a gas-jet transport system. For six of these, each half-life was determined: {sup 159}Pm (2{+-}1 s), {sup 161}Sm (4.8{+-}0.8 s), {sup 165}Gd (10.3{+-}1.6 s), {sup 166}Tb (21{+-}6 s), {sup 167}Tb (19.4{+-}2.7 s) and {sup 168}Tb (8.2{+-}1.3 s). The observed half-lives were compared with theoretical calculations. The recent calculation by the gross theory with the new one-particle strength function shows quite good agreement with the experimental half-lives.

  16. {beta}-Decay Half-Lives of New Neutron-Rich Isotopes of Elements from Pm to Tb

    SciTech Connect

    S. Ichikawa; M. Asai; K. Tsukada; A. Osa; M. Sakama; Y. Kojima; M. Shibata; I. Nishinaka; Y. Nagame; Y. Oura; K. Kawade

    1999-12-31

    Eight new neutron-rich lanthanide isotopes produced in the proton-induced fission of {sup 238}U have been identified using the JAERI on-line isotope separator (JAERI-ISOL) coupled to a gas-jet transport system. For six of these, each half-life was determined: {sup 159}Pm (2 {+-} 1 s), {sup 161}Sm (4.8 {+-} 0.8 s), {sup 165}Gd (10.3 {+-} 1.6 s), {sup 166}Tb (21 {+-} 6 s), {sup 167}Tb (19.4 {+-} 2.7 s) and {sup 168}Tb (8.2 {+-} 1.3 s). The observed half-lives were compared with theoretical calculations. The recent calculation by the gross theory with the new one-particle strength function shows quite good agreement with the experimental half-lives.

  17. Continuum quasiparticle random-phase approximation for astrophysical direct neutron capture reactions on neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Matsuo, Masayuki

    2015-03-01

    I formulate a many-body theory to calculate the cross section of direct radiative neutron capture reaction by means of the Hartree-Fock-Bogoliubov mean-field model and the continuum quasiparticle random-phase approximation (QRPA). A focus is put on very-neutron-rich nuclei and low-energy neutron kinetic energy in the range from 1 keV to several MeV, which is relevant to the rapid neutron capture process of nucleosynthesis. I begin with the photoabsorption cross section and the E 1 strength function. Next, in order to apply the reciprocity theorem, I decompose the cross section into partial cross sections corresponding to different channels of one- and two-neutron emission decays of photo-excited states. A numerical example is shown for the photo-absorption of 142Sn and the neutron capture of 141Sn .

  18. Competing γ-rigid and γ-stable vibrations in neutron-rich Gd and Dy isotopes

    NASA Astrophysics Data System (ADS)

    Budaca, R.; Budaca, A. I.

    2015-10-01

    An exactly separable version of the Bohr Hamiltonian which combines the γ-stable and γ-rigid axial vibration-rotation is used to describe the collective properties of few neutron-rich transitional nuclei. The coupling between the two types of collective motion is managed through a rigidity parameter which also influences the geometry of the shape phase space. While the γ-angular part of the problem associated to axially symmetric shapes is treated within the small angles approximation and the stiff γ oscillation hypothesis, the β vibration is described by means of a Davidson potential. The resulting model have three free parameters not counting the scale and was successfully applied for the description of the collective spectra for few heavier isotopes of Gd and Dy. In both cases a critical nucleus was identified through a discontinuous behavior in respect to the rigidity parameter and relevant experimental observables.

  19. A New Island of Inversion Far From Stability: Structure of Neutron-Rich Nuclei Near N = 40

    SciTech Connect

    Lenzi, Silvia M.

    2010-08-04

    Recent results obtained for neutron-rich nuclei of mass A{approx}60-70 are presented together with the theoretical interpretation. The development of a new region of deformation approaching the neutron number N = 40 in Cr and Fe isotopes is discussed. A new effective interaction that considers the full fp shell model space for protons and the p{sub 3/2}, p{sub 1/2}, f{sub 5/2}, g{sub 9/2}, d{sub 5/2} orbitals for the neutrons allows to reproduce, for the first time, the different structure properties of these nuclei. The configuration of the calculated states suggests the development of a new island of inversion at N{approx}40. The perspectives offered by the forthcoming operation of the AGATA Demonstrator Array coupled to the magnetic spectrometer PRISMA at LNL are also discussed.

  20. Shell quenching in {sup 78}Ni: A hint from the structure of neutron-rich copper isotopes

    SciTech Connect

    Sieja, K.; Nowacki, F.

    2010-06-15

    Recent progress in experimental techniques allows us to study very exotic systems like neutron-rich nuclei in the vicinity of {sup 78}Ni. The spectroscopy of this region can nowadays be studied theoretically in the large scale shell model calculations. In this work, we perform a shell model study of odd copper nuclei with N=40-50, in a large valence space with the {sup 48}Ca core, using a realistic interaction derived from the CD-Bonn potential. We present the crucial importance of the proton core excitations for the description of spectra and magnetic moments, which are for the first time correctly reproduced in theoretical calculations. Shell evolution from {sup 68}Ni to {sup 78}Ni is discussed in detail. A weakening of the Z=28 gap when approaching the N=50 shell closure, suggested by the experimental evidence, is confirmed in the calculations.

  1. Zirconium—Hafnium Isotope Evidence from Meteorites for the Decoupled Synthesis of Light and Heavy Neutron-rich Nuclei

    NASA Astrophysics Data System (ADS)

    Akram, W.; Schönbächler, M.; Sprung, P.; Vogel, N.

    2013-11-01

    Recent work based on analyses of meteorite and terrestrial whole-rock samples showed that the r- and s- process isotopes of Hf were homogeneously distributed throughout the inner solar system. We report new Hf isotope data for Calcium-Aluminum-rich inclusions (CAIs) of the CV3 carbonaceous chondrite Allende, and novel high-precision Zr isotope data for these CAIs and three carbonaceous chondrites (CM, CO, CK). Our Zr data reveal enrichments in the neutron-rich isotope 96Zr (<=1ɛ in 96Zr/90Zr) for bulk chondrites and CAIs (~2ɛ). Potential isotope effects due to incomplete sample dissolution, galactic and cosmic ray spallation, and the nuclear field shift are assessed and excluded, leading to the conclusion that the 96Zr isotope variations are of nucleosynthetic origin. The 96Zr enrichments are coupled with 50Ti excesses suggesting that both nuclides were produced in the same astrophysical environment. The same CAIs also exhibit deficits in r-process Hf isotopes, which provides strong evidence for a decoupling between the nucleosynthetic processes that produce the light (A <= 130) and heavy (A > 130) neutron-rich isotopes. We propose that the light neutron-capture isotopes largely formed in Type II supernovae (SNeII) with higher mass progenitors than the supernovae that produced the heavy r-process isotopes. In the context of our model, the light isotopes (e.g. 96Zr) are predominantly synthesized via charged-particle reactions in a high entropy wind environment, in which Hf isotopes are not produced. Collectively, our data indicates that CAIs sampled an excess of materials produced in a normal mass (12-25 M ⊙) SNII.

  2. ZIRCONIUM—HAFNIUM ISOTOPE EVIDENCE FROM METEORITES FOR THE DECOUPLED SYNTHESIS OF LIGHT AND HEAVY NEUTRON-RICH NUCLEI

    SciTech Connect

    Akram, W.; Schönbächler, M.; Sprung, P.; Vogel, N.

    2013-11-10

    Recent work based on analyses of meteorite and terrestrial whole-rock samples showed that the r- and s- process isotopes of Hf were homogeneously distributed throughout the inner solar system. We report new Hf isotope data for Calcium-Aluminum-rich inclusions (CAIs) of the CV3 carbonaceous chondrite Allende, and novel high-precision Zr isotope data for these CAIs and three carbonaceous chondrites (CM, CO, CK). Our Zr data reveal enrichments in the neutron-rich isotope {sup 96}Zr (≤1ε in {sup 96}Zr/{sup 90}Zr) for bulk chondrites and CAIs (∼2ε). Potential isotope effects due to incomplete sample dissolution, galactic and cosmic ray spallation, and the nuclear field shift are assessed and excluded, leading to the conclusion that the {sup 96}Zr isotope variations are of nucleosynthetic origin. The {sup 96}Zr enrichments are coupled with {sup 50}Ti excesses suggesting that both nuclides were produced in the same astrophysical environment. The same CAIs also exhibit deficits in r-process Hf isotopes, which provides strong evidence for a decoupling between the nucleosynthetic processes that produce the light (A ≤ 130) and heavy (A > 130) neutron-rich isotopes. We propose that the light neutron-capture isotopes largely formed in Type II supernovae (SNeII) with higher mass progenitors than the supernovae that produced the heavy r-process isotopes. In the context of our model, the light isotopes (e.g. {sup 96}Zr) are predominantly synthesized via charged-particle reactions in a high entropy wind environment, in which Hf isotopes are not produced. Collectively, our data indicates that CAIs sampled an excess of materials produced in a normal mass (12-25 M{sub ☉}) SNII.

  3. Nuclear Structure Between N = 20 and N = 28: Beta-Decay in the Neutron-Rich Mg and Al Isotopes

    NASA Astrophysics Data System (ADS)

    Crawford, Heather; NSCL Experiment E14063 Team

    2015-10-01

    The structure of nuclei in the vicinity of expected nuclear shell closures away from stability has been, and continues to be, a cornerstone for nuclear structure study. The confirmation of certain ``magic numbers'' in exotic nuclei provides insight into the evolution of nucleon configurations with isospin, but perhaps even more light is shed into the structure of the atomic nucleus when expected shell closures are found to be weakened, or entirely disappear. Two instances where this has been the case are the N = 20 and N = 28 neutron shell closures in the neutron-rich Mg, Si and S nuclei. However, a question which is only beginning to be answered is the nature of the transitional nuclei between N = 20 and 28. Recent experimental work in the Mg isotopes has suggested a chain of prolate-deformed nuclei at Z = 12, but the nature of the Al and Si isotopes just above remains a question. An experiment was conducted at NSCL to study the β-decay of neutron-rich Na, Mg, Al and Si isotopes to provide additional, and in some cases, first information on the level structures of the daughter isotopes in the region between N = 20 and N = 28. First results from this work will be presented, and the implications for nuclear structural evolution in this region discussed. This work was supported by the NSF under Grant No. PHY-1068217 (NSCL) and by the U. S. Department of Energy, Office of Science, Office of Nuclear Physics under Contract No. DE-AC02-05CH11231 (LBNL).

  4. Neutron-proton effective mass splitting in neutron-rich matter and its impacts on nuclear reactions

    NASA Astrophysics Data System (ADS)

    Li, Bao-An; Chen, Lie-Wen

    2015-04-01

    The neutron-proton effective mass splitting in neutron-rich nucleonic matter reflects the spacetime nonlocality of the isovector nuclear interaction. It affects the neutron/proton ratio during the earlier evolution of the Universe, cooling of proto-neutron stars, structure of rare isotopes and dynamics of heavy-ion collisions. While there is still no consensus on whether the neutron-proton effective mass splitting is negative, zero or positive and how it depends on the density as well as the isospin-asymmetry of the medium, significant progress has been made in recent years in addressing these issues. There are different kinds of nucleon effective masses. In this mini-review, we focus on the total effective masses often used in the non-relativistic description of nuclear dynamics. We first recall the connections among the neutron-proton effective mass splitting, the momentum dependence of the isovector potential and the density dependence of the symmetry energy. We then make a few observations about the progress in calculating the neutron-proton effective mass splitting using various nuclear many-body theories and its effects on the isospin-dependence of in-medium nucleon-nucleon cross-sections. Perhaps, our most reliable knowledge so far about the neutron-proton effective mass splitting at saturation density of nuclear matter comes from optical model analyses of huge sets of nucleon-nucleus scattering data accumulated over the last five decades. The momentum dependence of the symmetry potential from these analyses provide a useful boundary condition at saturation density for calibrating nuclear many-body calculations. Several observables in heavy-ion collisions have been identified as sensitive probes of the neutron-proton effective mass splitting in dense neutron-rich matter based on transport model simulations. We review these observables and comment on the latest experimental findings.

  5. Neutron-rich isotope production using a uranium carbide - carbon nanotubes SPES target prototype

    NASA Astrophysics Data System (ADS)

    Corradetti, S.; Biasetto, L.; Manzolaro, M.; Scarpa, D.; Carturan, S.; Andrighetto, A.; Prete, G.; Vasquez, J.; Zanonato, P.; Colombo, P.; Jost, C. U.; Stracener, D. W.

    2013-05-01

    The SPES (Selective Production of Exotic Species) project, under development at the Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali di Legnaro (INFN-LNL), is a new-generation Isotope Separation On-Line (ISOL) facility for the production of radioactive ion beams by means of the proton-induced fission of uranium. In the framework of the research on the SPES target, seven uranium carbide discs, obtained by reacting uranium oxide with graphite and carbon nanotubes, were irradiated with protons at the Holifield Radioactive Ion Beam Facility (HRIBF) of Oak Ridge National Laboratory (ORNL). In the following, the yields of several fission products obtained during the experiment are presented and discussed. The experimental results are then compared to those obtained using a standard uranium carbide target. The reported data highlights the capability of the new type of SPES target to produce and release isotopes of interest for the nuclear physics community.

  6. Single-Neutron Structure of Neutron-Rich Nuclei near N=50 and N=82

    SciTech Connect

    Cizewski, J. A.; Jones, K. L.; Kozub, R. L.; Pain, S. D.; Bardayan, Daniel W; Blackmon, Jeff C; Adekola, Aderemi S; Chae, K. Y.; Chipps, K.; Erikson, Luke; Gaddis, A. L.; Harlin, Christopher W; Hatarik, Robert; Howard, Joshua A; Kaplan, Ron; Krolas, W.; Liang, J Felix; Livesay, Jake; Ma, Zhanwen; Matei, Catalin; Moazen, Brian; Nesaraja, Caroline D; O'Malley, Patrick; Patterson, N. P.; Paulauskas, Stanley; Shapira, Dan; Shriner, Jr., John F; Sissom, D. J.; Smith, Michael Scott; Swan, T. P.; Thomas, J. S.; Wilson, Gemma L

    2009-01-01

    The 82Ge, 84Se, 132Sn, 130Sn, and 134Te (d,p) reactions have been measured with {approx}4-5-MeV-A rare isotope beams and CD2 targets at the HRIBF at ORNL. Energies and spectroscopic strengths have been measured for excitations in 83Ge and 85Se. Direct neutron capture calculations on 82Ge are presented. Preliminary results for single-neutron excitations in 131Sn, 133Sn, and 135Te are reported.

  7. Deformation in the neutron rich sulfur isotopes {sup 40}S and {sup 42}S

    SciTech Connect

    Glasmacher, T.; Scheit, H.; Brown, B.A.

    1996-12-31

    In the experiment described here radioactive beams of {sup 40,42}S and {sup 44,46}Ar (E{approx}40 MeV/nucl.) were produced in the A1200 fragment separator at the National Superconducting Cyclotron Laboratory at Michigan State University by fragmenting an 80 MeV/nucleon {sup 48}Ca{sup 13+} beam in a 379 mg/cm{sup 2} {sup 9}Be target. The exotic ions were positively identified by a time of flight measurement before interacting with the secondary gold target (93.5 mg/cm{sup 2} or 184.1 mg/cm{sup 2}). After interacting with the virtual photon field in the gold target, fragments scattered into a lab angle of less than 4.1{degrees} were detected in a fast/slow plastic phoswich detector located downstream from the secondary target. The energy loss - total energy measurement allowed the rejection of events which led to the breakup of the projectile in the target. Photons from the deexcitation of the projectile were measured in coincidence with beam particles. The photons emitted from the excited projectile can be clearly distinguished from photons coming from the target by their Doppler shift and Doppler broadening.

  8. Photoionization of argon clusters

    SciTech Connect

    Dehmer, Patricia M.; Pratt, Stephen T.

    1982-01-01

    Argon clusters were produced in a free supersonic molecular beam expansion of pure argon at room temperature and the photoionization efficiency curves of the trimer through hexamer were measured in the wavelength regions from threshold to 700 Â. A study of the Ar⁺3 photoionization efficiency curve as a function of nozzle stagnation pressure shows that fragmentation of heavier clusters can dominate the spectrum, even near threshold, and even when the nozzle conditions are such that the Ar⁺4 intensity is only a small fraction of the Ar⁺3 intensity. The Ar⁺3 photoionization efficiency curve, obtained using nozzle stagnation conditions such that no heavier ions were detected, exhibits several broad peaks near threshold which show similarities to bands of the dimer. At high nozzle stagnation pressures, the photoionization efficiency curves for Ar⁺3 to Ar⁺6 are nearly identical due to the effects of fragmentation. These spectra exhibit two very broad features which are similar to features observed in the solid. The threshold regions for all the positive ions show extremely gradual onsets, making it difficult to determine the appearance potentials accurately. The appearance potentials for Ar⁺2 and Ar⁺3 are 855.0±1.5 and 865.0±1.5 Â, respectively, yielding a value of 0.18±0.05 eV for the dissociation energy of Ar⁺3. The appearance potentials for the heavier clusters Ar⁺4 through Ar⁺6 are all approximately 870±2 Â.

  9. Predicted yields of new neutron-rich isotopes of nuclei with Z=64-80 in the multinucleon transfer reaction {sup 48}Ca+{sup 238}U

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Sargsyan, V. V.; Scheid, W.

    2010-05-15

    The production cross sections of new neutron-rich isotopes of nuclei with charge numbers Z=64-80 are estimated for future experiments in the multinucleon transfer reaction {sup 48}Ca+{sup 238}U at bombarding energy E{sub c.m.}=189 MeV close to the Coulomb barrier.

  10. Giant and Low-Energy Dipole Modes in Neutron-Rich Nuclei

    NASA Astrophysics Data System (ADS)

    Rossi, D. M.; Adrich, P.; Aksouh, F.; Alvarez-Pol, H.; Aumann, T.; Benlliure, J.; Böhmer, M.; Boretzky, K.; Casarejos, E.; Chartier, M.; Chatillon, A.; Cortina-Gil, D.; Datta Pramanik, U.; Emling, H.; Ershova, O.; Fernandez-Dominguez, B.; Geissel, H.; Gorska, M.; Heil, M.; Johansson, H.; Junghans, A.; Kiselev, O.; Klimkiewicz, A.; Kratz, J. V.; Kurz, N.; Labiche, M.; Le Bleis, T.; Lemmon, R.; Litvinov, Yu. A.; Mahata, K.; Maierbeck, P.; Movsesyan, A.; Nilsson, T.; Nociforo, C.; Palit, R.; Paschalis, S.; Plag, R.; Reifarth, R.; Simon, H.; Sümmerer, K.; Wagner, A.; Walus, W.; Weick, H.; Winkler, M.

    2014-09-01

    The E1 strength of exotic Ni isotopes has been measured at the R3B-LAND setup at GSI in Darmstadt. The experimental method relied on Coulomb excitation in inverse kinematics, for beam energies around 500 MeV/u. The excitation energy was reconstructed using the invariant mass, enabling the observation of the GDR and of additional low-lying E1 strength. The analysis of the neutron kinetic energies also allowed the extraction of the branching ratio for the direct neutron decay of 68Ni, amounting to 25(2)%.