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Sample records for neutron rich isotopes

  1. A microscopic description of neutron-rich lithium isotopes

    SciTech Connect

    Burov, V.V.; Rzjanin, M.V.; Miller, H.G.; Shitikova, K.V.; Yen, G.D.

    1994-12-01

    A unified calculation of neutron-rich isotopes in lithium is performed using the hyperspherical basis in which the underlying symmetry of each isotope exhibits a simple structure. The variation of the binding energy as a function of mass number is qualitatively reproduced, and the asymptotic of radial distribution of each isotope decreases exponentially. The form factors of the lithium isotopes are calculated and display diffraction minima. 27 refs., 3 figs., 3 tabs.

  2. 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.

  3. Search for octupole deformation in neutron rich Xe isotopes

    SciTech Connect

    Bentaleb, M.; Schulz, N.; Lubkiewicz, E.

    1994-07-01

    A search for octupole deformation in neutron rich Xe isotopes has been conducted through gamma-ray spectroscopy of primary fragments produced in the spontaneous fission of {sup 248}Cm. The spectrometer consisted of the Eurogam array and a set of 5 LEPS detectors. Level schemes were constructed for Xe isotopes with masses ranging from 138 to 144. Except for {sup 139}Xe, none of them exhibit an alternating parity quasimolecular band, {alpha} feature usually encountered in octupole deformed nuclei. Substantial evidence for reflection asymmetric shape in the intrinsic system of the nucleus exists for the light actinide nuclei.

  4. Dipole response of neutron-rich Sn isotopes

    NASA Astrophysics Data System (ADS)

    Klimkiewicz, A.; Adrich, P.; Boretzky, K.; Fallot, M.; Aumann, T.; Cortina-Gil, D.; Datta Pramanik, U.; Elze, Th. W.; Emling, H.; Geissel, H.; Hellstroem, M.; Jones, K. L.; Kratz, J. V.; Kulessa, R.; Leifels, Y.; Nociforo, C.; Palit, R.; Simon, H.; Surowka, G.; Sümmerer, K.; Typel, S.; Walus, W.

    2007-05-01

    The neutron-rich isotopes 129-133Sn were studied in a Coulomb excitation experiment at about 500 AMeV using the FRS-LAND setup at GSI. From the exclusive measurement of all projectile-like particles following the excitation and decay of the projectile in a high-Z target, the energy differential cross section can be extracted. At these beam energies dipole transitions are dominating, and within the semi-classical approach the Coulomb excitation cross sections can be transformed into photoabsorption cross sections. In contrast to stable Sn nuclei, a substantial fraction of dipole strength is observed at energies below the giant dipole resonance (GDR). For 130Sn and 132Sn this strength is located in a peak-like structure around 10 MeV excitation energy and exhibits a few percent of the Thomas-Reiche Kuhn (TRK) sum-rule strength. Several calculations predict the appearance of dipole strength at low excitation energies in neutron-rich nuclei. This low-lying strength is often referred to as pygmy dipole resonance (PDR) and, in a macroscopic picture, is discussed in terms of a collective oscillation of excess neutrons versus the core nucleons. Moreover, a sharp rise is observed at the neutron separation threshold around 5 MeV for the odd isotopes. A possible contribution of 'threshold strength', which can be described within the direct-breakup model is discussed. The results for the neutron-rich Sn isotopes are confronted with results on stable nuclei investigated in experiments using real photons.

  5. 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.

  6. Measurement of picosecond lifetimes in neutron-rich Xe isotopes

    NASA Astrophysics Data System (ADS)

    Ilieva, S.; Kröll, Th.; Régis, J.-M.; Saed-Samii, N.; Blanc, A.; Bruce, A. M.; Fraile, L. M.; de France, G.; Hartig, A.-L.; Henrich, C.; Ignatov, A.; Jentschel, M.; Jolie, J.; Korten, W.; Köster, U.; Lalkovski, S.; Lozeva, R.; Mach, H.; Mǎrginean, N.; Mutti, P.; Paziy, V.; Regan, P. H.; Simpson, G. S.; Soldner, T.; Thürauf, M.; Ur, C. A.; Urban, W.; Warr, N.

    2016-09-01

    Background: Lifetimes of nuclear excited states in fission fragments have been studied in the past following isotope separation, thus giving access mainly to the fragments' daughters and only to long-lived isomeric states in the primary fragments. For the first time now, short-lived excited states in the primary fragments, produced in neutron-induced prompt fission of 235U and 241Pu, were studied within the EXILL&FATIMA campaign at the intense neutron-beam facility of the Institute Laue-Langevin in Grenoble. Purpose: We aim to investigate the quadrupole collective properties of neutron-rich even-even 138,140,142Xe isotopes lying between the double shell closure N =82 and Z =50 and a deformed region with octupole collectivity. Method: The γ rays emitted from the excited fragments were detected with a mixed array consisting of 8 HPGe EXOGAM Clover detectors (EXILL) and 16 LaBr3(Ce) fast scintillators (FATIMA). The detector system has the unique ability to select the interesting fragment making use of the high resolution of the HPGe detectors and determine subnanosecond lifetimes using the fast scintillators. For the analysis the generalized centroid difference method was used. Results: We show that quadrupole collectivity increases smoothly with increasing neutron number above the closed N =82 neutron shell. Our measurements are complemented by state-of-the-art theory calculations based on shell-model descriptions. Conclusions: The observed smooth increase in quadrupole collectivity is similar to the evolution seen in the measured masses of the xenon isotopic chain and is well reproduced by theory. This behavior is in contrast to higher Z even-even nuclei where abrupt change in deformation occurs around N =90 .

  7. Proton radii of neutron-rich B isotopes and neutron surface thickness in 17B

    NASA Astrophysics Data System (ADS)

    Kanungo, Rituparna; Estrade, Alfredo; Horiuchi, Wataru

    2014-09-01

    As the neutron to proton asymmetry increases nuclei develop exotic structures such as neutron skin and halo. It is important to investigate how this asymmetry affects the proton distribution. The matter and proton radii have started unfolding a complete picture of the halo. For two-neutron halos the correlation between the halo neutrons and their distance from the core can be derived to define the average halo geometry. The proton radii are crucial information to extract the neutron skin thickness to constrain the equation of state of asymmetric nuclear matter. Very limited information is available on the proton radii of very neutron-rich nuclei. In this presentation, we will describe the new technique of extracting proton radii from charge changing cross sections using relativistic beams at GSI, Germany. The presentation will show first measurements of proton radii of the neutron-rich boron isotopes. The implications of the results in understanding the neutron surface thickness in the Borromean 17B and its possible halo structure will be discussed. As the neutron to proton asymmetry increases nuclei develop exotic structures such as neutron skin and halo. It is important to investigate how this asymmetry affects the proton distribution. The matter and proton radii have started unfolding a complete picture of the halo. For two-neutron halos the correlation between the halo neutrons and their distance from the core can be derived to define the average halo geometry. The proton radii are crucial information to extract the neutron skin thickness to constrain the equation of state of asymmetric nuclear matter. Very limited information is available on the proton radii of very neutron-rich nuclei. In this presentation, we will describe the new technique of extracting proton radii from charge changing cross sections using relativistic beams at GSI, Germany. The presentation will show first measurements of proton radii of the neutron-rich boron isotopes. The implications

  8. Efimov physics around the neutron-rich 60Ca isotope.

    PubMed

    Hagen, G; Hagen, P; Hammer, H-W; Platter, L

    2013-09-27

    We calculate the neutron-60Ca S-wave scattering phase shifts using state of the art coupled-cluster theory combined with modern ab initio interactions derived from chiral effective theory. Effects of three-nucleon forces are included schematically as density dependent nucleon-nucleon interactions. This information is combined with halo effective field theory in order to investigate the 60Ca-neutron-neutron system. We predict correlations between different three-body observables and the two-neutron separation energy of 62Ca. This provides evidence of Efimov physics along the calcium isotope chain. Experimental key observables that facilitate a test of our findings are discussed.

  9. Photoneutron cross sections for unstable neutron-rich oxygen isotopes.

    PubMed

    Leistenschneider, A; Aumann, T; Boretzky, K; Cortina, D; Cub, J; Datta Pramanik, U; Dostal, W; Elze, T W; Emling, H; Geissel, H; Grünschloss, A; Hellstr, M; Holzmann, R; Ilievski, S; Iwasa, N; Kaspar, M; Kleinböhl, A; Kratz, J V; Kulessa, R; Leifels, Y; Lubkiewicz, E; Münzenberg, G; Reiter, P; Rejmund, M; Scheidenberger, C; Schlegel, C; Simon, H; Stroth, J; Sümmerer, K; Wajda, E; Walús, W; Wan, S

    2001-06-11

    The dipole response of stable and unstable neutron-rich oxygen nuclei of masses A = 17 to A = 22 has been investigated experimentally utilizing electromagnetic excitation in heavy-ion collisions at beam energies about 600 MeV/nucleon. A kinematically complete measurement of the neutron decay channel in inelastic scattering of the secondary beam projectiles from a Pb target was performed. Differential electromagnetic excitation cross sections d sigma/dE were derived up to 30 MeV excitation energy. In contrast to stable nuclei, the deduced dipole strength distribution appears to be strongly fragmented and systematically exhibits a considerable fraction of low-lying strength.

  10. Ground-state properties of neutron-rich Mg isotopes

    NASA Astrophysics Data System (ADS)

    Watanabe, S.; Minomo, K.; Shimada, M.; Tagami, S.; Kimura, M.; Takechi, M.; Fukuda, M.; Nishimura, D.; Suzuki, T.; Matsumoto, T.; Shimizu, Y. R.; Yahiro, M.

    2014-04-01

    We analyze recently measured total reaction cross sections for 24-38Mg isotopes incident on 12C targets at 240 MeV/nucleon by using the folding model and antisymmetrized molecular dynamics (AMD). The folding model well reproduces the measured reaction cross sections, when the projectile densities are evaluated by the deformed Woods-Saxon (def-WS) model with AMD deformation. Matter radii of 24-38Mg are then deduced from the measured reaction cross sections by fine tuning the parameters of the def-WS model. The deduced matter radii are largely enhanced by nuclear deformation. Fully microscopic AMD calculations with no free parameter well reproduce the deduced matter radii for 24-36Mg, but still considerably underestimate them for 37,38Mg. The large matter radii suggest that 37,38Mg are candidates for deformed halo nucleus. AMD also reproduces other existing measured ground-state properties (spin parity, total binding energy, and one-neutron separation energy) of Mg isotopes. Neutron-number (N) dependence of deformation parameter is predicted by AMD. Large deformation is seen from 31Mg with N =19 to a drip-line nucleus 40Mg with N =28, indicating that both the N =20 and 28 magicities disappear. N dependence of neutron skin thickness is also predicted by AMD.

  11. Quadrupole collectivity in neutron-rich Fe and Cr isotopes.

    PubMed

    Crawford, H L; Clark, R M; Fallon, P; Macchiavelli, A O; Baugher, T; Bazin, D; Beausang, C W; Berryman, J S; Bleuel, D L; Campbell, C M; Cromaz, M; de Angelis, G; Gade, A; Hughes, R O; Lee, I Y; Lenzi, S M; Nowacki, F; Paschalis, S; Petri, M; Poves, A; Ratkiewicz, A; Ross, T J; Sahin, E; Weisshaar, D; Wimmer, K; Winkler, R

    2013-06-14

    Intermediate-energy Coulomb excitation measurements are performed on the N ≥ 40 neutron-rich nuclei (66,68)Fe and (64)Cr. The reduced transition matrix elements providing a direct measure of the quadrupole collectivity B(E2;2(1)(+) → 0(1)(+)) are determined for the first time in (68)Fe(42) and (64)Cr(40) and confirm a previous recoil distance method lifetime measurement in (66)Fe(40). The results are compared to state-of-the-art large-scale shell-model calculations within the full fpgd neutron orbital model space using the Lenzi-Nowacki-Poves-Sieja effective interaction and confirm the results of the calculations that show these nuclei are well deformed.

  12. Charge Radius Changes Of Even-even Neutron-Rich Tellurium Isotopes

    SciTech Connect

    Sifi, R.; Le Blanc, F.; Barre, N.; Ducourtieux, M.; Essabaa, S.; Lau, C.; Oms, J.; Roussiere, B.; Sauvage, J.; Cabaret, L.; Pinard, J.; Crawford, J.; Lee, J. K. P.; Genevey, J.; Huber, G.; Kowalska, M.; Seliverstov, M.; Le Scornet, G.; Stroke, H.

    2006-04-26

    Laser spectroscopy based on resonant ionization of laser-desorbed atoms has been used to study the neutron-rich tellurium isotopes with the COMPLIS facility at ISOLDE-CERN. The isotope shift and the hyperfine structure of several neutron-rich Te isotopes: 120-136Te and 123m-133mTe have been measured. From the hyperfine structure and the isotope shift we can extract the magnetic and quadrupole moments and the change in the mean square charge radius respectively. The mean square charge radii of the even-even isotopes have been deduced and their comparison with the known data for the other elements near Z=50 is presented. The experimental {delta} is compared with that obtained from the relativistic mean field calculations.

  13. {beta}{sup -}-delayed spectroscopy of neutron-rich tantalum nuclei: Shape evolution in neutron-rich tungsten isotopes

    SciTech Connect

    Alkhomashi, N.; Regan, P. H.; Podolyak, Zs.; Pietri, S.; Garnsworthy, A. B.; Steer, S. J.; Farrelly, G.; Cullen, I. J.; Gelletly, W.; Walker, P. M.; Benlliure, J.; Caserejos, E.; Estevez, M. E.; Morales, A. I.; Casten, R. F.; Gerl, J.; Wollersheim, H. J.; Gorska, M.; Kojouharov, I.; Schaffner, H.

    2009-12-15

    The low-lying structure of {sup 188,190,192}W has been studied following {beta} decays of the neutron-rich mother nuclei {sup 188,190,192}Ta produced following the projectile fragmentation of a 1-GeV-per-nucleon {sup 208}Pb primary beam on a natural beryllium target at the GSI Fragment Separator. The {beta}-decay half-lives of {sup 188}Ta, {sup 190}Ta, and {sup 192}Ta have been measured, with {gamma}-ray decays of low-lying states in their respective W daughter nuclei, using heavy-ion {beta}-{gamma} correlations and a position-sensitive silicon detector setup. The data provide information on the low-lying excited states in {sup 188}W, {sup 190}W, and {sup 192}W, which highlight a change in nuclear shape at {sup 190}W compared with that of lighter W isotopes. This evolution of ground-state structure along the W isotopic chain is discussed as evidence for a possible proton subshell effect for the A{approx}190 region and is consistent with maximization of the {gamma}-softness of the nuclear potential around N{approx}116.

  14. β -decay properties of neutron-rich rare-earth isotopes

    NASA Astrophysics Data System (ADS)

    Sarriguren, P.

    2017-01-01

    In this paper, β -decay properties of even-even neutron-rich isotopes in the rare-earth mass region are studied within a microscopic theoretical approach based on a proton-neutron quasiparticle random-phase approximation. The underlying mean field is constructed self-consistently from a deformed Hartree-Fock calculation with Skyrme interactions and pairing correlations to which particle-hole and particle-particle residual interactions are added. Nuclei in this mass region participate in the astrophysical rapid neutron capture process and are directly involved in the generation of the rare-earth peak in the isotopic abundance pattern centered at A ≃160 . The energy distributions of the Gamow-Teller strength as well as the β -decay half-lives and the β -delayed neutron-emission probabilities are discussed and compared with the available experimental information and with calculations based on different approaches.

  15. Fusion of neutron-rich oxygen isotopes in the crust of accreting neutron stars

    SciTech Connect

    Horowitz, C. J.; Dussan, H.; Berry, D. K.

    2008-04-15

    Fusion reactions in the crust of an accreting neutron star are an important source of heat, and the depth at which these reactions occur is important for determining the temperature profile of the star. Fusion reactions depend strongly on the nuclear charge Z. Nuclei with Z{<=}6 can fuse at low densities in a liquid ocean. However, nuclei with Z=8 or 10 may not burn until higher densities where the crust is solid and electron capture has made the nuclei neutron rich. We calculate the S factor for fusion reactions of neutron rich nuclei including {sup 24}O+{sup 24}O and {sup 28}Ne+{sup 28}Ne. We use a simple barrier penetration model. The S factor could be further enhanced by dynamical effects involving the neutron rich skin. This possible enhancement in S should be studied in the laboratory with neutron rich radioactive beams. We model the structure of the crust with molecular dynamics simulations. We find that the crust of accreting neutron stars may contain micro-crystals or regions of phase separation. Nevertheless, the screening factors that we determine for the enhancement of the rate of thermonuclear reactions are insensitive to these features. Finally, we calculate the rate of thermonuclear {sup 24}O+{sup 24}O fusion and find that {sup 24}O should burn at densities near 10{sup 11} g/cm{sup 3}. The energy released from this and similar reactions may be important for the temperature profile of the star.

  16. 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.

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

    NASA Astrophysics Data System (ADS)

    Chen, Wei-Chia; Piekarewicz, Jorge

    2015-04-01

    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 24 O isotope. In the case of the calcium isotopes, the drip line is predicted to be reached beyond 60 Ca. 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 208 Pb is rather small: Rskin208 = (0 . 161 +/- 0 . 011) fm. This same model, labelled FSUGarnet , predicts R1 . 4 = (13 . 1 +/- 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.

  18. 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.

  19. Shell Evolution in the Neutron-Rich Cu and Zn Isotopes

    NASA Astrophysics Data System (ADS)

    Belarge, Joe; Bazin, Daniel; Gade, Alexandra; Ayyad, Yassid; Bender, Peter; Elder, Robert; Elman, Brandon; Iwasaki, Hiro; Kobayashi, Nobuyuki; Loelius, Charles; Longfellow, Brenden; Lunderberg, Eric; Morfouace, Pierre; Sullivan, Chris; Weisshaar, Dirk; Whitmore, Kenneth

    2016-09-01

    Recent shell model calculations predict a gradual reduction of the Z=28 shell gap in Ni isotopes as the ν 1g9 / 2 orbital is filled from 68Ni to 78Ni [Otsuka et al. PRL 95, 232502]. These predictions can be experimentally tested by measuring the spectroscopic strength of a given orbital in an isotopic chain. The neutron-rich Cu isotopes, with one proton outside of a filled π 1f7 / 2 orbital, are some of the best candidates to exhibit the effects of the underlying structure evolution in this region. The high luminosity provided by fast beam, thick target experiments performed at the NSCL, coupled with the high resolution, high efficiency gamma-ray array GRETINA, provide a unique opportunity to study the neutron-rich Cu isotopes. The current experiment aims to measure the strength of 2p-1h excitations in 69-77Cu, populated through one proton knockout from 70-78Zn beams on a Be target, thereby probing the effective single particle energy and spectroscopic strength of the π 1f7 / 2 orbital. Results from the ongoing analysis will be presented.

  20. A Systematic Study of β- Decay of Neutron-Rich Rh and Ag Isotopes

    NASA Astrophysics Data System (ADS)

    Wang, Y.-B.; Dendooven, P.; Huikari, J.; Jokinen, A.; Kolhinen, V. S.; Lhersonneau, G.; Nieminen, A.; Nummela, S.; Penttilä, H.; Peräjärvi, K.; Rinta-Antila, S.; Szerypo, J.; Wang, J. C.; ńystö, J.

    2006-11-01

    Beta decay of neutron-rich even-mass 114-118Rh and 116-120Ag isotopes has been studied using on-line mass-separated sources that were produced by applying 25 MeV proton induced symmetric fission of natural uranium at the IGISOL facility. The β-γ and γ-γ coincidence spectroscopy is employed in all cases that enables for the construction of the decay scheme and for the deduction of the decay properties. Systematics for two-quasineutron states in 114,116,118Pd and for three-phonon multiplet in 114,116,118Cd are presented and discussed.

  1. Application of the generator coordinate method to neutron-rich Se and Ge isotopes

    NASA Astrophysics Data System (ADS)

    Higashiyama, Koji; Yoshinaga, Naotaka

    2014-03-01

    The quantum-number projected generator coordinate method (GCM) is applied to the neutron-rich Se and Ge isotopes, where the monopole and quadrupole pairing plus quadrupole-quadrupole interaction is employed as an effective interaction. The energy spectra obtained by the GCM are compared to both the shell model results and the experimental data. The GCM reproduces well the energy levels of high-spin states as well as the low-lying states. The structure of the low-lying collective states is analyzed through the GCM wave functions.

  2. Isomers of Pm Isotopes on the Neutron-Rich Frontier of the Deformed Z ~ 60 Region

    NASA Astrophysics Data System (ADS)

    Yokoyama, Rin; Ideguchi, Eiji; Simpson, Gary; Tanaka, Mana; Nishimura, Shunji; Doornnbal, Pieter; Söderström, Pär-Anders; Lorusso, Giuseppe; Xu, Zhengyu; Wu, Jin; Sumikama, Toshiyuki; Aoi, Nori; Baba, Hidetada; Bello, Frank; Browne, Frank; Daido, Rie; Fang, Yifan; Fukuda, Naoki; Gey, Guillaume; Go, Shintaro; Inabe, Naohiro; Isobe, Tadaaki; Kameda, Daisuke; Kobayashi, Kazuma; Kobayashi, Motoki; Komatsubara, Tetsuro; Kubo, Toshiyuki; Kuti, Istvan; Li, Zhihuan; Matsushita, Masafumi; Michimasa, Shin'ichiro; Moon, Chang-Bum; Nishibata, Hiroki; Nishizuka, Ippei; Odahara, Atsuko; Patel, Zena; Rice, Simon; Sahin, Eda; Sinclair, Laura; Suzuki, Hiroshi; Takeda, Hiroyuki; Taprogge, Jan; Vajta, Zsolt; Watanabe, Hiroshi; Yagi, Ayumi

    Neutron-rich Pm (Z = 61) isotopes were studied by delayed γ-ray spectroscopy at RIBF, Riken Nishina Center using the in-flight fission of 345 MeV/u 238U beam. An array of cluster-type Ge detectors, EURICA, was used to measure the delayed γ rays from stopped ions. Isomers were observed in 158Pm, 159Pm and 161Pm with half-lives of >16, 4.64(21), and 0.88(10) µs respectively. Preliminary level schemes for 159Pm and 161Pm were constructed in this study. They have ground-state bands similar to those of 153Pm and 155Pm. The isomeric state of 161Pm could be interpreted as a two quasi-particle excitation of neutrons with configuration of ν 7/2[633] otimes ν 1/2[521] as other Kπ = 4 - isomers observed systematically in other N = 100 isotones.

  3. Shape coexistence in neutron-rich odd-mass S isotopes

    NASA Astrophysics Data System (ADS)

    Mijatovic, Tea; Kobayashi, Nobuyuki; Iwasaki, Hiro; Loelius, Charles; Whitmore, Kenneth; Elder, Robert; Gade, Alexandra; Bazin, Daniel; Weisshaar, Dirk; Bender, Peter; Belarge, Joe; Lunderberg, Eric; Elman, Brandon; Longfellow, Brenden; Dewald, Alfred; Haylett, Thoryn; Mathry, Michael; Heil, Sebastian

    2017-01-01

    Collective motions in atomic nuclei at low excitation energies have been characterized by the ground-state shape as a single basis. This picture can be altered in exotic nuclei with unusual proton-to-neutron ratios if the nuclear shape can change drastically at low spin. Recently, there has been an increasing interest for shape-coexistence phenomena in neutron-rich S isotopes and studies suggested fairly large collectivity in 40 , 42 , 44S isotopes. We will discuss the search for isomeric or long-lived states in 45S for which no excited states are known in the literature and the pursuit to fully characterize the band structure of the low-lying states in 43,45S, which provide key information to establish a comprehensive picture of the shape coexistence in this region. Direct model-independent measurements of the 43,45S excited states were realized by applying the Recoil Distance Method with the TRIPLEX Plunger in conjunction with GRETINA to fast rare isotope beams at the NSCL.

  4. Low-energy Coulomb excitation of neutron-rich zinc isotopes

    NASA Astrophysics Data System (ADS)

    van de Walle, J.; Aksouh, F.; Behrens, T.; Bildstein, V.; Blazhev, A.; Cederkäll, J.; Clément, E.; Cocolios, T. E.; Davinson, T.; Delahaye, P.; Eberth, J.; Ekström, A.; Fedorov, D. V.; Fedosseev, V. N.; Fraile, L. M.; Franchoo, S.; Gernhauser, R.; Georgiev, G.; Habs, D.; Heyde, K.; Huber, G.; Huyse, M.; Ibrahim, F.; Ivanov, O.; Iwanicki, J.; Jolie, J.; Kester, O.; Köster, U.; Kröll, T.; Krücken, R.; Lauer, M.; Lisetskiy, A. F.; Lutter, R.; Marsh, B. A.; Mayet, P.; Niedermaier, O.; Pantea, M.; Raabe, R.; Reiter, P.; Sawicka, M.; Scheit, H.; Schrieder, G.; Schwalm, D.; Seliverstov, M. D.; Sieber, T.; Sletten, G.; Smirnova, N.; Stanoiu, M.; Stefanescu, I.; Thomas, J.-C.; Valiente-Dobón, J. J.; Duppen, P. Van; Verney, D.; Voulot, D.; Warr, N.; Weisshaar, D.; Wenander, F.; Wolf, B. H.; Zielińska, M.

    2009-01-01

    At the radioactive ion beam facility REX-ISOLDE, neutron-rich zinc isotopes were investigated using low-energy Coulomb excitation. These experiments have resulted in B(E2,21+→01+) values in Zn74-80, B(E2,41+→21+) values in Zn74,76 and the determination of the energy of the first excited 21+ states in Zn78,80. The zinc isotopes were produced by high-energy proton- (A=74,76,80) and neutron- (A=78) induced fission of U238, combined with selective laser ionization and mass separation. The isobaric beam was postaccelerated by the REX linear accelerator and Coulomb excitation was induced on a thin secondary target, which was surrounded by the MINIBALL germanium detector array. In this work, it is shown how the selective laser ionization can be used to deal with the considerable isobaric beam contamination and how a reliable normalization of the experiment can be achieved. The results for zinc isotopes and the N=50 isotones are compared to collective model predictions and state-of-the-art large-scale shell-model calculations, including a recent empirical residual interaction constructed to describe the present experimental data up to 2004 in this region of the nuclear chart.

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

    NASA Astrophysics Data System (ADS)

    Yoshida, Kenichi

    2009-10-01

    We investigate the microscopic structure of the low-lying isovector-dipole excitation mode in neutron-rich Mg36,38,40 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 Ex<10 MeV exhausts about 6.0% of the classical Thomas-Reiche-Kuhn dipole sum rule in Mg40. 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.

  6. 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.

  7. New isotope {sup 44}Si and systematics of the production cross sections of the most neutron-rich nuclei

    SciTech Connect

    Tarasov, O. B.; Baumann, T.; Bazin, D.; III, C. M. Folden; Ginter, T. N.; Hausmann, M.; Matos, M.; Portillo, M.; Schiller, A.; Stolz, A.; Amthor, A. M.; Gade, A.; Nettleton, A.; Sherrill, B. M.; Thoennessen, M.; Morrissey, D. J.

    2007-06-15

    The results of measurements of the production of neutron-rich nuclei by the fragmentation of a {sup 48}Ca beam at 142 MeV/nucleon are presented. Evidence was found for the production of a new isotope that is the most neutron-rich silicon nuclide, {sup 44}Si, in a net neutron pickup process. A simple systematic framework was found to describe the production cross sections based on thermal evaporation from excited prefragments that allows extrapolation to other weak reaction products.

  8. Coulomb breakup of neutron-rich 29,30Na isotopes near the island of inversion

    NASA Astrophysics Data System (ADS)

    Rahaman, A.; Datta, Ushasi; Aumann, T.; Beceiro-Novo, S.; Boretzky, K.; Caesar, C.; Carlson, B. V.; Catford, W. N.; Chakraborty, S.; Chartier, M.; Cortina-Gil, D.; De Angelis, G.; Diaz Fernandez, P.; Emling, H.; Ershova, O.; Fraile, L. M.; Geissel, H.; Gonzalez-Diaz, D.; Johansson, H.; Jonson, B.; Kalantar-Nayestanaki, N.; Kröll, T.; Krücken, R.; Kurcewicz, J.; Langer, C.; Le Bleis, T.; Leifels, Y.; Marganiec, J.; Münzenberg, G.; Najafi, M. A.; Nilsson, T.; Nociforo, C.; Panin, V.; Paschalis, S.; Plag, R.; Reifarth, R.; Ricciardi, M. V.; Rigollet, C.; Rossi, D.; Scheidenberger, C.; Scheit, H.; Simon, H.; Taylor, J. T.; Togano, Y.; Typel, S.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Weigand, M.; Winfield, J. S.; Yakorev, D.; Zoric, M.

    2017-04-01

    First results are reported on the ground state configurations of the neutron-rich 29,30Na isotopes, obtained via Coulomb dissociation (CD) measurements. The invariant mass spectra of these nuclei have been obtained through measurement of the four-momenta of all decay products after Coulomb excitation of those nuclei on a 208Pb target at energies of 400–430 MeV/nucleon using the FRS-ALADIN-LAND setup at GSI, Darmstadt. Integrated inclusive CD cross-sections (CD) of 89 (7) mb and 167 (13) mb for one neutron removal from 29Na and 30Na, respectively, have been extracted up to an excitation energy of 10 MeV. The major part of one neutron removal, CD cross-sections of those nuclei populate the core, in its ground state. A comparison with the direct breakup model, suggests the predominant occupation of the valence neutron in the ground state of 29Na (3/{2}+) and 30Na ({2}+) is the d-orbital with a small contribution from the s-orbital, which are coupled with the ground state of the core. One of the major components of the ground state configurations of these nuclei are 28Na{}{gs}({1}+)\\otimes {ν }s,d and 29Na{}{gs}(3/{2}+)\\otimes {ν }s,d, respectively. The ground state spin and parity of these nuclei obtained from this experiment are in agreement with earlier reported values. The spectroscopic factors for the valence neutron occupying the s and d orbitals for these nuclei in the ground state have been extracted and reported for the first time. A comparison of the experimental findings with shell model calculation using the MCSM suggests a lower limit of around 4.3 MeV of the sd–pf shell gap in 30Na.

  9. Lattice HFB calculations for nuclei far from stability: neutron-rich sulfur and tin isotopes

    NASA Astrophysics Data System (ADS)

    Oberacker, Volker; Umar, Sait; Teran, Edgar

    2002-10-01

    We have developed a new Hartree-Fock-Bogoliubov (HFB) code to study ground state and pairing properties of nuclei near the neutron and proton drip lines. The unique feature of our code is that it takes into account the strong coupling to high energy continuum states (up to an equivalent s.p. energy of about 60 MeV). We solve the HFB equations for deformed, axially symmetric even-even nuclei on a two-dimensional lattice using high accuracy Basis-Spline methods (Galerkin and collocation schemes). The effective N-N interaction in the p-h channel is of Skyrme-type (SLy4), and in the p-p and h-h channel it is a (modified) delta interaction. We present results for binding energies, 2-neutron separation energies, Fermi levels, pairing gaps, normal densities and pairing densities, and other observables. In particular, we will discuss neutron-rich sulfur (S-48,S-52) and tin (Sn-150) isotopes. [1] E. Teran, V.E. Oberacker and A.S. Umar, "Axially symmetric Hartree-Fock-Bogoliubov Calculations for Nuclei Near the Drip-Lines; nucl-th/0205042 * Research supported by U.S. DOE grant DE-FG02-96ER40963, and by the National Energy Research Scientific Computing Center (NERSC)

  10. 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.

  11. 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.

  12. Astrophysical implication of low E(21+) in neutron-rich Sn isotopes

    NASA Astrophysics Data System (ADS)

    Sarkar, S.; Sarkar, M. Saha

    2009-10-01

    The observation and prediction of unusually depressed first excited 21+ states in even-A neutron-rich isotopes of semi-magic Sn above 132Sn provide motivations for reviewing the problems related to the nuclear astrophysics in general. In the present work, the β-decay rates of the exotic even Sn isotopes (134,136Sn) above the 132Sn core have been calculated as a function of temperature (T). In order to get the necessary ft values, B(GT) values corresponding to allowed Gamow Teller (GT-) β-decay have been theoretically calculated using shell model. The total decay rate shows decrease with increasing temperature as the ground state population is depleted and population of excited states with slower decay rates increases. The abundance at each Z value is inversely proportional to the decay constant of the waiting point nucleus for that particular Z. So the increase in half-life of isotopes of Sn, like 136Sn, might have substantial impact on the r-process nucleosynthesis.

  13. 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.

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

    DOE PAGES

    Iskra, Ł. W.; Broda, R.; Janssens, R. V.F.; ...

    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

  15. Enhanced Quadrupole Collectivity at N=40: The Case of Neutron-Rich Fe Isotopes

    SciTech Connect

    Rother, W.; Dewald, A.; Fransen, C.; Hackstein, M.; Jolie, J.; Pissulla, Th.; Zell, K.-O.; Iwasaki, H.; Baugher, T.; Brown, B. A.; Gade, A.; Glasmacher, T.; McDaniel, S.; Ratkiewicz, A.; Voss, P.; Walsh, K. A.; Lenzi, S. M.; Ur, C. A.; Starosta, K.; Bazin, D.

    2011-01-14

    The transition rates for the 2{sub 1}{sup +} states in {sup 62,64,66}Fe were studied using the recoil distance Doppler-shift technique applied to projectile Coulomb excitation reactions. The deduced E2 strengths illustrate the enhanced collectivity of the neutron-rich Fe isotopes up to N=40. The results are interpreted using the generalized concept of valence proton symmetry which describes the evolution of nuclear structure around N=40 as governed by the number of valence protons with respect to Z{approx_equal}30. The trend of collectivity suggested by the experimental data is described by state-of-the-art shell-model calculations with a new effective interaction developed for the fpgd valence space.

  16. Enhanced quadrupole collectivity at N = 40: the case of neutron-rich Fe isotopes.

    PubMed

    Rother, W; Dewald, A; Iwasaki, H; Lenzi, S M; Starosta, K; Bazin, D; Baugher, T; Brown, B A; Crawford, H L; Fransen, C; Gade, A; Ginter, T N; Glasmacher, T; Grinyer, G F; Hackstein, M; Ilie, G; Jolie, J; McDaniel, S; Miller, D; Petkov, P; Pissulla, Th; Ratkiewicz, A; Ur, C A; Voss, P; Walsh, K A; Weisshaar, D; Zell, K-O

    2011-01-14

    The transition rates for the 2(1)+ states in (62,64,66)Fe were studied using the recoil distance Doppler-shift technique applied to projectile Coulomb excitation reactions. The deduced E2 strengths illustrate the enhanced collectivity of the neutron-rich Fe isotopes up to N = 40. The results are interpreted using the generalized concept of valence proton symmetry which describes the evolution of nuclear structure around N = 40 as governed by the number of valence protons with respect to Z ≈ 30. The trend of collectivity suggested by the experimental data is described by state-of-the-art shell-model calculations with a new effective interaction developed for the fpgd valence space.

  17. Systematic study of neutron-rich rare isotope production in peripheral heavy-ion collisions below the Fermi energy

    NASA Astrophysics Data System (ADS)

    Fountas, P. N.; Souliotis, G. A.; Veselsky, M.; Bonasera, A.

    2014-12-01

    Detailed calculations of the yields of projectilelike fragments (with focus on the neutron-rich isotopes) are presented for the interaction of 86Kr (15 MeV/nucleon) with 64Ni, 58Ni, and 124Sn, 112Sn, as well as 86Kr (25 MeV/nucleon) with 124Sn and compared with our recently published experimental data for these reactions. The calculations are based on a two-step approach: the dynamical stage of the collision was described with the microscopic constrained molecular dynamics (CoMD) model, as well as the phenomenological deep-inelastic transfer (DIT) model and its modified (DITm) version. The deexcitation of the hot projectile fragments was performed with the statistical multifragmentation model (SMM) and the binary-decay model gemini, which provided nearly similar results for the neutron-rich products from the reactions studied. An overall good agreement of the calculations with the experimental results, especially for near-projectile isotopes was observed using both the CoMD model and the DITm model for the dynamical stage. The successful description of the production of neutron-rich isotopes with the CoMD model is of particular importance, due to the predictive power of the microscopic approach that essentially does not depend on the reaction dynamics. Our studies to date suggest that peripheral heavy-ion collisions at this energy range (i.e., well above the Coulomb barrier, but below the Fermi energy), if induced by neutron-rich rare-isotope beams of adequate intensity may offer a unique route to access extremely neutron-rich rare isotopes toward the astrophysical r -process path and the presently uncharted neutron drip line.

  18. 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.

  19. Chiral three-nucleon forces and bound excited states in neutron-rich oxygen isotopes

    NASA Astrophysics Data System (ADS)

    Holt, J. D.; Menéndez, J.; Schwenk, A.

    2013-03-01

    We study the spectra of neutron-rich oxygen isotopes based on chiral two- and three-nucleon interactions. First, we benchmark our many-body approach by comparing ground-state energies to coupled-cluster results for the same two-nucleon interaction, with overall good agreement. We then calculate bound excited states in 21, 22, 23O , focusing on the role of three-nucleon forces, in the standard sd shell and an extended sdf_{7/2}p_{3/2} valence space. Chiral three-nucleon forces provide important one- and two-body contributions between valence neutrons. We find that both these contributions and an extended valence space are necessary to reproduce key signatures of novel shell evolution, such as the N = 14 magic number and the low-lying states in 21O and 23O , which are too compressed with two-nucleon interactions only. For the extended space calculations, this presents first work based on nuclear forces without adjustments. Future work is needed and open questions are discussed.

  20. Spectroscopy of neutron-rich nickel isotopes: Experimental results and microscopic interpretation

    NASA Astrophysics Data System (ADS)

    Girod, M.; Dessagne, Ph.; Bernas, M.; Langevin, M.; Pougheon, F.; Roussel, P.

    1988-06-01

    The spectroscopy of neutron-rich isotopes of 67Ni and 68Ni is studied using the quasi-elastic transfer reactions (14C,16O) and (14C,17O) on a 70Zn mass separated target. The structure of these exotic nuclei is investigated in the framework of a microscopic collective model based on the Hartree-Fock-Bogoliubov theory. Gogny's two-body effective interaction is used. Collective excited states of 68Ni are obtained by solving the Bohr Hamiltonian in which inertia parameters are calculated in the cranking approximation. Spin and parity assignments to observed excited levels are suggested on the basis of information deduced from this analysis. This assignment is further checked by comparing measured angular distributions to predictions. Predictions of the level structure of 70Ni and 78Ni isotopes are given. A more precise test of the 0+ wave functions is provided by the calculation of monopole operator of the 0+1-->0+2 transition in 68Ni. An impressive agreement is obtained between the measured and calculated half-life.

  1. β-decay spectroscopy of neutron-rich 160,161,162Sm isotopes

    NASA Astrophysics Data System (ADS)

    Patel, Z.; Podolyák, Zs.; Walker, P. M.; Regan, P. H.; Söderström, P.-A.; Watanabe, H.; Ideguchi, E.; Simpson, G. S.; Nishimura, S.; Browne, F.; Doornenbal, P.; Lorusso, G.; Rice, S.; Sinclair, L.; Sumikama, T.; Wu, J.; Xu, Z. Y.; Aoi, N.; Baba, H.; Bello Garrote, F. L.; Benzoni, G.; Daido, R.; Dombrádi, Zs.; Fang, Y.; Fukuda, N.; Gey, G.; Go, S.; Gottardo, A.; Inabe, N.; Isobe, T.; Kameda, D.; Kobayashi, K.; Kobayashi, M.; Komatsubara, T.; Kojouharov, I.; Kubo, T.; Kurz, N.; Kuti, I.; Li, Z.; Liu, H. L.; Matsushita, M.; Michimasa, S.; Moon, C.-B.; Nishizuka, H.; Nishizuka, I.; Odahara, A.; Şahin, E.; Sakurai, H.; Schaffner, H.; Suzuki, H.; Takeda, H.; Tanaka, M.; Taprogge, J.; Vajta, Zs.; Xu, F. R.; Yagi, A.; Yokoyama, R.

    2016-09-01

    Neutron-rich 160,161,162Sm isotopes have been populated at the RIBF, RIKEN via β first time. β-coincident γ rays were observed in all three isotopes including γ rays from the isomeric decay of 160Sm and 162Sm. The isomers in 160Sm and 162Sm have previously been observed but have been populated via β decay for the first time. The isomeric state in 162Sm is assigned a {4^ - }v{{7 over 2}^ + }≤ft[ {633} right] otimes v{{1 over 2}^ - }≤ft[ {521} right] configuration based on the decay pattern. The level schemes of 160Sm and 162Sm are presented. The ground states in the parent nuclei 160Pm and 162Pm are both assigned a {6^ - }v{{7 over 2}^ + }≤ft[ {633} right] otimes π {{5 over 2}^ - }≤ft[ {532} right] configuration based on the population of states in the daughter nuclei. Blocked BCS calculations were performed to further investigate the spin-parities of the ground states in 160Pm, 161Pm, and 162Pm, and the isomeric state in 162Sm

  2. On the synthesis of neutron-rich isotopes along the N = 126 shell in multinucleon transfer reactions

    NASA Astrophysics Data System (ADS)

    Beliuskina, O.; Heinz, S.; Zagrebaev, V.; Comas, V.; Heinz, C.; Hofmann, S.; Knöbel, R.; Stahl, M.; Ackermann, D.; Heßberger, F. P.; Kindler, B.; Lommel, B.; Maurer, J.; Mann, R.

    2014-10-01

    We performed experimental and theoretical studies of deep inelastic multinucleon transfer reactions in heavy-ion collisions at Coulomb barrier energies. Our goal was to investigate if deep inelastic transfer is superior to fragmentation reactions for producing neutron-rich isotopes in the astrophysically interesting region along the closed neutron shell N = 126 . Here, we will present our results obtained in reactions of 64Ni + 207Pb at 5.0 MeV/nucleon. The experiment was performed at the velocity filter SHIP at GSI Darmstadt. Several transfer products on the neutron-rich side were populated but new isotopes were not observed. A comparison of the measured transfer cross-sections and production yields with those from fragmentation reactions allowed for interesting conclusions.

  3. Elastic Scattering of Neutron-Rich Helium Isotopes from Polarized Protons at 71 MeV/A

    NASA Astrophysics Data System (ADS)

    Sakaguchi, S.; Uesaka, T.; Kawabata, T.; Wakui, T.; Aoi, N.; Hashimoto, Y.; Ichikawa, Y.; Itoh, K.; Itoh, M.; Iwasaki, H.; Kawahara, T.; Kondo, Y.; Kuboki, H.; Maeda, Y.; Nakamura, T.; Nakao, T.; Nakayama, Y.; Okamura, H.; Sakai, H.; Sasamoto, Y.; Sasano, M.; Satou, Y.; Sekiguchi, K.; Shimamura, T.; Shimizu, Y.; Shinohara, M.; Suda, K.; Suzuki, D.; Takahashi, Y.; Tamii, A.; Yako, K.; Yamaguchi, M.

    2011-09-01

    The vector analyzing power has been measured for the elastic scattering of neutron-rich 6He and 8He from polarized protons at 71 MeV/A making use of a newly constructed solid polarized proton target operated in a low magnetic field of 0.1 T and at a relatively high temperature of 100 K. An optical model analysis revealed that the spin-orbit potentials for 6He and 8He are characterized by shallow and long-ranged shape compared with the global systematics of stable nuclei. Such a characteristics reflect a diffused density distribution of the neutron-rich isotopes.

  4. 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.

  5. Leap to explore the region of neutron-rich heavy element isotopes

    SciTech Connect

    Hoffman, D.C.

    1985-10-01

    The research aims of the Large Einsteinium Activation Program (LEAP) are described. This program is a major initiative to exploit currently existing expertise in heavy element research and the potential for producing very heavy actinide target materials such as 285-day /sup 254/Es at the High Flux Isotope Reactor at Oak Ridge National Laboratory. The stated aims of the program are to produce heavy element isotopes, to conduct chemical studies of these isotopes, to study the nuclear properties of such isotopes, and to produce a superheavy element (183 neutrons) by the using a /sup 254/Es target and /sup 48/Ca projectiles. 13 refs., 2 figs., 2 tabs. (DWL)

  6. CARIBU: a new facility for the study of neutron-rich isotopes

    NASA Astrophysics Data System (ADS)

    Savard, G.; Pardo, R. C.; Baker, S.; Davids, C. N.; Levand, A.; Peterson, D.; Phillips, D. G.; Sun, T.; Vondrasek, R.; Zabransky, B. J.; Zinkann, G. P.

    2011-07-01

    The Californium Rare Ion Breeder Upgrade (CARIBU) to the ATLAS superconducting linac facility is currently being commissioned. It provides low-energy and re-accelerated beams of neutron-rich isotopes obtained from 252Cf fission. The fission products from a 252Cf source are stopped in a large high-intensity gas catcher, thermalized and extracted through an RFQ cooler, accelerated to 50 kV and mass separated in a high-resolution separator before being sent to either an ECR charge breeder for post-acceleration through the ATLAS linac or to a low-energy experimental area. This approach gives access to beams of very neutron-rich isotopes, many of which have not been available at low or Coulomb barrier energies previously. These beams provide unique opportunities for measurements along the r-process path. To take advantage of these unique possibility, the reaccelerated beams from CARIBU will be made available at the experimental stations of ATLAS to serve equipment such as Gammasphere, HELIOS and the reaction spectrometers. In addition, the Canadian Penning Trap (CPT) mass spectrometer has been moved to the CARIBU low-energy experimental area and a new injection line has been built. The new injection line consists of a RFQ buncher sitting on a 50 kV high-voltage platform that will accumulate the mass separated 50 kV radioactive beams, cool and extract them as a pulsed beam of 3 keV. This beam can be sent either to a tape station for diagnostics and tuning, or a cryogenic linear trap for preparation before transfer to the high-precision Penning trap where the mass measurements will take place. Initial CARIBU commissioning is proceeding with a 2 mCi source that will be replaced by a 100 mCi source as the commissioning proceeds. Final operation will use a 1 Ci source and attain yield in excess of 107 ions/sec for the most intense beams at low energy, an order of magnitude less for reaccelerated beams.

  7. IRiS—Exploring new frontiers in neutron-rich isotopes of the heaviest elements with a new Inelastic Reaction Isotope Separator

    NASA Astrophysics Data System (ADS)

    Dvorak, J.; Block, M.; Düllmann, Ch. E.; Heinz, S.; Herzberg, R.-D.; Schädel, M.

    2011-10-01

    A dedicated Inelastic Reaction Isotope Separator (IRiS) for multi-nucleon transfer products will be designed and installed at GSI. Research at IRiS will focus on the investigation of new neutron-rich isotopes of the heaviest elements, study of which will advance various research fields, such as nuclear chemistry, nuclear and atomic physics, as well as nuclear astrophysics. The scientific motivation for this project and the alternative design options for the separator and its main components are discussed.

  8. -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.

  9. β decay of neutron-rich 118Ag and 120Ag isotopes

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Rinta-Antila, S.; Dendooven, P.; Huikari, J.; Jokinen, A.; Kolhinen, V. S.; Lhersonneau, G.; Nieminen, A.; Nummela, S.; Penttilä, H.; Peräjärvi, K.; Szerypo, J.; Wang, J. C.; Äystö, J.

    2003-06-01

    β decays of on-line mass-separated neutron-rich 118Ag and 120Ag isotopes have been studied by using β-γ and γ-γ coincidence spectroscopy. Extended decay schemes to the 118,120Cd daughter nuclei have been constructed. The three-phonon quintuplet in 118Cd is completed by including a new level at 2023.0 keV, which is tentatively assigned the spin and parity of 2+4. The intruder band in 118Cd is proposed up to the 4+ level at 2322.4 keV. The measured β-decay half-life for the high-spin isomer of 120Ag is 0.40±0.03 s. Candidates for the three-phonon states, as well as the lowest members of the intruder band in 120Cd, are also presented. These data support the coexistence of quadrupole anharmonic vibration and proton particle-hole intruder excitations in 118,120Cd.

  10. Ground-state nuclear-moment measurement of neutron-rich sulfur isotopes

    NASA Astrophysics Data System (ADS)

    Ohtomo, Yuichi; Ichikawa, Yuichi; Shirai, Hazuki; Ueno, Hideki; Ishibashi, Youko; Suzuki, Takahiro; Furukawa, Takeshi; Yoshimi, Akihiro; Abe, Yasushi; Asahi, Koichiro; Daugasu, J. M.; Fujita, Tomomi; Hayasaka, Miki; Imamura, Kei; Kishi, Shota; Kojima, Shuichiro; Nagae, Daisuke; Nakao, Aiko; Sagayama, Tsubasa; Sakamoto, Yu; Sato, Tomoya

    2014-09-01

    Recently the erosion of N = 28 shell gap has been suggested from several spectroscopic experimental data on neutron-rich nuclei. In particular, 43S isotope is of much interest since shape coexistence is expected to occur which provides key information to understand the evolution of shell gaps far from the stability. The isomeric state of 43S at 320 keV is suggested to have a shape close to sphericity with spin-parity of 7/2, but both the spin-parity and deformed parameter of the ground-state have not been determined directly. In order to investigate mechanisms leading to such an anomalous nuclear structure, we aim at measuring the ground-state nuclear-moment for 41,43S. As the first step, the measurement of μ moment of 41S was performed using the technique of β-NMR method at the RIPS facility at RIKEN. In the presentation, the result of this work will be reported.

  11. Recent activities for β-decay half-lives and β-delayed neutron emission of very neutron-rich isotopes

    SciTech Connect

    Dillmann, Iris; Abriola, Daniel; Singh, Balraj

    2014-05-02

    Beta-delayed neutron (βn) emitters play an important, two-fold role in the stellar nucleosynthesis of heavy elements in the 'rapid neutron-capture process' (r process). On one hand they lead to a detour of the material β-decaying back to stability. On the other hand, the released neutrons increase the neutron-to-seed ratio, and are re-captured during the freeze-out phase and thus influence the final solar r-abundance curve. A large fraction of the isotopes inside the r-process reaction path are not yet experimentally accessible and are located in the (experimental) 'Terra Incognita'. With the next generation of fragmentation and ISOL facilities presently being built or already in operation, one of the main motivation of all projects is the investigation of these very neutron-rich isotopes. A short overview of one of the planned programs to measure βn-emitters at the limits of the presently know isotopes, the BRIKEN campaign (Beta delayed neutron emission measurements at RIKEN) will be given. Presently, about 600 β-delayed one-neutron emitters are accessible, but only for a third of them experimental data are available. Reaching more neutron-rich isotopes means also that multiple neutron-emission becomes the dominant decay mechanism. About 460 β-delayed two-, three-or four-neutron emitters are identified up to now but for only 30 of them experimental data about the neutron branching ratios are available, most of them in the light mass region below A=30. The International Atomic and Energy Agency (IAEA) has identified the urgency and picked up this topic recently in a 'Coordinated Research Project' on a 'Reference Database for Beta-Delayed Neutron Emission Data'. This project will review, compile, and evaluate the existing data for neutron-branching ratios and half-lives of β-delayed neutron emitters and help to ensure a reliable database for the future discoveries of new isotopes and help to constrain astrophysical and theoretical models.

  12. 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.

  13. 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.

  14. Direct mass measurements of neutron-rich 86Kr projectile fragments and the persistence of neutron magic number N=32 in Sc isotopes

    NASA Astrophysics Data System (ADS)

    Xu, Xing; Wang, Meng; Zhang, Yu-Hu; Xu, Hu-Shan; Shuai, Peng; Tu, Xiao-Lin; Yuri, A. Litvinov; Zhou, Xiao-Hong; Sun, Bao-Hua; Yuan, You-Jin; Xia, Jia-Wen; Yang, Jian-Cheng; Klaus, Blaum; Chen, Rui-Jiu; Chen, Xiang-Cheng; Fu, Chao-Yi; Ge, Zhuang; Hu, Zheng-Guo; Huang, Wen-Jia; Liu, Da-Wei; Lam, Yi-Hua; Ma, Xin-Wen; Mao, Rui-Shi; Uesaka, T.; Xiao, Guo-Qing; Xing, Yuan-Ming; Yamaguchi, T.; Yamaguchi, Y.; Zeng, Qi; Yan, Xin-Liang; Zhao, Hong-Wei; Zhao, Tie-Cheng; Zhang, Wei; Zhan, Wen-Long

    2015-10-01

    In this paper, we present direct mass measurements of neutron-rich 86Kr projectile fragments conducted at the HIRFL-CSR facility in Lanzhou by employing the Isochronous Mass Spectrometry (IMS) method. The new mass excesses of 52-54Sc nuclides are determined to be -40492(82), -38928(114), -34654(540) keV, which show a significant increase of binding energy compared to the reported ones in the Atomic Mass Evaluation 2012 (AME12). In particular, 53Sc and 54Sc are more bound by 0.8 MeV and 1.0 MeV, respectively. The behavior of the two neutron separation energy with neutron numbers indicates a strong sub-shell closure at neutron number N=32 in Sc isotopes. Supported by 973 Program of China (2013CB834401), the NSFC (U1232208, U1432125, 11205205, 11035007) and the Helmholtz-CAS Joint Research Group (HCJRG-108)

  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. New Levels in 118Pd Observed in the β Decay of Very Neutron-Rich 118Rh Isotope

    NASA Astrophysics Data System (ADS)

    Wang, You-Bao; Dendooven, P.; Huikari, J.; Jokinen, A.; Kolhinen S., V.; Lhersonneau, G.; Nieminen, A.; Nummela, S.; Penttilä, H.; Peräjärvi, K.; Rinta-Antila, S.; Szerypo, J.; Wang C., J.; Äystö, J.

    2006-04-01

    We investigate the β decay of very neutron-rich 118Rh isotope using on-line mass-separated sources which are produced by applying 25 MeV proton induced symmetric fission of natural uranium at the IGISOL facility. The β-γ and γ-γ coincidence spectroscopy is employed to establish the level scheme of daughter nucleus 118Pd. Five low-lying new levels are identified for the first time with tentative spin and parity assignments based on the even-mass Pd systematics.

  17. {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.

  18. {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.

  19. Theoretical study of neutron-rich 107,109,111,113Rh isotopes

    NASA Astrophysics Data System (ADS)

    Kumar, Amit; Singh, Suram; Khosa, S. K.; Bharti, Arun; Bhat, G. H.; Sheikh, J. A.

    2015-10-01

    A theoretical study of the structure of some odd mass Rh nuclei in the A 100 mass region is carried out by using the angular momentum projection technique implemented in the projected shell model (PSM). The influence of the high-j orbitals (h11/2 for neutrons and g9/2 for protons) on the structure of 107-113Rh isotopes is investigated in the present case by assuming an axial symmetry in the deformed basis. For these isotopes, the structure of multi-quasi-particle qp bands is studied along the yrast line in detail. Further, the phenomenon of back-bending is also studied theoretically and is found to be in agreement with the experimental data. The reduced transition probabilities, i.e., B(E2) and B(M1) for the yrast band are also obtained from the PSM wave functions for the first time, thereby providing an opportunity for the experimentalists to work for this data.

  20. Shell quenching in Ni78: A hint from the structure of neutron-rich copper isotopes

    NASA Astrophysics Data System (ADS)

    Sieja, K.; Nowacki, F.

    2010-06-01

    Recent progress in experimental techniques allows us to study very exotic systems like neutron-rich nuclei in the vicinity of Ni78. 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 Ca48 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 Ni68 to Ni78 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. Low-lying dipole resonance in neutron-rich Ne isotopes

    NASA Astrophysics Data System (ADS)

    Yoshida, Kenichi; van Giai, Nguyen

    2008-07-01

    Microscopic structure of the low-lying isovector dipole excitation mode in neutron-rich Ne26,28,30 is investigated by performing deformed quasiparticle-random-phase-approximation (QRPA) calculations. The particle-hole residual interaction is derived from a Skyrme force through a Landau-Migdal approximation. We obtain the low-lying resonance in Ne26 at around 8.6 MeV. It is found that the isovector dipole strength at Ex<10 MeV exhausts about 6.0% of the classical Thomas-Reiche-Kuhn dipole sum rule. This excitation mode is composed of several QRPA eigenmodes, one is generated by a ν(2s1/2-12p3/2) transition dominantly and the other mostly by a ν(2s1/2-12p1/2) transition. The neutron excitations take place outside of the nuclear surface reflecting the spatially extended structure of the 2s1/2 wave function. In Ne30, the deformation splitting of the giant resonance is large, and the low-lying resonance overlaps with the giant resonance.

  2. Time-of-flight mass measurements of neutron-rich chromium isotopes up to N = 40 and implications for the accreted neutron star crust

    DOE PAGES

    Meisel, Z.; George, S.; Ahn, S.; ...

    2016-03-22

    Here, we present the mass excesses of 59-64Cr, obtained from recent time-of-flight nuclear mass measurements at the National Superconducting Cyclotron Laboratory at Michigan State University. The mass of 64Cr is determined for the first time, with an atomic mass excess of -33.48(44) MeV. We find a significantly different two-neutron separation energy S2n trend for neutron-rich isotopes of chromium, removing the previously observed enhancement in binding at N = 38. Additionally, we extend the S2n trend for chromium to N = 40, revealing behavior consistent with the previously identified island of inversion in this region. We compare our results to state-of-the-artmore » shell-model calculations performed with a modified Lenzi-Nowacki-Poves-Sieja interaction in the fp shell, including the g9/2 and d5/2 orbits for the neutron valence space. We employ our result for the mass of 64Cr in accreted neutron star crust network calculations and find a reduction in the strength and depth of electron-capture heating from the A = 64 isobaric chain, resulting in a cooler than expected accreted neutron star crust. This reduced heating is found to be due to the >1-MeV reduction in binding for 64Cr with respect to values from commonly used global mass models.« less

  3. 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.

  4. Triaxial shapes in the ground states of even-even neutron-rich Ru isotopes

    SciTech Connect

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

    1995-08-01

    Partial level schemes for {sup 108,110,112}Ru, and {sup 114}Ru about which nothing was previously known, were determined from the measurement of prompt, triple-gamma coincidences in {sup 248}Cm fission fragments. A 5-mg {sup 249}Cm source, mixed with 65-mg KCl and pressed in the form of a 7-mm diameter pellet, was used for the experiment. Prompt {gamma} rays emitted from the fission fragments were detected with the Eurogam array at Daresbury, which at that time consisted of 45 Compton suppressed Ge detectors and 5 LEPS spectrometers. Transitions in Ru were identified by gating on {gamma} rays in the complementary Te fragments. Figure I-25 shows the technique used to identify the previously unknown transitions in {sup 114}Ru and its partial level scheme. High spin states up to spin 10 h were observed and the {gamma}-ray branching ratios were determined. The ratios of electric quadrupole transition probabilities deduced from the experimental branching ratios were found to be in good agreement with the predictions of a simple model of rigid triaxial rotor. Our analysis shows that gamma deformation in Ru isotopes is increasing with the neutron number and the gamma value for {sup 112}Ru and {sup 114}Ru is {approximately} 25 degrees. This is one of the highest gamma values encountered in nuclei, suggesting soft triaxial shapes for {sup 112}Ru and {sup 114}Ru. The results of this investigation were published.

  5. Electric dipole response of neutron-rich calcium isotopes in relativistic quasiparticle time blocking approximation

    NASA Astrophysics Data System (ADS)

    Egorova, Irina A.; Litvinova, Elena

    2016-09-01

    New results for electric dipole strength in the chain of even-even calcium isotopes with the mass numbers A =40 -54 are presented. Starting from the covariant Lagrangian of quantum hadrodynamics, spectra of collective vibrations (phonons) and phonon-nucleon coupling vertices for J ≤6 and natural parity were computed in a self-consistent relativistic quasiparticle random-phase approximation (RQRPA). These vibrations coupled to Bogoliubov two-quasiparticle configurations (2 q ⊗phonon ) formed the model space for the calculations of the dipole response function in the relativistic quasiparticle time blocking approximation. The calculations in the latter approach were performed for the giant dipole resonance (GDR) and compared to those obtained with the RQRPA and to available data. The evolution of the dipole strength with the neutron number is investigated for both high-frequency GDRs and low-lying strengths. The development of a pygmy resonant structure on the low-energy shoulder of the GDR is traced and analyzed in terms of transition densities. A dependence of the pygmy dipole strength on the isospin asymmetry parameter is extracted.

  6. 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 .

  7. 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.

  8. Time-of-flight mass measurements of neutron-rich chromium isotopes up to N = 40 and implications for the accreted neutron star crust

    SciTech Connect

    Meisel, Z.; George, S.; Ahn, S.; Bazin, D.; Brown, B. A.; Browne, J.; Carpino, J. F.; Chung, H.; Cyburt, R. H.; Estrade, A.; Famiano, M.; Gade, A.; Langer, C.; Matos, M.; Mittig, W.; Montes, F.; Morrissey, D. J.; Pereira, J.; Schatz, H.; Schatz, J.; Scott, M.; Shapira, Dan; Sieja, K.; Smith, K.; Stevens, J.; Tan, W.; Tarasov, O.; Towers, S.; Wimmer, K.; Winkelbauer, J. R.; Yurkon, J.; Zegers, R. G. T.

    2016-03-22

    Here, we present the mass excesses of 59-64Cr, obtained from recent time-of-flight nuclear mass measurements at the National Superconducting Cyclotron Laboratory at Michigan State University. The mass of 64Cr is determined for the first time, with an atomic mass excess of -33.48(44) MeV. We find a significantly different two-neutron separation energy S2n trend for neutron-rich isotopes of chromium, removing the previously observed enhancement in binding at N = 38. Additionally, we extend the S2n trend for chromium to N = 40, revealing behavior consistent with the previously identified island of inversion in this region. We compare our results to state-of-the-art shell-model calculations performed with a modified Lenzi-Nowacki-Poves-Sieja interaction in the fp shell, including the g9/2 and d5/2 orbits for the neutron valence space. We employ our result for the mass of 64Cr in accreted neutron star crust network calculations and find a reduction in the strength and depth of electron-capture heating from the A = 64 isobaric chain, resulting in a cooler than expected accreted neutron star crust. This reduced heating is found to be due to the >1-MeV reduction in binding for 64Cr with respect to values from commonly used global mass models.

  9. Beta spectroscopy of some neutron-rich cerium isotopes in252Cf fission products

    NASA Astrophysics Data System (ADS)

    Ebong, I. D. U.; Roy, R. R.

    1981-09-01

    The method of cyclic-time optimization has been used, in conjunction with a beta-Kx-ray coincidence technique, to obtain the beta spectrum of some decaying cerium isotopes in the fission products of252Cf. A Kurie plot of the beta spectrum revealed at least four beta groups. From the relative isotopic yields of Kx-ray the isotopic origin of each group has been determined. The coincidence method used in this study allows the measurement of beta groups feeding excited levels of daughter products with high internal conversion coefficients. The end-point energies and isotopic origin of the measured beta groups were as follows: 2.349(±0.100)MeV,145Ce; 1.715(±0.103)MeV,145Ce and148Ce; 1.267 (±0.103)MeV,145Ce; 0.748(±0.109) MeV,146Ce and148Ce.

  10. Half-lives and branchings for {beta}-delayed neutron emission for neutron-rich Co-Cu isotopes in the r-process

    SciTech Connect

    Hosmer, P.; Estrade, A.; Montes, F.; Ouellette, M.; Pellegrini, E.; Schatz, H.; Aprahamian, A.; Arndt, O.; Pfeiffer, B.; Clement, R. R. C.; Mueller, W. F.; Morton, A. C.; Pereira, J.; Santi, P.; Steiner, M.; Stolz, A.; Farouqi, K.; Kratz, K.-L.; Liddick, S. N.; Mantica, P. F.

    2010-08-15

    The {beta} decays of very neutron-rich nuclides in the Co-Zn region were studied experimentally at the National Superconducting Cyclotron Laboratory using the NSCL {beta}-counting station in conjunction with the neutron detector NERO. We measured the branchings for {beta}-delayed neutron emission (P{sub n} values) for {sup 74}Co (18{+-}15%) and {sup 75-77}Ni (10{+-}2.8%, 14{+-}3.6%, and 30{+-}24%, respectively) for the first time, and remeasured the P{sub n} values of {sup 77-79}Cu, {sup 79,81}Zn, and {sup 82}Ga. For {sup 77-79}Cu and for {sup 81}Zn we obtain significantly larger P{sub n} values compared to previous work. While the new half-lives for the Ni isotopes from this experiment had been reported before, we present here in addition the first half-life measurements of {sup 75}Co (30{+-}11 ms) and {sup 80}Cu (170{sub -50}{sup +110} ms). Our results are compared with theoretical predictions, and their impact on various types of models for the astrophysical rapid neutron-capture process (r-process) is explored. We find that with our new data, the classical r-process model is better able to reproduce the A=78-80 abundance pattern inferred from the solar abundances. The new data also influence r-process models based on the neutrino-driven high-entropy winds in core collapse supernovae.

  11. Deformation effect on total reaction cross sections for neutron-rich Ne isotopes

    SciTech Connect

    Minomo, Kosho; Sumi, Takenori; Ogata, Kazuyuki; Shimizu, Yoshifumi R.; Yahiro, Masanobu; Kimura, Masaaki

    2011-09-15

    The isotope dependence of measured reaction cross sections in the scattering of {sup 28-32}Ne isotopes from a {sup 12}C target at 240 MeV/nucleon is analyzed by the double-folding model with the Melbourne g matrix. The density of the projectile is calculated by the mean-field model with the deformed Woods-Saxon potential. The deformation is evaluated by antisymmetrized molecular dynamics. The deformation of the projectile enhances calculated reaction cross sections to the measured values.

  12. Coulomb Excitation of Neutron-Rich Zn Isotopes: First Observation of the 21+ State in Zn80

    NASA Astrophysics Data System (ADS)

    van de Walle, J.; Aksouh, F.; Ames, F.; Behrens, T.; Bildstein, V.; Blazhev, A.; Cederkäll, J.; Clément, E.; Cocolios, T. E.; Davinson, T.; Delahaye, P.; Eberth, J.; Ekström, A.; Fedorov, D. V.; Fedosseev, V. N.; Fraile, L. M.; Franchoo, S.; Gernhauser, R.; Georgiev, G.; Habs, D.; Heyde, K.; Huber, G.; Huyse, M.; Ibrahim, F.; Ivanov, O.; Iwanicki, J.; Jolie, J.; Kester, O.; Köster, U.; Kröll, T.; Krücken, R.; Lauer, M.; Lisetskiy, A. F.; Lutter, R.; Marsh, B. A.; Mayet, P.; Niedermaier, O.; Nilsson, T.; Pantea, M.; Perru, O.; Raabe, R.; Reiter, P.; Sawicka, M.; Scheit, H.; Schrieder, G.; Schwalm, D.; Seliverstov, M. D.; Sieber, T.; Sletten, G.; Smirnova, N.; Stanoiu, M.; Stefanescu, I.; Thomas, J.-C.; Valiente-Dobón, J. J.; van Duppen, P.; Verney, D.; Voulot, D.; Warr, N.; Weisshaar, D.; Wenander, F.; Wolf, B. H.; Zielińska, M.

    2007-10-01

    Neutron-rich, radioactive Zn isotopes were investigated at the Radioactive Ion Beam facility REX-ISOLDE (CERN) using low-energy Coulomb excitation. The energy of the 21+ state in Zn78 could be firmly established and for the first time the 2+→01+ transition in Zn80 was observed at 1492(1) keV. B(E2,21+→01+) values were extracted for Zn74,76,78,80 and compared to large scale shell model calculations. With only two protons outside the Z=28 proton core, Zn80 is the lightest N=50 isotone for which spectroscopic information has been obtained to date. Two sets of advanced shell model calculations reproduce the observed B(E2) systematics. The results for N=50 isotones indicate a good N=50 shell closure and a strong Z=28 proton core polarization. The new results serve as benchmarks to establish theoretical models, predicting the nuclear properties of the doubly magic nucleus Ni78.

  13. Tetrahedral shapes of neutron-rich Zr isotopes from a multidimensionally constrained relativistic Hartree-Bogoliubov model

    NASA Astrophysics Data System (ADS)

    Zhao, Jie; Lu, Bing-Nan; Zhao, En-Guang; Zhou, Shan-Gui

    2017-01-01

    We develop a multidimensionally constrained relativistic Hartree-Bogoliubov (MDC-RHB) model in which the pairing correlations are taken into account by making the Bogoliubov transformation. In this model, the nuclear shape is assumed to be invariant under the reversion of x and y axes; i.e., the intrinsic symmetry group is V4 and all shape degrees of freedom βλ μ with even μ are included self-consistently. The RHB equation is solved in an axially deformed harmonic oscillator basis. A separable pairing force of finite range is adopted in the MDC-RHB model. The potential energy curves of neutron-rich even-even Zr isotopes are calculated with relativistic functionals DD-PC1 and PC-PK1 and possible tetrahedral shapes in the ground and isomeric states are investigated. The ground state shape of 110Zr is predicted to be tetrahedral with both functionals and so is that of 112Zr with the functional DD-PC1. The tetrahedral ground states are caused by large energy gaps around Z =40 and N =70 when β32 deformation is included. Although the inclusion of the β30 deformation can also reduce the energy around β20=0 and lead to minima with pear-like shapes for nuclei around 110Zr, these minima are unstable due to their shallowness.

  14. Signatures of shape transitions in odd-A neutron-rich rubidium isotopes

    SciTech Connect

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

    2010-12-15

    The isotopic evolution of the ground-state nuclear shapes and the systematics of one-quasiproton configurations are studied in odd-A Rubidium isotopes. We use a self-consistent Hartree-Fock-Bogoliubov formalism based on the Gogny energy density functional with two parametrizations, D1S and D1M, and implemented with the equal-filling approximation. We find clear signatures of a sharp shape transition at N=60 in both the charge radii and spin parity of the ground states, which are robust, consistent with each other, and in agreement with experiment. We point out that the combined analysis of these two observables could be used to predict unambiguously new regions where shape transitions might develop.

  15. Nature of Collective Dipole and Octupole Transitions in Neutron-Rich Barium Isotopes

    NASA Astrophysics Data System (ADS)

    Bucher, B.; Zhu, S.; ANL, LBNL, LLNL, Rochester, FSU, Liverpool, Maryland, Notre Dame, Ohio, W. Scotland Collaboration

    2016-09-01

    Recently, a direct measurement of octupole strength in 144Ba was carried out via Coulomb excitation with a radioactive beam from Argonne's CARIBU facility using GRETINA and CHICO2. The results verify the presence of enhanced octupole collectivity in this isotope, as predicted by theory. In the neighboring isotope 146Ba, however, the importance of octupole correlations is more uncertain. Specifically, the electric dipole strength, expected to be closely correlated with the octupole one, displays what is perhaps the most significant drop in strength between neighboring isotopes of any medium- to heavy-mass nuclei. To address this puzzling question, a Coulomb excitation experiment was also performed on 146Ba under the same conditions. The new measurement yields an enhanced octupole strength of the same magnitude as that observed in 144Ba. This supports the notion that the strong-weak dipole behavior in this region results from the unique single-particle structure characteristic of Z 56 and N 90 in the presence of a pear-shaped mean-field potential. This work is supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357 (ANL), DE-AC02-05CH11231 (LBNL, GRETINA), DOE DE-AC52-07NA27344 (LLNL), and NSF.

  16. Evolution of deformation in the neutron-rich krypton isotopes: The Kr96 nucleus

    NASA Astrophysics Data System (ADS)

    Mărginean, N.; Bucurescu, D.; Ur, C. A.; Mihai, C.; Corradi, L.; Farnea, E.; Filipescu, D.; Fioretto, E.; Ghiţă, D.; Guiot, B.; Górska, M.; Ionescu-Bujor, M.; Iordăchescu, A.; Jelavić-Malenica, D.; Lenzi, S. M.; Mason, P.; Mărginean, R.; Mengoni, D.; Montagnoli, G.; Napoli, D. R.; Pascu, S.; Pollarolo, G.; Recchia, F.; Stefanini, A. M.; Silvestri, R.; Sava, T.; Scarlassara, F.; Szilner, S.; Zamfir, N. V.

    2009-08-01

    The energy of the first excited 2+ state in Kr96 was measured as 241 keV. The nucleus was produced in the fission of U238 induced by a 954-MeV Xe136 beam and prompt γ rays were observed using the clover array CLARA in coincidence with fission products identified with the PRISMA spectrometer. The evolution of the quadrupole collectivity in the Kr isotopes with N⩾50 is discussed by comparison with that from the Rb to Mo isotones and with predictions of various theoretical calculations.

  17. New Isomers in the Full Seniority Scheme of Neutron-Rich Lead Isotopes: The Role of Effective Three-Body Forces

    NASA Astrophysics Data System (ADS)

    Gottardo, A.; Valiente-Dobón, J. J.; Benzoni, G.; Nicolini, R.; 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.; Klupp, S.; Kojouharov, I.; Kurz, N.; Lenzi, S. M.; Leoni, S.; Mandal, S.; Menegazzo, R.; Mengoni, D.; Million, B.; Morales, A. I.; 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.; Wieland, O.; Wollersheim, H.-J.; Nowacki, F.; Maglione, E.; Zuker, A. P.

    2012-10-01

    The neutron-rich lead isotopes, up to Pb216, have been studied for the first time, exploiting the fragmentation of a primary uranium beam at the FRS-RISING setup at GSI. The observed isomeric states exhibit electromagnetic transition strengths which deviate from state-of-the-art shell-model calculations. It is shown that their complete description demands the introduction of effective three-body interactions and two-body transition operators in the conventional neutron valence space beyond Pb208.

  18. Neutron-Rich Isotopes from 208Pb at 86 MeV/u

    NASA Astrophysics Data System (ADS)

    Tarasov, O. B.; Portillo, M.; Amthor, A. M.; Baumann, T.; Bazin, D.; Folden, C.; Ginter, T.; Hausmann, M.; Morrissey, D. J.; Pereira, J.; Sherrill, B. M.; Thoennessen, M.; Nociforo, C.

    2008-10-01

    An experiment to measure production yields from a beam of ^208Pb (86 MeV/u) on Be and Ni-targets has recently been performed. The A1900 fragment-separator [1] was used to analyze products from projectile fragmentation and abrasion-fission [2]. Isotopic identification of nuclides having A˜200 has been achieved, demonstrating that adequate A,Z,Q resolution at this energy region is possible when using silicon detectors. The verification of PID is done via detection of multiple charge state distributions of the primary beam, as well as γ-decay of known isomers with half-lives in the microsecond range. The results demonstrate that experiments with heavy nuclei are possible at the NSCL using beams of A>200. Production cross-sections have been extracted from the data that can help improve the accuracy of production models such as Abrasion-Ablation and Abrasion-Fission used in the LISE++ code [3]. The data reveal the existence of previously unreported isomeric transitions and further analysis is ongoing that may also lead to the observation of new isotopes. References: [1] D.J.Morrissey et al., Nucl. Instrum. Meth. B204 (2003) 90--96. [2] O.B. Tarasov, Tech. Rep. MSUCL1300, NSCL, Michigan St.Univ., 2005. [3] O.B. Tarasov, D. Bazin, Nucl. Phys. A 746 (2004) 411; www.nscl.msu.edu/lise .

  19. 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.

  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. Precision excited-state lifetime measurements of neutron-rich Li isotopes

    NASA Astrophysics Data System (ADS)

    Morse, C.; Lister, C. J.; Wilson, G. L.; McCutchan, E. A.; Hackman, G.; Bowry, M.; Caballero-Folch, R.; Evitts, L. J.; Garnsworthy, A. B.; Henderson, J.; Kurkjian, A.; Measures, J. P.; Moukaddam, M.; Ruotsalainen, P.; Smallcombe, J.; Smith, J. K.; Southall, D.; Williams, M.; Mitchell, A. J.; Wu, C. Y.

    2016-09-01

    Recent successes with ab initio calculations are allowing increasingly subtle nuclear phenomena to be investigated, such as Δ-isobar and meson exchange effects which are necessary to reproduce M 1 properties of nuclei. In order to guide such explorations, precise experimental data are required to discriminate between various theoretical descriptions. The lithium isotopes, which are dominated by M 1 spin-flip transitions, provide an ideal testing ground for such studies. We have performed lifetime measurements of the excited states of 7,8Li, as well as explored the feasibility of such an experiment on 9Li, to provide precise data on the M 1 transition matrix elements in these nuclei. The experiment used the Doppler Shift Attenuation Method to measure the lifetimes at TRIUMF with TIGRESS, with the excited states populated by inverse (d , p) reactions. Preliminary results from the analysis will be presented. This research was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Grants DE-FG02-94ER40848.

  2. Quadrupole transition strength in the (74)Ni nucleus and core polarization effects in the neutron-rich Ni isotopes.

    PubMed

    Marchi, T; de Angelis, G; Valiente-Dobón, J J; Bader, V M; Baugher, T; Bazin, D; Berryman, J; Bonaccorso, A; Clark, R; Coraggio, L; Crawford, H L; Doncel, M; Farnea, E; Gade, A; Gadea, A; Gargano, A; Glasmacher, T; Gottardo, A; Gramegna, F; Itaco, N; John, P R; Kumar, R; Lenzi, S M; Lunardi, S; McDaniel, S; Michelagnoli, C; Mengoni, D; Modamio, V; Napoli, D R; Quintana, B; Ratkiewicz, A; Recchia, F; Sahin, E; Stroberg, R; Weisshaar, D; Wimmer, K; Winkler, R

    2014-10-31

    The reduced transition probability B(E2;0(+)→2(+)) has been measured for the neutron-rich nucleus (74)Ni in an intermediate energy Coulomb excitation experiment performed at the National Superconducting Cyclotron Laboratory at Michigan State University. The obtained B(E2;0(+)→2(+))=642(-226)(+216)  e(2) fm(4) value defines a trend which is unexpectedly small if referred to (70)Ni and to a previous indirect determination of the transition strength in (74)Ni. This indicates a reduced polarization of the Z=28 core by the valence neutrons. Calculations in the pfgd model space reproduce well the experimental result indicating that the B(E2) strength predominantly corresponds to neutron excitations. The ratio of the neutron and proton multipole matrix elements supports such an interpretation.

  3. Isotope-Identifying neutron reflectometry

    SciTech Connect

    Nikitenko, Yu. V. Petrenko, A. V.; Gundorin, N. A.; Gledenov, Yu. M.; Aksenov, V. L.

    2015-07-15

    The possibilities of an isotope-indentifying study of layered structures in different regimes of a neutron wave field are considered. The detection of specularly reflected neutrons and secondary radiation (caused by neutron capture) in the form of charged particles, γ quanta, and nuclear fission fragments, as well as neutrons spin-flipped in a noncollinear magnetic field and on nuclei of elements with spin, makes it possible to implement isotope-indentifying neutron reflectometry.

  4. Identification of 45 New Neutron-Rich Isotopes Produced by In-Flight Fission of a 238U Beam at 345 MeV/nucleon

    NASA Astrophysics Data System (ADS)

    Tetsuya Ohnishi,; Toshiyuki Kubo,; Kensuke Kusaka,; Atsushi Yoshida,; Koichi Yoshida,; Masao Ohtake,; Naoki Fukuda,; Hiroyuki Takeda,; Daisuke Kameda,; Kanenobu Tanaka,; Naohito Inabe,; Yoshiyuki Yanagisawa,; Yasuyuki Gono,; Hiroshi Watanabe,; Hideaki Otsu,; Hidetada Baba,; Takashi Ichihara,; Yoshitaka Yamaguchi,; Maya Takechi,; Shunji Nishimura,; Hideki Ueno,; Akihiro Yoshimi,; Hiroyoshi Sakurai,; Tohru Motobayashi,; Taro Nakao,; Yutaka Mizoi,; Masafumi Matsushita,; Kazuo Ieki,; Nobuyuki Kobayashi,; Kana Tanaka,; Yosuke Kawada,; Naoki Tanaka,; Shigeki Deguchi,; Yoshiteru Satou,; Yosuke Kondo,; Takashi Nakamura,; Kenta Yoshinaga,; Chihiro Ishii,; Hideakira Yoshii,; Yuki Miyashita,; Nobuya Uematsu,; Yasutsugu Shiraki,; Toshiyuki Sumikama,; Junsei Chiba,; Eiji Ideguchi,; Akito Saito,; Takayuki Yamaguchi,; Isao Hachiuma,; Takeshi Suzuki,; Tetsuaki Moriguchi,; Akira Ozawa,; Takashi Ohtsubo,; Michael A. Famiano,; Hans Geissel,; Anthony S. Nettleton,; Oleg B. Tarasov,; Daniel P. Bazin,; Bradley M. Sherrill,; Shashikant L. Manikonda,; Jerry A. Nolen,

    2010-07-01

    A search for new isotopes using in-flight fission of a 345 MeV/nucleon 238U beam has been carried out at the RI Beam Factory at the RIKEN Nishina Center. Fission fragments were analyzed and identified by using the superconducting in-flight separator BigRIPS. We observed 45 new neutron-rich isotopes: 71Mn, 73,74Fe, 76Co, 79Ni, 81,82Cu, 84,85Zn, 87Ga, 90Ge, 95Se, 98Br, 101Kr, 103Rb, 106,107Sr, 108,109Y, 111,112Zr, 114,115Nb, 115,116,117Mo, 119,120Tc, 121,122,123,124Ru, 123,124,125,126Rh, 127,128Pd, 133Cd, 138Sn, 140Sb, 143Te, 145I, 148Xe, and 152Ba.

  5. 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.

  6. 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

  7. 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

  8. Neutron-rich rare-isotope production from projectile fission of heavy nuclei near 20 MeV/nucleon beam energy

    NASA Astrophysics Data System (ADS)

    Vonta, N.; Souliotis, G. A.; Loveland, W.; Kwon, Y. K.; Tshoo, K.; Jeong, S. C.; Veselsky, M.; Bonasera, A.; Botvina, A.

    2016-12-01

    We investigate the possibilities of producing neutron-rich nuclides in projectile fission of heavy beams in the energy range of 20 MeV/nucleon expected from low-energy facilities. We report our efforts to theoretically describe the reaction mechanism of projectile fission following a multinucleon transfer collision at this energy range. Our calculations are mainly based on a two-step approach: The dynamical stage of the collision is described with either the phenomenological deep-inelastic transfer model (DIT) or with the microscopic constrained molecular dynamics model (CoMD). The de-excitation or fission of the hot heavy projectile fragments is performed with the statistical multifragmentation model (SMM). We compared our model calculations with our previous experimental projectile-fission data of 238U (20 MeV/nucleon) + 208Pb and 197Au (20 MeV/nucleon) + 197Au and found an overall reasonable agreement. Our study suggests that projectile fission following peripheral heavy-ion collisions at this energy range offers an effective route to access very neutron-rich rare isotopes toward and beyond the astrophysical r-process path.

  9. {beta}-decay half-lives of new neutron-rich rare-earth isotopes {sup 159}Pm,{sup 162}Sm, and {sup 166}Gd

    SciTech Connect

    Ichikawa, S.; Asai, M.; Tsukada, K.; Nagame, Y.; Haba, H.; Shibata, M.; Sakama, M.; Kojima, Y.

    2005-06-01

    The new neutron-rich rare-earth isotopes {sup 159}Pm, {sup 162}Sm, and {sup 166}Gd produced in the proton-induced fission of {sup 238}U were identified using the JAERI on-line isotope separator (JAERI-ISOL) coupled to a gas-jet transport system. The half-lives of {sup 159}Pm, {sup 162}Sm, and {sup 166}Gd were determined to be 1.5 {+-} 0.2, 2.4 {+-} 0.5, and 4.8 {+-} 1.0 s respectively. The partial decay scheme of {sup 166}Gd was constructed from {gamma}{gamma}-coincidence data. A more accurate half-life value of 25.6 {+-} 2.2 s was obtained for the previously identified isotope {sup 166}Tb. The half-lives measured in the present study are in good agreement with the theoretical predictions calculated by the second generation of the gross theory with the atomic masses evaluated by Audi and Wapstra.

  10. Neutron transition strengths of 2{sub 1}{sup +} states in the neutron-rich oxygen isotopes determined from inelastic proton scattering

    SciTech Connect

    Nguyen Dang Chien; Khoa, Dao T.

    2009-03-15

    A coupled-channel analysis of the {sup 18,20,22}O(p,p{sup '}) data has been performed to determine the neutron transition strengths of the 2{sub 1}{sup +} states in oxygen targets, using the microscopic optical potential and inelastic form factor calculated in the folding model. A complex density- and isospin-dependent version of the CDM3Y6 interaction was constructed, based on the Brueckner-Hartree-Fock calculation of nuclear matter, for the folding model input. Given an accurate isovector density dependence of the CDM3Y6 interaction, the isoscalar ({delta}{sub 0}) and isovector ({delta}{sub 1}) deformation lengths of the 2{sub 1}{sup +} states in {sup 18,20,22}O have been extracted from the folding model analysis of the (p,p{sup '}) data. A specific N dependence of {delta}{sub 0} and {delta}{sub 1} has been established which can be linked to the neutron shell closure occurring at N approaching 16. The strongest isovector deformation was found for the 2{sub 1}{sup +} state in {sup 20}O, with {delta}{sub 1} about 2.5 times larger than {delta}{sub 0}, which indicates a strong core polarization by the valence neutrons in {sup 20}O. The ratios of the neutron/proton transition matrix elements (M{sub n}/M{sub p}) determined for the 2{sub 1}{sup +} states in {sup 18,20}O have been compared with those deduced from the mirror symmetry, using the measured B(E2) values of the 2{sub 1}{sup +} states in the proton-rich {sup 18}Ne and {sup 20}Mg nuclei, to discuss the isospin impurity in the 2{sub 1}{sup +} excitation of the A=18, T=1 and A=20, T=2 isobars.

  11. Identification of 45 new neutron-rich isotopes produced by in-flight fission of a {sup 238}U beam at 345 MeV/nucleon.

    SciTech Connect

    Ohnishi, T.; Kubo, T.; Kusaka, K.; Yoshida, A.; Yoshida, K.; Manikonda, S.; Nolen, J.

    2010-07-12

    A search for new isotopes using in-flight fission of a 345 MeV/nucleon {sup 238}U beam has been carried out at the RI Beam Factory at the RIKEN Nishina Center. Fission fragments were analyzed and identified by using the superconducting in-flight separator BigRIPS. We observed 45 new neutron-rich isotopes: {sup 71}Mn, {sup 73,74}Fe, {sup 76}Co, {sup 79}Ni, {sup 81,82}Cu, {sup 84,85}Zn, {sup 87}Ga, {sup 90}Ge, {sup 95}Se, {sup 98}Br, {sup 101}Kr, {sup 103}Rb, {sup 106,107}Sr, {sup 108,109}Y, {sup 111,112}Zr, {sup 114,115}Nb, {sup 115,116,117}Mo, {sup 119,120}Tc, {sup 121,122,123,124}Ru, {sup 123,124,125,126}Rh, {sup 127,128}Pd, {sup 133}Cd, {sup 138}Sn, {sup 140}Sb, {sup 143}Te, {sup 145}I, {sup 148}Xe, and {sup 152}Ba.

  12. First direct mass measurements of stored neutron-rich 129,130,131Cd isotopes with FRS-ESR

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    A 410 MeV/u 238U projectile beam was used to create cadmium isotopes via abrasion-fission in a beryllium target placed at the entrance of the in-flight separator FRS at GSI. The fission fragments were separated by the FRS and injected into the isochronous storage ring ESR for mass measurements. Isochronous Mass Spectrometry (IMS) was performed under two different experimental conditions, with and without Bρ-tagging at the high-resolution central focal plane of the FRS. In the experiment with Bρ-tagging the magnetic rigidity of the injected fragments was determined with an accuracy of 2 ṡ10-4. A new method of data analysis, which uses a correlation matrix for the combined data set from both experiments, has provided experimental mass values of 25 rare isotopes for the first time. The high sensitivity and selectivity of the method have given access to nuclides detected with a rate of a few atoms per week. In this letter we present for the 129,130,131Cd isotopes mass values directly measured for the first time. The experimental mass values of cadmium as well as for tellurium and tin isotopes show a pronounced shell effect towards and at N = 82. Shell quenching cannot be deduced from a single new mass value, nor by a better agreement with a theoretical model which explicitly takes into account a quenching feature. This is in agreement with the conclusion from γ-ray spectroscopy and confirms modern shell-model calculations.

  13. Theoretical study on production of heavy neutron-rich isotopes around the N = 126 shell closure in radioactive beam induced transfer reactions

    NASA Astrophysics Data System (ADS)

    Zhu, Long; Su, Jun; Xie, Wen-Jie; Zhang, Feng-Shou

    2017-04-01

    In order to produce more unknown neutron-rich nuclei around N = 126, the transfer reactions 136Xe + 198Pt, 136-144Xe + 208Pb, and 132Sn + 208Pb are investigated within the framework of the dinuclear system (DNS) model. The influence of neutron excess of projectile on production cross sections of target-like products is studied through the reactions 136,144Xe + 208Pb. We find that the radioactive projectile 144Xe with much larger neutron excess is favorable to produce neutron-rich nuclei with charge number less than the target rather than produce transtarget nuclei. The incident energy dependence of yield distributions of fragments in the reaction 132Sn + 208Pb are also studied. The production cross sections of neutron-rich nuclei with Z = 72- 77 are predicted in the reactions 136-144Xe + 208Pb and 132Sn + 208Pb. It is noticed that the production cross sections of unknown neutron-rich nuclei in the reaction 144Xe + 208Pb are at least two orders of magnitude larger than those in the reaction 136Xe + 208Pb. The radioactive beam induced transfer reactions 139,144Xe + 208Pb, considering beam intensities proposed in SPIRAL2 (Production System of Radioactive Ion and Acceleration On-Line) project as well, for production of neutron-rich nuclei around the N = 126 shell closure are investigated for the first time. It is found that, in comparison to the stable beam 136Xe, the radioactive beam 144Xe shows great advantages for producing neutron-rich nuclei with N = 126 and the advantages get more obvious for producing nuclei with less charge number.

  14. 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).

  15. 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.

  16. 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.

  17. Production of new neutron-rich isotopes of heavy elements in fragmentation reactions of {sup 238}U projectiles at 1A GeV

    SciTech Connect

    Alvarez-Pol, H.; Benlliure, J.; Casarejos, E.; Cortina-Gil, D.; Fernandez-Dominguez, B.; Pereira, J.; Audouin, L.; Enqvist, T.; Schmidt, K.-H.; Yordanov, O.; Junghans, A. R.; Jurado, B.; Rejmund, F.

    2010-10-15

    The production of heavy neutron-rich nuclei has been investigated using cold-fragmentation reactions of {sup 238}U projectiles at relativistic energies. The experiment performed at the high-resolving-power magnetic spectrometer Fragment Separator at GSI made it possible to identify 40 new heavy neutron-rich nuclei: {sup 205}Pt, {sup 207-210}Au, {sup 211-216}Hg, {sup 214-217}Tl, {sup 215-220}Pb, {sup 219-224}Bi, {sup 223-227}Po, {sup 225-229}At, {sup 230,231}Rn, and {sup 233}Fr. The production cross sections of these nuclei were also determined and used to benchmark reaction codes that predict the production of nuclei far from stability.

  18. New mass measurements of neutron rich nuclides at the NSCL.

    NASA Astrophysics Data System (ADS)

    Estrade, Alfredo; Matos, Milan; Amthor, Matthew; Bazin, Daniel; Becerril, Ana; Elliot, Thom; Gade, Alexandra; Galaviz, Daniel; Lorusso, Giuseppe; Pereira, Jorge; Portillo, Mauricio; Rogers, Andrew; Schatz, Hendrik; Shapira, Dan; Smith, Ed; Stolz, Andreas; Wallace, Mark

    2007-10-01

    A mass measurement of exotic isotopes in the region of 68Fe has been performed at the NSCL using the time-of-flight technique recently established. Experimental knowledge of the mass of very neutron rich nuclides is an important input for astrophysical applications, such as nucleosynthesis during the r-process and the evolution of matter in the crust of an accreting neutron star, where present calculations are mostly limited to using theoretical mass extrapolations. We present the details of the experimental set up, as well as preliminary results.

  19. 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.

  20. Triaxial Deformations and the Proton Intruder Orbital π1/2+[431] in Very Neutron-Rich Odd-Odd Nb Isotopes

    NASA Astrophysics Data System (ADS)

    Luo, Y. X.; Hamilton, J. H.; Rasmussen, J. O.; Ramayya, A. V.; Wang, E.; Wang, J. G.; Zhu, S. J.; Liu, Y. X.; Jiao, C. F.; Liang, W. Y.; Xu, F. R.; Sun, Y.; Frauendorf, S.; Hwang, J. K.; Liu, S. H.; Brewer, N. T.; Lee, I. Y.; Ter-Akopian, G. M.; Oganessian, Yu.; Donangelo, R.; Ma, W. C.

    Rotational bands were identified and extended in 104,106Nb by means of γ-γ-γ and γ-γ-γ-γ measurements of prompt fission γ rays from 252Cf. The triple-gated 4d data with a high event accumulation turned out to be very powerful. Potential energy surface (PES) and projected shell model (PSM) calculations were made and compared to the data. Spin/parity, configuration and shape were assigned to the ground, low-lying levels and band-heads of 104,106Nb. The proton intruder orbital π1/2+[431] coupled with neutron excitations explains the isomeric decay of 106Nb, and reveals a shape evolution from partially triaxial deformations at ground levels to nearly axially-symmetric shapes at band-heads of both Nb isotopes. The PES and PSM calculations reproduced very well the similar bands as well as the differences in 106Nb and 104Nb.

  1. Time-of-Flight Mass Measurements of Neutron Rich Nuclides

    NASA Astrophysics Data System (ADS)

    Estrade, A.; Matos, M.; Amthor, A. M.; Becerril, A.; Elliot, T.; Lorusso, G.; Rogers, A.; Schatz, H.; Bazin, D.; Gade, A.; Portillo, M.; Stolz, A.; Galaviz, D.; Pereira, J.; Shapira, D.; Smith, E.; Wallace, M.

    2008-10-01

    Nuclear masses of neutron rich isotopes in the region of Z ˜ 20-30 have been measured using the time-of-flight technique at the National Superconducting Cyclotron Laboratory (NSCL). The masses of 5 isotopes have been measured for the first time, and the precision of several other masses has been improved. The time-of-flight technique has shown the potential to access nuclear masses very far from stability when applied at radioactive beam facilities like the NSCL. Such measurements are important for understanding nuclear structure far from the valley of β-stability, and provide valuable information for astrophysical model calculations of processes involving very unstable nuclides.

  2. Charge radii of neon isotopes across the sd neutron shell

    SciTech Connect

    Marinova, K.; Geithner, W.; Kappertz, S.; Kloos, S.; Kotrotsios, G.; Neugart, R.; Wilbert, S.; Kowalska, M.; Keim, M.; Blaum, K.; Lievens, P.; Simon, H.

    2011-09-15

    We report on the changes in mean square charge radii of unstable neon nuclei relative to the stable {sup 20}Ne, based on the measurement of optical isotope shifts. The studies were carried out using collinear laser spectroscopy on a fast beam of neutral neon atoms. High sensitivity on short-lived isotopes was achieved thanks to nonoptical detection based on optical pumping and state-selective collisional ionization, which was complemented by an accurate determination of the beam kinetic energy. The new results provide information on the structural changes in the sequence of neon isotopes all across the neutron sd shell, ranging from the proton drip line nucleus and halo candidate {sup 17}Ne up to the neutron-rich {sup 28}Ne in the vicinity of the ''island of inversion.'' Within this range the charge radius is smallest for {sup 24}Ne with N=14 corresponding to the closure of the neutron d{sub 5/2} shell, while it increases toward both neutron shell closures, N=8 and N=20. The general trend of the charge radii correlates well with the deformation effects which are known to be large for several neon isotopes. In the neutron-deficient isotopes, structural changes arise from the onset of proton-halo formation for {sup 17}Ne, shell closure in {sup 18}Ne, and clustering effects in {sup 20,21}Ne. On the neutron-rich side the transition to the island of inversion plays an important role, with the radii in the upper part of the sd shell confirming the weakening of the N=20 magic number. The results add new information to the radii systematics of light nuclei where data are scarce because of the small contribution of nuclear-size effects to the isotope shifts which are dominated by the finite-mass effect.

  3. The new neutron rich nuclei

    SciTech Connect

    Gridnev, K. A.; Gridnev, D. K.; Tarasov, V. N.; Tarasov, D. V.; Viñas, X.; Greiner, W.

    2014-07-23

    Using HF+BCS method with Skyrme forces we analyze the neutron drip line. It is shown that around magic and new magic numbers the drip line may form stability peninsulas. It is shown that the location of these peninsulas does not depend on the choice of Skyrme forces. It is found that the size of the peninsulas is sensitive to the choice of Skyrme forces and the most extended peninsulas appear with the SkI2 set.

  4. Investigating nuclear shell structure in the vicinity of 78Ni: Low-lying excited states in the neutron-rich isotopes Zn,8280

    NASA Astrophysics Data System (ADS)

    Shiga, Y.; Yoneda, K.; Steppenbeck, D.; Aoi, N.; Doornenbal, P.; Lee, J.; Liu, H.; Matsushita, M.; Takeuchi, S.; Wang, H.; Baba, H.; Bednarczyk, P.; Dombradi, Zs.; Fulop, Zs.; Go, S.; Hashimoto, T.; Honma, M.; Ideguchi, E.; Ieki, K.; Kobayashi, K.; Kondo, Y.; Minakata, R.; Motobayashi, T.; Nishimura, D.; Otsuka, T.; Otsu, H.; Sakurai, H.; Shimizu, N.; Sohler, D.; Sun, Y.; Tamii, A.; Tanaka, R.; Tian, Z.; Tsunoda, Y.; Vajta, Zs.; Yamamoto, T.; Yang, X.; Yang, Z.; Ye, Y.; Yokoyama, R.; Zenihiro, J.

    2016-02-01

    The low-lying level structures of nuclei in the vicinity of 78Ni were investigated using in-beam γ -ray spectroscopy to clarify the nature of the nuclear magic numbers Z =28 and N =50 in systems close to the neutron drip line. Nucleon knockout reactions were employed to populate excited states in 80Zn and 82Zn. A candidate for the 41+ level in 80Zn was identified at 1979(30) keV, and the lifetime of this state was estimated to be 136-67+92 ps from a line-shape analysis. Moreover, the energy of the 21+ state in 82Zn is reported to lie at 621(11) keV. The large drop in the 21+ energy at 82Zn indicates the presence of a significant peak in the E (21+) systematics at N =50 . Furthermore, the E (41+) /E (21+) and B (E 2 ;41+→21+) /B (E 2 ;21+→0g.s . +) ratios in 80Zn were deduced to be 1.32 (3 ) and 1 .12-60+80 , respectively. These results imply that 80Zn can be described in terms of two-proton configurations with a 78Ni core and are consistent with a robust N =50 magic number along the Zn isotopic chain. These observations, therefore, indicate a persistent N =50 shell closure in nuclei far from the line of β stability, which in turn suggests a doubly magic structure for 78Ni.

  5. Beta-Decay and Delayed Neutron Emission of Very Neutron-Rich Nuclei

    NASA Astrophysics Data System (ADS)

    Borzov, I. N.

    2014-09-01

    Extended self-consistent beta-decay model has been applied for beta-decay rates and delayed multi-neutron emission probabilities of quasi-spherical neutron-rich isotopes. The Gamow-Teller and first-forbidden decays are treated within the coordinate-space formalism of the continuum QRPA based on the density functional theory description of the ground state. A new set of the Fayans density functional parameters (DF3a) have been employed giving a better spin-orbit splitting due to a stronger tensor term. A provision has been included to fix the odd particle in the proper orbit (before variation). This accounts for ground-state spin inversion effect which has been shown to exist in the region of the most neutron-rich doubly-magic nucleus 78Ni.

  6. 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.

  7. Production and identification of new, neutron-rich nuclei in the [sup 208]Pb region

    SciTech Connect

    Rykaczewski, K. ); Szerypo, J.; Evensen, A.-H.; Kugler, E.; Lettry, J.; Ravn, H. ); Kurpeta, J.; Pkochocki, A.; Karny, M.; Szerypo, J. ); Szerypo, J. ); Andreyev, H.; Huyse, M.; Wo uml; hr, A. ); Aystuml, J.; Nieminen, A.; Huhta, M. ); Walter, G. ) Hoff, P. )

    1998-12-01

    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. [copyright] [ital 1998 American Institute of Physics.

  8. 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

  9. Neutron-Proton Asymmetry Dependence of Spectroscopic Factors in Ar Isotopes

    SciTech Connect

    Lee, Jenny; Tsang, Betty; Shapira, Dan

    2010-01-01

    Spectroscopic factors have been extracted for proton-rich 34Ar and neutron-rich 46Ar using the (p, d) neutron transfer reaction. The experimental results show little reduction of the ground state neutron spectroscopic factor of the proton-rich nucleus 34Ar compared to that of 46Ar. The results suggest that correlations, which generally reduce such spectroscopic factors, do not depend strongly on the neutron-proton asymmetry of the nucleus in this isotopic region as was reported in knockout reactions. The present results are consistent with results from systematic studies of transfer reactions but inconsistent with the trends observed in knockout reaction measurements.

  10. 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.

  11. Identification of new neutron-rich isotopes produced by in-flight fission of ^238U at 345 MeV/u

    NASA Astrophysics Data System (ADS)

    Ohnishi, Tetsuya; Kubo, Toshiyuki; Takeda, Hiroyuki; Fukuda, Naoki; Kameda, Daisuke; Kusaka, Kensuke; Yoshida, Atsushi; Yoshida, Koichi; Ohtake, Masao; Inabe, Naohito; Yanagisawa, Yoshiyuki; Tanaka, Kanenobu

    2009-10-01

    At RI Beam Factory (RIBF) at RIKEN Nishina Center, an in-flight radioactive isotope beam separator BigRIPS[1] was commissioned in 2007. Then we made a search for new isotopes using in-flight fission of a ^238U beam at 345 MeV/u, and observed two new palladium isotopes ^125Pd and ^126Pd.[2] In November 2008, we revisited this experiment with improved experimental conditions and better tuning of BigRIPS. The intensity of the ^238U beam was 1.6x10^9 particle/sec on average, which was about 40 times higher than in 2007. The search was performed for three Bρ settings that targeted different isotope regions. The achieved resolution of particle identification was good enough to well identify fission fragments even if some of them were not fully stripped. We observed more than 20 new isotopes with Z = 26 to 53, including ^128Pd, which demonstrated the RI-beam production power of BigRIPS at RIBF. The details of the experiment will be reported. [1]T. Kubo, Nucl. Instr. and Meth. B204, 97(2003). [2]T. Ohnishi et al, J. Phys. Soci. Jpn. 77, 083201(2008).

  12. Delayed neutrons in fission of polonium isotopes

    SciTech Connect

    Ramazanov, R.; Urikbaev, Z.S.; Maksyutenko, B.P.; Ignat'ev, S.V.

    1988-06-01

    A strong difference is found in the relative yields of delayed neutrons in the production of compound nuclei of polonium isotopes in reactions in which bismuth and lead are bombarded by various charged particles. The effect can be partially explained by the different lengths of the ..beta..-decay chains of the light and heavy fission products.

  13. Californium-252: A New Isotopic Source for Neutron Radiography

    SciTech Connect

    Reinig, W.C.

    2001-08-29

    This report discusses a new isotopic source for neutron radiography, Californium-252. Nuclear reactors are the usual source of neutrons for radiography, primarily because of their intense neutron beams. If neutron radiography is to have widespread use, intense transportable neutron sources are required that can be used in plants, in laboratories and in the field.

  14. Discovery and investigation of heavy neutron-rich isotopes with time-resolved Schottky spectrometry in the element range from thallium to actinium

    NASA Astrophysics Data System (ADS)

    Chen, L.; Plaß, W. R.; Geissel, H.; Knöbel, R.; Kozhuharov, C.; Litvinov, Yu. A.; Patyk, Z.; Scheidenberger, C.; Siegień-Iwaniuk, K.; Sun, B.; Weick, H.; Beckert, K.; Beller, P.; Bosch, F.; Boutin, D.; Caceres, L.; Carroll, J. J.; Cullen, D. M.; Cullen, I. J.; Franzke, B.; Gerl, J.; Górska, M.; Jones, G. A.; Kishada, A.; Kurcewicz, J.; Litvinov, S. A.; Liu, Z.; Mandal, S.; Montes, F.; Münzenberg, G.; Nolden, F.; Ohtsubo, T.; Podolyák, Zs.; Propri, R.; Rigby, S.; Saito, N.; Saito, T.; Shindo, M.; Steck, M.; Ugorowski, P.; Walker, P. M.; Williams, S.; Winkler, M.; Wollersheim, H.-J.; Yamaguchi, T.

    2010-08-01

    238U projectile fragments have been created at the entrance of the fragment separator FRS, spatially separated in flight within 0.45 μs and injected into the storage-cooler ring ESR at 7.9 Tm corresponding to about 70% light velocity. Accurate new mass values and lifetime information of the stored exotic nuclei in the element range from platinum to uranium have been obtained with single-particle Schottky spectrometry. In this experiment the new isotopes of 236Ac, 224At, 221Po, 222Po, and 213Tl were discovered. The isotopes were unambiguously identified and their masses measured. In addition, the time-correlated data have provided information on the lifetime of the new nuclides. The discovery of isotopes along with accurate mass measurement has been achieved for the first time at the FRS-ESR facility. The results will contribute to the knowledge of the decay products from the r-process nuclei and enable a crucial test of the predictive power of modern nuclear mass and half-life models.

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

    SciTech Connect

    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 Sn119,121,123,125 isotopes produced by fusion-fission of 6.9-MeV/ACa48 beams with Pb208 and U238 targets and by fission of a U238 target bombarded with 6.7-MeV/ANi64 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 Sn119, a new 23/2+ isomer was identified, while a similar 23/2+ long-lived state, proposed earlier in Sn121, 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 Sn121,123 isotopes, these sequences also enabled the delineation of higher-lying levels, up to (43/2+) states. In Sn123, a short half-life was determined for the (35/2+) state. Shell-model calculations were carried out for all the odd Sn isotopes, from Sn129 down to Sn119, and the results were

  16. Portable, high intensity isotopic neutron source provides increased experimental accuracy

    NASA Technical Reports Server (NTRS)

    Mohr, W. C.; Stewart, D. C.; Wahlgren, M. A.

    1968-01-01

    Small portable, high intensity isotopic neutron source combines twelve curium-americium beryllium sources. This high intensity of neutrons, with a flux which slowly decreases at a known rate, provides for increased experimental accuracy.

  17. Neutron-poor Nickel Isotope Anomalies in Meteorites

    NASA Astrophysics Data System (ADS)

    Steele, Robert C. J.; Coath, Christopher D.; Regelous, Marcel; Russell, Sara; Elliott, Tim

    2012-10-01

    We present new, mass-independent, Ni isotope data for a range of bulk chondritic meteorites. The data are reported as ɛ60Ni58/61, ɛ62Ni58/61, and ɛ64Ni58/61, or the parts per ten thousand deviations from a terrestrial reference, the NIST SRM 986 standard, of the 58Ni/61Ni internally normalized 60Ni/61Ni, 62Ni/61Ni, and 64Ni/61Ni ratios. The chondrites show a range of 0.15, 0.29, and 0.84 in ɛ60Ni58/61, ɛ62Ni58/61, and ɛ64Ni58/61 relative to a typical sample precision of 0.03, 0.05, and 0.08 (2 s.e.), respectively. The carbonaceous chondrites show the largest positive anomalies, enstatite chondrites have approximately terrestrial ratios, though only EH match Earth's composition within uncertainty, and ordinary chondrites show negative anomalies. The meteorite data show a strong positive correlation between ɛ62Ni58/61 and ɛ64Ni58/61, an extrapolation of which is within the error of the average of previous measurements of calcium-, aluminium-rich inclusions. Moreover, the slope of this bulk meteorite array is 3.003 ± 0.166 which is within the error of that expected for an anomaly solely on 58Ni. We also determined to high precision (~10 ppm per AMU) the mass-dependent fractionation of two meteorite samples which span the range of ɛ62Ni58/61 and ɛ64Ni58/61. These analyses show that "absolute" ratios of 58Ni/61Ni vary between these two samples whereas those of 62Ni/61Ni and 64Ni/61Ni do not. Thus, Ni isotopic differences seem most likely explained by variability in the neutron-poor 58Ni, and not correlated anomalies in the neutron-rich isotopes, 62Ni and 64Ni. This contrasts with previous inferences from mass-independent measurements of Ni and other transition elements which invoked variable contributions of a neutron-rich component. We have examined different nucleosynthetic environments to determine the possible source of the anomalous material responsible for the isotopic variations observed in Ni and other transition elements within bulk samples. We find

  18. NEUTRON-POOR NICKEL ISOTOPE ANOMALIES IN METEORITES

    SciTech Connect

    Steele, Robert C. J.; Coath, Christopher D.; Regelous, Marcel; Elliott, Tim; Russell, Sara

    2012-10-10

    We present new, mass-independent, Ni isotope data for a range of bulk chondritic meteorites. The data are reported as {epsilon}{sup 60}Ni{sub 58/61}, {epsilon}{sup 62}Ni{sub 58/61}, and {epsilon}{sup 64}Ni{sub 58/61}, or the parts per ten thousand deviations from a terrestrial reference, the NIST SRM 986 standard, of the {sup 58}Ni/{sup 61}Ni internally normalized {sup 60}Ni/{sup 61}Ni, {sup 62}Ni/{sup 61}Ni, and {sup 64}Ni/{sup 61}Ni ratios. The chondrites show a range of 0.15, 0.29, and 0.84 in {epsilon}{sup 60}Ni{sub 58/61}, {epsilon}{sup 62}Ni{sub 58/61}, and {epsilon}{sup 64}Ni{sub 58/61} relative to a typical sample precision of 0.03, 0.05, and 0.08 (2 s.e.), respectively. The carbonaceous chondrites show the largest positive anomalies, enstatite chondrites have approximately terrestrial ratios, though only EH match Earth's composition within uncertainty, and ordinary chondrites show negative anomalies. The meteorite data show a strong positive correlation between {epsilon}{sup 62}Ni{sub 58/61} and {epsilon}{sup 64}Ni{sub 58/61}, an extrapolation of which is within the error of the average of previous measurements of calcium-, aluminium-rich inclusions. Moreover, the slope of this bulk meteorite array is 3.003 {+-} 0.166 which is within the error of that expected for an anomaly solely on {sup 58}Ni. We also determined to high precision ({approx}10 ppm per AMU) the mass-dependent fractionation of two meteorite samples which span the range of {epsilon}{sup 62}Ni{sub 58/61} and {epsilon}{sup 64}Ni{sub 58/61}. These analyses show that 'absolute' ratios of {sup 58}Ni/{sup 61}Ni vary between these two samples whereas those of {sup 62}Ni/{sup 61}Ni and {sup 64}Ni/{sup 61}Ni do not. Thus, Ni isotopic differences seem most likely explained by variability in the neutron-poor {sup 58}Ni, and not correlated anomalies in the neutron-rich isotopes, {sup 62}Ni and {sup 64}Ni. This contrasts with previous inferences from mass-independent measurements of Ni and other

  19. Studies of neutron-rich nuclei using the CPT mass spectrometer at CARIBU

    NASA Astrophysics Data System (ADS)

    Chaudhuri, A.; Bertone, P. F.; Buchinger, F.; Caldwell, S.; Clark, J. A.; Crawford, J. E.; Deibel, C. M.; Gulick, S.; Lascar, D.; Levand, A. F.; Li, G.; Savard, G.; Segel, R. E.; Sharma, K. S.; Sternberg, M. G.; Sun, T.; Van Schelt, J.

    2011-09-01

    The nucleosynthetic path of the astrophysical r-process and the resulting elemental abundances depend on neutron-separation energies which can be determined from the masses of the nuclei along the r-process reaction path. Due to the current lack of experimental data, mass models are often used. The mass values provided by the mass models are often too imprecise or disagree with each other. Therefore, direct high-precision mass measurements of neutron-rich nuclei are necessary to provide input parameters to the calculations and help refine the mass models. The Californium Rare Isotope Breeder Upgrade (CARIBU) facility of Argonne National Laboratory will provide experiments with beams of short-lived neutron-rich nuclei. The Canadian Penning Trap (CPT) mass spectrometer has been relocated to the CARIBU low-energy beam line to extend measurements of the neutron-rich nuclei into the mostly unexplored region along the r-process path. This will allow precise mass measurements (~ 10 keV/c2) of more than a hundred very neutron-rich isotopes that have not previously been measured.

  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. 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.

  2. Formalism for the determination of structural isotope effects with neutrons

    SciTech Connect

    Neuefeind, Joerg C; Benmore, Chris J

    2009-01-01

    In general the analysis of neutron isotopic substitution experiments in terms of partial structure factors and partial pair distribution functions is based on the assumption that the structure of isotopic variants of a molecule is identical. This assumption is clearly only an approximation especially in the case of hydrogen bonding molecular liquids like liquid water and structural isotope effects have been measured with X-rays for more than 20 years. A analysis method of neutron isotope data is presented that avoids the necessity to assume structural equality and allows the determination of the isotope effect in the hydrogen-hydrogen partial structure factor of liquid water from neutron data. It is shown that a combination of X-ray and neutron scattering measurements allows in principle the determination of the isotope effects on all all partials structure factors of liquid water.

  3. 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.

  4. 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.

  5. 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.

  6. Evidence for octupole excitations in the odd-odd neutron-rich nucleus {sup 142}Cs

    SciTech Connect

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

    2010-05-15

    High-spin states in the neutron-rich nucleus {sup 142}Cs are reinvestigated from a study of the spontaneous fission of {sup 252}Cf with the Gammasphere detector array. A new level scheme is built and spin-parities are assigned to levels based on angular correlation measurements and systematics. The new structure of {sup 142}Cs is proposed to be related to octupole correlations. The electric dipole moment of {sup 142}Cs is measured and a dramatic decrease of the dipole moments with increasing neutron numbers in the Cs isotopic chain is found.

  7. First Measurement of Several β -Delayed Neutron Emitting Isotopes Beyond N =126

    NASA Astrophysics Data System (ADS)

    Caballero-Folch, R.; Domingo-Pardo, C.; Agramunt, J.; Algora, A.; Ameil, F.; Arcones, A.; Ayyad, Y.; Benlliure, J.; Borzov, I. N.; Bowry, M.; Calviño, F.; Cano-Ott, D.; Cortés, G.; Davinson, T.; Dillmann, I.; Estrade, A.; Evdokimov, A.; Faestermann, T.; Farinon, F.; Galaviz, D.; García, A. R.; Geissel, H.; Gelletly, W.; Gernhäuser, R.; Gómez-Hornillos, M. B.; Guerrero, C.; Heil, M.; Hinke, C.; Knöbel, R.; Kojouharov, I.; Kurcewicz, J.; Kurz, N.; Litvinov, Yu. A.; Maier, L.; Marganiec, J.; Marketin, T.; Marta, M.; Martínez, T.; Martínez-Pinedo, G.; Montes, F.; Mukha, I.; Napoli, D. R.; Nociforo, C.; Paradela, C.; Pietri, S.; Podolyák, Zs.; Prochazka, A.; Rice, S.; Riego, A.; Rubio, B.; Schaffner, H.; Scheidenberger, Ch.; Smith, K.; Sokol, E.; Steiger, K.; Sun, B.; Taín, J. L.; Takechi, M.; Testov, D.; Weick, H.; Wilson, E.; Winfield, J. S.; Wood, R.; Woods, P.; Yeremin, A.

    2016-07-01

    The β -delayed neutron emission probabilities of neutron rich Hg and Tl nuclei have been measured together with β -decay half-lives for 20 isotopes of Au, Hg, Tl, Pb, and Bi in the mass region N ≳126 . These are the heaviest species where neutron emission has been observed so far. These measurements provide key information to evaluate the performance of nuclear microscopic and phenomenological models in reproducing the high-energy part of the β -decay strength distribution. This provides important constraints on global theoretical models currently used in r -process nucleosynthesis.

  8. Multiquasiparticle states in the neutron-rich nucleus 174Tm

    NASA Astrophysics Data System (ADS)

    Hughes, R. O.; Lane, G. J.; Dracoulis, G. D.; Byrne, A. P.; Nieminen, P.; Watanabe, H.; Carpenter, M. P.; Chowdhury, P.; Janssens, R. V. F.; Kondev, F. G.; Lauritsen, T.; Seweryniak, D.; Zhu, S.

    2013-07-01

    Deep inelastic and transfer reactions with an 820-MeV, 136Xe beam and various ytterbium and lutetium targets have been employed to study high-spin structures in the neutron-rich thulium isotopes beyond 171Tm. Results in the doubly odd nucleus, 174Tm, include the identification of numerous new two- and four-quasiparticle intrinsic states including several isomers below 1 MeV, and the observation of the Kπ=4- ground state rotational band populated via direct decay from a τ=153(10)-μs, Kπ=14- isomer at 2092 keV. The 398-keV, M1 transition linking the isomer and ground state band is abnormally fast for a highly forbidden, ΔK=10 decay. This relative enhancement is explained in terms of mixing of the 13- level with the nearby 13- member of a Kπ=8- rotational band, with an interaction strength of V ≈ 1.4 keV. Multiquasiparticle calculations are compared with the observed states.

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

    SciTech Connect

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

    2015-09-10

    Here, 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. The purpose of this study is 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. As a result, our self-consistent DFT calculations predict triaxial ground-state deformations in 106,108Mo and 108,110,112Ru and reproduce the observed low-frequency behavior of moments of inertia. As the rotational frequency increases, a negative-gamma 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. Lastly, the structure of neutron-rich even-even nuclei around Ru-110 is consistent with triaxial shape deformations. Our DFT and TPSM frameworks provide a consistent and complementary description of experimental data.

  10. 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.

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

    DOE PAGES

    Zhang, C. L.; Bhat, G. H.; Nazarewicz, W.; ...

    2015-09-10

    Here, 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. The purpose of this study is 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-richmore » 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. As a result, our self-consistent DFT calculations predict triaxial ground-state deformations in 106,108Mo and 108,110,112Ru and reproduce the observed low-frequency behavior of moments of inertia. As the rotational frequency increases, a negative-gamma 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. Lastly, the structure of neutron-rich even-even nuclei around Ru-110 is consistent with triaxial shape deformations. Our DFT and TPSM frameworks provide a consistent and complementary description of experimental data.« less

  12. Neutron Capture Reactions on lu Isotopes at Dance

    NASA Astrophysics Data System (ADS)

    Roig, O.; Meot, V.; Daugas, J.-M.; Morel, P.; Jandel, M.; Vieira, D. J.; Bond, E. M.; Bredeweg, T. A.; Couture, A. J.; Haight, R. C.; Keksis, A. L.; Rundberg, R. S.; Ullmann, J. L.; Wouters, J. M.

    2013-03-01

    The DANCE1 (Detector for Advanced Neutron Capture Experiments) array at LANSCE spallation neutron source in Los Alamos has been used to obtain the neutron radiative capture cross sections for 175Lu and 176Lu with neutron energies from thermal up to 100 keV. Both isotopes are of current interest for the nucleosynthesis s-process.2,3 Three targets were used to perform these measurements. One was natural Lu foil of 31 mg/cm2 and the other two were isotope-enriched targets of 175Lu and 176Lu. Firstly, the cross sections were obtained by normalizing yield to a well-known cross section at the thermal neutron energy. Now, we want to obtain absolute cross sections of radiative capture through a precise neutron flux determination, an accurate target mass measurement and an efficiency determination of the DANCE array.

  13. Study of weakening of shell N = 28 for neutron rich nuclei through particle number fluctuation and pairing energy

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Rupayan

    2017-03-01

    Evolution of shells has been studied through fluctuations of particle numbers, pairing energies of large number of isotopes and isotones of nuclei evaluated through Skyrme-Hartree-Fock theory after inclusion of optimized tensor interaction. For neutron rich isotopes of Mg, Si, S and Ar no indication of shell closure at N = 28 has been observed. Calculations show occurrence of a doubly shell closed nucleus 114 Fl 184 .

  14. Direct Mass Measurements of Fluorine Through Chlorine Neutron-Rich Nuclei.

    NASA Astrophysics Data System (ADS)

    Zhou, Xiao-Gang

    1991-02-01

    Mass measurements have been made of the neutron -rich isotopes of fluorine through chlorine at the Los Alamos Meson Physics Facility. The masses of 34 neutron-rich isotopes are reported. Ten of these measurements represent first-time mass determinations of these species. The nuclei of interest are produced in fragmentation reaction. A transport line is used to capture a small fraction of the ions and transport them into the time-of-flight isochronous (TOFI) spectrometer. The TOFI spectrometer is isochronously designed, such that the transit time of the ion passing through the spectrometer is independent of the ion velocity, and only depends on its mass-to-charge ratio. A gas ionization counter located at the exit of the TOFI spectrometer is used to identify the ion atomic number and to measure the total energy. Three fast timing detectors are placed in the middle of the transport line, entrance, and exit of the TOFI spectrometer to determine the ion velocity and the M/Q ratio. We calculate each ion's charge state by using velocity, total energy, and M/Q ratio. With A, Z, Q assigned to each ion, we fit M/Q linearly to the known masses to obtain a high precision M/Q calibration. The masses of unknown nuclei are calculated through the M/Q calibration. The final results are generated by taking a weighted average for all runs and charge states. These results have confirmed the anomaly of enhanced binding found in neutron-rich Na and Mg isotopes and also suggest that the binding energies for those nuclei are less than that originally reported. The masses of several F through Al isotopes are compared with the shell model calculations. These comparisons demonstrate that the anomaly can be understood in terms of one or two neutron promotions from the sd shell to the fp shell. The results for some neutron-rich isotopes of P through Cl are compared to several mass models and good agreement in all cases is found.

  15. Production of very neutron-rich nuclei with a {sup 76}Ge beam

    SciTech Connect

    Tarasov, O. B.; Portillo, M.; Baumann, T.; Bazin, D.; Ginter, T. N.; Hausmann, M.; Pereira, J.; Stolz, A.; Amthor, A. M.; Gade, A.; Nettleton, A.; Sherrill, B. M.; Thoennessen, M.; Inabe, N.; Kubo, T.; Morrissey, D. J.

    2009-09-15

    Production cross sections for neutron-rich nuclei from the fragmentation of a {sup 76}Ge beam at 132 MeV/u were measured. The longitudinal momentum distributions of 34 neutron-rich isotopes of elements 13{<=}Z{<=}27 were scanned using a novel experimental approach of varying the target thickness. Production cross sections with beryllium and tungsten targets were determined for a large number of nuclei, including 15 isotopes first observed in this work. These are the most neutron-rich nuclides of the elements 17{<=}Z{<=}25 ({sup 50}Cl, {sup 53}Ar, {sup 55,56}K, {sup 57,58}Ca, {sup 59,60,61}Sc, {sup 62,63}Ti, {sup 65,66}V, {sup 68}Cr, and {sup 70}Mn). A one-body Q{sub g} systematics is used to describe the production cross sections based on thermal evaporation from excited prefragments. Some of the fragments near {sup 58}Ca show anomalously large production cross sections.

  16. Neutron Knockout to Probe 3N Forces in the Ca Isotopes

    NASA Astrophysics Data System (ADS)

    Crawford, Heather; NSCL Experiment e12029 Collaboration

    2013-10-01

    Recent calculations by Holt et al. have suggested that the inclusion of 3N forces to describe the structure of neutron-rich Ca isotopes provides a more realistic description of the nuclear structure. Mass measurements have confirmed the importance of including 3N forces compared to NN-only interactions, but cannot discriminate between the predictions of phenomenological interactions and the NN+3N microscopic calculations. Neutron knockout along the Z = 20 isotopes provides an opportunity to test the results of NN+3N calculations against phenomenological interactions. The calculations of Holt et al. predict a fragmentation of the 1f7 / 2 neutron strength from the first 7/2- state in 49Ca into higher lying states, in contrast to the predictions of both GXPF1 and KB3G which concentrate the strength in the lowest lying 7/2- state. Differences are also observed in the summed f7 / 2 strength to bound nuclear states in both 50Ca and 49Ca neutron knockout. We will report on a systematic study of one-neutron knockout along the Ca isotopes using GRETINA+S800. Comparison of experimental spectroscopic factors to calculations will provide insight into the role of 3N forces in describing the Z = 20 isotopes. With collaborators from LBNL, NSCL/MSU, ANL, Central Michigan University, TRIUMF/UBC and TU-Darmstadt.

  17. 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.

  18. Synthesis of neutron-rich transuranic nuclei in fissile spallation targets

    NASA Astrophysics Data System (ADS)

    Mishustin, Igor; Malyshkin, Yury; Pshenichnov, Igor; Greiner, Walter

    2015-04-01

    A possibility of synthesizing neutron-rich superheavy elements in spallation targets of Accelerator Driven Systems (ADS) is considered. A dedicated software called Nuclide Composition Dynamics (NuCoD) was developed to model the evolution of isotope composition in the targets during a long-time irradiation by intense proton and deuteron beams. Simulation results show that transuranic elements up to 249Bk can be produced in multiple neutron capture reactions in macroscopic quantities. However, the neutron flux achievable in a spallation target is still insufficient to overcome the so-called fermium gap. Further optimization of the target design, in particular, by including moderating material and covering it by a reflector could turn ADS into an alternative source of transuranic elements in addition to nuclear fission reactors.

  19. Fission and Properties of Neutron-Rich Nuclei - Proceedings of the Second International Conference

    NASA Astrophysics Data System (ADS)

    Hamilton, J. H.; Phillips, W. R.; Carter, H. K.

    The Table of Contents for the book is as follows: * Preface * Structure of Elementary Matter: Cold Valleys and Their Importance in Fission, Fusion and for Superheavy Nuclei * Tunnelling Phenomena in Nuclear Physics * Heavy Nuclei Studies Using Transfer Reactions * Isomeric Properties of Nuclei Near 78Ni * Investigation of Light Actinide Nuclei at Yale and Beyond * U-Projectile Fission at Relativistic Energies * Cluster Description of Cold Fission Modes in 252Cf * Neutron-pair Transfer Theory for Pear-shaped Ba Fission Fragments * New RMFA Parameters of Normal and Exotic Nuclei * Study of Fission Fragments from 12C+238U Reactions: Prompt and Delayed Spectroscopy * γ-Ray Angular Correlations in 252Cf and 248Cm Fission Fragments * Fragment Angular Momentum and Descent Dynamics in 252Cf Spontaneous Fission * The Experimental Investigation of Neutron-Rich Nuclei * High-Spin Structure of Some Odd-Z Nuclei with A ≈ 100 From Heavy-Ion Induced Fission * Coexistence of Symmetric and Asymmetric Nuclear Shapes and 10Be Ternary Fission * Octupole Effects in the Lanthanides * High Spin Structure of the 113-1l6Cd Isotopes Produced by Heavy-Ion Induced Fission Reaction * Temperature-Dependent Fission Barriers and Mass Distributions for 239U * Strength Distributions for Gamow Teller Transitions in Very Weakly Bound Systems * High Spin Fragmentation Spectroscopy * Search for a Four-Neutron Transfer From 8He to 4He * Microsecond Isomers in Fission Fragments in the Vicinity of the Doubly Magic 132Sn * Recent On-Line NMR/on Nuclear Magnetic Dipole Moments Near 132Sn: Meson Exchange Current Effects at the Shell Closure and Shell Model Treatment of Variation with Proton and Neutron Number * High-spin K-Isomers Beyond the Fusion Limit * High Energy Neutron Induced Fission: Charge Yield Distributions and Search and Spectroscopy of New Isomers * Hartree-Fock Mean-Field Models Using Separable Interactions * Variation of Fission Characteristics Over the Nuclear Chart * Investigation of

  20. 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.

  1. Few groups neutron spectra, and dosimetric features, of isotopic neutron sources.

    PubMed

    Vega-Carrillo, Hector Rene; Martinez-Ovalle, Segundo Agustín

    2016-11-01

    Using Monte Carlo methods, the neutron spectra in 31 energy groups of several isotopic neutron sources were estimated. For each source the neutron mean energy; the Ambient dose equivalent, the Personal dose equivalent and the Effective dose per unit fluence rate were calculated. A convenient way to produce neutrons is the isotopic neutron source, where the production is through (α, n), (γ, n), and spontaneous fission reactions. Isotopic neutron sources are small, easy to handle, and have a relative low cost. On the other hand the neutron yield is small and mostly of them produces neutrons with a wide energy distribution. In this work, the main features of (24)NaBe, (24)NaD2O, (116)InBe, (140)LaBe, (238)PuLi, (239)PuBe, (241)AmB, (241)AmBe, (241)AmF, (241)AmLi, (242)CmBe, (210)PoBe, (226)RaBe, (252)Cf and (252)Cf/D2O isotopic neutron source are also compiled.

  2. Shape Evolution in Neutron-Rich Ru Nuclei

    NASA Astrophysics Data System (ADS)

    Söderström, P.-A.; Lorusso, G.; Watanabe, H.; Nishimura, S.; Doornenbal, P.; Browne, F.; Bruce, A. M.; Daido, R.; Fang, Y.; Gey, G.; Jung, H. S.; Nishizuka, I.; Patel, Z.; Rice, S.; Sinclair, L.; Sumikama, T.; Taprogge, J.; Vajta, Zs.; Wu, J.; Xu, Z. Y.; Baba, H.; Benzoni, G.; Carroll, R. J.; Chae, K. Y.; Crespi, F. C. L.; Fukuda, N.; Gernhäuser, R.; Ideguchi, E.; Inabe, N.; Isobe, T.; Jungclaus, A.; Kameda, D.; Kim, G. D.; Kim, Y.-K.; Kojouharov, I.; Kondev, F. G.; Kubo, T.; Kurz, N.; Kwon, Y. K.; Lalkovski, S.; Lane, G. J.; Li, Z.; Lozeva, R.; Montaner-Piza, A.; Moschner, K.; Naqvi, F.; Niikura, M.; Nishibata, H.; Odahara, A.; Orlandi, R.; Podolyak, Zs.; Regan, P. H.; Roberts, O. J.; Sakurai, H.; Schaffner, H.; Simpson, G. S.; Steiger, K.; Suzuki, H.; Takeda, H.; Tanaka, M.; Wendt, A.; Werner, V.; Wieland, O.; Yagi, A.; Yoshinaga, K.

    Recent experimental work has been carried out at the RIBF using the EURICA HPGe detector array. In this contribution, we discuss the recently published results on the shape evolution of the even-even isotopes 116,118Ru and present an outlook of β-delayed γ-ray spectroscopy of the odd-neutron nuclei and possibilities for life-time measurements of excited states.

  3. Isotopic anomalies from neutron reactions during explosive carbon burning

    NASA Technical Reports Server (NTRS)

    Lee, T.; Schramm, D. N.; Wefel, J. P.; Blake, J. B.

    1979-01-01

    The heavy isotopic anomalies observed recently in the fractionation and unknown nuclear inclusions from the Allende meteorite are explained by neutron reactions during the explosive carbon burning (ECB). This model produces heavy anomalies in the same zone where Al-26 and O-16 are produced, thus reducing the number of source zones required for the isotopic anomalies. Unlike the classical r-process, the ECB n-process avoids the problem with the Sr anomaly and may resolve the problem of conflicting time scales between Al-26 and the r-process isotopes I-129 and Pu-244. Experimental studies of Zr and Ce isotopic composition are proposed to test this model.

  4. Krypton and xenon in Apollo 14 samples - Fission and neutron capture effects in gas-rich samples

    NASA Technical Reports Server (NTRS)

    Drozd, R.; Hohenberg, C.; Morgan, C.

    1975-01-01

    Gas-rich Apollo 14 breccias and trench soil are examined for fission xenon from the decay of the extinct isotopes Pu-244 and I-129, and some samples have been found to have an excess fission component which apparently was incorporated after decay elsewhere and was not produced by in situ decay. Two samples have excess Xe-129 resulting from the decay of I-129. The excess is correlated at low temperatures with excess Xe-128 resulting from neutron capture on I-127. This neutron capture effect is accompanied by related low-temperature excesses of Kr-80 and Kr-82 from neutron capture on the bromine isotopes. Surface correlated concentrations of iodine and bromine are calculated from the neutron capture excesses.

  5. Nuclear shape and structure in neutron-rich {sup 110,111}Tc

    SciTech Connect

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

    2006-08-15

    The high-spin nuclear structure of Tc isotopes is extended to more neutron-rich regions based on the measurements of prompt {gamma} rays from the spontaneous fission of {sup 252}Cf at the Gammasphere. The high-spin level scheme of N=67 neutron-rich {sup 110}Tc (Z=43) is established for the first time, and that of {sup 111}Tc is extended and expanded. The ground band of {sup 111}Tc reaches the band-crossing region, and the new observation of the weakly populated {alpha}=-1/2 member of the band provides important information on signature splitting. The systematics of band crossings in the isotopic and isotonic chains and a CSM calculation suggest that the band crossing of the ground band of {sup 111}Tc is due to alignment of a pair of h{sub 11/2} neutrons. The best fit to signature splitting, branching ratios, and excitations of the ground band of {sup 111}Tc by the rigid triaxial rotor plus particle model calculations result in a shape of {epsilon}{sub 2}=0.32 and {gamma}=-26 deg. for this nucleus. Its triaxiality is larger than that of {sup 107,109}Tc, which indicates increasing triaxiality in Tc isotopes with increasing neutron number. The identification of the weakly populated K+2 satellite band provides strong evidence for the large triaxiality of {sup 111}Tc. In {sup 110}Tc, the four lowest-lying levels observed are very similar to those in {sup 108}Tc. At an excitation of 478.9 keV above the lowest state observed, ten states of a {delta}I=1 band are observed. This band of {sup 110}Tc is very analogous to the {delta}I=1 bands in {sup 106,108}Tc, but it has greater and reversal signature splitting at higher spins.

  6. Thermonuclear runaways in thick hydrogen rich envelopes of neutron stars

    NASA Technical Reports Server (NTRS)

    Starrfield, S. G.; Kenyon, S.; Truran, J. W.; Sparks, W. M.

    1981-01-01

    A Lagrangian, fully implicit, one dimensional hydrodynamic computer code was used to evolve thermonuclear runaways in the accreted hydrogen rich envelopes of 1.0 Msub solar neutron stars with radii of 10 km and 20 km. Simulations produce outbursts which last from about 750 seconds to about one week. Peak effective temeratures and luninosities were 26 million K and 80 thousand Lsub solar for the 10 km study and 5.3 millison and 600 Lsub solar for the 20 km study. Hydrodynamic expansion on the 10 km neutron star produced a precursor lasting about one ten thousandth seconds.

  7. Collectivity at N=40 in neutron-rich {sup 64}Cr

    SciTech Connect

    Gade, A.; Baugher, T.; Brown, B. A.; McDaniel, S.; Ratkiewicz, A.; Stroberg, S. R.; Walsh, K. A.; Janssens, R. V. F.; Carpenter, M. P.; Hoffman, C. R.; Kay, B. P.; Lauritsen, T.; Zhu, S.; Bazin, D.; Grinyer, G. F.; Weisshaar, D.; Winkler, R.; Chiara, C. J.; Deacon, A. N.; Freeman, S. J.

    2010-05-15

    {sup 9}Be-induced inelastic scattering of {sup 62,64,66}Fe and {sup 60,62,64}Cr was performed at intermediate beam energies. Excited states in {sup 64}Cr were measured for the first time. Energies and population patterns of excited states in these neutron-rich Fe and Cr nuclei are compared and interpreted in the framework of large-scale shell-model calculations in different model spaces. Evidence for increased collectivity and for distinct structural changes between the neighboring Fe and Cr isotopic chains near N=40 is presented.

  8. Collectivity at N = 40 in neutron-rich {sup 64}Cr.

    SciTech Connect

    Gade, A.; Janssens, R. V. F.; Baugher, T.; Bazin, D.; Brown, B. A.; Carpenter, M. P.; Chiara, C. J.; Deacon, A. N.; Freeman, S. J.; Grinyer, G. F.; Hoffman, C. R.; Kay, B. P.; Kondev, F. G.; Lauritsen, T.; McDaniel, S.; Meierbachtol, K.; Ratkiewicz, A.; Stroberg, S. R.; Walsh, K. A.; Weisshaar, D.; Zhu, S.; Winkler, R.; Michigan State Univ.; Univ. of Maryland; Univ. of Manchester

    2010-05-01

    9Be-induced inelastic scattering of 62,64,66Fe and 60,62,64Cr was performed at intermediate beam energies. Excited states in 64Cr were measured for the first time. Energies and population patterns of excited states in these neutron-rich Fe and Cr nuclei are compared and interpreted in the framework of large-scale shell-model calculations in different model spaces. Evidence for increased collectivity and for distinct structural changes between the neighboring Fe and Cr isotopic chains near N=40 is presented.

  9. 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.

  10. Neutron multiplicity distributions for neutron-rich projectile fragments at the NSCL

    NASA Astrophysics Data System (ADS)

    Mazza, Maria; Christ, Peter; Stephenson, Sharon; MoNA Collaboration

    2016-09-01

    Projectile fragmentation is one of the mechanisms used at nuclear science facilities around the world for the production of rare isotope beams. The study of the projectile fragmentation mechanism informs beam simulation codes, but relatively few studies of the fragmentation process have been done, especially at intermediate energies. The MoNA Collaboration used an 86 MeV/u 32Mg beam on a natural beryllium target at the National Superconducting Cyclotron Laboratory to produce neutron multiplicities distributions in coincidence with charged fragments for isotopes ranging from 29Na to 20F. Particle identification for the isotopes from fluorine, neon, and sodium will be presented, as well as preliminary neutron multiplicities distributions. Supported by NSF Grants 1203357, 1613429 and HHMI Grant 52007540.

  11. Thermal Neutron Capture onto the Stable Tungsten Isotopes

    NASA Astrophysics Data System (ADS)

    Hurst, A. M.; Firestone, R. B.; Sleaford, B. W.; Summers, N. C.; Revay, Zs.; Szentmiklósi, L.; Belgya, T.; Basunia, M. S.; Capote, R.; Choi, H.; Dashdorj, D.; Escher, J.; Krticka, M.; Nichols, A.

    2012-02-01

    Thermal neutron-capture measurements of the stable tungsten isotopes have been carried out using the guided thermal-neutron beam at the Budapest Reactor. Prompt singles spectra were collected and analyzed using the HYPERMET γ-ray analysis software package for the compound tungsten systems 183W, 184W, and 187W, prepared from isotopically-enriched samples of 182W, 183W, and 186W, respectively. These new data provide both confirmation and new insights into the decay schemes and structure of the tungsten isotopes reported in the Evaluated Gamma-ray Activation File based upon previous elemental analysis. The experimental data have also been compared to Monte Carlo simulations of γ-ray emission following the thermal neutron-capture process using the statistical-decay code DICEBOX. Together, the experimental cross sections and modeledfeeding contribution from the quasi continuum, have been used to determine the total radiative thermal neutron-capture cross sections for the tungsten isotopes and provide improved decay-scheme information for the structural- and neutron-data libraries.

  12. Excited states of neutron rich Pd from fragmentation

    NASA Astrophysics Data System (ADS)

    Hecht, A. A.; Walters, W. B.; Hoteling, N.; Mantica, P. F.; Becerril, A.; Fleckenstein, T.; Lorusso, G.; Pereira, J.; Pinter, J.; Stoker, J.; Quinn, M.

    2007-04-01

    The neutron rich region approaching N=82 and Z=50 is interesting for nuclear structure and nuclear astrophysics, both as a test of the shell closures far from stability and as the path for r-process nucleosynthesis. This region is difficult to access with fusion-evaporation reactions and novel techniques must be used. At the National Superconducting Cyclotron Laboratory (NSCL) an experiment was recently performed by fragmentation of a Xe beam using a Be target to examine isomers and beta decay from these neutron rich nuclei. The radioisotope fragments passed through several Si planar detectors and were implanted in a double-sided Si strip detector (DSSD) in the Beta Counting System (BCS). Fragments were identified via δE and TOF. Particle emitting decays were tracked in several layers of single sided strip detectors following the DSSD, while the SEGA array surrounding the DSSD was used to collect gamma emission following beta and isomer decay. Several neutron rich nuclei were observed in this experiment, including Ru, Rh, Pd, Ag, Cd, and In. Results on Pd will be discussed.

  13. Neutron Capture Measurements on Tl-isotopes at DANCE

    NASA Astrophysics Data System (ADS)

    Couture, A.; Bredeweg, T. A.; Esch, E.-I.; Jandel, M.; Haight, R. C.; O'Donnell, J. M.; Reifarth, R.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wouters, J. M.

    2006-10-01

    The thallium isotopes play an important role in the s-process nucleosynthesis at the s-process endpoint. Furthermore, ^204Tl is one of few branch point isotopes in the endpoint region. The understanding of branch point isotopes provides modeling constraints on the temperatures during which the process takes place. The production of s-only ^204Pb is controlled entirely by ^204Tl. Measurements of the capture cross-sections of the stable Tl isotopes have recently been made using the DANCE 4-π array at LANSCE. This provides needed resonance information in the region as well as preparing the way for measurements of as yet unmeasured capture cross-section of the unstable ^204Tl. The neutron capture data for the stable isotopes as well as the plan for future measurements will be discussed.

  14. 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.

  15. Additional Sr Isotopic Heterogeneity in Zagami Olivine-Rich Lithology

    NASA Technical Reports Server (NTRS)

    Misawa, K.; Niihara, T.; Shih, C.-Y; Reese, Y. D.; Nyquist, L. E.; Yoneda, S.; Yamashita, H.

    2012-01-01

    Prior isotopic analyses of Zagami have established differing initial Sr-87/Sr-86 (ISr) ratios of among Zagami lithologies, fine-grained (FG), coarse-grained (CG), and dark mottled lithologies (DML)]. The Zagami sample (KPM-NLH000057) newly allocated from the Kanagawa Prefectural Museum of Natural History contained DML and the Ol-rich lithology which included more ferroan olivines (Ol-rich: Fa(sub 97- 99) vs late-stage melt pockets: Fa(sub 90-97)]). We have combined mineralogy-petrology and Rb-Sr isotopic studies on the Kanagawa Zagami sample, which will provide additional clues to the genesis of enriched shergottites and to the evolution of Martian crust and mantle

  16. Antisymmetrized molecular dynamics studies for exotic clustering phenomena in neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Kimura, M.; Suhara, T.; Kanada-En'yo, Y.

    2016-12-01

    We present a review of recent works on clustering phenomena in unstable nuclei studied by antisymmetrized molecular dynamics (AMD). The AMD studies in these decades have uncovered novel types of clustering phenomena brought about by the excess neutrons. Among them, this review focuses on the molecule-like structure of unstable nuclei. One of the earliest discussions on the clustering in unstable nuclei was made for neutron-rich Be and B isotopes. AMD calculations predicted that the ground state clustering is enhanced or reduced depending on the number of excess neutrons. Today, the experiments are confirming this prediction as the change of the proton radii. Behind this enhancement and reduction of the clustering, there are underlying shell effects called molecular and atomic orbits. These orbits form covalent and ionic bonding of the clusters analogous to the atomic molecules. It was found that this "molecular-orbit picture" reasonably explains the low-lying spectra of Be isotopes. The molecular-orbit picture is extended to other systems having parity asymmetric cluster cores and to the three cluster systems. O and Ne isotopes are the candidates of the former, while the 3 α linear chains in C isotopes are the latter. For both subjects, many intensive studies are now in progress. We also pay a special attention to the observables which are the fingerprint of the clustering. In particular, we focus on the monopole and dipole transitions which are recently regarded as good probe for the clustering. We discuss how they have and will reveal the exotic clustering.

  17. Isotopic anomalies from neutron reactions during explosive carbon burning

    NASA Technical Reports Server (NTRS)

    Lee, T.; Schramm, D. N.; Wefel, J. P.; Blake, J. B.

    1978-01-01

    The possibility that the newly discovered correlated isotopic anomalies for heavy elements in the Allende meteorite were synthesized in the secondary neutron capture episode during the explosive carbon burning, the possible source of the O-16 and Al-26 anomalies, is examined. Explosive carbon burning calculations under typical conditions were first performed to generate time profiles of temperature, density, and free particle concentrations. These quantities were inputted into a general neutron capture code which calculates the resulting isotopic pattern from exposing the preexisting heavy seed nuclei to these free particles during the explosive carbon burning conditions. The interpretation avoids the problem of the Sr isotopic data and may resolve the conflict between the time scales inferred from 1-129, Pu-244, and Al-26.

  18. Neutronics Modeling of the High Flux Isotope Reactor using COMSOL

    SciTech Connect

    Chandler, David; Primm, Trent; Freels, James D; Maldonado, G Ivan

    2011-01-01

    The High Flux Isotope Reactor located at the Oak Ridge National Laboratory is a versatile 85 MWth research reactor with cold and thermal neutron scattering, materials irradiation, isotope production, and neutron activation analysis capabilities. HFIR staff members are currently in the process of updating the thermal hydraulic and reactor transient modeling methodologies. COMSOL Multiphysics has been adopted for the thermal hydraulic analyses and has proven to be a powerful finite-element-based simulation tool for solving multiple physics-based systems of partial and ordinary differential equations. Modeling reactor transients is a challenging task because of the coupling of neutronics, heat transfer, and hydrodynamics. This paper presents a preliminary COMSOL-based neutronics study performed by creating a two-dimensional, two-group, diffusion neutronics model of HFIR to study the spatially-dependent, beginning-of-cycle fast and thermal neutron fluxes. The 238-group ENDF/B-VII neutron cross section library and NEWT, a two-dimensional, discrete-ordinates neutron transport code within the SCALE 6 code package, were used to calculate the two-group neutron cross sections required to solve the diffusion equations. The two-group diffusion equations were implemented in the COMSOL coefficient form PDE application mode and were solved via eigenvalue analysis using a direct (PARDISO) linear system solver. A COMSOL-provided adaptive mesh refinement algorithm was used to increase the number of elements in areas of largest numerical error to increase the accuracy of the solution. The flux distributions calculated by means of COMSOL/SCALE compare well with those calculated with benchmarked three-dimensional MCNP and KENO models, a necessary first step along the path to implementing two- and three-dimensional models of HFIR in COMSOL for the purpose of studying the spatial dependence of transient-induced behavior in the reactor core.

  19. Neutron-rich hypernuclei: H6Λ and beyond

    NASA Astrophysics Data System (ADS)

    Gal, A.; Millener, D. J.

    2013-10-01

    Recent experimental evidence presented by the FINUDA Collaboration for a particle-stable H6Λ has stirred renewed interest in charting domains of particle-stable neutron-rich Λ hypernuclei, particularly for unbound nuclear cores. We have studied within a shell-model approach several neutron-rich Λ hypernuclei in the nuclear p shell that could be formed in (π-, K+) or in (K-, π+) reactions on stable nuclear targets. Hypernuclear shell-model input is taken from a theoretically inspired successful fit of γ-ray transitions in p-shell Λ hypernuclei which includes also ΛN ↔ ΣN coupling (ΛΣ coupling). The particle stability of H6Λ is discussed and predictions are made for binding energies of He9Λ, Li10Λ, Be12Λ, B14Λ. None of the large effects conjectured by some authors to arise from ΛΣ coupling is borne out, neither by these realistic p-shell calculations, nor by quantitative estimates outlined for heavier hypernuclei with substantial neutron excess.

  20. 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.

  1. Measuring the collectivity of neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Görgen, Andreas

    2012-10-01

    Measuring the lifetimes of excited nuclear states provides direct information on electromagnetic transition rates and on the collectivity of nuclear excitations. The recoil distance Doppler-shift (RDDS) method is a well-established technique for measuring picosecond lifetimes of excited states, which has been extensively used in combination with fusion-evaporation reactions to measure lifetimes in neutron-deficient nuclei. Here we discuss novel ways of combining the RDDS technique with multi-nucleon transfer and fusion-fission reactions, which allow measurement of picosecond lifetimes in neutron-rich nuclei. Experiments were performed at both GANIL and Legnaro National Laboratories (LNL) with the goal to investigate the onset of collectivity around 68Ni and the evolution of shapes and shape coexistence in medium-heavy fission fragments.

  2. Exotic structure in light neutron-rich nuclei

    SciTech Connect

    Itagaki, N.; Zhao, P. W.; Meng, J.; Matsuno, H.; Suhara, T.

    2015-10-15

    In this presentation I discussed two subjects. One is the persistence of threefold symmetry in the ground state of {sup 12}C. Recently D{sub 3h} symmetry has been established in {sup 12}C, which reflects the geometric symmetry of the three α particles. Although the spin-orbit interaction plays a significant role and this interaction breaks the α clusters, we show that threefold symmetry of {sup 12}C is still there. We use AQCM approach and discuss that inclusion of spin-orbit interaction, which is absent in the conventional microscopic α cluster models, is possible keeping the threefold symmetry. The second subject is the appearance of rod shape in C isotopes, which has been investigated in the framework of the cranking covariant density functional theory. The relationship between the stability of such states and the spin and isospin degrees of freedom is discussed; adding valence neutrons and rotating the system. These two effects stabilize the rod shape, and in addition, their coherent effect has been found; the σ-orbits (parallel to the symmetry axis) of the valence neutrons, which enhances the rod shape, is lowered by the rotation of the system, and this σ-orbit pulls down the single particle energies of protons with linear configuration owing to the proton-neutron interaction effect.

  3. Structure And Decay Of Neutron-Rich Nuclides In The 115 {<=} A {<=} 138 Mass Range And r-Process Nucleosynthesis

    SciTech Connect

    Walters, W.B.; Stoyer, M.A.; Shergur, J.; Hoteling, N.; Ressler, J.J.; Rikovska, J.; Kratz, K.-L.; Woehr, A.; Pfeiffer, B.; Arndt, O.; Mantica, P.F.; Tomlin, B.; Schatz, H.; Montes, F.; Brown, B.A.; Seweryniak, D.; Ravn, H.; Fedoseyev, V.; Koester, U.; Wu, C.Y.

    2005-04-05

    The structure and decay of neutron-rich r-process nuclides has been studied by a variety of means that take advantage of enhanced selectivity to permit identification of exotic nuclides. New level structures are presented for 134,135Sb along with data for Ag isomers and Cd yrast structures. Some of the properties measured play an important role in calculations of the yields of elements and isotopes produced in r-process nucleosynthesis that takes place at high temperature in the presence of large densities of neutrons.

  4. Stellar neutron capture cross sections of the tin isotopes

    SciTech Connect

    Wisshak, K.; Voss, F.; Theis, C.; Kaeppeler, F.; Guber, K.; Kazakov, L.; Kornilov, N.; Reffo, G.

    1996-09-01

    The neutron capture cross sections of {sup 114}Sn, {sup 115}Sn, {sup 116}Sn, {sup 117}Sn, {sup 118}Sn, and {sup 120}Sn were measured in the energy range from 3 to 225 keV at the Karlsruhe 3.75 MV Van de Graaff accelerator. Neutrons were produced via the {sup 7}Li({ital p},{ital n}){sup 7}Be reaction using a pulsed proton beam. Capture events were registered with the Karlsruhe 4{pi} barium fluoride detector. The experiment was complicated by the small ({ital n},{gamma}) cross sections of the proton magic tin isotopes and by the comparably low enrichment of the rare isotopes {sup 114}Sn and {sup 115}Sn. Despite significant corrections for capture of scattered neutrons and for isotopic impurities, the high efficiency and the spectroscopic quality of the BaF{sub 2} detector allowed the determination of the cross-section ratios with overall uncertainties of 1{endash}2{percent}, five times smaller compared to existing data. Based on these results, Maxwellian averaged ({ital n},{gamma}) cross sections were calculated for thermal energies between {ital kT}=10 and 100 keV. These data are used for a discussion of the solar tin abundance and for an improved determination of the isotopic {ital s}- and {ital r}-process components. {copyright} {ital 1996 The American Physical Society.}

  5. Neutron-Rich Nuclei and Neutron Stars: A New Accurately Calibrated Interaction for the Study of Neutron-Rich Matter

    SciTech Connect

    Todd-Rutel, B.G.; Piekarewicz, J.

    2005-09-16

    An accurately calibrated relativistic parametrization is introduced to compute the ground state properties of finite nuclei, their linear response, and the structure of neutron stars. While similar in spirit to the successful NL3 parameter set, it produces an equation of state that is considerably softer--both for symmetric nuclear matter and for the symmetry energy. This softening appears to be required for an accurate description of several collective modes having different neutron-to-proton ratios. Among the predictions of this model are a symmetric nuclear-matter incompressibility of K=230 MeV and a neutron skin thickness in {sup 208}Pb of R{sub n}-R{sub p}=0.21 fm. The impact of such a softening on various neutron-star properties is also examined.

  6. 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.

  7. Medical Isotope Production Analyses In KIPT Neutron Source Facility

    SciTech Connect

    Talamo, Alberto; Gohar, Yousry

    2016-01-01

    Medical isotope production analyses in Kharkov Institute of Physics and Technology (KIPT) neutron source facility were performed to include the details of the irradiation cassette and the self-shielding effect. An updated detailed model of the facility was used for the analyses. The facility consists of an accelerator-driven system (ADS), which has a subcritical assembly using low-enriched uranium fuel elements with a beryllium-graphite reflector. The beryllium assemblies of the reflector have the same outer geometry as the fuel elements, which permits loading the subcritical assembly with different number of fuel elements without impacting the reflector performance. The subcritical assembly is driven by an external neutron source generated from the interaction of 100-kW electron beam with a tungsten target. The facility construction was completed at the end of 2015, and it is planned to start the operation during the year of 2016. It is the first ADS in the world, which has a coolant system for removing the generated fission power. Argonne National Laboratory has developed the design concept and performed extensive design analyses for the facility including its utilization for the production of different radioactive medical isotopes. 99Mo is the parent isotope of 99mTc, which is the most commonly used medical radioactive isotope. Detailed analyses were performed to define the optimal sample irradiation location and the generated activity, for several radioactive medical isotopes, as a function of the irradiation time.

  8. Neutron capture and neutron-induced fission experiments on americium isotopes with DANCE

    SciTech Connect

    Jandel, Marian

    2008-01-01

    Neutron capture cross section data on Am isotopes were measured using the Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory. The neutron capture cross section was determined for {sup 241}Am for neutron energies between thermal and 320 keV. Preliminary results were also obtained for {sup 243}Am for neutron energies between 35 eV and 200 keV. The results on concurrent neutron-induced fission and neutron-capture measurements on {sup 242m}Am will be presented, where the fission events were actively triggered during the experiments. In these experiments, the Parallel-Plate Avalanche Counter (PPAC) detector that surrounds the target located in the center of the DANCE array was used as a fission-tagging detector to separate (n,{gamma}) from (n,f) events. The first evidence of neutron capture on {sup 242m}Am in the resonance region in between 2 and 9 eV of the neutron energy was obtained.

  9. Neutron capture and neutron-induced fission experiments on americium isotopes with DANCE

    SciTech Connect

    Jandel, M.; Bredeweg, T. A.; Fowler, M. M.; Bond, E. M.; Couture, A.; Haight, R. C.; Keksis, A. L.; O'Donnell, J. M.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.; Stoyer, M. A.; Wu, C. Y.; Becker, J. A.; Haslett, R. J.; Henderson, R. A.

    2009-01-28

    Neutron capture cross section data on Am isotopes were measured using the Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory. The neutron capture cross section was determined for {sup 241}Am for neutron energies between thermal and 320 keV. Preliminary results were also obtained for {sup 243}Am for neutron energies between 10 eV and 250 keV. The results on concurrent neutron-induced fission and neutron-capture measurements on {sup 242m}Am will be presented where the fission events were actively triggered during the experiments. In these experiments, a Parallel-Plate Avalanche Counter (PPAC) detector that surrounds the target located in the center of the DANCE array was used as a fission-tagging detector to separate (n,{gamma}) events from (n,f) events. The first direct observation of neutron capture on {sup 242m}Am in the resonance region in between 2 and 9 eV of the neutron energy was obtained.

  10. Collinear resonance ionization spectroscopy of neutron-deficient francium isotopes.

    PubMed

    Flanagan, K T; Lynch, K M; Billowes, J; Bissell, M L; Budinčević, I; Cocolios, T E; de Groote, R P; De Schepper, S; Fedosseev, V N; Franchoo, S; Garcia Ruiz, R F; Heylen, H; Marsh, B A; Neyens, G; Procter, T J; Rossel, R E; Rothe, S; Strashnov, I; Stroke, H H; Wendt, K D A

    2013-11-22

    The magnetic moments and isotope shifts of the neutron-deficient francium isotopes (202-205)Fr were measured at ISOLDE-CERN with use of collinear resonance ionization spectroscopy. A production-to-detection efficiency of 1% was measured for (202)Fr. The background from nonresonant and collisional ionization was maintained below one ion in 10(5) beam particles. Through a comparison of the measured charge radii with predictions from the spherical droplet model, it is concluded that the ground-state wave function remains spherical down to (205)Fr, with a departure observed in (203)Fr (N=116).

  11. Collinear Resonance Ionization Spectroscopy of Neutron-Deficient Francium Isotopes

    NASA Astrophysics Data System (ADS)

    Flanagan, K. T.; Lynch, K. M.; Billowes, J.; Bissell, M. L.; Budinčević, I.; Cocolios, T. E.; de Groote, R. P.; De Schepper, S.; Fedosseev, V. N.; Franchoo, S.; Garcia Ruiz, R. F.; Heylen, H.; Marsh, B. A.; Neyens, G.; Procter, T. J.; Rossel, R. E.; Rothe, S.; Strashnov, I.; Stroke, H. H.; Wendt, K. D. A.

    2013-11-01

    The magnetic moments and isotope shifts of the neutron-deficient francium isotopes Fr202-205 were measured at ISOLDE-CERN with use of collinear resonance ionization spectroscopy. A production-to-detection efficiency of 1% was measured for Fr202. The background from nonresonant and collisional ionization was maintained below one ion in 105 beam particles. Through a comparison of the measured charge radii with predictions from the spherical droplet model, it is concluded that the ground-state wave function remains spherical down to Fr205, with a departure observed in Fr203 (N=116).

  12. Neutron-spectroscopic strength in Ru isotopes

    SciTech Connect

    Duarte, J.L.M.; Borello-Lewin, T.; Horodynski-Matsushigue, L.B. )

    1994-08-01

    A systematic, high resolution (6--8 keV) study of ([ital d],[ital t]) reactions on [sup 100,102,104]Ru is reported. Spectroscopic factors were extracted by comparison of experimental angular distributions with distorted wave Born approximation predictions. All of the information for [sup 99]Ru and, for excitation energies above 0.9 MeV, for [sup 103]Ru is new. Most of the strength expected for the 50--82 neutron shell was found. The strength distributions are discussed, also in comparison with the corresponding stripping reactions. Special attention is focused on extremely low and relatively intense [ital l]=3 excitations and on the [ital l]=4 transfer pattern observed.

  13. New K isomers in the neutron-rich N =100 isotones 162Sm, 163Eu, and 164Gd

    NASA Astrophysics Data System (ADS)

    Yokoyama, R.; Go, S.; Kameda, D.; Kubo, T.; Inabe, N.; Fukuda, N.; Takeda, H.; Suzuki, H.; Yoshida, K.; Kusaka, K.; Tanaka, K.; Yanagisawa, Y.; Ohtake, M.; Sato, H.; Shimizu, Y.; Baba, H.; Kurokawa, M.; Nishimura, D.; Ohnishi, T.; Iwasa, N.; Chiba, A.; Yamada, T.; Ideguchi, E.; Fujii, T.; Nishibata, H.; Ieki, K.; Murai, D.; Momota, S.; Sato, Y.; Hwang, J. W.; Kim, S.; Tarasov, O. B.; Morrissey, D. J.; Sherrill, B. M.; Simpson, G.; Praharaj, C. R.

    2017-03-01

    Very neutron-rich Z ˜60 isotopes produced by in-flight fission of a 345 MeV/nucleon 238U beam at the RI Beam Factory, RIKEN Nishina Center, have been studied by delayed γ -ray spectroscopy. New isomers were discovered in the neutron-rich N =100 isotones 162Sm, 163Eu, and 164Gd. Half-lives, γ -ray energies, and relative intensities of these isomers were obtained. Level schemes were proposed for these nuclei and the first 2+ and 4+ states were assigned for the even-even nuclei. The first 2+ and 4+ state energies decrease as the proton numbers get smaller. The energies and the half-lives of the new isomers are very similar to those of 4- isomers known in less neutron-rich N =100 isotones 168Er and 170Yb. A deformed Hartree-Fock with angular momentum projection model suggests Kπ=4- two-quasiparticle states with ν 7 /2 [633 ]⊗ν 1 /2 [521 ] configurations with similar excitation energy. The results suggest that neutron-rich N =100 nuclei are well deformed and the deformation gets larger as Z decreases to 62. The onset of K isomers with the same configuration at almost the same energy in N =100 isotones indicates that the neutron single-particle structures of neutron-rich isotones down to Z =62 do not change significantly from those of the Z =70 stable nuclei. Systematics of the excitation energies of new isomers can be explained without the predicted N =100 shell gap.

  14. Heavy Ion Reactions with Neutron-Rich Beams - Proceedings of the Riken International Workshop

    NASA Astrophysics Data System (ADS)

    Yamaji, S.; Ishihara, M.; Takigawa, N.

    1993-11-01

    The Table of Contents for the book is as follows: * Preface * Opening Address * Fusion I * Heavy Ion Fusion at Subbarrier Energies: Progress and Questions * Angular Momentum in Heavy Ion Subbarrier Interaction * Fusion II * High Precision Fusion Excitation Function Measurements: What Can We Learn from Them? * Transfer Reactions for 16O + 144,152Sm near the Coulomb Barrier * Fusion III * Recent Theoretical Developments in the Study of Subbarrier Fusion * Direct Reaction Approach to Heavy Ion Scattering and Fusion at Energies near Coulomb Barrier * Fusion IV * Roles of Multi-Step Transfer in Fusion Process Induced by Heavy Ion Reactions * Special Session * RIKEN Accelerator Research Facility (RARF) * Fission I * Bimodal Nature of Nuclear Fission * Systematics of Isotope Production Rates: Mass Excess Dependence of Fission Products * Semiclassical Methods for the Multi-Dimensional Quantum Decay * Dynamics of Di-Nucleus Systems: Molecular Resonances * Fission II * The Competition Between Fusion-Fission and Deeply Inelastic Reactions in the Medium Mass Systems * Unstable Nuclei I * Coulomb Dissociation and Momentum Distributions for 11Li → 9Li+n+n Breakup Reactions * Unstable Nuclei II * Elastic Scattering and Fragmentation of Halo Nuclei * Secondary Reactions of Neutron-Rich Nuclei at Intermediate Energies * Life Time of Soft Dipole Excitation * Unstable Nuclei III * Shell Structure of Exotic Unstable Nuclei * Properties of Unstable Nuclei Within the Relativistic Many-Body Theory * Fusion with Unstable Nuclei * Barrier Distributions for Heavy Ion Fusion * Heavy Ion Reactions with Neutron-Rich Beams * Heavy Ion Fusion with Neutron-Rich Beams * Superheavy Elements * Study of α Decays Following 40Ar Bombardment on 238U * Production of Superheavy Elements via Fusion: What is Limiting Us? * Panel Session * Comments * List of Participants

  15. 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.

  16. Sulfur Isotopes in Gas-rich Impact-Melt Glasses in Shergottites

    NASA Technical Reports Server (NTRS)

    Rao, M. N.; Hoppe, P.; Sutton, S. R.; Nyquist, Laurence E.; Huth, J.

    2010-01-01

    Large impact melt glasses in some shergottites contain huge amounts of Martian atmospheric gases and they are known as gas-rich impact-melt (GRIM) glasses. By studying the neutron-induced isotopic deficits and excesses in Sm-149 and Sm-150 isotopes resulting from Sm-149 (n,gamma) 150Sm reaction and 80Kr excesses produced by Br-79 (n,gamma) Kr-80 reaction in the GRIM glasses using mass-spectrometric techniques, it was shown that these glasses in shergottites EET79001 and Shergotty contain regolith materials irradiated by a thermal neutron fluence of approx.10(exp 15) n/sq cm near Martian surface. Also, it was shown that these glasses contain varying amounts of sulfates and sulfides based on the release patterns of SO2 (sulfate) and H2S (sulfide) using stepwise-heating mass-spectrometric techniques. Furthermore, EMPA and FE-SEM studies in basaltic-shergottite GRIM glasses EET79001, LithB (,507& ,69), Shergotty (DBS I &II), Zagami (,992 & ,994) showed positive correlation between FeO and "SO3" (sulfide + sulfate), whereas those belonging to olivine-phyric shergottites EET79001, LithA (,506, & ,77) showed positive correlation between CaO/Al2O3 and "SO3".

  17. 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.

  18. New Band Structures in Aapprox110 Neutron-Rich Nuclei

    SciTech Connect

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

    2010-05-12

    The high spin states of neutron-rich nuclei in Aapprox110 region have been carefully investigated by measuring prompt gamma-gamma-gamma coincident measurements populated in the spontaneous fission of {sup 252}Cf with the Gammasphere detector array. Many new collective bands have been discovered. In this proceeding paper, we introduce some interesting new band structures recently observed by our cooperative groups, that is, the one-phonon- and two-phonon gamma-vibrational bands in odd-A {sup 103}Nb, {sup 105}Mo and {sup 107}Tc, the chiral doublet bands in even-even {sup 106}Mo, {sup 110}Ru and {sup 112}Ru, and the pseudospin partner bands with in {sup 108}Tc. The characteristics of these band structures have been discussed.

  19. Decay Spectroscopy of Neutron-Rich Cd Around the N = 82 Shell Closure

    NASA Astrophysics Data System (ADS)

    Bernier, Nikita; Dillmann, Iris; Kruecken, Reiner; Griffin Collaboration

    2016-09-01

    The neutron-rich region around A = 132 is of special interest for nuclear astrophysics and nuclear structure. This region is connected with the second r-process abundance peak at A 130 and the waiting-point nuclei around N = 82. For nuclear structure studies, the neighbours of the doubly-magic 132Sn (Z = 50, N = 82) are an ideal test ground for shell model predictions. The beta-decay of the N = 82 isotope 130Cd into 130In was first investigated a decade ago, but the information for states of the lighter indium isotopes (128,129In) is still limited. In the present experiment, a detailed gamma-spectroscopy of the beta-decay of 128-132Cd was achieved with the newly commissioned GRIFFIN (Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei) gamma-ray spectrometer, which is capable of measuring down to rates of 0.1 pps. The low-energy cadmium isotopes were implanted into a movable tape at the central focus of the array from the ISAC-I facility at TRIUMF. The beta-tagging was performed using the auxiliary beta-particle detector SCEPTAR. The required beta-gamma(-gamma) coincidence data in high statistics needed to fill the spectroscopic gaps described in literature were obtained. The ongoing analysis of these data will be presented. Work supported by the Natural Sciences and Engineering Research Council of Canada and the National Research Council of Canada.

  20. Tellurium isotope compositions of calcium-aluminum-rich inclusions

    NASA Astrophysics Data System (ADS)

    Fehr, M. A.; Rehkämper, M.; Halliday, A. N.; Hattendorf, B.; Günther, D.

    2009-08-01

    A method for the precise and accurate determination of the tellurium (Te) isotope compositions of calcium-aluminum-rich inclusions (CAIs) has been developed. The technique utilizes multiple-collector inductively coupled plasma-mass spectrometry (MC-ICPMS) with either Faraday detectors or a dual ion-counting system. The external reproducibility (2σ) for 126Te/125Te was ~15‰ and ~2‰ when 3 pg and 65 pg of Te were analyzed with the electron multipliers. Measurements performed on 200 pg of Te using Faraday detectors and time-resolved software displayed an external reproducibility of ~8‰ for 126Te/124Te, whereas 3 ng Te could be measured to a precision of about 0.6‰. Analyses of five CAIs from the Allende chondrite yielded Te concentrations that range from 12 to 537 ppb and the inclusions are therefore depleted in Te relative to bulk Allende by factors of about 2 to 86. The Sn/Te ratios of the CAIs are also fractionated compared to bulk Allende (which displays 124Sn/128Te ≍ 0.1) with 124Sn/128Te ratios of about 0.1 to 2.5. The Te isotope measurements for these refractory inclusions yielded no 126Te excesses from the decay of the short-lived radionuclide 126Sn (τ½ = 234,500 years) and the most precise analysis provided a ɛ126Te value of 1 ± 6 (ɛ126Te = 126Te/ 124Te normalized to 122Te/124Te = 0.53594 and reported relative to the JMC Te standard). Minor differences in the Te isotope composition of the CAIs relative to the terrestrial standard and bulk Allende hint at the presence of small deficits in r-process Te isotopes or excess of s-process Te, but these nucleosynthetic anomalies are barely resolvable given the analytical uncertainties. Hence, it is also conceivable that these effects reflect small unresolved analytical artifacts.

  1. Cluster emissions with ? daughter from neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Kumar, Satish; Batra, J. S.; Gupta, Raj K.

    1996-02-01

    Cluster emissions from neutron-rich 0954-3899/22/2/006/img2, and 0954-3899/22/2/006/img3 nuclei are studied within the preformed cluster model of Malik and Gupta. Q-value estimates of the decays selected on the basis of shell effects in binding energies and their relative preformation probabilities show that these nuclei are stable (Q<0) against 0954-3899/22/2/006/img4 and 0954-3899/22/2/006/img5 decays and all the metastable (Q>0) decays are of non-alpha-like heavy clusters. The most probable decays (minimum half-life times) are the ones with a doubly magic 0954-3899/22/2/006/img6 nucleus as the daughter nucleus, arising due to the WKB penetrability. Compared to the presently measurable alpha-like cluster decays of the corresponding neutron-deficient parents into a 0954-3899/22/2/006/img7 daughter nucleus, these decays are suppressed by many orders of magnitude.

  2. Production of heavy and superheavy neutron-rich nuclei in neutron capture processes

    NASA Astrophysics Data System (ADS)

    Zagrebaev, V. I.; Karpov, A. V.; Mishustin, I. N.; Greiner, Walter

    2011-10-01

    The neutron capture process is considered as an alternative method for production of superheavy (SH) nuclei. Strong neutron fluxes might be provided by nuclear reactors and nuclear explosions in the laboratory frame and by supernova explosions in nature. All these cases are discussed in the paper. There are two gaps of short-lived nuclei (one is the well-known fermium gap and the other one is located in the region of Z=106-108 and N˜170) which impede the formation of SH nuclei by rather weak neutron fluxes realized at available nuclear reactors. We find that in the course of multiple (rather “soft”) nuclear explosions these gaps may be easily bypassed, and thus, a measurable amount of the neutron-rich long-living SH nuclei located at the island of stability may be synthesized. Existing pulsed reactors do not allow one to bypass these gaps. We formulate requirements for the pulsed reactors of the next generation that could be used for production of long-living SH nuclei. Natural formation of SH nuclei (in supernova explosions) is also discussed. The yield of SH nuclei relative to lead is estimated to be about 10-12, which is not beyond the experimental sensitivity for a search of SH elements in cosmic rays.

  3. High Flux Isotope Reactor cold neutron source reference design concept

    SciTech Connect

    Selby, D.L.; Lucas, A.T.; Hyman, C.R.

    1998-05-01

    In February 1995, Oak Ridge National Laboratory`s (ORNL`s) deputy director formed a group to examine the need for upgrades to the High Flux Isotope Reactor (HFIR) system in light of the cancellation of the Advanced neutron Source Project. One of the major findings of this study was that there was an immediate need for the installation of a cold neutron source facility in the HFIR complex. In May 1995, a team was formed to examine the feasibility of retrofitting a liquid hydrogen (LH{sub 2}) cold source facility into an existing HFIR beam tube. The results of this feasibility study indicated that the most practical location for such a cold source was the HB-4 beam tube. This location provides a potential flux environment higher than the Institut Laue-Langevin (ILL) vertical cold source and maximizes the space available for a future cold neutron guide hall expansion. It was determined that this cold neutron beam would be comparable, in cold neutron brightness, to the best facilities in the world, and a decision was made to complete a preconceptual design study with the intention of proceeding with an activity to install a working LH{sub 2} cold source in the HFIR HB-4 beam tube. During the development of the reference design the liquid hydrogen concept was changed to a supercritical hydrogen system for a number of reasons. This report documents the reference supercritical hydrogen design and its performance. The cold source project has been divided into four phases: (1) preconceptual, (2) conceptual design and testing, (3) detailed design and procurement, and (4) installation and operation. This report marks the conclusion of the conceptual design phase and establishes the baseline reference concept.

  4. Temperature dependence of the symmetry energy and neutron skins in Ni, Sn, and Pb isotopic chains

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

    The temperature dependence of the symmetry energy for isotopic chains of even-even Ni, Sn, and Pb nuclei is investigated in the framework of the local density approximation (LDA). The Skyrme energy density functional with two Skyrme-class effective interactions, SkM* and SLy4, is used in the calculations. The temperature-dependent proton and neutron densities are calculated through the hfbtho code that solves the nuclear Skyrme-Hartree-Fock-Bogoliubov problem by using the cylindrical transformed deformed harmonic-oscillator basis. In addition, two other density distributions of 208Pb, namely the Fermi-type density determined within the extended Thomas-Fermi (TF) method and symmetrized-Fermi local density obtained within the rigorous density functional approach, are used. The kinetic energy densities are calculated either by the hfbtho code or, for a comparison, by the extended TF method up to second order in temperature (with T2 term). Alternative ways to calculate the symmetry energy coefficient within the LDA are proposed. The results for the thermal evolution of the symmetry energy coefficient in the interval T =0 -4 MeV show that its values decrease with temperature. The temperature dependence of the neutron and proton root-mean-square radii and corresponding neutron skin thickness is also investigated, showing that the effect of temperature leads mainly to a substantial increase of the neutron radii and skins, especially in the more neutron-rich nuclei, a feature that may have consequences on astrophysical processes and neutron stars.

  5. Configuration assignments to isomers in the neutron-rich 186Ta (Z =73 ) nucleus

    NASA Astrophysics Data System (ADS)

    Sood, P. C.; Gowrishankar, R.

    2014-12-01

    Though the neutron-rich odd-odd nucleus Ta18673113 was first produced in 1955, even after 60 years its ground state (g.s.) and both of its two other isomers remain undefined. We use the well-tested two-quasiparticle rotor model, which explicitly includes residual neutron-proton n -p interaction and other contributing factors, to evaluate the bandhead energies of the physically admissible low-lying two-particle structures in 186Ta with inputs from experimentally observed structures in neighboring isotopes and isotones to characterize these levels. Our analysis assigns Kπ = 5-{p :7 /2 [404 ]⊗n :3 /2 [512 ]} configuration to the 10.5 min 186Ta (g.s.) and the antiparallel-spin Kπ=2- of the same configuration to the 1.54 min isomer with Ex = 90(10) keV. We further assign Kπ=8-{p :7 /2 [404 ]⊗n :9 /2 [505 ]} configuration to the recently identified 3.0 min isomer with Ex=336 (20) keV. These assignments are shown to be consistent with all the available experimental data. Further, they are seen to fit nicely as another instance of highly hindered Δ I =3 isomeric transitions, and also of low-lying long-lived isomer triplets, frequently observed in numerous odd-odd Z =61 (2 )75 nuclides.

  6. 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.

  7. 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.

  8. 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.

  9. 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+) .

  10. Beta Decay Measurements of Neutron Deficient Cesium Isotopes.

    NASA Astrophysics Data System (ADS)

    Parry, Roger Franklin

    The study of nuclei far from beta stability provides information on nuclear binding energies and nuclear structure. However, as one progresses away from the valley of stability, the associated half-lives and production cross sections decrease with increasing interference from the decays of adjacent nuclei. An experimental solution to these problems was the use of the He-jet fed on-line mass separator, RAMA. This instrument provided a fast and selective technique for the mass separation necessary for the investigation of exotic nuclei. Using this device, a beta decay Q-value study of the neutron deficient cesium isotopes, ('119-123)Cs, was conducted. Beta decay endpoint energy measurements of the neutron deficient cesium isotopes were done using an energy spectrum shape fitting technique. This was a departure from the typical method of endpoint energy analysis, the Fermi-Kurie plot. A discussion of the shape fitting procedure and its improved features are discussed. These beta endpoint measurements have led to total decay energies (Q(,EC)) of the neutron deficient ('119 -123)Cs isotopes. The total decay energies of ('122m)Cs (Q(,EC) = 6.95 (+OR-) 0.25 MeV) and ('119)Cs (Q(,EC) = 6.26 (+OR-) 0.29 MeV) were new measurements. The total decay energies of ('123)Cs (Q(,EC) = 4.05 (+OR-) 0.18 MeV), ('122g)Cs (Q(,EC) = 7.05 (+OR-) 0.18 MeV), ('121)Cs (Q(,EC) = 5.21 (+OR-) 0.22 MeV), and ('120)Cs (Q(,EC) = 7.38 (+OR -) 0.23 MeV) were measurements with significantly improved uncertainties as compared to the literature. Further, a combination of the energy levels derived from previous literature gamma-gamma coincident measurements and the experimental beta-coincident gamma decay energies has supported an improved level scheme for ('121)Xe and the proposal of three new energy levels in ('119)Xe. Comparison of the experimental cesium mass excesses (determined with our Q(,EC) values and known xenon mass excesses) with both the literature and theoretical predicted values showed

  11. Stellar neutron capture cross sections of the Ba isotopes

    NASA Astrophysics Data System (ADS)

    Voss, F.; Wisshak, K.; Guber, K.; Käppeler, F.; Reffo, G.

    1994-11-01

    The neutron capture cross sections of 134Ba, 135Ba, 136Ba, and 137Ba were measured in the energy range from 5 to 225 keV at the Karlsruhe 3.75 MV Van de Graaff accelerator. Neutrons were produced via the 7Li (p,n)7 Be reaction by bombarding metallic Li targets with a pulsed proton beam. Capture events were registered with the Karlsruhe 4π barium fluoride detector. The cross section ratios were determined with an overall uncertainty of ~3%, an improvement by factors of 5 to 8 compared to existing data. Severe discrepancies were found with respect to previous results. As a new possibility in time of flight experiments, isomeric cross section ratios could be determined for 135Ba, 136Ba, and 137Ba. Maxwellian averaged neutron capture cross sections were calculated for thermal energies between kT=10 keV and 100 keV. These stellar cross sections were used in an s-process analysis. For the s-only isotopes 134Ba and 136Ba the Ns<σ> ratio was determined to 0.875+/-0.025. Hence, a significant branching of the s-process path at 134Cs can be claimed for the first time, in contrast to predictions from the classical approach. This branching yields information on the s-process temperature, indicating values around T8=2. The new cross sections are also important for the interpretation of barium isotopic anomalies, which were recently discovered in SiC grains of carbonaceous chondrite meteorites. Together with the results from previous experiments on tellurium and samarium, a general improvement of the Ns<σ> systematics in the mass range A=120-150 is achieved. This yields a more reliable separation of s- and r-process contributions for comparison with stellar observations, but reveals a 20% discrepancy with respect to the solar barium abundance.

  12. Stellar neutron capture cross sections of the Lu isotopes

    SciTech Connect

    Wisshak, K.; Voss, F.; Kaeppeler, F.; Kazakov, L.

    2006-01-15

    The neutron capture cross sections of {sup 175}Lu and {sup 176}Lu have been measured in the energy range 3-225 keV at the Karlsruhe 3.7 MV Van de Graaff accelerator. Neutrons were produced via the {sup 7}Li(p,n){sup 7}Be reaction by bombarding metallic Li targets with a pulsed proton beam, and capture events were registered with the Karlsruhe 4{pi} barium fluoride detector. The cross sections were determined relative to the gold standard using isotopically enriched as well as natural lutetium oxide samples. Overall uncertainties of {approx}1% could be achieved in the final cross section ratios to the gold standard, about a factor of 5 smaller than in previous works. Maxwellian averaged neutron capture cross sections were calculated for thermal energies between kT = 8 and 100 keV. These values are systematically larger by {approx}7% than those reported in recent evaluations. These results are of crucial importance for the assessment of the s-process branchings at A 175/176.

  13. Neutron transmutation doped natural and isotopically engineered germanium thermistors

    NASA Astrophysics Data System (ADS)

    Haller, Eugene E.; Itoh, K. M.; Beeman, Jeffrey W.; Hansen, William L.; Ozhogin, V. I.

    1994-06-01

    We report on the development, fabrication and performance of a new class of thermal sensors for far IR and millimeter wave detection. These devices consist of small single crystal samples of ultra-pure, natural or isotopically engineered germanium which have been doped by the neutron transmutation doping (NTD) technique. The concentrations of the acceptor and donor dopants (N(subscript A),N(subscript D)) can be accurately controlled with this technique. They depend on the thermal neutron fluence, the neutron absorption cross sections and the atomic fractions of (superscript 70)Ge (for the Ga acceptors) and (superscript 74)Ge (for the As donors), respectively. The values of N(subscript A) and N(subscript D) and their ratio result in a predictable resistivity of the Ge crystals down to temperatures of a few milliKelvin. The excellent control of the resistivity down to very low temperatrues, together with the development of ohmic contacts working at the lowest temperatures, allows the fabrication of high sensitivity bolometer arrays with over 100 pixels and highly uniform response.

  14. 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.

  15. 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 .

  16. Shape coexistence in the neutron-deficient Pt isotopes in a configuration mixing IBM

    SciTech Connect

    Morales, Irving O.; Vargas, Carlos E.; Frank, Alejandro

    2004-09-13

    The recently proposed matrix-coherent state approach for configuration mixing IBM is used to describe the evolving geometry of the neutron deficient Pt isotopes. It is found that the Potential Energy Surface (PES) of the Platinum isotopes evolves, when the number of neutrons decreases, from spherical to oblate and then to prolate shapes, in agreement with experimental measurements. Oblate-Prolate shape coexistence is observed in 194,192Pt isotopes.

  17. Shape coexistence in the neutron-deficient Pt isotopes in the configuration-mixed IBM

    SciTech Connect

    Vargas, Carlos E.; Campuzano, Cuauhtemoc; Morales, Irving O.; Frank, Alejandro; Van Isacker, Piet

    2008-05-12

    The matrix-coherent state approach in the IBM with configuration mixing is used to describe the geometry of neutron-deficient Pt isotopes. Employing a parameter set for all isotopes determined previously, it is found that the lowest minimum goes from spherical to oblate and finally acquires a prolate shape when approaching the mid-shell Pt isotopes.

  18. Precision Mass Measurements of Short-Lived, Neutron-Rich, R-Process Nuclei About the N=82 Waiting Point

    NASA Astrophysics Data System (ADS)

    Lascar, Daniel David

    This thesis details the precision mass measurements of 33 neutron-rich ground-state nuclei and isomeric states that approach or lie on the proposed rapid neutron capture process (r-process) path. For many of the nuclei measured the work presented here will be the rst direct mass measurements of these nuclei, including 130In, 137Sb, 133I, and 134I. The measurements were made using the Canadian Penning Trap mass spectrometer (CPT), located at the ATLAS heavy ion-linac at Argonne National Laboratory. Ground states and isomers have been measured with the CPT at fractional precisions (δm/m) between 10-7, and 10-8. The nuclei were produced at the new CAlifornium Rare Isotope Breeder Upgrade (CARIBU) to ATLAS. Because nuclear masses are required for measuring neutron separation energies, and neutron separation energies are important inputs in r-process network calculations, precision mass measurements are critical for advancing our knowledge of the r-process. This thesis will give the astrophysical motivation for making these mass measurements, the theoretical background behind ion trapping and mass measurements using ion traps, an explanation of the CPT apparatus, the mass measurements themselves, and the results of those measurements as they pertain to r-process network calculations. Results of these mass measurements show significant shifts in the r-process path over a range of temperatures and neutron densities.

  19. Thermal neutron capture cross sections of the potassium isotopes

    NASA Astrophysics Data System (ADS)

    Firestone, R. B.; Krtička, M.; Révay, Zs.; Szentmiklosi, L.; Belgya, T.

    2013-02-01

    Precise thermal neutron capture γ-ray cross sections σγ for 39,40,41K were measured on a natural potassium target with the guided neutron beam at the Budapest Reactor. The cross sections were internally standardized using a stoichiometric KCl target with well-known 35Cl(n,γ) γ-ray cross sections [Révay and Molnár, Radiochimica ActaRAACAP0033-823010.1524/ract.91.6.361.20027 91, 361 (2003); Molnár, Révay, and Belgya, Nucl. Instrum. Meth. Phys. Res. BNIMBEU0168-583X10.1016/S0168-583X(03)01529-5 213, 32 (2004)]. These data were combined with γ-ray intensities from von Egidy [von Egidy, Daniel, Hungerford, Schmidt, Lieb, Krusche, Kerr, Barreau, Borner, Brissot , J. Phys. G. Nucl. Phys.JPHGBM0305-461610.1088/0305-4616/10/2/013 10, 221 (1984)] and Krusche [Krusche, Lieb, Ziegler, Daniel, von Egidy, Rascher, Barreau, Borner, and Warner, Nucl. Phys. ANUPABL0375-947410.1016/0375-9474(84)90506-2 417, 231 (1984); Krusche, Winter, Lieb, Hungerford, Schmidt, von Egidy, Scheerer, Kerr, and Borner, Nucl. Phys. ANUPABL0375-947410.1016/0375-9474(85)90429-4 439, 219 (1985)] to generate nearly complete capture γ-ray level schemes. Total radiative neutron cross sections were deduced from the total γ-ray cross section feeding the ground state, σ0=Σσγ(GS) after correction for unobserved statistical γ-ray feeding from levels near the neutron capture energy. The corrections were performed with Monte Carlo simulations of the potassium thermal neutron capture decay schemes using the computer code dicebox where the simulated populations of low-lying levels are normalized to the measured cross section depopulating those levels. Comparisons of the simulated and experimental level feeding intensities have led to proposed new spins and parities for selected levels in the potassium isotopes where direct reactions are not a significant contribution. We determined the total radiative neutron cross sections σ0(39K)=2.28±0.04 b, σ0(40K)=90±7 b, and σ0(41K)=1.62±0.03 b from the

  20. Neutron capture on Pt isotopes in iron meteorites and the Hf-W chronology of core formation in planetesimals

    NASA Astrophysics Data System (ADS)

    Kruijer, Thomas S.; Fischer-Gödde, Mario; Kleine, Thorsten; Sprung, Peter; Leya, Ingo; Wieler, Rainer

    2013-01-01

    The short-lived 182Hf-182W isotope system can provide powerful constraints on the timescales of planetary core formation, but its application to iron meteorites is hampered by neutron capture reactions on W isotopes resulting from exposure to galactic cosmic rays. Here we show that Pt isotopes in magmatic iron meteorites are also affected by capture of (epi)thermal neutrons and that the Pt isotope variations are correlated with variations in 182W/184W. This makes Pt isotopes a sensitive neutron dosimeter for correcting cosmic ray-induced W isotope shifts. The pre-exposure 182W/184W derived from the Pt-W isotope correlations of the IID, IVA and IVB iron meteorites are higher than most previous estimates and are more radiogenic than the initial 182W/184W of Ca-Al-rich inclusions (CAI). The Hf-W model ages for core formation range from +1.6±1.0 million years (Ma; for the IVA irons) to +2.7±1.3 Ma after CAI formation (for the IID irons), indicating that there was a time gap of at least ˜1 Ma between CAI formation and metal segregation in the parent bodies of some iron meteorites. From the Hf-W ages a time limit of <1.5-2 Ma after CAI formation can be inferred for the accretion of the IID, IVA and IVB iron meteorite parent bodies, consistent with earlier conclusions that the accretion of differentiated planetesimals predated that of most chondrite parent bodies.

  1. Noble gas isotopes and halogens in volatile-rich inclusions in diamonds

    NASA Technical Reports Server (NTRS)

    Burgess, Raymond; Turner, Grenville

    1994-01-01

    Application of the (40)Ar-(39)Ar method and noble gas studies to diamonds has increased our understanding of their age relationships to the host kimberlite or lamproite, and of the source and composition of volatile-rich fluids in the upper mantle. The properties of diamond (inert, high mechanical strength and low gas diffusivities) means they are especially useful samples for studying gases trapped deep within the earth (less than 150 km) as they are unlikely to have undergone loss or exchange of entrapped material since formation. Volatile-rich fluids (H2O-CO2) are important agents for metasomatic processes in the upper mantle, and the noble gases and halogens preferentially partition into this phase leading to a strong geochemical coherence between these groups of elements. The abundances of the halogens in the major reservoirs of the Earth shows a marked progression from chlorine, concentrated in the oceans, through to iodine which, through its affinity to organic material, is concentrated mainly in sediments. Abundances in the upper mantle are low. This is particularly true for iodine which is of special interest in view of its potential significance as an indicator of sediment recycling and by way of its link to (129)Xe amomalies in the mantle through the low extinct isotope (129)I. Extensions of the (40)Ar-(39)Ar technique enable measurements of halogens and other elements (K, Ca, Ba, U) by production of noble gas isotopes from these species during neutron irradiation. Samples analyzed in this way include 15 coated stones from an unknown source in Zaire, 3 boarts from the Jwaneng and 1 boart from the Orapa kimberlites, both in Botswana.

  2. Beta-decay measurements of neutron-deficient cesium isotopes

    SciTech Connect

    Parry, R.F.

    1983-03-01

    Beta decay endpoint energy measurements of the neutron deficient cesium isotopes were done using an energy spectrum shape fitting technique. This was a departure from the typical method of endpoint energy analysis, the Fermi-Kurie plot. A discussion of the shape fitting procedure and its improved features are discussed. These beta endpoint measurements have led to total decay energies (Q/sub EC/) of the neutron deficient /sup 119/ /sup 123/Cs isotopes. The total decay energies of /sup 122m/Cs (Q/sub EC/ = 6.95 +- 0.25 MeV) and /sup 119/Cs (Q/sub EC/ = 6.26 +- 0.29 MeV) were new measurements. The total decay energies of /sup 123/Cs (Q/sub EC/ = 4.05 +- 0.18 MeV), /sup 122g/Cs (Q/sub EC/ = 7.05 +- 0.18 MeV), /sup 121/Cs (Q/sub EC/ = 5.21 +- 0.22 MeV), and /sup 120/Cs (Q/sub EC/ = 7.38 +- 0.23 MeV) were measurements with significantly improved uncertainties as compared to the literature. Further, a combination of the energy levels derived from previous literature gamma-gamma coincident measurements and the experimental beta-coincident gamma decay energies has supported an improved level scheme for /sup 121/Xe and the proposal of three new energy levels in /sup 119/Xe. Comparison of the experimental cesium mass excesses (determined with our Q/sub EC/ values and known xenon mass excesses) with both the literature and theoretical predicted values showed general agreement except for /sup 120/Cs. Possible explanations for this deviation are discussed.

  3. 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.

  4. Production of Neutron-Rich Bi Isotopes by Electric Fields

    SciTech Connect

    Baranov, D. S.; Baranova, O. D.

    2010-04-30

    The short time (approx10 minutes) high voltage electrolysis of nitrate bismuth solution was performed. After electrolysis about 30 mg of electrolyte have been dried up on a thin polyethylene film. The sample obtained was placed into the detecting system (Si detector and plastic detector). Alpha-radioactivity of the sample was measured. The results showed that alpha-radioactivity increased about 100 times to the base level. The radioactivity decreasing was about 2 times for 50 minutes. Some signals from the Si detector was accompanied by a signal from the electron detector (22 events). The signal from the plastic detector for all the events the electron recorded preceded the Si detector signal with delay less than 1.4 musec. The conclusion was made that beta-decay of nuclei {sup 212}Bi and the subsequent alpha-decay of nuclei {sup 212}Po were recorded. The effect was reproduced in 28 experiments. The possible explanation of the phenomenon was given.

  5. The Need for a Neutron Source at the Rare Isotope Accelerator

    SciTech Connect

    Ahle, L E; Rusnak, B; Roberts, K E; Roeben, M D; Hausmann, M; Reifarth, R; Vieira, D

    2005-05-13

    An intense neutron source facility with radiochemical processing capability is necessary at the Rare Isotope Accelerator to fully realize its potential benefit to stockpile stewardship and astrophysics. While many of the important physics missions of RIA can be addressed with radioactive ion beams, direct neutron cross-section measurements of interest to stockpile stewardship and astrophysics cannot because one cannot make a neutron target. Thus, one must collect a sufficient amount of the appropriate short-lived isotope, quickly chemically process the material into a target, and promptly radiate the sample with an intense ''beam'' of neutrons. The unprecedented production rates expected at RIA enables many of these direct neutron cross-section measurements, but only if the proper infrastructure is in place. This document not only describes the major piece of this required infrastructure, a neutron source facility with radiochemical processing capabilities, but also the motivation for measuring such direct neutron cross-sections.

  6. Structure and reactions of light neutron rich nuclei

    SciTech Connect

    Esbensen, H.

    1993-01-01

    Radioactive beam experiments have made it possible to study the structure of nuclei at the neutron drip line. Pair correlations play a crucial role in such nuclei and characteristic features include an extended neutron halo density and a large dipole strength near threshold. The most detailed studies have been performed for [sup 11]Li. I will present a 3-body model that explains the main features of the data obtained for this nucleus.

  7. Structure and reactions of light neutron rich nuclei

    SciTech Connect

    Esbensen, H.

    1993-04-01

    Radioactive beam experiments have made it possible to study the structure of nuclei at the neutron drip line. Pair correlations play a crucial role in such nuclei and characteristic features include an extended neutron halo density and a large dipole strength near threshold. The most detailed studies have been performed for {sup 11}Li. I will present a 3-body model that explains the main features of the data obtained for this nucleus.

  8. Exotic clusters in an unbound region of light neutron-rich systems

    NASA Astrophysics Data System (ADS)

    Ito, Makoto

    2009-10-01

    In light neutron-rich systems, many kinds of molecular structures are discussed from the view point of the clustering phenomena.In particular, much attention has been concentrated on Be isotopes. The molecular orbital (MO), such as &-circ; and &+circ; associated with the covalent binding of atomic molecules, have been shown to give a good description for the low-lying states of these isotopes. In their highly-excited states, furthermore, recent experiments revealed the existence of the interesting resonant states which dominantly decay to the ^6,8He fragments. In this report, we show the unified study of the exotic structures of ^12Be=α+α+4N in an unbound region and the α+^6,8He resonant scattering. We applied the generalized two-center cluster model in which the covalent MO and the atomic orbital (AO) configurations with ^xHe+^yHe could be described in a unified manner. First, we calculated the energy spectra below an α decay-threshold. The (π32^-)^2 (σ12^+)^2 configuration corresponding to ν(0p)^4(sd)^2 becomes the ground state, while (π3 2^-)^2(π12^-)^2 having a large overlap with ν(0p)^6 appears as the first excited state. The rotational band of the ground state reaches to the maximum spin of J^π = 8^+. This result means that the magicity of N=8 is broken in ^12Be due to the formation of (π3 2^-)^2(σ12^+)^2. Next, we solved the scattering problem of α+^8He and identified the several resonance poles. In the continuum region, we found the rotational bands having the AO configurations of α+^8He, ^6He+^6He, and ^5He+^7 He. Furthermore, a much more exotic band appears in the same energy region. In this band, two valence neutrons are localized at individual α-cores (the ^5He+^5He cluster), while the other two neutrons form the covalent &+circ;- bonding between two ^5He clusters; hence, it has a ``hybrid structure'' between the MO configuration and the AO one. In the J^π=0^+ state, it is strongly excited by the two-neutron transfer reaction, α+^8He

  9. Decay studies of the highly neutron-deficient indium isotopes

    SciTech Connect

    Wouters, J.M.

    1982-02-01

    An extension of the experimentally known nuclidic mass surface to nuclei far from the region of beta-stability is of fundamental interest in providing a better determination of the input parameters for the various nuclear mass formulae, allowing a more accurate prediction of the ultimate limits of nuclear stability. In addition, a study of the shape of the mass surface in the vicinity of the doubly-closed nuclide /sup 100/Sn provides initial information on the behavior of the shell closure to be expected when Z = N = 50. Experiments measuring the decay energies of /sup 103/ /sup 105/In by ..beta..-endpoint measurements are described with special attention focused on the development of a plastic scintillator ..beta..-telescope coupled to the on-line mass separator RAMA (Recoil Atom Mass Analyzer). An attempt to measure the ..beta..-endpoint energy of /sup 102/In is also briefly described. The experimentally determined decay energies and derived masses for /sup 103/ /sup 105/In are compared with the predictions of different mass models to identify which models are more successful in this region. Furthermore, the inclusion in these comparisons of the available data on the neutron-rich indium nuclei permits a systematic study of their ground state mass behavior as a function of the neutron number between the shell closures at N = 50 and N = 82. These analyses indicate that the binding energy of /sup 103/In is 1 MeV larger than predicted by the majority of the mass models. An examination of the Q/sub EC/ surface and the single- and two-neutron separation energies in the vicinity of /sup 103/ /sup 105/In is also performed to investigate further the deviation and other possible systematic variations in the mass surface in a model-independent way.

  10. 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.

  11. Decay spectroscopy of neutron-rich 134Sb at the CARIBU facility

    NASA Astrophysics Data System (ADS)

    Kolos, Karolina; Scielzo, Nicholas; Padgett, Stephen; McCutchan, Elizabeth A.; Mitchell, Alan John; Lister, Christopher J.; Copp, Patrick; Clark, Jason A.; Carpenter, Mike P.; Savard, Guy; Zhu, Shaofei; Norman, Eric B.; Apbrahamian, Ani; Siegl, Kevin; Heckmaier, Elizabeth; Marley, Scott

    2016-09-01

    Neutron-rich 134Sb is one of a few isotopes (together with 92Rb, 96Y and 142Cs) that have a large branching ratio to decay to the ground state via a 0- ->0+ first-forbidden transition. Previous measurements have indicated that 97.5% of the decays of 134Sb ground state populate the ground state of 134Te directly. However, a recent experiment using an ion trap indicated that this number may be lower. In order to confirm the β-decay branching ratios, an experiment was carried out to measure the decay properties of 134Sb/134mSb using the X-Array (a highly efficient HPGe clover array) and SATURN (a plastic scintillators and tape-transport system) decay-spectroscopy station at the CARIBU radioactive ion-beam facility at Argonne National Laboratory. Results on the analysis will be presented. The U.S. DOE No. DE-AC52-07NA27344, DE-FG02-94ER40848, DE-AC02-98CH10886, DE-AC02-06CH11357, DE-NA-0000979. The NSF under Grant No. PHY-1203100 and the ARCD Project 120104176. This research used resources of ANL's ATLAS facility.

  12. Exotic neutron-rich medium-mass nuclei with realistic nuclear forces

    NASA Astrophysics Data System (ADS)

    Tsunoda, Naofumi; Otsuka, Takaharu; Shimizu, Noritaka; Hjorth-Jensen, Morten; Takayanagi, Kazuo; Suzuki, Toshio

    2017-02-01

    We present the first application of the newly developed extended Kuo-Krenciglowa (EKK) theory of the effective nucleon-nucleon interaction to shell-model studies of exotic nuclei, including those where conventional approaches with fitted interactions encounter difficulties. This EKK theory enables us to derive an interaction that is suitable for several major shells (s d +p f in this work). By using such an effective interaction obtained from the Entem-Machleidt QCD-based χ N3LO interaction and the Fujita-Miyazawa three-body force, the energies, E 2 properties, and spectroscopic factors of low-lying states of neutron-rich Ne, Mg, and Si isotopes are nicely described, as the first shell-model description of the "island of inversion" without fit of the interaction. The long-standing question as to how particle-hole excitations occur across the s d -p f magic gap is clarified with distinct differences from the conventional approaches. The shell evolution is shown to appear similarly to earlier studies.

  13. Precision mass measurements of neutron-rich nuclei, and limitations on the r-process environment

    NASA Astrophysics Data System (ADS)

    Van Schelt, Jonathon A.

    2012-05-01

    The masses of 65 neutron-rich nuclides and 6 metastable states from Z = 49 to 64 were measured at a typical precision of δm/m= 10-7 using the Canadian Penning Trap mass spectrometer at Argonne National Laboratory. The measurements are on fission fragments from 252Cf spontaneous fission sources, including those measurements made at the new Californium Rare Isotope Breeder Upgrade facility (CARIBU) and an earlier source. The measured nuclides lie on or approach the predicted path of the astrophysical r process. Where overlap exists, this data set is largely consistent with previous measurements from Penning traps, storage rings, and reaction energetics, but large systematic deviations are apparent in β-endpoint measurements. Simulations of the r process were undertaken to determine how quickly material can pass through the studied elements for a variety of conditions, placing limits on what temperatures densities allow passage on a desired timescale. The new masses produce manifold differences in effective lifetime compared to simulations performed with some model masses.

  14. Stellar (n, gamma) cross sections of neutron-rich nuclei

    SciTech Connect

    Marganiec, J.; Domingo Pardo, C.; Kaeppeler, F.

    2010-03-01

    The present measurements were performed by means of the activation technique. Neutrons were produced at the Karlsruhe Van de Graaff accelerator via the {sup 7}Li(p,n){sup 7}Be reaction. For proton energies just above threshold, one obtains a neutron spectrum similar to a Maxwellian distribution for kT = 25 keV. This quasi-stellar neutron spectrum allowed us to measure the Maxwellian averaged cross sections directly. The experimental results of {sup 174,176}Yb, {sup 184,186}W, {sup 190,192}Os, {sup 196,198}Pt, and {sup 202}Hg were extrapolated from kT = 25 keV to lower and higher temperatures.

  15. Measurement of uranium and plutonium in solid waste by passive photon or neutron counting and isotopic neutron source interrogation

    SciTech Connect

    Crane, T.W.

    1980-03-01

    A summary of the status and applicability of nondestructive assay (NDA) techniques for the measurement of uranium and plutonium in 55-gal barrels of solid waste is reported. The NDA techniques reviewed include passive gamma-ray and x-ray counting with scintillator, solid state, and proportional gas photon detectors, passive neutron counting, and active neutron interrogation with neutron and gamma-ray counting. The active neutron interrogation methods are limited to those employing isotopic neutron sources. Three generic neutron sources (alpha-n, photoneutron, and /sup 252/Cf) are considered. The neutron detectors reviewed for both prompt and delayed fission neutron detection with the above sources include thermal (/sup 3/He, /sup 10/BF/sub 3/) and recoil (/sup 4/He, CH/sub 4/) proportional gas detectors and liquid and plastic scintillator detectors. The instrument found to be best suited for low-level measurements (< 10 nCi/g) is the /sup 252/Cf Shuffler. The measurement technique consists of passive neutron counting followed by cyclic activation using a /sup 252/Cf source and delayed neutron counting with the source withdrawn. It is recommended that a waste assay station composed of a /sup 252/Cf Shuffler, a gamma-ray scanner, and a screening station be tested and evaluated at a nuclear waste site. 34 figures, 15 tables.

  16. DANCEing with the Stars: Measuring Neutron Capture on Unstable Isotopes with DANCE

    NASA Astrophysics Data System (ADS)

    Couture, A.; Agvaanluvsan, U.; Baker, J. D.; Bayarbadrahk, B.; Becker, J. A.; Bond, E.; Bredeweg, T. A.; Chyzh, A.; Dashdorj, D.; Fowler, M.; Haight, R. C.; Jandel, M.; Keksis, A. L.; O'Donnell, J. M.; Reifarth, R.; Rundberg, R.; Ullmann, J. L.; Vieira, D. J.; Wouters, J. M.

    2009-03-01

    Isotopes heavier than iron are known to be produced in stars through neutron capture processes. Two major processes, the slow (s) and rapid (r) processes are each responsible for 50% of the abundances of the heavy isotopes. The neutron capture cross sections of the isotopes on the s process path reveal information about the expected abundances of the elements as well as stellar conditions and dynamics. Until recently, measurements on unstable isotopes, which are most important for determining stellar temperatures and reaction flow, have not been experimentally feasible. The Detector for Advance Neutron Capture Experiments (DANCE) located at the Los Alamos Neutron Science Center (LANSCE) was designed to perform time-of-flight neutron capture measurements on unstable isotopes for nuclear astrophysics, stockpile stewardship, and reactor development. DANCE is a 4-π BaF2 scintillator array which can perform measurements on sub-milligram samples of isotopes with half-lives as short as a few hundred days. These cross sections are critical for advancing our understanding of the production of the heavy isotopes.

  17. DANCEing with the Stars: Measuring Neutron Capture on Unstable Isotopes with DANCE

    SciTech Connect

    Couture, A.; Bond, E.; Bredeweg, T. A.; Fowler, M.; Haight, R. C.; Jandel, M.; Keksis, A. L.; O'Donnell, J. M.; Rundberg, R.; Ullmann, J. L.; Vieira, D. J.; Wouters, J. M.; Agvaanluvsan, U.; Becker, J. A.; Baker, J. D.; Bayarbadrahk, B.; Chyzh, A.; Dashdorj, D.; Reifarth, R.

    2009-03-10

    Isotopes heavier than iron are known to be produced in stars through neutron capture processes. Two major processes, the slow (s) and rapid (r) processes are each responsible for 50% of the abundances of the heavy isotopes. The neutron capture cross sections of the isotopes on the s process path reveal information about the expected abundances of the elements as well as stellar conditions and dynamics. Until recently, measurements on unstable isotopes, which are most important for determining stellar temperatures and reaction flow, have not been experimentally feasible. The Detector for Advance Neutron Capture Experiments (DANCE) located at the Los Alamos Neutron Science Center (LANSCE) was designed to perform time-of-flight neutron capture measurements on unstable isotopes for nuclear astrophysics, stockpile stewardship, and reactor development. DANCE is a 4-{pi}BaF{sub 2} scintillator array which can perform measurements on sub-milligram samples of isotopes with half-lives as short as a few hundred days. These cross sections are critical for advancing our understanding of the production of the heavy isotopes.

  18. Production of neutron-rich transcalifornium nuclei in 238U-induced transfer reactions

    NASA Astrophysics Data System (ADS)

    Zhu, Long; Su, Jun; Xie, Wen-Jie; Zhang, Feng-Shou

    2016-11-01

    In order to produce more unknown neutron-rich transcalifornium nuclei, the collisions of 238U with the targets 248Cm, 249Cf, and 250Cm are investigated within the framework of the dinuclear system model. The production cross sections of unknown neutron-rich nuclei with Z =99 -104 in these reactions are predicted. The influences of N /Z ratios and charge numbers of the targets on the production cross sections are studied. It is found that high N /Z ratios of 248Cm and 250Cm targets enhance the production cross sections of neutron-rich transcalifornium nuclei. However, due to high charge number of the target 249Cf the predicted production cross sections of unknown neutron-rich nuclei with Z =104 in the reaction 238U+249Cf are higher than those in 238U+248Cm . We also have studied the entrance angular momentum effects on production probabilities of transfer products in the reaction 238U+248Cm . It is found that the formation probabilities of the final neutron-rich products increase first and then decrease with the increasing J .

  19. Oxygen isotopic abundances in calcium- aluminum-rich inclusions from ordinary chondrites: implications for nebular heterogeneity.

    PubMed

    McKeegan, K D; Leshin, L A; Russell, S S; MacPherson, G J

    1998-04-17

    The oxygen isotopic compositions of two calcium-aluminum-rich inclusions (CAIs) from the unequilibrated ordinary chondrite meteorites Quinyambie and Semarkona are enriched in 16O by an amount similar to that in CAIs from carbonaceous chondrites. This may indicate that most CAIs formed in a restricted region of the solar nebula and were then unevenly distributed throughout the various chondrite accretion regions. The Semarkona CAI is isotopically homogeneous and contains highly 16O-enriched melilite, supporting the hypothesis that all CAI minerals were originally 16O-rich, but that in most carbonaceous chondrite inclusions some minerals exchanged oxygen isotopes with an external reservoir following crystallization.

  20. Nuclear Shape And Size Properties For Rare-earth Neutron-rich Nuclei

    SciTech Connect

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

    2009-01-28

    Two-neutron separation energies, quadrupole moments and mean square charge radii, are evaluated for even-even Osmium isotopes with 78{<=}N{<=}114. The calculations are performed in the framework of a microscopic model including the pairing correlations rigorously by means of the FSBCS (Fixed-Sharp-BCS) method.

  1. Mineralogy and Oxygen Isotope Compositions of Two C-Rich Hydrated Interplanetary Dust Particles

    NASA Technical Reports Server (NTRS)

    Snead, C. J.; McKeegan, K. D.; Messenger, S.; Nakamura-Messenger, K.

    2012-01-01

    Oxygen isotopic compositions of chondrites reflect mixing between a O-16-rich reservoir and a O-17,O-18-rich reservoir produced via mass-independent fractionation. The composition of the O-16-rich reservoir is reasonably well constrained, but material representing the O-17,O-18-rich end-member is rare. Self-shielding models predict that cometary water, presumed to represent this reservoir, should be enriched in O-17 and O-18 18O by > 200%. Hydrated interplanetary dust particles (IDPs) rich in carbonaceous matter may be derived from comets; such particles likely contain the products of reaction between O-16-poor water and anhydrous silicates that formed in the inner solar system. Here we present mineralogy and oxygen isotope compositions of two C-rich hydrated IDPs, L2083E47 and L2071E35.

  2. Isotopic excesses of proton-rich nuclei related to space weathering observed in a gas-rich meteorite Kapoeta

    SciTech Connect

    Hidaka, Hiroshi; Yoneda, Shigekazu E-mail: s-yoneda@kahaku.go.jp

    2014-05-10

    The idea that solar system materials were irradiated by solar cosmic rays from the early Sun has long been suggested, but is still questionable. In this study, Sr, Ba, Ce, Nd, Sm, and Gd isotopic compositions of sequential acid leachates from the Kapoeta meteorite (howardite) were determined to find systematic and correlated variations in their isotopic abundances of proton-rich nuclei, leading to an understanding of the irradiation condition by cosmic rays. Significantly large excesses of proton-rich isotopes (p-isotopes), {sup 84}Sr, {sup 130}Ba, {sup 132}Ba, {sup 136}Ce, {sup 138}Ce, and {sup 144}Sm, were observed, particularly in the first chemical separate, which possibly leached out of the very shallow layer within a few μm from the surface of regolith grains in the sample. The results reveal the production of p-isotopes through the interaction of solar cosmic rays with the superficial region of the regolith grains before the formation of the Kapoeta meteorite parent body, suggesting strong activity in the early Sun.

  3. Boron-rich benzene and pyrene derivatives for the detection of thermal neutrons

    NASA Astrophysics Data System (ADS)

    Yemam, Henok A.; Mahl, Adam; Koldemir, Unsal; Remedes, Tyler; Parkin, Sean; Greife, Uwe; Sellinger, Alan

    2015-09-01

    A synthetic methodology is developed to generate boron rich aromatic small molecules based on benzene and pyrene moieties for the detection of thermal neutrons. The prepared aromatic compounds have a relatively high boron content up to 7.4 wt%, which is important for application in neutron detection as 10B (20% of natural abundance boron) has a large neutron induced reaction cross-section. This is demonstrated by preparing blends of the synthesized molecules with fluorescent dopants in poly(vinyltoluene) matrices resulting in comparable scintillation light output and neutron capture as state-of-the art commercial scintillators, but with the advantage of much lower cost. The boron-rich benzene and pyrene derivatives are prepared by Suzuki conditions using both microwave and traditional heating, affording yields of 40-93%. This new procedure is simple and straightforward, and has the potential to be scaled up.

  4. 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

  5. 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.

  6. First in-beam γ -ray study of the level structure of neutron-rich 39S

    NASA Astrophysics Data System (ADS)

    Chapman, R.; Wang, Z. M.; Bouhelal, M.; Haas, F.; Liang, X.; 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.; Lunardi, S.; Mǎrginean, 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.

    2016-08-01

    The neutron-rich 39S nucleus has been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of 36S ions with a thin 208Pb target. The magnetic spectrometer, PRISMA, and the γ -ray array, CLARA, were used in the measurements. Gamma-ray transitions of the following energies were observed: 339, 398, 466, 705, 1517, 1656, and 1724 keV. Five of the observed transitions have been tentatively assigned to the decay of excited states with spins up to (11 /2- ). The results of a state-of-the-art shell-model calculation of the level scheme of 39S using the SDPF-U effective interaction are also presented. The systematic behavior of the excitation energy of the first 11 /2- states in the odd-A isotopes of sulfur and argon is discussed in relation to the excitation energy of the first excited 2+ states of the adjacent even-A isotopes. The states of 39S that have the components in their wave functions corresponding to three neutrons in the 1 f7 /2 orbital outside the N =20 core have also been discussed within the context of the 0 ℏ ω shell-model calculations presented here.

  7. Neutron-Rich {sup 62,64,64}Fe Show Enhanced Collectivity: The Washout of N = 40 in Terms of Experiment, Valence Proton Symmetry and Shell Model

    SciTech Connect

    Rother, W.; Dewald, A.; Fransen, C.; Hackstein, M.; Jolie, J.; Pissulla, Th.; Zel, K.-O.; Iwasaki, H.; Baugher, T.; Brown, B. A.; Gade, A.; Glasmacher, T.; McDaniel, S.; Ratkiewicz, A.; Voss, P.; Walsh, K. A.; Lenzi, S. M.; Ur, C. A.; Starosta, K.; Bazin, D.

    2011-10-28

    Probing shell structure at a large neutron excess has been of particular interest in recent times. Neutron-rich nuclei between the proton shell closures Z = 20 and Z = 28 offer an exotic testing ground for shell evolution. The development of the N = 40gap between neutron fp and lg{sub 9/2} shells gives rise to highly interesting variations of collectivity for nuclei in this region. While {sup 68}Ni shows doubly magic properties in level energies and transition strengths, this was not observed in neighbouring nuclei. Especially neutron-rich Fe isotopes proved particularly resistant to calculational approaches using the canonical valence space (fpg) resulting in important deviations of the predicted collectivity. Only an inclusion of the d{sub 5/2}-orbital could solve the problem [1]. Hitherto no transition strengths for {sup 66}Fe have been reported. We determined B(E2,2{sup +}{sub 1}{yields}0{sup +}{sub 1}) values from lifetimes measured with the recoil distance Doppler-shift method using the Cologne plunger for radioactive beams at National Superconducting Cyclotron Laboratory at Michigan State University. Excited states were populated by projectile Coulomb excitation for {sup 62,64,66}Fe. The data show a rise in collectivity for Fe isotopes towards N = 40. Results [2] are interpreted by means of a modified version of the Valence Proton Symmetry [3] and compared to shell model calculations using a new effective interaction recently developed for the fpgd valence space [4].

  8. 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.

  9. Method for correcting for isotope burn-in effects in fission neutron dosimeters

    DOEpatents

    Gold, Raymond; McElroy, William N.

    1988-01-01

    A method is described for correcting for effect of isotope burn-in in fission neutron dosimeters. Two quantities are measured in order to quantify the "burn-in" contribution, namely P.sub.Z',A', the amount of (Z', A') isotope that is burned-in, and F.sub.Z', A', the fissions per unit volume produced in the (Z', A') isotope. To measure P.sub.Z', A', two solid state track recorder fission deposits are prepared from the very same material that comprises the fission neutron dosimeter, and the mass and mass density are measured. One of these deposits is exposed along with the fission neutron dosimeter, whereas the second deposit is subsequently used for observation of background. P.sub.Z', A' is then determined by conducting a second irradiation, wherein both the irradiated and unirradiated fission deposits are used in solid state track recorder dosimeters for observation of the absolute number of fissions per unit volume. The difference between the latter determines P.sub.Z', A' since the thermal neutron cross section is known. F.sub.Z', A' is obtained by using a fission neutron dosimeter for this specific isotope, which is exposed along with the original threshold fission neutron dosimeter to experience the same neutron flux-time history at the same location. In order to determine the fissions per unit volume produced in the isotope (Z', A') as it ingrows during the irradiation, B.sub.Z', A', from these observations, the neutron field must generally be either time independent or a separable function of time t and neutron energy E.

  10. 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.

  11. Changes in the mean square charge radii and electromagnetic moments of neutron-deficient Bi isotopes

    SciTech Connect

    Barzakh, A. E. Batist, L. Kh.; Fedorov, D. V.; Ivanov, V. S.; Molkanov, P. L.; Moroz, F. V.; Orlov, S. Yu.; Panteleev, V. N.; Seliverstov, M. D.; Volkov, Yu. M.

    2015-10-15

    In-source laser spectroscopy experiments for neutron deficient bismuth isotopes at the 306.77 nm atomic transition were carried out at the IRIS (Investigation of Radioactive Isotopes on Synchrocyclotron) facility of Petersburg Nuclear Physics Institute (PNPI). New data on isotope shifts and hyperfine structure for {sup 189–198,} {sup 211}Bi isotopes and isomers were obtained. The changes in the mean-square charge radii and the magnetic moment values were deduced. Marked deviation from the nearly spherical behavior for ground states of bismuth isotopes at N < 109 is demonstrated, in contrast to the lead and thallium isotopic chains. The big isomer shift between I = 1/2 (intruder) and I = 9/2 (normal) states for odd Bi isotopes (A = 193, 195, 197) was found.

  12. Iron isotope fractionation during sulfide-rich felsic partial melting in early planetesimals

    NASA Astrophysics Data System (ADS)

    Wang, Kun; Day, James M. D.; Korotev, Randy L.; Zeigler, Ryan A.; Moynier, Frédéric

    2014-04-01

    New Fe isotope data of feldspar-rich meteorites Graves Nunataks 06128 and 06129 (GRA 06128/9) reveal that they are the only known examples of crustal materials with isotopically light Fe isotope compositions (δFe56=-0.08±0.06‰; δ56Fe is defined as the per mille deviation of a sample's 56Fe/54Fe ratio from the IRMM-014 standard) in the Solar System. In contrast, associated brachinites, as well as brachinite-like achondrites, have Fe isotope compositions (δFe56=+0.01±0.02‰) that are isotopically similar to carbonaceous chondrites and the bulk terrestrial mantle. In order to understand the cause of Fe isotope variations in the GRA 06128/9 and brachinite parent body, we also report the Fe isotope compositions of metal, silicate and sulfide fractions from three ordinary chondrites (Semarkona, Kernouve, Saint-Séverin). Metals from ordinary chondrites are enriched in the heavier isotopes of Fe (average δFe56=0.15‰), sulfide fractions are enriched in the lighter isotopes of Fe (average δFe56=-0.14‰), and the δ56Fe values of the silicates are coincident with that of the bulk rock (average δFe56=0.03‰). The enrichment of light isotopes of Fe isotopes in GRA 06128/9 is consistent with preferential melting of sulfides in precursor chondritic source materials leading to the formation of Fe-S-rich felsic melts. Conceptual models show that melt generation to form a GRA 06128/9 parental melt occurred prior to the onset of higher-temperature basaltic melting (<1200 °C) in a volatile-rich precursor and led to the generation of buoyant felsic melt with a strong Fe-S signature. These models not only reveal the origin of enrichment in light isotopes of Fe for GRA 06128/9, but are also consistent with petrological and geochemical observations, experimental studies for the origin of Fe-S-rich felsic melts, and for the cessation of early melting on some asteroidal parent bodies because of the effective removal of the major radioactive heat-source, 26Al. The mode of

  13. Evidence for a Change in the Nuclear Mass Surface with the Discovery of the Most Neutron-Rich Nuclei with 17{<=}Z{<=}25

    SciTech Connect

    Tarasov, O. B.; Morrissey, D. J.; Amthor, A. M.; Gade, A.; Nettleton, A.; Sherrill, B. M.; Thoennessen, M.; Baumann, T.; Bazin, D.; Ginter, T. N.; Hausmann, M.; Pereira, J.; Portillo, M.; Stolz, A.; Inabe, N.; Kubo, T.

    2009-04-10

    The results of measurements of the production of neutron-rich nuclei by the fragmentation of a {sup 76}Ge beam are presented. The cross sections were measured for a large range of nuclei including 15 new isotopes that are the most neutron-rich nuclides of the elements chlorine to manganese ({sup 50}Cl, {sup 53}Ar, {sup 55,56}K, {sup 57,58}Ca, {sup 59,60,61}Sc, {sup 62,63}Ti, {sup 65,66}V, {sup 68}Cr, {sup 70}Mn). The enhanced cross sections of several new nuclei relative to a simple thermal evaporation framework, previously shown to describe similar production cross sections, indicates that nuclei in the region around {sup 62}Ti might be more stable than predicted by current mass models and could be an indication of a new island of inversion similar to that centered on {sup 31}Na.

  14. Coupled cluster calculations of neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Hagen, Gaute

    2016-09-01

    In this talk I will present recent highlights from ab initio computations of atomic nuclei using coupled-cluster methods with state-of-the-art interactions from chiral effective field theory (EFT). The recent progress in computing nuclei from scratch is based on new optimizations of interactions from chiral EFT, and ab initio methods with a polynomial computational cost together with available super computing resources. The physics advancements I will discuss include: (i) accurate nuclear binding energies and radii of light and medium-mass nuclei, (ii) the neutron distribution and electric dipole polarizability of the nucleus 48Ca, (iii) and the structure of the rare nucleus 78Ni from first principles. All these quantities are currently targeted by precision measurements worldwide.

  15. Bands and Isomers in Neutron-Rich Rare-Earth Nuclei in PHF Model

    NASA Astrophysics Data System (ADS)

    Praharaj, C. R.; Ghorui, S. K.; Naik, Z.; Sahu, B. B.

    Rotational structures of neutron-rich Gd and Dy nuclei in the REE peak region are studied with deformed Hartee-Fock (HF) and angular momentum (J) projection model. Spectra of ground band and a few more excited, positive and negative parity bands have been studied up to high spin values. Some 4-quasiparticle K-isomeric bands and their electromagnetic properties are predicted.

  16. TOF-Bρ Mass Measurement of Neutron Rich Nuclei at the NSCL

    NASA Astrophysics Data System (ADS)

    Estradé, Alfredo; Matoš, Milan; Amthor, Matthew A.; Bazin, Daniel; Becerril, Ana D.; Elliot, Thom J.; Gade, Alexandra; Galaviz, Daniel; Lorusso, Giuseppe; Pereira, Jorge; Portillo, Mauricio; Rogers, Andrew; Schatz, Hendrik; Shapira, Dan; Smith, Edward; Stolz, Andreas; Wallace, Mark S.

    2007-10-01

    Experimental knowledge of nuclear masses of exotic nuclei is important for understanding nuclear structure far from the valley of β-stability, and as a direct input into astrophysical models. In the case of astrophysical processes involving neutron rich nuclei, such as nucleosynthesis during the r-process and the evolution of matter in the crust of an accreting neutron star, we are mostly limited to using theoretical mass models. The time of flight (TOF) mass measurement technique allows measuring very short-lived nuclei. It has been effectively applied using the fast fragment beams produced at the A1900 fragment separator at the National Superconducting Cyclotron Lab (NSCL) to reach masses very far from stability. We describe a recent mass measurement experiment in the neutron rich Fe region performed at the NSCL, and present preliminary results.

  17. Half-lives of neutron-rich Cd-130128

    NASA Astrophysics Data System (ADS)

    Dunlop, R.; Bildstein, V.; Dillmann, I.; Jungclaus, A.; Svensson, C. E.; Andreoiu, C.; Ball, G. C.; Bernier, N.; Bidaman, H.; Boubel, P.; Burbadge, C.; Caballero-Folch, R.; Dunlop, M. R.; Evitts, L. J.; Garcia, F.; Garnsworthy, A. B.; Garrett, P. E.; Hackman, G.; Hallam, S.; Henderson, J.; Ilyushkin, S.; Kisliuk, D.; Krücken, R.; Lassen, J.; Li, R.; MacConnachie, E.; MacLean, A. D.; McGee, E.; Moukaddam, M.; Olaizola, B.; Padilla-Rodal, E.; Park, J.; Paetkau, O.; Petrache, C. M.; Pore, J. L.; Radich, A. J.; Ruotsalainen, P.; Smallcombe, J.; Smith, J. K.; Tabor, S. L.; Teigelhöfer, A.; Turko, J.; Zidar, T.

    2016-06-01

    The β -decay half-lives of Cd-130128 have been measured with the newly commissioned GRIFFIN γ -ray spectrometer at the TRIUMF-ISAC facility. The time structures of the most intense γ rays emitted following the β decay were used to determine the half-lives of 128Cd and 130Cd to be T1 /2=246.2 (21 ) ms and T1 /2=126 (4 ) ms, respectively. The half-lives of the 3 /2+ and 11 /2- states of 129Cd were measured to be T1 /2(3 /2+) =157 (8 ) ms and T1 /2(11 /2-) =147 (3 ) ms. The half-lives of the Cd isotopes around the N =82 shell closure are an important ingredient in astrophysical simulations to derive the magnitude of the second r -process abundance peak in the A ˜130 region. Our new results are compared with recent literature values and theoretical calculations.

  18. Isotope identification capabilities using time resolved prompt gamma emission from epithermal neutrons

    NASA Astrophysics Data System (ADS)

    Festa, G.; Arcidiacono, L.; Pappalardo, A.; Minniti, T.; Cazzaniga, C.; Scherillo, A.; Andreani, C.; Senesi, R.

    2016-03-01

    We present a concept of integrated measurements for isotope identification which takes advantage of the time structure of spallation neutron sources for time resolved γ spectroscopy. Time resolved Prompt Gamma Activation Analysis (T-PGAA) consists in the measurement of gamma energy spectrum induced by the radioactive capture as a function of incident neutron Time Of Flight (TOF), directly related with the energy of incident neutrons. The potential of the proposed concept was explored on INES (Italian Neutron Experimental Station) at the ISIS spallation neutron source (U.K.). Through this new technique we show an increase in the sensitivity to specific elements of archaeometric relevance, through incident neutron energy selection in prompt γ spectra for multicomponent samples. Results on a standard bronze sample are presented.

  19. Medical Isotope Production using High Intensity Accelerator Neutrons

    NASA Astrophysics Data System (ADS)

    Nagai, Yasuki

    We proposed aprototype facility for the generation of radioisotopes with accelerator neutrons by deuterons. The neutrons are producedbynatC(d,n) with 40MeV 2 mA deuteron beams, and about 8.1 TBq/week of 99Mois produced by irradiating an enriched 100Mo sample with the neutrons.High-quality 99mTc can be separatedfrom an irradiated 100MoO3 sample by thermo-chromatographic separation.In this contribution we present the system to produce medical radioisotopes, such as 99Mo, 90Y, and 67Cu, and experimental studies on 99Mo and 67Cu produced by using accelerator neutrons.

  20. Shape changes in neutron rich N = 43 isotones

    NASA Astrophysics Data System (ADS)

    Sethi, Jasmine; Forney, A.; Walters, W. B.; Harker, J.; Chiara, C. J.; Stefanescu, I.; Janssens, R. V. F.; Zhu, S.; Carpenter, M. P.

    2016-09-01

    et al. Nuclei in the transitional region with 28 < Z < 50 and 40 < N < 50 are very sensitive to shape changes with addition of individual nucleons due to close-lying neutron orbitals in the fpg model space. A systematic comparison of the structure of N = 43 isotones, focussing on new results on 75Ge and 73Zn will be presented. Both nuclei were populated in deep inelastic scattering reactions, 76Ge+208Pb and 76Ge+238 U , at 25 % above the Coulomb barrier, using Gammasphere and ATLAS facility at ANL. A number of new transitions and levels have been identified in both nuclei. The experimental results and their comparison to the theoretical calculations will be presented. This work is supported by the U.S. Department of Energy, Office of Nuclear Physics under Contract Numbers DE-AC02-06CH11357 and DE- AC02-05CH11231 and under Grant Numbers DE-FG02-94ER40834 and by the Polish Ministry of Science Grant Numbers 1P03B05929 and NN202103333. This research used resources of ANL's ATLAS facility, which is a DOE Office of Science User Facility.

  1. Fluorescent atom coincidence spectroscopy of extremely neutron-deficient barium isotopes

    NASA Astrophysics Data System (ADS)

    Wells, S. A.; Evans, D. E.; Griffith, J. A. R.; Eastham, D. A.; Groves, J.; Smith, J. R. H.; Tolfree, D. W. L.; Warner, D. D.; Billowes, J.; Grant, I. S.; Walker, P. M.

    1988-09-01

    Fluorescent atom coincidence spectroscopy (FACS) has been used to measure the nuclear mean square radii and moments of the extremely neutron-deficient isotopes 120-124Ba. At N=65 an abrupt change in nuclear mean square charge radii is observed which can be understood in terms of the occupation of the spin-orbit partner g7/25/2[413] neutron and g9/29/2[404] proton orbitals and the consequent enhancement of the n-p interaction.

  2. Theoretical Calculation of Prompt Neutron Spectra from Fission of Curium Isotopes

    NASA Astrophysics Data System (ADS)

    Ohsawa, Takaaki; Tani, Kazuhiro; Kishimoto, Yasufumi

    2003-06-01

    Prompt neutron spectra for Cm-isotopes (242Cm, 243Cm, 244Cm, 245Cm, 246Cm, 248Cm) were calculated on the basis of a modified version of the Madland-Nix model combined with a multimodal fission model. The predicted spectra were found to be in fair agreement with recent data. A slight enhancement of the low-energy component of the spectrum was interpreted in terms of neutron emission during fragment acceleration.

  3. Search for long-lived isomeric states in neutron-deficient thorium isotopes

    SciTech Connect

    Lachner, J.; Dillmann, I.; Faestermann, T.; Korschinek, G.; Poutivtsev, M.; Rugel, G.

    2008-12-15

    The discovery of naturally occurring long-lived isomeric states (t{sub 1/2}>10{sup 8} yr) in the neutron-deficient isotopes {sup 211,213,217,218}Th[A. Marinov et al., Phys. Rev. C 76, 021303(R) (2007)] was reexamined using accelerator mass spectrometry (AMS). Because AMS does not suffer from molecular isobaric background in the detection system, it is an extremely sensitive technique. Despite our up to two orders of magnitude higher sensitivity we cannot confirm the discoveries of neutron-deficient thorium isotopes and provide upper limits for their abundances.

  4. Neutron multiplicity measurements of Cf and Fm isotopes

    SciTech Connect

    Hoffman, D.C.; Ford, G.P.; Balagna, J.P.; Veeser, L.R.

    1980-02-01

    Prompt neutrons in coincidence with the fission fragments from the spontaneous fission of /sup 250,252,254/Cf and /sup 257/Fm were measured inside a 75-cm-diameter, Gd-loaded liquid scintillation counter having a neutron-detection efficiency of about 78%. Measurements for /sup 256/Fm were done just outside the counter with an efficiency of 31%. The kinetic energies of both fission fragments and the number of neutrons for each fission event were recorded. From these data, the fragment kinetic energies and masses and the neutron multiplicity distributions were determined for /sup 250,252,254/Cf and /sup 257/Fm. Variances of neutron multiplicity distributions as a function of total fragment kinetic energy and the ratio of fragment masses have been calculated and are presented for all the nuclides studied.

  5. Neutron imaging of hydrogen-rich fluids in geomaterials and engineered porous media: A review

    NASA Astrophysics Data System (ADS)

    Perfect, E.; Cheng, C.-L.; Kang, M.; Bilheux, H. Z.; Lamanna, J. M.; Gragg, M. J.; Wright, D. M.

    2014-02-01

    Recent advances in visualization technologies are providing new discoveries as well as answering old questions with respect to the phase structure and flow of hydrogen-rich fluids, such as water and oil, within porous media. Magnetic resonance and x-ray imaging are sometimes employed in this context, but are subject to significant limitations. In contrast, neutrons are ideally suited for imaging hydrogen-rich fluids in abiotic non-hydrogenous porous media because they are strongly attenuated by hydrogen and can "see" through the solid matrix in a non-destructive fashion. This review paper provides an overview of the general principles behind the use of neutrons to image hydrogen-rich fluids in both 2-dimensions (radiography) and 3-dimensions (tomography). Engineering standards for the neutron imaging method are examined. The main body of the paper consists of a comprehensive review of the diverse scientific literature on neutron imaging of static and dynamic experiments involving variably-saturated geomaterials (rocks and soils) and engineered porous media (bricks and ceramics, concrete, fuel cells, heat pipes, and porous glass). Finally some emerging areas that offer promising opportunities for future research are discussed.

  6. 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.

  7. Calculations of neutron and proton radii of cesium isotopes. Final report, April 23--September 30, 1993

    SciTech Connect

    Not Available

    1993-12-31

    This task involved the calculation of neutron and proton radii of cesium isotopes. The author has written a computer code that calculates radii according to two models: Myers 1983 and FRDM 1992. Results of calculations in both these models for both cesium and francium isotopes are attached as figures. He is currently interpreting these results in collaboration with D. Vieira and J.R. Nix, and they expect to use the computer code for further studies of nuclear radii.

  8. 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.

  9. 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.

  10. Neutron Generation from Laser-Accelerated Ion Beams: Use of Alternative Deuteron-Rich Targets for Improved Neutron Yield and Control of Neutron Spectra

    NASA Astrophysics Data System (ADS)

    Albright, B. J.; Yin, L.; Favalli, A.

    2016-10-01

    Laser-ion-beam generation in the break-out afterburner (BOA) acceleration regime has been modeled for several deuteron-rich solid-density targets using the VPIC particle-in-cell code. Monte Carlo modeling of the transport of these beams in a beryllium converter in a pitcher-catcher neutron source configuration shows significant increases in neutron yields may be achievable through judicious choices of laser target material. Additionally, species-separation dynamics in some target materials during the BOA ion acceleration phase can be exploited to control the shapes of the neutron spectra. Work performed under the auspices of the U.S. DOE by the LANS, LLC, Los Alamos National Laboratory under Contract No. DE-AC52-06NA25396. Funding provided by the Los Alamos National Laboratory Directed Research and Development Program.

  11. Abundances in red giant stars - Carbon and oxygen isotopes in carbon-rich molecular envelopes

    NASA Technical Reports Server (NTRS)

    Wannier, P. G.; Sahai, R.

    1987-01-01

    Millimeter-wave observations have been made of isotopically substituted CO toward the envelopes of 11 carbon-rich stars. In every case, C-13O was detected and model calculations were used to estimate the C-12/C-13 abundance ratio. C-17O was detected toward three, and possibly four, envelopes, with sensitive upper limits for two others. The CO-18 variant was detected in two envelopes. New results include determinations of oxygen isotopic ratios in the two carbon-rich protoplanetary nebulae CRL 26688 and CRL 618. As with other classes of red giant stars, the carbon-rich giants seem to be significantly, though variably, enriched in O-17. These results, in combination with observations in interstellar molecular clouds, indicate that current knowledge of stellar production of the CNO nuclides is far from satisfactory.

  12. Ca-,Al-rich inclusions in the unique chondrite ALH85085 - Petrology, chemistry, and isotopic compositions

    NASA Astrophysics Data System (ADS)

    Kimura, M.; El Goresy, A.; Palme, H.; Zinner, E.

    1993-05-01

    A comprehensive study is performed for the Ca-,Al-rich inclusions (CAIs) in the unique chondrite ALH85085. The ALH85085 inclusions are smaller (5-80 microns) and more refractory than their counterparts in carbonaceous chondrites. The study includes 42 inclusions for petrography and mineralogy, 15 for bulk major and minor element chemical composition, six for Mg-Al isotopic systematics, 10 for Ca isotopes, nine for Ti isotopes, and six for trace element abundances. In addition, oxygen-isotopic compositions were determined in minerals from a single inclusion. No correlation is found between mineralogy, major element chemistry, and trace element abundances. It is further shown that the high-temperature geochemical behavior of ultrarefractory trace elements is decoupled from that of the major elements Ca and Ti (Ti is correlated with the relatively volatile elements Nb and Yb) implying that perovskite is of only minor importance as carrier of ultrarefractories.

  13. Observation of new neutron-deficient isotopes with Z ≥ 92 in multinucleon transfer reactions

    NASA Astrophysics Data System (ADS)

    Devaraja, H. M.; Heinz, S.; Beliuskina, O.; Comas, V.; Hofmann, S.; Hornung, C.; Münzenberg, G.; Nishio, K.; Ackermann, D.; Gambhir, Y. K.; Gupta, M.; Henderson, R. A.; Heßberger, F. P.; Khuyagbaatar, J.; Kindler, B.; Lommel, B.; Moody, K. J.; Maurer, J.; Mann, R.; Popeko, A. G.; Shaughnessy, D. A.; Stoyer, M. A.; Yeremin, A. V.

    2015-09-01

    In deep inelastic multinucleon transfer reactions of 48Ca + 248Cm we observed about 100 residual nuclei with proton numbers between Z = 82 and Z = 100. Among them, there are five new neutron-deficient isotopes: 216U, 219Np, 223Am, 229Am and 233Bk. As separator for the transfer products we used the velocity filter SHIP of GSI while the isotope identification was performed via the α decay chains of the nuclei. These first results reveal that multinucleon transfer reactions together with here applied fast and sensitive separation and detection techniques are promising for the synthesis of new isotopes in the region of heaviest nuclei.

  14. Decay properties of neutron-deficient isotopes of elements from Z = 101 to Z = 108

    NASA Astrophysics Data System (ADS)

    Heßberger, F. P.; Hofmann, S.; Streicher, B.; Sulignano, B.; Antalic, S.; Ackermann, D.; Heinz, S.; Kindler, B.; Kojouharov, I.; Kuusiniemi, P.; Leino, M.; Lommel, B.; Mann, R.; Popeko, A. G.; Šáro, Š.; Uusitalo, J.; Yeremin, A. V.

    2009-08-01

    In a series of experiments performed at the velocity filter SHIP, new or improved decay data of neutron-deficient isotopes of elements from mendelevium ( Z = 101) to hassium ( Z = 108) were obtained. In particular, evidence for α -decay or electron capture from isomeric states in 265Hs and 258Db was found.

  15. Neutron-Induced Fission Cross Section Measurements for Uranium Isotopes and Other Actinides at LANSCE

    SciTech Connect

    Laptev, Alexander B.; Tovesson, Fredrik K.; Hill, Tony S.

    2012-08-16

    A well established program of neutron-induced fission cross section measurement at Los Alamos Neutron Science Center (LANSCE) is supporting the Fuel Cycle Research program (FC R&D). The incident neutron energy range spans from sub-thermal up to 200 MeV by combining two LANSCE facilities, the Lujan Center and the Weapons Neutron Research center (WNR). The time-of-flight method is implemented to measure the incident neutron energy. A parallel-plate fission ionization chamber was used as a fission fragment detector. The event rate ratio between the investigated foil and a standard {sup 235}U foil is translated into a fission cross section ratio. Thin actinide targets with deposits of <200 {micro}g/cm{sup 2} on stainless steel backing were loaded into a fission chamber. In addition to previously measured data for {sup 237}Np, {sup 239-242}Pu, {sup 243}Am, new measurements include the recently completed {sup 233,238}U isotopes, {sup 236}U data which is being analyzed, and {sup 234}U data acquired in the 2011-2012 LANSCE run cycle. The new data complete the full suite of Uranium isotopes which were investigated with this experimental approach. When analysis of the new measured data is completed, data will be delivered to evaluators. Having data for multiple Uranium isotopes will support theoretical modeling capabilities and strengthens nuclear data evaluation.

  16. Analysis of Pu Isotopes in Melted Fuel by Neutron Resonance Transmission: Examination by Linear Absorption Model

    NASA Astrophysics Data System (ADS)

    Kitatani, F.; Harada, H.; Takamine, J.; Kureta, M.; Seya, M.

    2014-04-01

    We have been studying the feasibility of neutron resonance transmission analysis (NRTA) for quantifying nuclear materials (Pu/U isotopes) in particle-like debris of melted fuel for nuclear material accountability and safeguards. The achievable measurement accuracy of NRTA was examined using a linear absorption model for the sample which contain substances other than nuclear fuel materials, such as boron and iron. The impurities (boron and iron etc.) in melted fuel are from the support structure and criticality control materials of the reactor core, and should be included to study the feasibility of NRTA for actual application. Neutron transmission spectra were calculated using the total neutron cross-sections in JENDL-4.0. The transmission spectra together with their uncertainties were evaluated. The study showed quantitatively that the statistical uncertainty in the determination of atomic number density of each isotope depends on the impurity density in the sample. The optimal thickness of the sample was determined for various impurity densities.

  17. β-decay properties of neutron-deficient Pt, Hg, and Pb isotopes

    SciTech Connect

    Sarriguren, P.; Boillos, J. M.; Moreno, O.; Moya de Guerra, E.

    2015-10-15

    Neutron-deficient isotopes in the lead region are well established examples of the shape coexistence phenomenon in nuclei. In this work, bulk and decay properties, including deformation energy curves, charge mean square radii, Gamow-Teller (GT) strength distributions, and β-decay half-lives, are studied in neutron-deficient Pt, Hg, and Pb isotopes. The nuclear structure involved is described microscopically from deformed quasiparticle random-phase approximation calculations with residual interactions in both particle-hole and particle-particle channels, performed on top of a self-consistent deformed quasiparticle Skyrme Hartree-Fock basis. The sensitivity to deformation of the GT strength distributions in those isotopes is proposed as an additional complementary signature of the nuclear shape. The β-decay half-lives resulting from the GT strength distributions are compared to experiment to demonstrate the ability of the method.

  18. Selenium redox cycling during weathering of Se-rich shales: A selenium isotope study

    NASA Astrophysics Data System (ADS)

    Zhu, Jian-Ming; Johnson, Thomas M.; Clark, Scott K.; Zhu, Xiang-Kun; Wang, Xiang-Li

    2014-02-01

    Selenium isotopes are becoming an important paleoenvironmental proxy. However, few studies have focused on the behavior of Se isotopes during oxidative weathering. In this paper, a comprehensive set of Se isotopic composition and concentration data were collected from the weathering profiles of Se-rich shales of the Permian Maokou Formation in Yutangba and Shadi, China to investigate Se isotopic fractionation and Se enrichment during weathering processes. The δ82/76Se in fresh shales (148 ± 118 mg/kg Se, 1SD, n = 40) from Shadi and Yutangba drill cores varies from -1.69‰ to 1.74‰ with an average of 0.40 ± 0.71‰ (1SD, n = 40), consistent with the range in other Phanerozoic shales, suggesting that Se isotopes are not strongly fractionated during Se sequestration in the primary sedimentary environment. However, the strongly weathered Se-rich shales from Shadi and Yutangba profiles are isotopically lighter with average δ82/76Se values of -1.96 ± 1.08‰ (1SD, n = 5) and -1.08 ± 1.83‰ (1SD, n = 23), respectively. These data suggest that Se isotopes can be fractionated during oxidation and reduction processes associated with weathering, with heavier isotopes removed preferentially during oxidative weathering of shales. Such a shift, if found to be a global phenomenon, would have implications for models of the global Se cycle and interpretation of Se isotope data from past biogeochemical regimes. Locally altered shales exposed in a quarry at Yutangba are extremely enriched in Se with 1642 ± 1505 mg/kg (1SD, n = 45), approximately 10 times greater than that in unaltered drill core samples. These rocks display very strong variation in δ82/76Se over short distances, with a single 60 cm transect showing the most strongly negative and positive δ82/76Se values (-14.20‰ to +11.37‰) observed to date in natural samples. This suggests that Se has undergone multiple cycles of oxidation, mobilization, and re-reduction, resulting in a Se-rich redox front that has

  19. {alpha} decay studies of very neutron-deficient francium and radium isotopes

    SciTech Connect

    Uusitalo, J.; Leino, M.; Enqvist, T.; Grahn, T.; Greenlees, P.T.; Jones, P.; Julin, R.; Juutinen, S.; Keenan, A.; Kettunen, H.; Koivisto, H.; Kuusiniemi, P.; Leppaenen, A.-P.; Nieminen, P.; Pakarinen, J.; Rahkila, P.; Scholey, C.; Eskola, K.

    2005-02-01

    Very neutron-deficient francium and radium isotopes have been produced in fusion evaporation reactions using {sup 63}Cu and {sup 65}Cu ions on {sup 141}Pr targets and {sup 36}Ar ions on {sup 170}Yb targets. The gas-filled recoil separator RITU was employed to collect the fusion products and to separate them from the scattered beam. The activities were implanted into a position-sensitive silicon detector after passing through a gas-counter system. The isotopes were identified using spatial and time correlations between the implants and decays. Two new {alpha} decaying radium isotopes, {sup 201}Ra and {sup 202}Ra, were identified. The {alpha} decay energy and half-life of {sup 203}Ra were measured with improved precision. The {alpha} decay properties measured for the francium isotopes {sup 201}Fr,{sup 202}Fr,{sup 203}Fr, and {sup 204}Fr were confirmed, in many cases with improved precision. For the first time, a ({pi}s{sub 1/2}{sup -1})1/2{sup +} proton intruder state was identified in francium isotopes, namely in {sup 201}Fr and tentatively in {sup 203}Fr. The measured decay properties for the neutron-deficient odd-mass Fr isotopes suggest an onset of substantial deformation at N=112.

  20. Neutron flux measurement using activated radioactive isotopes at the Baksan underground scintillation telescope

    NASA Astrophysics Data System (ADS)

    Kochkarov, M. M.; Alikhanov, I. A.; Boliev, M. M.; Dzaparova, I. M.; Novoseltseva, R. V.; Novoseltsev, Yu. F.; Petkov, V. B.; Volchenko, V. I.; Volchenko, G. V.; Yanin, A. F.

    2016-11-01

    Preliminary results of a neutron background measurement at the Baksan underground scintillation telescope (BUST) are presented. The external planes of the BUST are fully covered with standard scintillation detectors shielding the internal planes and suppressing thus background events due to cosmogenic and local radioactivity. The shielded internal planes were used as target for the neutron flux registration. The experimental method is based on the delayed coincidences between signals from any of the BUST counters. It is assumed that the first signal is due to inelastic interaction of a neutron with the organic scintillator, while the second signal comes from the decay of an unstable radioactive isotope formed when the fast neutron interacts with the 12C nuclei. Using the Monte-Carlo method (GEANT4) we also simulated propagation of neutrons through a layer of scintillator. The experimentally found muon induced neutron flux is j =1.3 -0.3 +0.7 ×10-10cm-2s-1 for neutron energies E ≥ 22MeV, which is in a qualitative agreement with similar measurements of other underground laboratories as well as with predictions of the GEANT4.

  1. Decay Pattern of Pygmy States Observed in Neutron-Rich Ne26

    NASA Astrophysics Data System (ADS)

    Gibelin, J.; Beaumel, D.; Motobayashi, T.; Blumenfeld, Y.; Aoi, N.; Baba, H.; Elekes, Z.; Fortier, S.; Frascaria, N.; Fukuda, N.; Gomi, T.; Ishikawa, K.; Kondo, Y.; Kubo, T.; Lima, V.; Nakamura, T.; Saito, A.; Satou, Y.; Scarpaci, J.-A.; Takeshita, E.; Takeuchi, S.; Teranishi, T.; Togano, Y.; Vinodkumar, A. M.; Yanagisawa, Y.; Yoshida, K.

    2008-11-01

    Coulomb excitation of the exotic neutron-rich nucleus Ne26 on a Pb208 target was measured at 58MeV/u in order to search for low-lying E1 strength above the neutron emission threshold. This radioactive beam experiment was carried out at the RIKEN Accelerator Research Facility. Using the invariant mass method in the Ne25+n channel, we observe a sizable amount of E1 strength between 6 and 10 MeV excitation energy. By performing a multipole decomposition of the differential cross section, a reduced dipole transition probability of B(E1)=0.49±0.16e2fm2 is deduced, corresponding to 4.9±1.6% of the Thomas-Reiche-Kuhn sum rule. For the first time, the decay pattern of low-lying strength in a neutron-rich nucleus is measured. The extracted decay pattern is not consistent with several mean-field theory descriptions of the pygmy states.

  2. Microscopic dynamics simulations of heavy-ion fusion reactions induced by neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Wang, Ning; Ou, Li; Zhang, Yingxun; Li, Zhuxia

    2014-06-01

    The heavy-ion fusion reactions induced by neutron-rich nuclei are investigated with the improved quantum molecular dynamics (ImQMD) model. With a subtle consideration of the neutron skin thickness of nuclei and the symmetry potential, the stability of nuclei and the fusion excitation functions of heavy-ion fusion reactions O16 + Ge76, O16 + Sm154, Ca40 + Zr96, and Sn132 + Ca40 are systematically studied. The fusion cross sections of these reactions at energies around the Coulomb barrier can be well reproduced by using the ImQMD model. The corresponding slope parameter of the symmetry energy adopted in the calculations is L ≈78 MeV and the surface energy coefficient is gsur=18±1.5 MeV fm2. In addition, it is found that the surface-symmetry term significantly influences the fusion cross sections of neutron-rich fusion systems. For sub-barrier fusion, the dynamical fluctuations in the densities of the reaction partners and the enhanced surface diffuseness at neck side result in the lowering of the fusion barrier.

  3. Single-neutron excitations in neutron-rich Ge83 and Se85

    NASA Astrophysics Data System (ADS)

    Thomas, J. S.; Arbanas, G.; Bardayan, D. W.; Blackmon, J. C.; Cizewski, J. A.; Dean, D. J.; Fitzgerald, R. P.; Greife, U.; Gross, C. J.; Johnson, M. S.; Jones, K. L.; Kozub, R. L.; Liang, J. F.; Livesay, R. J.; Ma, Z.; Moazen, B. H.; Nesaraja, C. D.; Shapira, D.; Smith, M. S.; Visser, D. W.

    2007-10-01

    The H2(Ge82,p)Ge83 and H2(Se84,p)Se85 reactions were studied with radioactive beams of Ge82 and Se84 at beam energies of Ebeam=330 and 380 MeV, respectively. Excitation energies, proton angular distributions, and asymptotic normalization coefficients have been determined for the lowest lying states of Ge83 and Se85. Spectroscopic factors have also been extracted under normal assumptions of the bound-state potential properties in the distorted waves Born approximation analysis. However, the peripheral character of the measurements leads to large uncertainties in this extraction. Shell-model calculations have been performed in the region above Ni78, comparing the single-particle properties of the even-Z,N=51 nuclei up to Zr91 and including Ge83 and Se85. Direct-semidirect neutron capture calculations to Ge83 and Se85 have also been performed using the spectroscopic input from these (d,p) reaction measurements.

  4. Studies of neutron-deficient mendelevium isotopes at SHIP

    NASA Astrophysics Data System (ADS)

    Antalic, S.; Heßberger, F. P.; Hofmann, S.; Ackermann, D.; Heinz, S.; Kindler, B.; Kojouharov, I.; Kuusiniemi, P.; Leino, M.; Lommel, B.; Mann, R.; Šáro, Š.

    2010-01-01

    The radioactive decay of the isotopes 247Md , 246Md and their daughter products was investigated by means of α - α and α - γ coincidence spectroscopy. The isotopes were produced using the fusion reaction 40Ar + 209Bi. Decay schemes are suggested for 247Md and 243Es . A new isomeric state in 246Md with a half-life of ( 4.4±0.8 s was observed. Previous data of electron-capture delayed fission of 246Md and 242Es were confirmed. The probability for this decay branch in 246Md was measured to be P ECDF > 0.10 . The probability for electron-capture delayed fission in the case of 242Es was determined to be P ECDF = 0.013+0.012 -0.007.

  5. α decay of the very neutron-deficient isotopes 197-199Fr

    NASA Astrophysics Data System (ADS)

    Kalaninová, Z.; Andreyev, A. N.; Antalic, S.; Heßberger, F. P.; Ackermann, D.; Andel, B.; Drummond, M. C.; Hofmann, S.; Huyse, M.; Kindler, B.; Lane, J. F. W.; Liberati, V.; Lommel, B.; Page, R. D.; Rapisarda, E.; Sandhu, K.; Šáro, Š.; Thornthwaite, A.; Van Duppen, P.

    2013-04-01

    Decay properties of the very neutron-deficient isotopes 197-199Fr were studied at the velocity filter Separator for Heavy Ion reaction Products (SHIP) at GSI in Darmstadt. The isotopes were produced in the 2n-4n evaporation channels of the fusion-evaporation reaction 60Ni+141Pr → 201Fr*. Improved α-decay properties of 199Fr were determined and the possible existence of two α-decaying states in this nucleus is discussed. For the isotope 198Fr a broad α-decay energy distribution was detected in the range of (7470-7930) keV and two α-decaying states were observed with half-lives of 1.1(7) and 15(3) ms. The new isotope 197Fr was identified based on the observation of one α-decay chain yielding Eα=7728(15) keV and T1/2=0.6-0.3+3.0 ms. The systematics of reduced α-decay widths are presented for neutron-deficient francium, radon, and astatine isotopes.

  6. 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.

  7. Spectroscopy of Moderately Neutron-rich Nuclei with the CLARA-PRISMA Setup

    SciTech Connect

    Gadea, A.; Marginean, N.; De Angelis, G.; Napoli, D. R.; Corradi, L.; Stefanini, A. M.; Fioretto, E.; Axiotis, M.; Behera, B. R.; Latina, A.; Rusu, C.; Zhimin, W.; Valiente-Dobon, J.; Pokrovskiy, I.; Della Vedova, F.; Farnea, E.; Lenzi, S. M.; Bazzacco, D.; Beghini, S.; Ur, C.

    2006-04-26

    Deep-inelastic and multi-nucleon transfer reactions can be used to populate nuclei with relatively large neutron excess. Recently, at the Laboratori Nazionali di Legnaro, a setup consisting on an efficient {gamma}-ray detection system CLARA coupled to the large acceptance magnetic spectrometer PRISMA, capable of tracking the trajectories of the reaction products, has been assembled. During the first year of activity, the experiments performed with the CLARA-PRISMA setup, have been focused mainly on the nuclear structure of neutron-rich nuclei. In particular, nuclei around N=20, N=50 and lying in the A{approx}60 transitional region with N<40, have been investigated. In this contribution, results of these experiments will be reported.

  8. 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 neutron emission was observed. The shell-model calculations and apparent β transition intensities were used to guide the spin assignment to the

  9. Identification of a quasiparticle band in very neutron-rich {sup 104}Zr

    SciTech Connect

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

    2010-08-15

    The high spin levels of a very neutron-rich {sup 104}Zr nucleus have been reinvestigated by measuring the prompt {gamma} rays in the spontaneous fission of {sup 252}Cf. The ground-state band has been confirmed. A new sideband has been identified with a band-head energy at 1928.7 keV. The projected shell model is employed to investigate the band structure of {sup 104}Zr. The results of calculated levels are in good agreement with the experimental data, and suggest that the new band in {sup 104}Zr may be based on the neutron {nu}5/2{sup -}[532] x {nu}3/2{sup +}[411] configuration.

  10. Existence of long-lived isomeric states in naturally-occurring neutron-deficient Th isotopes

    SciTech Connect

    Marinov, A.; Kashiv, Y.; Rodushkin, I.; Halicz, L.; Segal, I.; Pape, A.; Miller, H. W.; Kolb, D.; Brandt, R.

    2007-08-15

    Four long-lived neutron-deficient Th isotopes with atomic mass numbers 211 to 218 and abundances of (1-10)x10{sup -11} relative to {sup 232}Th have been found in a study of naturally-occurring Th using inductively coupled plasma-sector field mass spectrometry. It is deduced that long-lived isomeric states exist in these isotopes. The hypothesis that they might belong to a new class of long-lived high spin super- and hyperdeformed isomeric states is discussed.

  11. Boron isotope geochemistry during diagenesis. Part II. Applications to organic-rich sediments

    NASA Astrophysics Data System (ADS)

    Williams, Lynda B.; Hervig, Richard L.; Hutcheon, Ian

    2001-06-01

    The measured clay-water isotope fractionation for boron was applied to natural organic-rich sediments undergoing illitization. Two field areas were chosen that show illitization occurring over a range of temperatures (80-500°C). Samples representing diagenetic temperatures of illitization (80-200°C) are from the Gulf of Mexico sedimentary basin at 4 to 6-km depth in the Eocene Wilcox Fm and Jurassic Norphlet Fm. The higher temperatures of illitization (200-500°C) occur in a contact metamorphic aureole of the Cretaceous Pierre shale near Walsenburg, Colorado. Here the kinetics of the illitization reaction are more rapid than in a slowly subsiding sedimentary basin, but the chemical and mineralogical variations are minimized as complete illitization occurs over a small lateral distance in a single bentonite layer. These studies indicate that B-isotopes provide a more sensitive indicator of fluid variations in sedimentary basins than O-isotopes, and that B-isotope analyses of authigenic illite can be a valuable geochemical tracer of fluid/rock interactions. Boron isotope ratios in authigenic illite (pore filling) and muscovite (stylolites) from reservoir sandstones in the Gulf of Mexico are distinct from adjacent illitic mudstones, whereas the oxygen isotopic ratios show little variation. Fluids in equilibrium with the mudstones cannot precipitate the authigenic clays with higher δ 11B values measured in the hydrocarbon reservoirs. This suggests that the reservoir fluids were not in communication with the adjacent mudstone pore fluids but were introduced from another source area, perhaps carrying a B-isotopic label derived from the hydrocarbon source region. Authigenic illite formed in the Pierre shale meta-bentonite shows large isotopic fractionations of boron (20‰) during illitization at high temperatures. Incorporation of 500 ppm B in illite formed at 500°C shows that illite is a host for B even at metamorphic temperatures. By using the experimentally

  12. Distribution of p-process 174Hf in early solar system materials and the origin of nucleosynthetic Hf and W isotope anomalies in Ca-Al rich inclusions

    NASA Astrophysics Data System (ADS)

    Peters, Stefan T. M.; Münker, Carsten; Pfeifer, Markus; Elfers, Bo-Magnus; Sprung, Peter

    2017-02-01

    Some nuclides that were produced in supernovae are heterogeneously distributed between different meteoritic materials. In some cases these heterogeneities have been interpreted as the result of interaction between ejecta from a nearby supernova and the nascent solar system. Particularly in the case of the oldest objects that formed in the solar system - Ca-Al rich inclusions (CAIs) - this view is confirm the hypothesis that a nearby supernova event facilitated or even triggered solar system formation. We present Hf isotope data for bulk meteorites, terrestrial materials and CAIs, for the first time including the low-abundance isotope 174Hf (∼0.16%). This rare isotope was likely produced during explosive O/Ne shell burning in massive stars (i.e., the classical "p-process"), and therefore its abundance potentially provides a sensitive tracer for putative heterogeneities within the solar system that were introduced by supernova ejecta. For CAIs and one LL chondrite, also complementary W isotope data are reported for the same sample cuts. Once corrected for small neutron capture effects, different chondrite groups, eucrites, a silicate inclusion of a IAB iron meteorite, and terrestrial materials display homogeneous Hf isotope compositions including 174Hf. Hafnium-174 was thus uniformly distributed in the inner solar system when planetesimals formed at the <50 ppm level. This finding is in good agreement with the evidently homogeneous distributions of p-process isotopes 180W, 184Os and possibly 190Pt between different iron meteorite groups. In contrast to bulk meteorite samples, CAIs show variable depletions in p-process 174Hf with respect to the inner solar system composition, and also variable r-process (or s-process) Hf and W contributions. Based on combined Hf and W isotope compositions, we show that CAIs sampled at least one component in which the proportion of r- and s-process derived Hf and W deviates from that of supernova ejecta. The Hf and W isotope

  13. Photon Scattering from the Stable Even-Mass Mo Isotopes Below the Neutron-Separation Energy

    NASA Astrophysics Data System (ADS)

    Rusev, G.; Hutcheson, A.; Kwan, E.; Tonchev, A. P.; Tornow, W.; Angell, C.; Hammond, S.; Karwowski, H. J.; Kelley, J. H.; Schwengner, R.; Dönau, F.; Wagner, A.

    2008-10-01

    We present results from photon-scattering experiments on the stable even-mass molybdenum isotopes below the neutron-separation energy carried out with bremsstrahlung at the superconducting electron accelerator ELBE at the Research Center Dresden-Rossendorf in Germany, and with monoenergetic photon beams at the HIγS facility at TUNL. We applied statistical methods in order to correct for the branching and cascade transitions and to determine the photoabsorption cross section. The obtained results allowed us to extend the tail of the Giant Dipole Resonance below the (,) threshold down to 4 MeV. The photoabsorption cross sections deduced from the present experiments show that the dipole strength increases with the neutron number of the Mo isotopes. The experimental results are discussed in the frame of Quasiparticle-Random-Phase-Approximation in a deformed basis which describe the increasing strength as a result of the deformation.

  14. Evolution of collectivity in neutron-rich nuclei in the Sn132 region

    NASA Astrophysics Data System (ADS)

    Kshetri, Ritesh; Sarkar, M. Saha; Sarkar, S.

    2006-09-01

    Motivated by the observed regularity in the energy spectra and the structure of the shell model wave functions for the levels of Te137 and I137, a few weakly and moderately deformed neutron-rich odd-A nuclei above the doubly magic nucleus Sn132 were studied using the particle rotor model (PRM). The calculated energy spectra and branching ratios agree reasonably well with the most recent experimental data. In a few cases ambiguity in level ordering was resolved and spin-parities were assigned to the levels. Observed octupole correlation in some of these nuclei is discussed in the light of the present results.

  15. Nuclear structure of the odd-odd N=85 neutron-rich nucleus {sup 140}Cs

    SciTech Connect

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

    2010-03-15

    High-spin excited states in the neutron-rich nucleus {sup 140}Cs were re-investigated from the spontaneous fission of {sup 252}Cf with the Gammasphere detector array. Seven new transitions at low and moderate spin and 13 at high spin were observed in {sup 140}Cs and the level scheme of {sup 140}Cs was extended to 3794 keV with a new sideband. Spins and parities were assigned to levels based on angular correlation measurements and the systematics in the N=85 isotones.

  16. Dependence of Fission-Fragment Properties On Excitation Energy For Neutron-Rich Actinides

    NASA Astrophysics Data System (ADS)

    Ramos, D.; Rodríguez-Tajes, C.; Caamaño, M.; Farget, F.; Audouin, L.; Benlliure, J.; Casarejos, E.; Clement, E.; Cortina, D.; Delaune, O.; Derkx, X.; Dijon, A.; Doré, D.; Fernández-Domínguez, B.; de France, G.; Heinz, A.; Jacquot, B.; Navin, A.; Paradela, C.; Rejmund, M.; Roger, T.; Salsac, M. D.; Schmitt, C.

    2016-03-01

    Experimental access to full isotopic fragment distributions is very important to determine the features of the fission process. However, the isotopic identification of fission fragments has been, in the past, partial and scarce. A solution based on the use of inverse kinematics to study transfer-induced fission of exotic actinides was carried out at GANIL, resulting in the first experiment accessing the full identification of a collection of fissioning systems and their corresponding fission fragment distribution. In these experiments, a 238U beam at 6.14 AMeV impinged on a carbon target to produce fissioning systems from U to Am by transfer reactions, and Cf by fusion reactions. Isotopic fission yields of 250Cf, 244Cm, 240Pu, 239Np and 238U are presented in this work. With this information, the average number of neutrons as a function of the atomic number of the fragments is calculated, which reflects the impact of nuclear structure around Z=50, N=80 on the production of fission fragments. The characteristics of the Super Long, Standard I, Standard II, and Standard III fission channels were extracted from fits of the fragment yields for different ranges of excitation energy. The position and contribution of the fission channels as function of excitation energy are presented.

  17. M1 excitation in Sm isotopes and the proton-neutron sdg interacting boson model

    NASA Astrophysics Data System (ADS)

    Mizusaki, Takahiro; Otsuka, Takaharu; Sugita, Michiaki

    1991-10-01

    The magnetic-dipole scissors mode in spherical to deformed Sm isotopes is studied in terms of the proton-neutron sdg interacting boson model, providing a good agreement with recent experiment by Ziegler et al. The present calculation correctly reproduces the increase of M1 excitation strength in going from spherical to deformed nuclei. It is suggested that there may be 1+ states which do not correspond to the scissors mode but absorb certain M1 strength from the ground state.

  18. Rates for neutron-capture reactions on tungsten isotopes in iron meteorites. [Abstract only

    NASA Technical Reports Server (NTRS)

    Masarik, J.; Reedy, R. C.

    1994-01-01

    High-precision W isotopic analyses by Harper and Jacobsen indicate the W-182/W-183 ratio in the Toluca iron meteorite is shifted by -(3.0 +/- 0.9) x 10(exp -4) relative to a terrestrial standard. Possible causes of this shift are neutron-capture reactions on W during Toluca's approximately 600-Ma exposure to cosmic ray particles or radiogenic growth of W-182 from 9-Ma Hf-182 in the silicate portion of the Earth after removal of W to the Earth's core. Calculations for the rates of neutron-capture reactions on W isotopes were done to study the first possibility. The LAHET Code System (LCS) which consists of the Los Alamos High Energy Transport (LAHET) code and the Monte Carlo N-Particle(MCNP) transport code was used to numerically simulate the irradiation of the Toluca iron meteorite by galactic-cosmic-ray (GCR) particles and to calculate the rates of W(n, gamma) reactions. Toluca was modeled as a 3.9-m-radius sphere with the composition of a typical IA iron meteorite. The incident GCR protons and their interactions were modeled with LAHET, which also handled the interactions of neutrons with energies above 20 MeV. The rates for the capture of neutrons by W-182, W-183, and W-186 were calculated using the detailed library of (n, gamma) cross sections in MCNP. For this study of the possible effect of W(n, gamma) reactions on W isotope systematics, we consider the peak rates. The calculated maximum change in the normalized W-182/W-183 ratio due to neutron-capture reactions cannot account for more than 25% of the mass 182 deficit observed in Toluca W.

  19. Enhancement of fusion at near-barrier energies for neutron-rich light nuclei: 19O +12 C

    NASA Astrophysics Data System (ADS)

    Singh, Varinderjit; Vadas, J.; Steinbach, T. K.; Wiggins, B. B.; Hudan, S.; Desouza, R. T.; Baby, L. T.; Kuvin, S. A.; Tripathi, Vandana; Wiedenhover, I.; Umar, A. S.

    2017-01-01

    Measuring the fusion excitation function for an isotopic chain of projectile nuclei provides a sensitive test of a microscopic description of fusion. To investigate the theoretically predicted fusion enhancement for neutron-rich light nuclei, an experiment was performed to measure the fusion excitation functions for 19 O +12 C and 18 O +12 C . Using the 18O(d,p) reaction and the RESOLUT mass spectrometer at Florida State University, a beam of 19O was produced with an intensity of 2-4 x 103 p/s. This beam bombarded a 100 μg/cm2 carbon target. Using an approach optimized for the measurement of fusion with a low-intensity beam, evaporation residues (ERs) resulting from the de-excitation of the fusion product were measured. The ERs were identified by measuring their energy and time-of-flight. At near-barrier energies, an enhancement of fusion by a factor of three has been observed for 19 O +12 C in comparison to 18 O +12 C . Comparison of the experimental results with the predictions of a density constrained time-dependent Hartree-Fock (DC-TDHF) model provide evidence for the importance of pairing in the fusion process. Supported by the US DOE under Grant No. DEFG02-88ER-40404.

  20. Resonance neutron-capture cross sections of stable magnesium isotopes and their astrophysical implications

    NASA Astrophysics Data System (ADS)

    Massimi, C.; Koehler, P.; Bisterzo, S.; Colonna, N.; Gallino, R.; Gunsing, F.; Käppeler, F.; Lorusso, G.; Mengoni, A.; Pignatari, M.; Vannini, G.; Abbondanno, U.; Aerts, G.; Álvarez, H.; Álvarez-Velarde, F.; Andriamonje, S.; Andrzejewski, J.; Assimakopoulos, P.; Audouin, L.; Badurek, G.; Barbagallo, M.; Baumann, P.; Bečvář, F.; Belloni, F.; Bennett, M.; Berthoumieux, E.; Calviani, M.; Calviño, F.; Cano-Ott, D.; Capote, R.; Carrapiço, C.; Carrillo de Albornoz, A.; Cennini, P.; Chepel, V.; Chiaveri, E.; Cortes, G.; Couture, A.; Cox, J.; Dahlfors, M.; David, S.; Dillmann, I.; Dolfini, R.; Domingo-Pardo, C.; Dridi, W.; Duran, I.; Eleftheriadis, C.; Embid-Segura, M.; Ferrant, L.; Ferrari, A.; Ferreira-Marques, R.; Fitzpatrick, L.; Frais-Koelbl, H.; Fujii, K.; Furman, W.; Goncalves, I.; González-Romero, E.; Goverdovski, A.; Gramegna, F.; Griesmayer, E.; Guerrero, C.; Haas, B.; Haight, R.; Heil, M.; Herrera-Martinez, A.; Herwig, F.; Hirschi, R.; Igashira, M.; Isaev, S.; Jericha, E.; Kadi, Y.; Karadimos, D.; Karamanis, D.; Kerveno, M.; Ketlerov, V.; Konovalov, V.; Kopecky, S.; Kossionides, E.; Krtička, M.; Lampoudis, C.; Leeb, H.; Lederer, C.; Lindote, A.; Lopes, I.; Losito, R.; Lozano, M.; Lukic, S.; Marganiec, J.; Marques, L.; Marrone, S.; Martínez, T.; Mastinu, P.; Mendoza, E.; Milazzo, P. M.; Moreau, C.; Mosconi, M.; Neves, F.; Oberhummer, H.; O'Brien, S.; Oshima, M.; Pancin, J.; Papachristodoulou, C.; Papadopoulos, C.; Paradela, C.; Patronis, N.; Pavlik, A.; Pavlopoulos, P.; Perrot, L.; Pigni, M. T.; Plag, R.; Plompen, A.; Plukis, A.; Poch, A.; Praena, J.; Pretel, C.; Quesada, J.; Rauscher, T.; Reifarth, R.; Rockefeller, G.; Rosetti, M.; Rubbia, C.; Rudolf, G.; Salgado, J.; Santos, C.; Sarchiapone, L.; Sarmento, R.; Savvidis, I.; Stephan, C.; Tagliente, G.; Tain, J. L.; Tarrío, D.; Tassan-Got, L.; Tavora, L.; Terlizzi, R.; Vaz, P.; Ventura, A.; Villamarin, D.; Vlachoudis, V.; Vlastou, R.; Voss, F.; Walter, S.; Wendler, H.; Wiescher, M.; Wisshak, K.

    2012-04-01

    We have measured the neutron capture cross sections of the stable magnesium isotopes 24,25,26Mg in the energy range of interest to the s process using the neutron time-of-flight facility n_TOF at CERN. Capture events from a natural metal sample and from samples enriched in 25Mg and 26Mg were recorded using the total energy method based on C62H6 detectors. Neutron resonance parameters were extracted by a simultaneous resonance shape analysis of the present capture data and existing transmission data on a natural isotopic sample. Maxwellian-averaged capture cross sections for the three isotopes were calculated up to thermal energies of 100 keV and their impact on s-process analyses was investigated. At 30 keV the new values of the stellar cross section for 24Mg, 25Mg, and 26Mg are 3.8±0.2 mb, 4.1±0.6 mb, and 0.14±0.01 mb, respectively.

  1. Can Handheld Plastic Detectors Do Both Gamma and Neutron Isotopic Identification with Directional Source Location?

    SciTech Connect

    Robert Hayes

    2008-04-18

    This paper demonstrates, through MCNPX simulations, that a compact hexagonal array of detectors can be utilized to do both gamma isotopic identification (ID) along with neutron identification while simultaneously finding the direction of the source relative to the detector array. The detector array itself is composed of seven borated polyvinyl toluene (PVT) hexagonal light pipes approximately 4 inches long and with a 1.25 inch face-to-face thickness assembled in a tight configuration. The gamma ID capability is realized through judicious windowing algorithms as is the neutron spectral unfolding. By having multiple detectors in different relative positions, directional determination of the source can be realized. By further adding multiplicity counters to the neutron counts, fission events can be measured.

  2. A binding energy study of the Atomic Mass Evaluation 2012 and an updated beta-decay study of neutron-rich 74Cu

    NASA Astrophysics Data System (ADS)

    Tracy, James L., Jr.

    A study of ground state binding energy values listed in the Atomic Mass Evaluation 2012 (AME2012) using an interpretive approach, as opposed to the exploratory methods of previous models, is presented. This model is based on a postulate requiring all protons to pair with available neutrons to form bound alpha clusters as the ground state for an N = Z core upon which excess neutrons are added. For each core, the trend of the binding energy as a function of excess neutrons in the isotopic chain can be fit with a three-term quadratic function. The quadratic parameter reveals a smooth decaying exponential function. By re-envisioning the determination of mass excess, the constant-term fit parameters, representing N = Z nuclei, reveal a near-symmetry around Z = 50. The linear fit parameters exhibit trends which are linear functions of core size. A neutron drip-line prediction is compared against current models. By considering the possibility of an alpha-cluster core, a new ground-state structure grouping scheme is presented; nucleon-nucleon pairing is shown to have a greater role in level filling. This model, referred to as the Alpha-Deuteron-Neutron Model, yields promising first results when considering root-mean-square variances from the AME2012. The beta-decay of the neutron-rich isotope 74Cu has been studied using three high-purity Germanium clover detectors at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. A high-resolution mass separator greatly improved the purity of the 74Cu beam by removing isobaric contaminants, thus allowing decay through its isobar chain to the stable 74Ge at the center of the LeRIBSS detector array without any decay chain member dominating. Using coincidence gating techniques, 121 gamma-rays associated with 74Cu were isolated from the collective singles spectrum. Eighty-seven of these were placed in an expanded level scheme, and updated beta-feeding level intensities and log( ft) values are presented based on

  3. Experiment for synthesis of neutron-deficient protactinium isotopes

    NASA Astrophysics Data System (ADS)

    Yang, Huabin; Ma, Long; Zhang, Zhiyuan; Yu, Lin; Jia, Guobin; Huang, Minghui; Gan, Zaiguo; Huang, Tianheng; Li, Guangshun; Wu, Xiaolei; Fang, Yongde; Wang, Zhigang; Gao, Bingshui; Hua, Wei

    2014-10-01

    The complete fusion reaction 40Ca+175Lu was studied at a beam energy of 5.1 MeV u-1. Evaporation residues recoiled from the target were separated from the primary beam by the gas-filled recoil separator SHANS and then implanted into the focal plane detection system. Based on the energy-position-time correlation measurement, neutron-deficient nuclei 208-213Ac, 212Pa and 211Th produced in this reaction were identified. Previously reported decay properties of the ground state in 212Pa were confirmed and improved values of 5.1_{-1.7}^{+5.1} ms and 8.250(20) MeV for the half-life and α-particle energy of 212Pa were obtained. No correlated decay chain arising from 211Pa was observed and an upper limit for the cross section of 211Pa was estimated.

  4. Iron and Nickel Isotopic Compositions of Presolar Silicon Carbide Grains from AGB Stars Measured with CHILI

    NASA Astrophysics Data System (ADS)

    Trappitsch, R.; Stephan, T.; Davis, A. M.; Pellin, M. J.; Savina, M. R.; Gyngard, F.; Bisterzo, S.; Gallino, R.; Dauphas, N.

    2016-08-01

    Simultaneous iron and nickel isotopic studies in presolar SiC mainstream grains measured on CHILI show the expected AGB star anomalies in the neutron-rich isotopes. Neutron-poor isotopes are dominated by GCE and show clear correlations with silicon.

  5. Decay studies of neutron deficient rare earth isotopes with OASIS

    SciTech Connect

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

    1987-09-01

    We report results on the decay of /sup 124/Pr, /sup 124,125/Ce, /sup 124,125/La, /sup 134-136/Eu, /sup 134-136/Sm, /sup 134-136/Pm, /sup 144/Ho, /sup 141,142,144/Dy, /sup 140,141,142,144/Tb, /sup 140-142/Gd, and /sup 140-142/Eu, produced by /sup 92/Mo(H.I.,xpyn) reactions at the Berkeley SuperHILAC, and studied with the OASIS on-line mass separator facility. Half-lives, delayed proton branching ratios, ..gamma..-ray energies and intensities, partial decay schemes and several J/sup ..pi../ assignments are presented. Level systematics of the even mass Nd and Sm isotopes and of the nu h/sub 11/2/ - nu s/sub 1/2/ isomers for N = 77 are discussed.

  6. 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

  7. A chemical and isotopic study of hibonite-rich refractory inclusions in primitive meteorites

    NASA Technical Reports Server (NTRS)

    Hinton, Richard W.; Davis, Andrew M.; Scatena-Wachel, Debra E.; Grossman, Lawrence; Draus, Ronald J.

    1988-01-01

    Isotopic and chemical analyses of hibonite-rich inclusions from a number of primitive meteorites and, in some cases, of coexisting minerals from carbonaceous and ordinary chondrites, were carried out using ion microprobe (IP). The results of the IP analyses were compared with literature data obtained by INAA and electron microprobe analysis. Results showed that the trace element patterns of the hibonite inclusions analyzed have a number of feautures in common. The results are discussed with reference to the possible chemical processes operating early in the history of the solar system.

  8. A chemical and isotopic study of hibonite-rich refractory inclusions in primitive meteorites

    NASA Astrophysics Data System (ADS)

    Hinton, Richard W.; Davis, Andrew M.; Scatena-Wachel, Debra E.; Grossman, Lawrence; Draus, Ronald J.

    1988-11-01

    Isotopic and chemical analyses of hibonite-rich inclusions from a number of primitive meteorites and, in some cases, of coexisting minerals from carbonaceous and ordinary chondrites, were carried out using ion microprobe (IP). The results of the IP analyses were compared with literature data obtained by INAA and electron microprobe analysis. Results showed that the trace element patterns of the hibonite inclusions analyzed have a number of feautures in common. The results are discussed with reference to the possible chemical processes operating early in the history of the solar system.

  9. Electromagnetic properties of neutron-rich nuclei adjacent to the Z = 50 shell closure

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    Low-lying high-spin yrast states in the exotic odd-odd isotopes 124-128Sb (Z = 51) and 118-128In (Z = 49), studied for the first time, show a striking difference in their observed γ-ray decay. With a single valence proton particle/hole occupying the g7/2 /g9/2 spin-orbit partners, dominant electric quadrupole transitions occur in Sb as opposed to magnetic dipole transitions in In. The observed properties are explained on the basis of general principles of symmetry and with large-scale shell-model calculations, and reveal novel aspects of the competition between the neutron-proton interaction and the like-nucleon pairing interaction.

  10. Rb-Sr Isotopic Systematics of Alkali-Rich Fragments in the Yamato-74442 LL-Chondritic Breccia

    NASA Technical Reports Server (NTRS)

    Yokoyama, T.; Misawa, K.; Okano, O.; Shih, C.-Y.; Nyquist, L. E.; Simo, J. I.; Tappa, M. J.; Yoneda, S.

    2012-01-01

    Alkali-rich igneous fragments were identified in the brecciated LL-chondrites, Kr henberg (LL5)], Bhola (LL3-6) and Yamato (Y)-74442 (LL4), and show characteristic fractionation patterns of alkaline elements. The K-Rb-Cs-rich fragments in Kr henberg, Bhola, and Y-74442 are very similar in mineralogy and petrography (olivine + pyroxene + glass), suggesting that they could have come from related precursor materials. We have undertaken Rb-Sr isotopic studies on alkali-rich fragments in Y-74442 to precisely determine their crystallization ages and the isotopic signatures of their precursor material(s).

  11. The HB-2D Polarized Neutron Development Beamline at the High Flux Isotope Reactor

    NASA Astrophysics Data System (ADS)

    Crow, Lowell; Hamilton, WA; Zhao, JK; Robertson, JL

    2016-09-01

    The Polarized Neutron Development beamline, recently commissioned at the HB-2D position on the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, provides a tool for development and testing of polarizers, polarized neutron devices, and prototyping of polarized neutron techniques. With available monochromators including pyrolytic graphite and polarizing enriched Fe-57 (Si), the instrument has operated at 4.25 and 2.6 Å wavelengths, using crystal, supermirror, or He-3 polarizers and analyzers in various configurations. The Neutron Optics and Development Team has used the beamline for testing of He-3 polarizers for use at other HFIR and Spallation Neutron Source (SNS) instruments, as well as a variety of flipper devices. Recently, we have acquired new supermirror polarizers which have improved the instrument performance. The team and collaborators also have continuing demonstration experiments of spin-echo focusing techniques, and plans to conduct polarized diffraction measurements. The beamline is also used to support a growing use of polarization techniques at present and future instruments at SNS and HFIR.

  12. Distribution of total radiation widths for neutron resonances of Pt isotopes

    NASA Astrophysics Data System (ADS)

    Koehler, P. E.; Bečvář, F.; Krtička, M.

    2015-05-01

    High quality neutron capture and transmission data were measured on isotopically enriched 192,194,195,196Pt and natural Pt samples at ORELA. R-matrix analysis of this data revealed resonance parameters for 159, 413, 423, 258, and 11 neutron resonances for neutron energies below 5.0, 16.0, 7.5, 16.0, and 5.0 keV for 192,194,195,196,198Pt+n, respectively. Earlier analysis of data on reduced neutron widths, Γ0n, showed that the distributions of Γ0n for 192,194Pt deviate significantly from the Porter-Thomas distribution (PTD) predicted by random matrix theory. In this contribution we report on preliminary results of the analysis of distribution of total radiation widths, Γγ, in 192,194,195,196Pt+n reactions. Comparison of experimental data with predictions made within the nuclear statistical model indicates that standard models of Photon Strength Functions (PSFs) and Nuclear Level Density predict Γγ distributions which are too narrow. We found that satisfactory agreement between experimental and simulated distributions can be obtained only by a strong suppression of the PSFs at low γ-ray energies and/or by violation of the usual assumption that primary transitions from neutron resonances follow the PTD. The shape of PSFs needed for reproduction of our Γγ data also nicely reproduces spectra from several (n,γ) experiments on the neighbor nuclide 198Au.

  13. Scission neutrons for U, Pu, Cm, and Cf isotopes: Relative multiplicities calculated in the sudden limit

    NASA Astrophysics Data System (ADS)

    Capote, R.; Carjan, N.; Chiba, S.

    2016-02-01

    The multiplicities of scission neutrons νs c are calculated for series of U, Pu, Cm, and Cf isotopes assuming a sudden transition between two different nuclear configurations (αi→αf ): one just before the neck rupture and one immediately after the disappearance of the neck. This calculation requires only the knowledge of the corresponding two sets of neutron eigenstates. The nuclear shapes around the scission point are described in terms of Cassinian ovals with only two parameters: α (that positions the shape with respect to the zero-neck shape) and α1 (that defines the mass asymmetry). Based on these shapes, a neutron mean field of the Woods-Saxon type is constructed using two prescriptions to calculate the distance to the nuclear surface. The accent in the present work is put on the dependence of νs c on the neutron number Nf of the fissioning nucleus and on the mass asymmetry AL/AH of the primary fission fragments. The relative dependence of these multiplicities, averaged over the mass yields, <νs c> , are finally compared with existing experimental data on prompt fission neutrons <νp> .

  14. Characterization of isomers in the neutron-rich odd-odd nucleus {sup 156}Pm

    SciTech Connect

    Sood, P. C.; Gowrishankar, R; Sai, K. Vijay; Sainath, M.

    2011-02-15

    Critical examination of the experimental data from {sup 156}Nd and {sup 156}Pm {beta} decays and the observed location of relevant neutron and proton orbitals in the neighboring odd-A isotones and isotopes, taken together with the low-lying two-quasiparticle (2qp) structures expected in {sup 156}Pm from the rotor-particle model, lead to the conclusion that a consistent description of all the available data is achieved with the I{sup {pi}}=4{sup +} spin-parity assignment to the 26.7s {sup 156}Pm ground state (g.s.) and assignment of I{sup {pi}}=1{sup +} to its 150.3-keV isomer with the 2qp configuration 4{sub g.s.}{sup +}{l_brace}p{sub o}:5/2[532{up_arrow}]{+-}n{sub o}:3/2[521{up_arrow}]{r_brace}1{sub 150}{sup +}. In the process, a two-neutron configuration is also suggested for the 1509-keV 4{sup +} level in the daughter nucleus {sup 156}Sm. The present analysis reiterates the important question of whether the {beta}-decay log ft value, by itself, can be employed to deduce the relative parity of the {beta}-connected states.

  15. Dineutron correlations in quasi-two-dimensional systems in a simplified model, and possible relation to neutron-rich nuclei

    SciTech Connect

    Kanada-En'yo, Yoshiko; Hinohara, Nobuo; Suhara, Tadahiro; Schuck, Peter

    2009-05-15

    Two-neutron correlation in the {sup 1}S channel in quasi-two-dimensional (2D) neutron systems at zero temperature is studied by means of the BCS theory with finite-range effective nuclear forces. The dineutron correlation in low density neutron systems confined in an infinite slab is investigated in a simplified model that neutron motion of one direction is frozen. When the slab is thin enough, two neutrons form a tightly bound dineutron with a small size in the quasi-2D system, and a Bose dineutron gas is found in low density limit. With increase of Fermi momentum, the neutron system changes from the Bose-gas phase to the superfluid Cooper pair phase. The density dependence of the neutron pairing shows the BCS-BEC crossover phenomena at finite low-density region. In the transition region, the size shrinking of neutron pair and enhancement of pairing gap are found. The relation to dineutron correlation at surface of neutron-rich nuclei is also discussed.

  16. Stellar neutron capture cross sections of Nd, Pm, and Sm isotopes

    SciTech Connect

    Toukan, K.A. ); Debus, K.; Kaeppeler, F. ); Reffo, G. )

    1995-03-01

    The neutron capture cross sections of [sup 146,148,150]Nd have been determined relative to that of gold by means of the activation method. The samples were irradiated in a quasistellar neutron spectrum for [ital kT]=25 keV using the [sup 7]Li([ital p],[ital n])[sup 7]Be reaction near threshold. Variation of the experimental conditions in different activations and the use of different samples allowed for the reliable determination of corrections and the evaluation of systematic uncertainties. The resulting stellar cross sections can be given with uncertainties around 6%, which represents a considerable improvement compared to previous measurements. These data are complemented by a new set of calculated cross sections for the unstable isotopes [sup 147]Nd, [sup 147,148,149]Pm, and [sup 151]Sm, which act as branching points in the [ital s]-process path. Based on these results, the [ital s]-process flow in the Nd-Pm-Sm region is discussed with respect to the neutron density during stellar helium burning and to isotopic anomalies in meteorites. The updated [ital s]-abundances are also used for a discussion of [ital r]- and [ital p]-process residuals.

  17. Nuclear tracks, SM isotopes and neutron capture effects in the Elephant Morraine shergottite

    NASA Astrophysics Data System (ADS)

    Rajan, R. S.; Lugmair, G.; Tamhane, A. S.; Poupeau, G.

    1986-06-01

    Nuclear track studies, uranium concentration measurements and Sm-isotope studies have been performed on both lithologies A and B of the Elephant Morraine shergottite, EETA 79001. Track studies show that EETA 79001 was a rather small object in space with a preatmospheric radius of 12 + or - 2 cm, corresponding to a preatmospheric mass of 28 + or - 13 kg. Phosphates have U concentrations ranging from 0.3 to 1.3 ppm. There are occasional phosphates with excess fission tracks, possibly produced from neutron-induced fission of U and Th, during the regolith exposure in the shergottite parent body (SPB). Sm-isotope studies, while not showing any clear-cut excess in Sm-150, make it possible to derive meaningful upper limits to thermal neutron fluences of 2 to 3 x 10 to the 15th n/sq cm, during a possible regolith irradiation. These limits are consistent with the track data and also make it possible to derive an upper limit to the neutron exposure age of EETA 79001 of 55 Myr in the SPB regolith.

  18. Nuclear tracks, Sm isotopes and neutron capture effects in the Elephant Morraine shergottite

    NASA Technical Reports Server (NTRS)

    Rajan, R. S.; Lugmair, G.; Tamhane, A. S.; Poupeau, G.

    1986-01-01

    Nuclear track studies, uranium concentration measurements and Sm-isotope studies have been performed on both lithologies A and B of the Elephant Morraine shergottite, EETA 79001. Track studies show that EETA 79001 was a rather small object in space with a preatmospheric radius of 12 + or - 2 cm, corresponding to a preatmospheric mass of 28 + or - 13 kg. Phosphates have U concentrations ranging from 0.3 to 1.3 ppm. There are occasional phosphates with excess fission tracks, possibly produced from neutron-induced fission of U and Th, during the regolith exposure in the shergottite parent body (SPB). Sm-isotope studies, while not showing any clear-cut excess in Sm-150, make it possible to derive meaningful upper limits to thermal neutron fluences of 2 to 3 x 10 to the 15th n/sq cm, during a possible regolith irradiation. These limits are consistent with the track data and also make it possible to derive an upper limit to the neutron exposure age of EETA 79001 of 55 Myr in the SPB regolith.

  19. 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.

  20. Nucleon-nucleon momentum-correlation function as a probe of the density distribution of valence neutrons in neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Cao, X. G.; Cai, X. Z.; Ma, Y. G.; Fang, D. Q.; Zhang, G. Q.; Guo, W.; Chen, J. G.; Wang, J. S.

    2012-10-01

    Proton-neutron, neutron-neutron, and proton-proton momentum-correlation functions (Cpn,Cnn, and Cpp) are systematically investigated for 15C and other C-isotope-induced collisions at different entrance channel conditions within the framework of the isospin-dependent quantum-molecular-dynamics model complemented by the correlation after burner (crab) computation code. 15C is a prime exotic nucleus candidate due to the weakly bound valence neutron coupling with closed-neutron-shell nucleus 14C. To study density dependence of the correlation function by removing the isospin effect, the initialized 15C projectiles are sampled from two kinds of density distribution from the relativistic mean-field (RMF) model in which the valence neutron of 15C is populated in both 1d5/2 and 2s1/2 states, respectively. The results show that the density distributions of the valence neutron significantly influence the nucleon-nucleon momentum-correlation function at large impact parameters and high incident energies. The extended density distribution of the valence neutron largely weakens the strength of the correlation function. The size of the emission source is extracted by fitting the correlation function by using the Gaussian source method. The emission source size as well as the size of the final-state phase space are larger for projectile samplings from more extended density distributions of the valence neutron, which corresponds to the 2s1/2 state in the RMF model. Therefore, the nucleon-nucleon momentum-correlation function can be considered as a potentially valuable tool to diagnose exotic nuclear structures, such as the skin and halo.

  1. Calcium isotope evidence for suppression of carbonate dissolution in carbonate-bearing organic-rich sediments

    NASA Astrophysics Data System (ADS)

    Turchyn, Alexandra V.; DePaolo, Donald J.

    2011-11-01

    Pore fluid calcium isotope, calcium concentration and strontium concentration data are used to measure the rates of diagenetic dissolution and precipitation of calcite in deep-sea sediments containing abundant clay and organic material. This type of study of deep-sea sediment diagenesis provides unique information about the ultra-slow chemical reactions that occur in natural marine sediments that affect global geochemical cycles and the preservation of paleo-environmental information in carbonate fossils. For this study, calcium isotope ratios (δ 44/40Ca) of pore fluid calcium from Ocean Drilling Program (ODP) Sites 984 (North Atlantic) and 1082 (off the coast of West Africa) were measured to augment available pore fluid measurements of calcium and strontium concentration. Both study sites have high sedimentation rates and support quantitative sulfate reduction, methanogenesis and anaerobic methane oxidation. The pattern of change of δ 44/40Ca of pore fluid calcium versus depth at Sites 984 and 1082 differs markedly from that of previously studied deep-sea Sites like 590B and 807, which are composed of nearly pure carbonate sediment. In the 984 and 1082 pore fluids, δ 44/40Ca remains elevated near seawater values deep in the sediments, rather than shifting rapidly toward the δ 44/40Ca of carbonate solids. This observation indicates that the rate of calcite dissolution is far lower than at previously studied carbonate-rich sites. The data are fit using a numerical model, as well as more approximate analytical models, to estimate the rates of carbonate dissolution and precipitation and the relationship of these rates to the abundance of clay and organic material. Our models give mutually consistent results and indicate that calcite dissolution rates at Sites 984 and 1082 are roughly two orders of magnitude lower than at previously studied carbonate-rich sites, and the rate correlates with the abundance of clay. Our calculated rates are conservative for these

  2. 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.

  3. Alpha decay and cluster decay of some neutron-rich actinide nuclei

    NASA Astrophysics Data System (ADS)

    Carmel Vigila Bai, G. M.; Agnes, R. Nithya

    2017-03-01

    Nuclei in the actinide region are good in exhibiting cluster radioactivity. In the present work, the half-lives of α-decay and heavy cluster emission from certain actinide nuclei have been calculated using cubic plus Yukawa plus exponential model (CYEM). Our model has a cubic potential for the overlapping region which is smoothly connected by a Yukawa plus exponential potential for the region after separation. The computed half-lives are compared with those of other theoretical models and are found to be in good agreement with each other. In this work, we have also studied the deformation effects on half-lives of cluster decay. These deformation effects lower the half-life values and it is also found that the neutron-rich parent nuclei slow down the cluster decay process. Geiger-Nuttal plots for various clusters are found to be linear and most of the emitted clusters are α-like nuclei.

  4. Stellar electron capture rates on neutron-rich nuclei and their impact on stellar core collapse

    NASA Astrophysics Data System (ADS)

    Raduta, Ad. R.; Gulminelli, F.; Oertel, M.

    2017-02-01

    During the late stages of gravitational core-collapse of massive stars, extreme isospin asymmetries are reached within the core. Due to the lack of microscopic calculations of electron-capture (EC) rates for all relevant nuclei, in general simple analytic parametrizations are employed. We study here several extensions of these parametrizations, allowing for a temperature, electron density, and isospin dependence as well as for odd-even effects. The latter extra degrees of freedom considerably improve the agreement with large-scale microscopic rate calculations. We find, in particular, that the isospin dependence leads to a significant reduction of the global EC rates during core collapse with respect to fiducial results, where rates optimized on calculations of stable f p -shell nuclei are used. Our results indicate that systematic microscopic calculations and experimental measurements in the N ≈50 neutron-rich region are desirable for realistic simulations of the core collapse.

  5. Awareness, Preference, Utilization, and Messaging Research for the Spallation Neutron Source and High Flux Isotope Reactor

    SciTech Connect

    Bryant, Rebecca; Kszos, Lynn A

    2011-03-01

    Oak Ridge National Laboratory (ORNL) offers the scientific community unique access to two types of world-class neutron sources at a single site - the Spallation Neutron Source (SNS) and the High Flux Isotope Reactor (HFIR). The 85-MW HFIR provides one of the highest steady-state neutron fluxes of any research reactor in the world, and the SNS is one of the world's most intense pulsed neutron beams. Management of these two resources is the responsibility of the Neutron Sciences Directorate (NScD). NScD commissioned this survey research to develop baseline information regarding awareness of and perceptions about neutron science. Specific areas of investigative interest include the following: (1) awareness levels among those in the scientific community about the two neutron sources that ORNL offers; (2) the level of understanding members of various scientific communities have regarding benefits that neutron scattering techniques offer; and (3) any perceptions that negatively impact utilization of the facilities. NScD leadership identified users of two light sources in North America - the Advanced Photon Source (APS) at Argonne National Laboratory and the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory - as key publics. Given the type of research in which these scientists engage, they would quite likely benefit from including the neutron techniques available at SNS and HFIR among their scientific investigation tools. The objective of the survey of users of APS, NSLS, SNS, and HFIR was to explore awareness of and perceptions regarding SNS and HFIR among those in selected scientific communities. Perceptions of SNS and FHIR will provide a foundation for strategic communication plan development and for developing key educational messages. The survey was conducted in two phases. The first phase included qualitative methods of (1) key stakeholder meetings; (2) online interviews with user administrators of APS and NSLS; and (3) one-on-one interviews

  6. SUPERBURST MODELS FOR NEUTRON STARS WITH HYDROGEN- AND HELIUM-RICH ATMOSPHERES

    SciTech Connect

    Keek, L.; Heger, A.; In 't Zand, J. J. M.

    2012-06-20

    Superbursts are rare day-long type I X-ray bursts due to carbon flashes on accreting neutron stars in low-mass X-ray binaries. They heat the neutron star envelope such that the burning of accreted hydrogen and helium becomes stable, and the common shorter X-ray bursts are quenched. Short bursts reappear only after the envelope cools down. We study multi-zone one-dimensional models of the neutron star envelope, in which we follow carbon burning during the superburst, and we include hydrogen and helium burning in the atmosphere above. We investigate the cases of both a solar-composition and a helium-rich atmosphere. This allows us to study for the first time a wide variety of thermonuclear burning behavior as well as the transitions between the different regimes in a self-consistent manner. For solar composition, burst quenching ends much sooner than previously expected. This is because of the complex interplay between the 3{alpha}, hot CNO, and CNO breakout reactions. Stable burning of hydrogen and helium transitions via marginally stable burning (mHz quasi-periodic oscillations) to less energetic bursts with short recurrence times. We find a short-lived bursting mode where weaker and stronger bursts alternate. Eventually the bursting behavior changes back to that of the pre-superburst bursts. Because of the scarcity of observations, this transition has not been directly detected after a superburst. Using the MINBAR burst catalog we identify the shortest upper limit on the quenching time for 4U 1636-536, and derive further constraints on the timescale on which bursts return.

  7. First Results From GRIFFIN: Half-Lives of Neutron Rich 128-130Cd

    NASA Astrophysics Data System (ADS)

    Dunlop, Ryan; Griffin Collaboration

    2016-09-01

    Half-lives of N = 82 nuclei below doubly-magic 132Sn are key input parameters for any astrophysical r-process scenario and play an important role in the formation and shape of the second r-process abundance peak. Shell-model calculations for neutron-rich nuclei near the N = 82 neutron shell closure that are not yet experimentally accessible have been performed by adjusting the quenching of the Gamow-Teller (GT) operator to reproduce the 130Cd half-life. The calculated half-lives of other nuclei in the region are known to be systematically too long. Recently, a shorter half-life for 130Cd was measured by the EURICA collaboration that resolves this discrepancy by scaling the GT quenching by a constant factor for all of the nuclei in the region. Distinguishing between these discrepant half-life measurements for 130Cd is thus of critical importance. We have measured the half-lives of 128-130Cd using the high-efficiency GRIFFIN γ-ray spectrometer at TRIUMF, which improves the precision of the 128,129Cd half-lives, and confirms the shorter half-life of 130Cd recently reported by the EURICA collaboration. Details of the GRIFFIN experiments will be presented and the implications of the resulting half-lives discussed.

  8. Intruder negative-parity states of neutron-rich {sup 33}Si

    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.; Bouhelal, M.; Caurier, E.; Curien, D.; Nowacki, F.; Azaiez, F.; Ibrahim, F.; Verney, D.; Behera, B. R.; Corradi, L.

    2010-06-15

    Yrast states in the neutron-rich {sub 14}{sup 33}Si{sub 19} 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. An experimental setup that combines the large-acceptance magnetic spectrometer PRISMA and the high-efficiency gamma-ray detection array CLARA was used in the experiment. Four new gamma-ray photopeaks at energies of 971, 1724, 1772, and 2655 keV were observed and assigned to the {sup 33}Si level scheme. The experimental level scheme is compared with the results of 1(Planck constant/2pi)omega p-sd-pf large-scale shell-model calculations using the recently developed PSDPFB effective interaction; good agreement is obtained. The structure of the populated states of {sup 33}Si is discussed within the context of an odd neutron coupled to states of the {sup 32}Si core.

  9. 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.

  10. 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.

  11. 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.

  12. {beta}-decay in neutron-deficient Hg, Pb, and Po isotopes

    SciTech Connect

    Moreno, O.; Sarriguren, P.; Alvarez-Rodriguez, R.; Guerra, E. Moya de

    2006-05-15

    The effect of nuclear deformation on the energy distributions of the Gamow-Teller strength is studied in neutron-deficient Hg, Pb, and Po even isotopes. The theoretical framework is based on a self-consistent deformed Skyrme Hartree-Fock mean field with pairing correlations between like nucleons in BCS approximation and residual spin-isospin interactions treated in the proton-neutron quasiparticle random-phase approximation. After a systematic study of the Gamow-Teller strength distributions in the low-excitation-energy region, relevant for {beta}{sup +} decay, we have identified the best candidates to look for deformation signatures in their {beta}{sup +}-decay patterns. {beta}{sup +} half-lives and total Gamow-Teller strengths B(GT{sup {+-}}) are analyzed as well.

  13. Stellar Neutron Capture Cross Sections of the Lu and Hf Isotopes

    SciTech Connect

    Wisshak, K.; Voss, F.; Kaeppeler, F.; Kazakov, L.; Krticka, M.

    2005-05-24

    The neutron capture cross sections of 175,176Lu and 176,177,178,179,180Hf have been measured in the energy range from 3 to 225 keV at the Karlsruhe 3.7 MV Van de Graaff accelerator relative to the gold standard. Neutrons were produced by the 7Li(p,n)7Be reaction and capture events were detected by the Karlsruhe 4{pi}BaF2 detector. The cross section ratios could be determined with uncertainties between 0.9 and 1.8% about a factor of five more accurate than previous data. A strong population of isomeric states was found in neutron capture of the Hf isotopes, which are only partially explained by CASINO/GEANT simulations based on the known level schemes.Maxwellian averaged neutron capture cross sections were calculated for thermal energies between kT = 8 keV and 100 keV. Severe differences up to40% were found to the data of a recent evaluation based on existing experimental results. The new data allow for a much more reliable analysis of the important branching in the s-process synthesis path at 176Lu which can be interpreted as an s-process thermometer.

  14. Neutron capture cross-section studies of Tellurium isotopes for neutrinoless double beta decay applications

    NASA Astrophysics Data System (ADS)

    Bhike, Megha; Tornow, Werner

    2014-09-01

    The CUORE detector at Gran Sasso, aimed at searching for neutrinoless double-beta decay of 130Te, employs an array of TeO2 bolometer modules. To understand and identify the contribution of muon and (α,n) induced neutrons to the CUORE background, fast neutron cature cross-section data of the tellurium isotopes 126Te, 128Te and 130Te have been measured with the activation method at eight different energies in the neutron energy range 0.5-7.5 MeV. Plastic pill boxes of diameter 1.6 cm and width 1 cm containing Te were irradiated with mono-energetic neutrons produced via the 3H(p,n)3He and 2H(d,n)3He reactions. The cross-sections were determined relative to the 197Au(n, γ)198Au and 115In(n,n')115m In standard cross sections. The activities of the products were measured using 60% lead-shielded HPGe detectors at TUNL's low background counting facility. The present results are compared with the evaluated data from TENDL-2012, ENDF/B-VII.1, JEFF-3.2 and JENDL-4.0, as well as with literature data.

  15. EVALUATION OF NEUTRON CROSS SECTIONS FOR A COMPLETE SET OF Nd ISOTOPES.

    SciTech Connect

    KIM,H.; HERMAN, M.; MUGHABGHAB, S.F.; OBLOZINSKY, P.; ROCHMAN, D.; LEE. Y.-O.

    2007-10-29

    Neutron cross sections for a complete set of Nd isotopes, {sup 142,143,144,145,146,147,148,150}Nd, were evaluated in the incident energy range from 10{sup -5} eV to 20 MeV. In the low energy region, including thermal and resolved resonances, our evaluations are based on the latest data published in the Atlas of Neutron Resonances. In the unresolved resonance region we performed additional evaluation by using the averages of the resolved resonances and adjusting them to the experimental data. In the fast neutron region, we used the nuclear reaction model code EMPIRE-2.19 validated against the experimental data. The results are compared to the existing nuclear data libraries, including ENDF/B-VI.8, JENDL-3.3 and JEFF-3.1, and to the available experimental data. The new evaluations are suitable for neutron transport calculations and they were adopted by the new evaluated nuclear data file of the United States, ENDF/B-VII.0, released in December 2006.

  16. Cross sections for fast-neutron interaction with Lu, Tb, and Ta isotopes

    SciTech Connect

    Dzysiuk, N.; Kadenko, I.; Yermolenko, R.; Koning, A. J.

    2010-01-15

    The cross sections for (n,x) reactions with Lu, Tb, and Ta isotopes were measured at (d,t) neutron energies around 14 MeV with the activation technique using metal foils of natural composition. Additionally, tantalum samples were irradiated with (d,d) neutrons and filtered neutron beams. To ensure an acceptable precision of the results all major sources of uncertainties were taken into account. Calculations of efficiency and correction factors were performed with the Monte Carlo technique. The cross section results obtained for the {sup 175}Lu(n,{alpha}){sup 172}Tm reaction at (d,t) neutron energies are reported for the first time. {sup 181}Ta(n,{gamma}){sup 182}Ta{sup m2} reaction cross sections were also measured for the first time at 1.9, 58.7, and 144.3 keV and at 2.85 MeV. The earlier evaluated cross section upper estimate for the nuclear reaction {sup 159}Tb(n,n{sup '}{alpha}){sup 155}Eu is reported in this article to be one order lower. Some other cross sections were obtained with higher precision. Theoretical calculations of excitation functions were performed with the TALYS-1.0 code and compared with the experimental cross section values.

  17. Ca isotope variations in Allende

    NASA Technical Reports Server (NTRS)

    Jungck, M. H. A.; Shimamura, T.; Lugmair, G. W.

    1984-01-01

    Ca-isotope measurements of Allende Ca-Al-rich inclusions (CAIs), together with those on an apatite-enriched fraction from Orgueil, indicate the existence of widespread excesses on the neutron-rich isotope Ca-48. Isotopic anomalies are noted in 7 out of 11 CAIs analyzed. This abundance of isotopic excesses places Ca alongside Ti and O, although no clear correlation has yet been found between Ca-48 and Ti-50, which are thought to be coproduced by neutron-rich nucleosynthetic processes within stars. It is suggested that the higher volatility of Ca, by comparison with Ti compounds, led to a variable dilution with isotopically normal Ca in vaporization and recondensation processes in stellar envelopes, the interstellar medium, and/or the solar nebula.

  18. Deformation in the neutron-deficient rare earth isotopes: Radioactive decay scheme studies in the neodymium, promethium, and samarium isotopes

    SciTech Connect

    Breitenbach, J.B.

    1993-12-31

    Several experiments were performed at the UNISOR isotope separator facility at HHIRF at the Oak Ridge National Laboratory on the {beta}{sup +}/EC decay of neutron-deficient rare earth isotopes. Data for the decay chain {sup 133}Sm {yields} {sup 133}Pm {yields} {sup 133}Nd was obtained, consisting of multiscaled spectra of {gamma} rays, X rays, and conversion electrons, as well as {gamma}{gamma}t, X{gamma}t, e{gamma}t and eXt coincidences. Gamma rays associated with the decay of {sup 133}Sm and {sup 133}Pm were observed for the first time. The decay of a new low-spin (1/2) isomeric state, with a half life of about 70 sec was established for {sup 133}Nd. The level schemes for {sup 133}Nd and {sup 133}Pr were constructed. An M3 and two E1 isomers are established in {sup 133}Nd and an E3 isomer is confirmed in {sup 133}Pr. The energy level systematics for the nuclear region bounded by Z {ge} 58 and N {le} 78 is discussed. Theoretical interpretations are based on the particle-plus-triaxial rotor model calculations. In the framework of these calculations, the {beta}{sub 2} deformation is moderate for these nuclei ({beta}{sub 2} {approx} 0.20-0.25). A sudden onset of strong deformation is not observed, in contrast with the theoretical predictions by Leander and Moeller [Lea82].

  19. Nuclear moments and charge radii of neutron-deficient francium isotopes and isomers

    NASA Astrophysics Data System (ADS)

    Voss, A.; Buchinger, F.; Cheal, B.; Crawford, J. E.; Dilling, J.; Kortelainen, M.; Kwiatkowski, A. A.; Leary, A.; Levy, C. D. P.; Mooshammer, F.; Ojeda, M. L.; Pearson, M. R.; Procter, T. J.; Tamimi, W. Al

    2015-04-01

    Collinear laser fluorescence spectroscopy has been performed on the ground and isomeric states of Fr,206204 in order to determine their spins, nuclear moments, and changes in mean-squared charge radii. A new experimental technique has been developed as part of this work which much enhances the data collection rate while maintaining the high resolution. This has permitted the extension of this study to the two isomeric states in each nucleus. The investigation of nuclear g factors and mean-squared charge radii indicates that the neutron-deficient Fr isotopes lie in a transitional region from spherical towards more collective structures.

  20. Neutron Spectral Brightness of Cold Guide 4 at the High Flux Isotope Reactor

    NASA Astrophysics Data System (ADS)

    Winn, B. L.; Robertson, J. L.; Iverson, E. B.; Selby, D. L.

    2010-11-01

    The High Flux Isotope Reactor resumed operation in June of 2007 with a supercritical hydrogen cold source in horizontal beam tube 4. Cold guide 4 is a guide system designed to deliver neutrons from this source with a reasonable flux at wavelengths greater than 4 Å to several instruments, and includes a 15-m, 96-section, 4-channel bender. A time-of-flight spectrum with calibrated detector was recorded at port C of cold guide 4, and compared to McStas simulations, to generate a brightness spectrum.

  1. 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.

  2. Deformation and mixing of coexisting shapes in neutron-deficient polonium isotopes

    NASA Astrophysics Data System (ADS)

    Kesteloot, N.; Bastin, B.; Gaffney, L. P.; Wrzosek-Lipska, K.; Auranen, K.; Bauer, C.; Bender, M.; Bildstein, V.; Blazhev, A.; Bönig, S.; Bree, N.; Clément, E.; Cocolios, T. E.; Damyanova, A.; Darby, I.; De Witte, H.; Di Julio, D.; Diriken, J.; Fransen, C.; García-Ramos, J. E.; Gernhäuser, R.; Grahn, T.; Heenen, P.-H.; Hess, H.; Heyde, K.; Huyse, M.; Iwanicki, J.; Jakobsson, U.; Konki, J.; Kröll, T.; Laurent, B.; Lecesne, N.; Lutter, R.; Pakarinen, J.; Peura, P.; Piselli, E.; Próchniak, L.; Rahkila, P.; Rapisarda, E.; Reiter, P.; Scheck, M.; Seidlitz, M.; Sferrazza, M.; Siebeck, B.; Sjodin, M.; Tornqvist, H.; Traykov, E.; Van De Walle, J.; Van Duppen, P.; Vermeulen, M.; Voulot, D.; Warr, N.; Wenander, F.; Wimmer, K.; Zielińska, M.

    2015-11-01

    Coulomb-excitation experiments are performed with postaccelerated beams of neutron-deficient Po 196 ,198 ,200 ,202 isotopes at the REX-ISOLDE facility. A set of matrix elements, coupling the low-lying states in these isotopes, is extracted. In the two heaviest isotopes, Po,202200, the transitional and diagonal matrix elements of the 21+ state are determined. In Po,198196 multistep Coulomb excitation is observed, populating the 41+,02+ , and 22+ states. The experimental results are compared to the results from the measurement of mean-square charge radii in polonium isotopes, confirming the onset of deformation from 196Po onwards. Three model descriptions are used to compare to the data. Calculations with the beyond-mean-field model, the interacting boson model, and the general Bohr Hamiltonian model show partial agreement with the experimental data. Finally, calculations with a phenomenological two-level mixing model hint at the mixing of a spherical structure with a weakly deformed rotational structure.

  3. Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

    PubMed Central

    Van Kooten, Elishevah M. M. E.; Wielandt, Daniel; Schiller, Martin; Nagashima, Kazuhide; Thomen, Aurélien; Olsen, Mia B.; Nordlund, Åke; Krot, Alexander N.; Bizzarro, Martin

    2016-01-01

    The short-lived 26Al radionuclide is thought to have been admixed into the initially 26Al-poor protosolar molecular cloud before or contemporaneously with its collapse. Bulk inner Solar System reservoirs record positively correlated variability in mass-independent 54Cr and 26Mg*, the decay product of 26Al. This correlation is interpreted as reflecting progressive thermal processing of in-falling 26Al-rich molecular cloud material in the inner Solar System. The thermally unprocessed molecular cloud matter reflecting the nucleosynthetic makeup of the molecular cloud before the last addition of stellar-derived 26Al has not been identified yet but may be preserved in planetesimals that accreted in the outer Solar System. We show that metal-rich carbonaceous chondrites and their components have a unique isotopic signature extending from an inner Solar System composition toward a 26Mg*-depleted and 54Cr-enriched component. This composition is consistent with that expected for thermally unprocessed primordial molecular cloud material before its pollution by stellar-derived 26Al. The 26Mg* and 54Cr compositions of bulk metal-rich chondrites require significant amounts (25–50%) of primordial molecular cloud matter in their precursor material. Given that such high fractions of primordial molecular cloud material are expected to survive only in the outer Solar System, we infer that, similarly to cometary bodies, metal-rich carbonaceous chondrites are samples of planetesimals that accreted beyond the orbits of the gas giants. The lack of evidence for this material in other chondrite groups requires isolation from the outer Solar System, possibly by the opening of disk gaps from the early formation of gas giants. PMID:26858438

  4. Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites.

    PubMed

    Van Kooten, Elishevah M M E; Wielandt, Daniel; Schiller, Martin; Nagashima, Kazuhide; Thomen, Aurélien; Larsen, Kirsten K; Olsen, Mia B; Nordlund, Åke; Krot, Alexander N; Bizzarro, Martin

    2016-02-23

    The short-lived (26)Al radionuclide is thought to have been admixed into the initially (26)Al-poor protosolar molecular cloud before or contemporaneously with its collapse. Bulk inner Solar System reservoirs record positively correlated variability in mass-independent (54)Cr and (26)Mg*, the decay product of (26)Al. This correlation is interpreted as reflecting progressive thermal processing of in-falling (26)Al-rich molecular cloud material in the inner Solar System. The thermally unprocessed molecular cloud matter reflecting the nucleosynthetic makeup of the molecular cloud before the last addition of stellar-derived (26)Al has not been identified yet but may be preserved in planetesimals that accreted in the outer Solar System. We show that metal-rich carbonaceous chondrites and their components have a unique isotopic signature extending from an inner Solar System composition toward a (26)Mg*-depleted and (54)Cr-enriched component. This composition is consistent with that expected for thermally unprocessed primordial molecular cloud material before its pollution by stellar-derived (26)Al. The (26)Mg* and (54)Cr compositions of bulk metal-rich chondrites require significant amounts (25-50%) of primordial molecular cloud matter in their precursor material. Given that such high fractions of primordial molecular cloud material are expected to survive only in the outer Solar System, we infer that, similarly to cometary bodies, metal-rich carbonaceous chondrites are samples of planetesimals that accreted beyond the orbits of the gas giants. The lack of evidence for this material in other chondrite groups requires isolation from the outer Solar System, possibly by the opening of disk gaps from the early formation of gas giants.

  5. Operando Lithium Dynamics in the Li-Rich Layered Oxide Cathode Material via Neutron Diffraction

    SciTech Connect

    Liu, Haodong; An, Ke; Venkatachalam, Subramanian; Qian, Danna; Zhang, Minghao; Meng, Ying Shirley

    2016-04-06

    Neutron diffraction under operando battery cycling is used to study the lithium and oxygen dynamics of high Li-rich Li(Lix/3Ni(3/8-3x/8)Co(1/4-x/4)Mn(3/8+7x/24)O2 (x = 0.6, HLR) and low Li-rich Li(Lix/3Ni(1/3-x/3)Co(1/3-x/3)Mn(1/3+x/3)O2 (x = 0.24, LLR) compounds that exhibit different degrees of oxygen activation at high voltage. The measured lattice parameter changes and oxygen position show largely contrasting changes for the two cathodes where the LLR exhibits larger movement of oxygen and lattice contractions in comparison to the HLR that maintains relatively constant lattice parameters and oxygen position during the high voltage plateau until the end of charge. Density functional theory calculations show the presence of oxygen vacancy during the high voltage plateau; changes in the lattice parameters and oxygen position are consistent with experimental observations. Lithium migration kinetics for the Li-rich material is observed under operando conditions for the first time to reveal the rate of lithium extraction from the lithium layer, and transition metal layer is related to the different charge and discharge characteristics. At the beginning of charging, the lithium extraction predominately occurs within the lithium layer. The lithium extraction from the lithium layer slows down and extraction from the transition metal layer evolves at a faster rate once the high voltage plateau is reached.

  6. Operando Lithium Dynamics in the Li-Rich Layered Oxide Cathode Material via Neutron Diffraction

    DOE PAGES

    Liu, Haodong; An, Ke; Venkatachalam, Subramanian; ...

    2016-04-06

    Neutron diffraction under operando battery cycling is used to study the lithium and oxygen dynamics of high Li-rich Li(Lix/3Ni(3/8-3x/8)Co(1/4-x/4)Mn(3/8+7x/24)O2 (x = 0.6, HLR) and low Li-rich Li(Lix/3Ni(1/3-x/3)Co(1/3-x/3)Mn(1/3+x/3)O2 (x = 0.24, LLR) compounds that exhibit different degrees of oxygen activation at high voltage. The measured lattice parameter changes and oxygen position show largely contrasting changes for the two cathodes where the LLR exhibits larger movement of oxygen and lattice contractions in comparison to the HLR that maintains relatively constant lattice parameters and oxygen position during the high voltage plateau until the end of charge. Density functional theory calculations show the presencemore » of oxygen vacancy during the high voltage plateau; changes in the lattice parameters and oxygen position are consistent with experimental observations. Lithium migration kinetics for the Li-rich material is observed under operando conditions for the first time to reveal the rate of lithium extraction from the lithium layer, and transition metal layer is related to the different charge and discharge characteristics. At the beginning of charging, the lithium extraction predominately occurs within the lithium layer. The lithium extraction from the lithium layer slows down and extraction from the transition metal layer evolves at a faster rate once the high voltage plateau is reached.« less

  7. Fabrication and characterization of novel boron and gadolinium rich power generation and real-time neutron detection materials and devices

    NASA Astrophysics Data System (ADS)

    Natta, Marcus L.

    In this work, the neutron capture capabilities of two naturally occurring isotopes, gadolinium-157 (157Gd) and boron-10 (10B), were investigated for use as neutron detecting diodes. The appeal of using 157Gd and 10B is due to their large thermal neutron absorption cross sections: gadolinium (on average ˜46,000 barns) and boron-10 (˜3800 barns). Boron carbide (B4C) films were grown on nickel, copper, silver, and aluminum substrates using plasma enhanced chemical vapor deposition (PECVD) techniques forming p-n junctions using various configurations of two isomers: closo-1,7-dicarbadodecaborane (metacarborane) or closo-1,7-phosphacaborane (phosphacarborane) for the n-type layers and closo-1,2-dicarbadodecaborane (orthocarborane) for the p-type layer. These all-boron carbide heterojunction diodes were investigated experimentally, with highly sensitive current voltage measurements in light and dark and under alpha, beta, and neutron irradiation. The heteroisomeric diodes exhibited photovoltaic and alphavoltaic behavior and successfully functioned as neutron detectors. Preliminary results of beta radiation response of these heteroisomeric diodes is also presented. The high-kappa dielectric oxide, hafnium oxide (HfO2), was doped with gadolinium and grown on silicon using pulsed laser deposition (PLD) to form a novel semiconducting diode. Three levels of Gd-doping (3%, 10%, and 15%) were explored. A shift from the unstable monoclinic phase to the stable cubic phase is seen with increased Gd-doping concentrations, which may possibly serve as a better semiconductor. The detection of charge pulses created by neutron capture was explored using neutron sources from Nebraska Wesleyan University and The Ohio State University Research Reactor (OSURR) neutron sources. The 10% and 15% doped diodes exhibited pulse height spectra in the presence of neutrons. Electronic signal processing remains the most significant challenge for these latter detectors.

  8. Zinc isotope evidence for sulfate-rich fluid transfer across subduction zones

    NASA Astrophysics Data System (ADS)

    Pons, Marie-Laure; Debret, Baptiste; Bouilhol, Pierre; Delacour, Adélie; Williams, Helen

    2016-12-01

    Subduction zones modulate the chemical evolution of the Earth's mantle. Water and volatile elements in the slab are released as fluids into the mantle wedge and this process is widely considered to result in the oxidation of the sub-arc mantle. However, the chemical composition and speciation of these fluids, which is critical for the mobility of economically important elements, remain poorly constrained. Sulfur has the potential to act both as oxidizing agent and transport medium. Here we use zinc stable isotopes (δ66Zn) in subducted Alpine serpentinites to decipher the chemical properties of slab-derived fluids. We show that the progressive decrease in δ66Zn with metamorphic grade is correlated with a decrease in sulfur content. As existing theoretical work predicts that Zn-SO42- complexes preferentially incorporate heavy δ66Zn, our results provide strong evidence for the release of oxidized, sulfate-rich, slab serpentinite-derived fluids to the mantle wedge.

  9. Zinc isotope evidence for sulfate-rich fluid transfer across subduction zones

    PubMed Central

    Pons, Marie-Laure; Debret, Baptiste; Bouilhol, Pierre; Delacour, Adélie; Williams, Helen

    2016-01-01

    Subduction zones modulate the chemical evolution of the Earth's mantle. Water and volatile elements in the slab are released as fluids into the mantle wedge and this process is widely considered to result in the oxidation of the sub-arc mantle. However, the chemical composition and speciation of these fluids, which is critical for the mobility of economically important elements, remain poorly constrained. Sulfur has the potential to act both as oxidizing agent and transport medium. Here we use zinc stable isotopes (δ66Zn) in subducted Alpine serpentinites to decipher the chemical properties of slab-derived fluids. We show that the progressive decrease in δ66Zn with metamorphic grade is correlated with a decrease in sulfur content. As existing theoretical work predicts that Zn-SO42− complexes preferentially incorporate heavy δ66Zn, our results provide strong evidence for the release of oxidized, sulfate-rich, slab serpentinite-derived fluids to the mantle wedge. PMID:27982033

  10. Zinc isotope evidence for sulfate-rich fluid transfer across subduction zones.

    PubMed

    Pons, Marie-Laure; Debret, Baptiste; Bouilhol, Pierre; Delacour, Adélie; Williams, Helen

    2016-12-16

    Subduction zones modulate the chemical evolution of the Earth's mantle. Water and volatile elements in the slab are released as fluids into the mantle wedge and this process is widely considered to result in the oxidation of the sub-arc mantle. However, the chemical composition and speciation of these fluids, which is critical for the mobility of economically important elements, remain poorly constrained. Sulfur has the potential to act both as oxidizing agent and transport medium. Here we use zinc stable isotopes (δ(66)Zn) in subducted Alpine serpentinites to decipher the chemical properties of slab-derived fluids. We show that the progressive decrease in δ(66)Zn with metamorphic grade is correlated with a decrease in sulfur content. As existing theoretical work predicts that Zn-SO4(2-) complexes preferentially incorporate heavy δ(66)Zn, our results provide strong evidence for the release of oxidized, sulfate-rich, slab serpentinite-derived fluids to the mantle wedge.

  11. Charge radii and nuclear moments of neutron-deficient potassium isotopes

    NASA Astrophysics Data System (ADS)

    Minamisono, K.; Barquest, B. R.; Bollen, G.; Hughes, M.; Strum, R.; Tarazona, D.; Asberry, H. B.; Cooper, K.; Hammerton, K.; Klose, A.; Mantica, P. F.; Morrissey, D. J.; Geppert, Ch.; Harris, J.; Ringle, R.; Rodriguez, J. A.; Rossi, D. M.; Ryder, C. A.; Smith, A.; Schwarz, S.; Sumithrarachchi, C.

    2014-09-01

    The monotonic change of charge radii of K isotopes across N = 20 suggests a reduction of the shell gap. A systematic study of the charge radii and ground state magnetic and quadrupole moments of neutron-deficient 35-37K isotopes is underway at the BEam COoling and LAser spectroscopy (BECOLA) facility at NSCL/MSU to investigate the anomalous trend in charge radii. The K isotopes were produced by fragmentation of a 40Ca beam, thermalized in a linear gas cell, extracted at an energy of 30 keV, and transported to BECOLA. The K ion beam was cooled and bunched, and neutralized in a Na vapor cell. Laser-induced fluorescence was detected as a function of the Doppler-tuned laser frequency and time relative to the release of the beam bunch. The beta-NMR technique was used to determine ground-state nuclear moments, where hyperfine splittings are too small to resolve using collinear laser spectroscopy. The monotonic change of charge radii of K isotopes across N = 20 suggests a reduction of the shell gap. A systematic study of the charge radii and ground state magnetic and quadrupole moments of neutron-deficient 35-37K isotopes is underway at the BEam COoling and LAser spectroscopy (BECOLA) facility at NSCL/MSU to investigate the anomalous trend in charge radii. The K isotopes were produced by fragmentation of a 40Ca beam, thermalized in a linear gas cell, extracted at an energy of 30 keV, and transported to BECOLA. The K ion beam was cooled and bunched, and neutralized in a Na vapor cell. Laser-induced fluorescence was detected as a function of the Doppler-tuned laser frequency and time relative to the release of the beam bunch. The beta-NMR technique was used to determine ground-state nuclear moments, where hyperfine splittings are too small to resolve using collinear laser spectroscopy. This work was supported in part by NSF Grant No. PHY-11-02511.

  12. Precision Oxygen Isotope Measurements of Two C-Rich Hydrated Interplanetary Dust Particles

    NASA Technical Reports Server (NTRS)

    Snead, C. J.; Keller, L. P.; McKeegan, K. D.; Messenger, S.

    2016-01-01

    Introduction: Chondritic-smooth IDPs (Interplanetary Dust Particles) are low porosity objects whose mineralogy is dominated by aqueous alteration products such as Mg-rich phyllosilicates (smectite and serpentine group) and Mg-Fe carbonate minerals. Their hydrated mineralogy combined with low atmospheric entry velocities have been used to infer an origin largely from asteroidal sources. Spectroscopic studies show that the types and abundance of organic matter in CS IDPs is similar to that in CP IDPs. Although CS IDPs show broad similarities to primitive carbonaceous chondrites, only a few particles have been directly linked to specific meteorite groups such as CM and CI chondrites based on the presence of diagnostic minerals. Many CS IDPs however, have carbon contents that greatly exceed that of known meteorite groups suggesting that they either may derive from comets or represent samples of more primitive parent bodies than do meteorites. It is now recognized that many large, dark primitive asteroids in the outer main belt, as well as some trans-Neptunian objects, show spectroscopic evidence for aqueous alteration products on their surfaces. Some CS IDPs exhibit large bulk D enrichments similar to those observed in the cometary CP IDPs. While hydrated minerals in comets have not been unambiguously identified to date, the presence of the smectite group mineral nontronite has been inferred from infrared spectra obtained from the ejecta from comet 9P/Tempel 1 during the Deep Impact mission. Recent observations of low temperature sulfide minerals in Stardust mission samples suggest that limited aqueous activity occurred on comet Wild-2. All of these observations, taken together, suggest that the high-carbon hydrated IDPs are abundant and important samples of primitive solar system objects not represented in meteorite collections. Oxygen isotopic compositions of chondrites reflect mixing between a 16O-rich reservoir and a 17O,18O-rich reservoir produced via mass

  13. Reexamination of the neutron skin thickness using neutron removal cross sections

    SciTech Connect

    Ma Chunwang; Wei Huiling; Yu Mian

    2010-11-15

    The neutron removal cross section [{sigma}{sub -N}(Z)] is defined for the projectile-like fragment isotopes and extended to the lower Z isotopes in the projectile fragmentation reaction. The cross sections of fragments in 1 A GeV even {sup 42-52}Ca+{sup 12}C projectile fragmentation reactions are calculated using the statistical abrasion-ablation model. The correlations between {sigma}{sub -N}(Z) of different fragment isotopes and neutron skin thickness (S{sub n}) for finite neutron-rich nuclei are revisited. Good linear {sigma}{sub -N}(Z)-S{sub n} correlations are observed in fragment isotopes, and it is suggested that {sigma}{sub -N}(Z) be used as an observable to determine S{sub n} of neutron-rich nucleus in addition to {sigma}{sub -N} for isotopes of the projectile nucleus.

  14. Petrology, mineralogy, and oxygen isotope compositions of aluminum-rich chondrules from CV3 chondrites

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Hsu, Weibiao; Li, Xianhua; Li, Qiuli; Liu, Yu; Tang, Guoqiang

    2016-01-01

    Bulk major element composition, petrography, mineralogy, and oxygen isotope compositions of twenty Al-rich chondrules (ARCs) from five CV3 chondrites (Northwest Africa [NWA] 989, NWA 2086, NWA 2140, NWA 2697, NWA 3118) and the Ningqiang carbonaceous chondrite were studied and compared with those of ferromagnesian chondrules and refractory inclusions. Most ARCs are marginally Al-richer than ferromagnesian chondrules with bulk Al2O3 of 10-15 wt%. ARCs are texturally similar to ferromagnesian chondrules, composed primarily of olivine, pyroxene, plagioclase, spinel, Al-rich glass, and metallic phases. Minerals in ARCs have intermediate compositions. Low-Ca pyroxene (Fs0.6-8.8Wo0.7-9.3) has much higher Al2O3 and TiO2 contents (up to 12.5 and 2.3 wt%, respectively) than that in ferromagnesian chondrules. High-Ca pyroxene (Fs0.3-2.0Wo33-54) contains less Al2O3 and TiO2 than that in Ca,Al-rich inclusions (CAIs). Plagioclase (An77-99Ab1-23) is much more sodic than that in CAIs. Spinel is enriched in moderately volatile element Cr (up to 6.7 wt%) compared to that in CAIs. Al-rich enstatite coexists with anorthite and spinel in a glass-free chondrule, implying that the formation of Al-enstatite was not due to kinetic reasons but is likely due to the high Al2O3/CaO ratio (7.4) of the bulk chondrule. Three ARCs contain relict CAIs. Oxygen isotope compositions of ARCs are also intermediate between those of ferromagnesian chondrules and CAIs. They vary from -39.4‰ to 13.9‰ in δ18O and yield a best fit line (slope = 0.88) close to the carbonaceous chondrite anhydrous mineral (CCAM) line. Chondrules with 5-10 wt% bulk Al2O3 have a slightly more narrow range in δ18O (-32.5 to 5.9‰) along the CCAM line. Except for the ARCs with relict phases, however, most ARCs have oxygen isotope compositions (>-20‰ in δ18O) similar to those of typical ferromagnesian chondrules. ARCs are genetically related to both ferromagnesian chondrules and CAIs, but the relationship between ARCs and

  15. Neutron density distributions analyzed in terms of relativistic impulse approximation for nickel isotopes

    NASA Astrophysics Data System (ADS)

    Kaki, Kaori

    2015-03-01

    Observables of proton elastic scattering from nickel isotopes (48-82Ni) are calculated based on relativistic impulse approximation (RIA), and nuclear density distributions are provided by relativistic mean-field (RMF) calculations. Contributions of a medium effect and multiple scattering to observables are evaluated and shown to be small at incident proton energies from 200 MeV through 500 MeV so that it is confirmed to perform a model analysis based on the fundamental RIA calculation. For 58,60,62,64Ni isotopes, are considered proton distributions which are obtained by means of unfolding the charge form factor of proton from charge densities determined by the experiments of electron scattering. Through comparisons between results for the different proton densities, contributions of proton form factor to proton distributions and to elastic scattering observables at 300 MeV are discussed. It is shown that the neutron distribution is determined from the restricted observables, reaction cross-section and the first dip of differential cross-section, based on a model analysis of Woods-Saxon distribution in the case of 64Ni target at 300 MeV. Contributions of tensor density and empirical proton density are shown to obtaining the neutron distribution with the model analysis. Compared with the similar studies for 40,60Ca and 208Pb, problems of the model analysis, which arise out of errors in observables, are discussed.

  16. Changes in the mean-square charge radii and magnetic moments of neutron-deficient Tl isotopes

    NASA Astrophysics Data System (ADS)

    Barzakh, A. E.; Batist, L. Kh.; Fedorov, D. V.; Ivanov, V. S.; Mezilev, K. A.; Molkanov, P. L.; Moroz, F. V.; Orlov, S. Yu.; Panteleev, V. N.; Volkov, Yu. M.

    2013-08-01

    In-source laser spectroscopy experiments for neutron-deficient thallium isotopes at the 276.9-nm atomic transition have been carried out at the Investigation of Radioactive Isotopes on Synchrocyclotron facility of Petersburg Nuclear Physics Institute. New data on isotope shifts and the hyperfine structure for 183-207Tl isotopes and isomers are presented. The changes in the mean-square charge radii and magnetic-moment values are deduced. It is shown that nuclear properties of Tl isotopes and isomers smoothly change at the neutron midshell and beyond without development of strong deformation in contrast to the adjacent Hg nuclei. A rather great isomer shift between I = 1/2 and I = 9/2 states for odd Tl isotopes is preserved for both sides of the previously investigated mass range. For the first time, a similar isomer shift is found for the odd-odd isotope 186Tl. The close resemblance of the charge radii isotopic behavior for the Tl and Pb ground states is demonstrated.

  17. Single-neutron orbits near 78Ni: Spectroscopy of the N=49 isotope 79Zn

    DOE PAGES

    Orlandi, R.; Mücher, D.; Raabe, R.; ...

    2014-12-09

    Single-neutron states in the Z=30, N=49 isotope 79Zn have been populated using the 78Zn(d, p)79Zn transfer reaction at REX-ISOLDE, CERN. The experimental setup allowed the combined detection of protons ejected in the reaction, and of γ rays emitted by 79Zn. The analysis reveals that the lowest excited states populated in the reaction lie at approximately 1 MeV of excitation, and involve neutron orbits above the N=50 shell gap. From the analysis of γ -ray data and of proton angular distributions, characteristic of the amount of angular momentum transferred, a 5/2+ configuration was assigned to a state at 983 keV. Comparisonmore » with large-scale-shell-model calculations supports a robust neutron N=50 shell-closure for 78Ni. Finally, these data constitute an important step towards the understanding of the magicity of 78Ni and of the structure of nuclei in the region.« less

  18. New Production Routes for Medical Isotopes 64Cu and 67Cu Using Accelerator Neutrons

    NASA Astrophysics Data System (ADS)

    Kin, Tadahiro; Nagai, Yasuki; Iwamoto, Nobuyuki; Minato, Futoshi; Iwamoto, Osamu; Hatsukawa, Yuichi; Segawa, Mariko; Harada, Hideo; Konno, Chikara; Ochiai, Kentaro; Takakura, Kosuke

    2013-03-01

    We have measured the activation cross sections producing 64Cu and 67Cu, promising medical radioisotopes for molecular imaging and radioimmunotherapy, by bombarding a natural zinc sample with 14 MeV neutrons. We estimated the production yields of 64Cu and 67Cu by fast neutrons from \\text{natC(d,n) with 40 MeV 5 mA deuterons. We used the present result together with the evaluated cross section of Zn isotopes. The calculated 64Cu yield is 1.8 TBq (175 g 64Zn) for 12 h of irradiation; the yields of 67Cu by 67Zn(n,p)67Cu and 68Zn(n,x)67Cu were 249 GBq (184 g 67Zn) and 287 GBq (186 g 68Zn) at the end of 2 days of irradiation, respectively. From the results, we proposed a new route to produce 67Cu with very little radionuclide impurity via the 68Zn(n,x)67Cu reaction, and showed the 64Zn(n,p)64Cu reaction to be a promising route to produce 64Cu. Both 67Cu and 64Cu are noted to be produced using fast neutrons.

  19. Determination of the scattering lengths of gallium isotopes by neutron interferometry with PNO-apparatus in JRR-3M

    NASA Astrophysics Data System (ADS)

    Tomimitsu, H.; Hasegawa, Y.; Aizawa, K.; Kikuta, S.

    1999-01-01

    For carrying out experiments in the field of the so-called precise neutron optics (PNO), we have implemented special multi-purpose apparatus called the "PNO-apparatus" at JRR-3M. Making use of an Si triple-Laue (LLL) neutron interferometer with the PNO-apparatus, we successfully determined the coherent neutron scattering lengths of gallium isotopes, 69Ga and 71Ga. The results are 8.053±0.013 fm for 69Ga and 6.170±0.011 fm for 71Ga, respectively.

  20. Description of the neutron deficient Sr and Zr isotopes in the interacting boson model

    NASA Astrophysics Data System (ADS)

    Bucurescu, D.; Cǎta, G.; Cutoiu, D.; Constantinescu, G.; Ivaşcu, M.; Zamfir, N. V.

    1983-05-01

    The available experimental data for the neutron deficient isotopes of Sr (78 to 86) and Zr (80 to 86) are collected and compared to the predictions of IBA-1 model calculations. The variations of the collectivity along these two isotopic chains is well reproduced with a set of smoothly varying parameters of the model. The description of both the energy levels and the B(E2) transition probabilities improves with decreasing N, the hamiltonian evolving towards an SU(3) dynamical symmetry. Both the large B(E2) value of the 2 1+ → 0 g.s.+ transition and the predicted prolate shape for the very light isotopes, agree well with the recent findings of superdeformed nuclei around Z, N ≈ 38. Transition strengths for the (p, t) reaction are calculated and compared to experimental observations for 0 + states, and a discussion is made about the possible intruder character of the 0 2+ state. The interacting boson-fermion approximation (IBFA) model is used to extend the calculations to some odd nuclei. Two shell (1g {9}/{2}, 2d {5}/{2}) calculations are performed for the positive-parity states in 83Sr, 81Sr and 85Y and they compare well with the experimental level scheme of these nuclei below 3 MeV excitation.

  1. 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.

  2. Excited State Properties in Neutron-rich Nuclei near N = 40

    NASA Astrophysics Data System (ADS)

    Crider, B. P.; Prokop, C. J.; Liddick, S. N.; Chiara, C. J.; Ayangeakaa, A. D.; Carroll, J. J.; Chen, J.; David, H. M.; Go, S.; Grzywacz, R.; Harker, J.; Janssens, R. V. F.; Lauritsen, T.; Seweryniak, D.; Walters, W. B.

    2015-10-01

    The neutron-rich nuclei near N = 40 have recently been the focus of many experimental and theoretical efforts. In this region, the competing energy cost for promoting pairs of nucleons across either Z = 28 or N = 40 and the energy gain from residual nucleon-nucleon interactions gives rise to several low-energy 0+ states and is a hallmark of shape coexistence. Low-energy 0+ states have been observed in 68Ni, and predicted for other nuclei in the region. Recent theoretical calculations are able to reproduce the energies of known states in 68Ni and stress the importance of the tensor component of the monopole interaction. Yet, while energies of the levels are a useful comparison, a more stringent test is the reproduction of level lifetimes, where the predicted half-lives can vary by several orders of magnitude depending on the interaction. To further benchmark theoretical calculations in this region, a setup designed to measure level lifetimes has been constructed. A description of the array and preliminary results will be presented. This work was supported by the DOE NNSA Award No. DE-NA0000979, NSF Contract No. PHY1102511, DOE SC NP Contract No. DE-AC-06CH11357 and Grant No. DE-FG02-94ER40834.

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

    SciTech Connect

    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.; Crawford, H. L.; Cromaz, M.; David, H. M.; Gregor, E. T.; Kondev, F. G.; Harker, J.; Hoffman, C. R.; Kay, B. P.; Korichi, A.; Lauritsen, T.; Macchiavelli, A. O.; Pardo, R. C.; Richard, A.; Riley, M. A.; Savard, G.; Scheck, M.; Seweryniak, D.; Smith, M. K.; Wiens, A.; Vondrasek, R.

    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 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.

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

    DOE PAGES

    Bucher, B.; Zhu, S.; Wu, C. Y.; ...

    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

  5. Revised Calculations of the Production Rates for Co Isotopes in Meteorites Using New Cross Sections for Neutron-induced Reactions

    NASA Technical Reports Server (NTRS)

    Sisterson, J. M.; Brooks, F. D.; Buffler, A.; Allie, M. S.; Herbert, M. S.; Nchodu, M. R.; Makupula, S.; Ullmann, J.; Reedy, R. C.; Jones, D. T. L.

    2002-01-01

    New cross section measurements for reactions induced by neutrons with energies greater than 70 MeV are used to calculate the production rates for cobalt isotopes in meteorites and these new calculations are compared to previous estimates. Additional information is contained in the original extended abstract.

  6. On the optimization of the isotopic neutron source method for measuring the thermal neutron absorption cross section: advantages and disadvantages of BF3 and 3He counters.

    PubMed

    Bolewski, A; Ciechanowski, M; Dydejczyk, A; Kreft, A

    2008-04-01

    The effect of the detector characteristics on the performance of an isotopic neutron source device for measuring thermal neutron absorption cross section (Sigma) has been examined by means of Monte Carlo simulations. Three specific experimental arrangements, alternately with BF(3) counters and (3)He counters of the same sizes, have been modelled using the MCNP-4C code. Results of Monte Carlo calculations show that devices with BF(3) counters are more sensitive to Sigma, but high-pressure (3)He counters offer faster assays.

  7. Neutron-proton effective mass splitting in neutron-rich matter at normal density from analyzing nucleon-nucleus scattering data within an isospin dependent optical model

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Hua; Guo, Wen-Jun; Li, Bao-An; Chen, Lie-Wen; Fattoyev, Farrukh J.; Newton, William G.

    2015-04-01

    The neutron-proton effective mass splitting in asymmetric nucleonic matter of isospin asymmetry δ and normal density is found to be mn-p* ≡ (mn* - mp*) / m = (0.41 ± 0.15) δ from analyzing globally 1088 sets of reaction and angular differential cross sections of proton elastic scattering on 130 targets with beam energies from 0.783 MeV to 200 MeV, and 1161 sets of data of neutron elastic scattering on 104 targets with beam energies from 0.05 MeV to 200 MeV within an isospin dependent non-relativistic optical potential model. It sets a useful reference for testing model predictions on the momentum dependence of the nucleon isovector potential necessary for understanding novel structures and reactions of rare isotopes.

  8. 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.

  9. Comparison of yields of neutron-rich nuclei in proton- and photon-induced 238U fission

    NASA Astrophysics Data System (ADS)

    Khan, F. A.; Bhowmick, Debasis; Basu, D. N.; Farooq, M.; Chakrabarti, Alok

    2016-11-01

    A comparative study of fission of actinides, especially 238U, by proton and bremsstrahlung photon is performed. The relative mass distribution of 238U fission fragments has been explored theoretically for both proton- and photon-induced fission. The integrated yield along with charge distribution of the products are calculated to find the neutron richness in comparison with the nuclei produced by the r process in nucleosynthesis. Some r -process nuclei in the intermediate-mass range for symmetric fission mode are found to be produced almost two orders of magnitude more for proton-induced fission than for photofission, although the rest of the neutron-rich nuclei in the asymmetric mode are produced in comparable proportion for both processes.

  10. New neutron-rich microsecond isomers observed among fission products of {sup 238}U at 80 MeV/nucleon

    SciTech Connect

    Folden, C. M. III; Ginter, T. N.; Hausmann, M.; Portillo, M.; Nettleton, A. S.; Amthor, A. M.; Sherrill, B. M.; Kubo, T.; Takeda, H.; Loveland, W.; Manikonda, S. L.; Morrissey, D. J.; Nakao, T.; Souliotis, G. A.; Strong, B. F.; Tarasov, O. B.

    2009-06-15

    Eight new isomeric states in neutron-rich nuclides have been discovered in fission fragments produced by the reaction of an 80 MeV/nucleon {sup 238}U beam with a {sup 9}Be target and separated in-flight using the A1900 fragment separator. The experiment was conducted at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. Gamma rays were detected in a high-purity germanium detector located at the focal plane within a time window of 20 {mu}s following ion implantation. In some cases the isomers were observed to decay into previously reported states, allowing us to assign the initial decay from the isomeric state. Among the outcomes, the results suggest that many studies on the nuclear structure of medium-mass neutron-rich nuclei are feasible at projectile fragmentation facilities using induced fission.

  11. Decay and In-Beam Studies of Neutron-Deficient Po and Ra Isotopes at JYFL

    NASA Astrophysics Data System (ADS)

    Leino, M.; Allatt, R. G.; Andreyev, A. N.; Cocks, J. F. C.; Dorvaux, O.; Enqvist, T.; Eskola, K.; Helariutta, K.; Huyse, M.; Jones, P. M.; Julin, R.; Juutinen, S.; Kankaanpaeae, H.; Keenan, A.; Kettunen, H.; Kuusiniemi, P.; Muikku, M.; Rahkila, P.; Savelius, A.; Trzaska, W. H.; Uusitalo, J.; van Duppen, P.

    1999-05-01

    An extensive program to study the production, decay properties, and nuclear structure of very neutron-deficient polonium and radium nuclei is underway at the Department of Physics, University of Jyvaeskylae, Finland (JYFL). The main tools used in these studies are the gas-filled recoil separator RITU and various germanium gamma-ray arrays. In the course of these studies, among others the following new isotopes have been produced: 204Ra, 203Ra, and 202Ra. Isomeric alpha decaying states have been discovered in 203Ra and 191Po. Fine structure in the decay of 192Po to the oblate and prolate band heads in 188Pb has been observed. In-beam gamma-ray spectra have been, for the first time, measured for 192Po, 206Ra, 208Ra, and 210Ra. Development of collectivity in nuclei in the Po-Ra region and the systematics of reduced alpha widths will be discussed.

  12. Failure of Stadard Optical Models to Reproduce Neutron Total Cross Section Difference in the W Isotopes

    SciTech Connect

    Anderson, J D; Bauer, R W; Dietrich, F S; Grimes, S M; Finlay, R W; Abfalterer, W P; Bateman, F B; Haight, R C; Morgan, G L; Bauge, E; Delaroche, J P; Romain, P

    2001-11-01

    Recently cross section differences among the isotopes{sup 182,184,186}W have been measured as part of a study of total cross sections in the 5-560 MeV energy range. These measurements show oscillations up to 150 mb between 5 and 100 MeV. Spherical and deformed phenomenological optical potentials with typical radial and isospin dependences show very small oscillations, in disagreement with the data. In a simple Ramsauer model, this discrepancy can be traced to a cancellation between radial and isospin effects. Understanding this problem requires a more detailed model that incorporates a realistic description of the neutron and proton density distributions. This has been done with results of Hartree-Fock-Bogolyubov calculations using the Gogny force, together with a microscopic folding model employing a modification of the JLM potential as an effective interaction. This treatment yields a satisfactory interpretation of the observed total cross section differences.

  13. A neutronic feasibility study for LEU conversion of the high flux isotope reactor (HFIR).

    SciTech Connect

    Mo, S. C.

    1998-01-14

    A neutronic feasibility study was performed to determine the uranium densities that would be required to convert the High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory (ORNL) from HEU (93%) to LEU (<20%)fuel. The LEU core that was studied is the same as the current HEU core, except for potential changes in the design of the fuel plates. The study concludes that conversion of HFIR from HEU to LEU fuel would require an advanced fuel with a uranium density of 6-7 gU/cm{sup 3} in the inner fuel element and 9-10 gU/cm{sup 3} in the outer fuel element to match the cycle length of the HEU core. LEU fuel with uranium density up to 4.8 gU/cm{sup 3} is currently qualified for research reactor use. Modifications in fuel grading and burnable poison distribution are needed to produce an acceptable power distribution.

  14. Neutron-induced fission-cross-section measurements and calculations of selected transplutonic isotopes

    SciTech Connect

    White, R.M.; Browne, J.C.

    1982-08-27

    The neutron-induced fission cross sections of /sup 242m/Am and /sup 245/Cm have been measured over an energy range of 10/sup -4/ eV to approx. 20 MeV in a series of experiments at three facilities during the past several years. The combined results of these measurements, in which only sub-milligram quantities of enriched isotopes were used, yield cross sections with uncertainties of approximately 5% below 10 MeV relative to the /sup 235/U standard cross section used to normalize the data. We summarize the resonance analysis of the /sup 242m/Am(n,f) cross section in the eV region. Hauser-Feshbach statistical calculations of the detailed fission cross sections of /sup 235/U and /sup 245/Cm have been carried out over the energy region from 0.1 to 5 MeV and these results are compared with our experimental data.

  15. A neutron diffraction and isotopic substitution measurement of the structure of liquid Cu2Se

    NASA Astrophysics Data System (ADS)

    Hamilton, M. A.; Barnes, A. C.; Beck, U.; Buchanan, P.; Howells, W. S.

    2000-11-01

    The partial structure factors and pair distribution functions of liquid Cu2Se have been determined by neutron diffraction with isotopic substitution. The structure shows characteristics typical of those of an ionic 2:1 melt consisting of Cu+ and Se2- ions with the cations moving through a more ordered Se2- sub-structure. A detailed comparison has been made with recent results obtained for liquid Ag2Se. The structure is similar although there is no evidence of the double peak structure in the cation-cation partial structure factor, SCuCu(Q), as has been found in SAgAg(Q) for liquid Ag2Se and, to a more limited extent, for liquid Ag2Te. There is also less order in the Se2- sub-structure based on a comparison of SSeSe(Q) and the Bhatia-Thornton concentration-concentration structure factor, SCC(Q), for the two liquids.

  16. Isotope effects in water as investigated by neutron diffraction and path integral molecular dynamics

    NASA Astrophysics Data System (ADS)

    Zeidler, Anita; Salmon, Philip S.; Fischer, Henry E.; Neuefeind, Jörg C.; Simonson, J. Mike; Markland, Thomas E.

    2012-07-01

    The structures of heavy and light water at 300 K were investigated by using a joint approach in which the method of neutron diffraction with oxygen isotope substitution was complemented by path integral molecular dynamics simulations. The diffraction results, which give intra-molecular O-D and O-H bond distances of 0.985(5) and 0.990(5) Å, were found to be in best agreement with those obtained by using the flexible anharmonic TTM3-F water model. Both techniques show a difference of ≃ 0.5% between the O-D and O-H intra-molecular bond lengths, and the results support a competing quantum effects model for water in which its structural and dynamical properties are governed by an offset between intra-molecular and inter-molecular quantum contributions. Further consideration of the O-O correlations is needed in order to improve agreement with experiment.

  17. Neutron Transfer Reactions on Neutron-Rich N=50 and N=82 Nuclei Near the r-Process Path

    SciTech Connect

    Cizewski, J. A.; Jones, K. L.; Kozub, R. L.; Pain, S. D.; Thomas, J. S.; Arbanas, Goran; Adekola, Aderemi S; Bardayan, Daniel W; Blackmon, Jeff C; Chae, K. Y.; Chipps, K.; Dean, David Jarvis; Erikson, Luke; Gaddis, A. L.; Harlin, Christopher W; Hatarik, Robert; Howard, Joshua A; Johnson, Micah; Kapler, R.; Krolas, W.; Liang, J Felix; Livesay, Jake; Ma, Zhanwen; Matei, Catalin; Moazen, Brian; Nesaraja, Caroline D; O'Malley, Patrick; Paulauskas, Stanley V; Shapira, Dan; ShrinerJr., J. F.; Sissom, D. J.; Smith, Michael Scott; Swan, T. P.; Wilson, Gemma L

    2009-01-01

    Neutron transfer (d,p) reaction studies on the N = 50 isotones, 82Ge and 84Se, and A{approx}130 nuclei, 130,132Sn and 134Te, have been measured. Direct neutron capture cross sections for 82Ge and 84Se (n,?) have been calculated and are combined with Hauser-Feshbach expectations to estimate total (n,?) cross sections. The A{approx}130 studies used an early implementation of the ORRUBA array of position-sensitive silicon strip detectors for reaction proton measurements. Preliminary excitation energy and angular distribution results from the A{approx}130 measurements are reported.

  18. Diffusion of lithium-6 isotopes in lithium aluminate ceramics using neutron depth profiling

    NASA Astrophysics Data System (ADS)

    McWhinney, Hylton G.; James, William D.; Schweikert, Emile A.; Williams, John R.; Hollenberg, Glen; Welsh, John; Sereatan, Washington

    1993-07-01

    Lithium Ceramics offer tremendous potential as a source for the production of tritium ( 3H) for fusion power reactors. Their successful application will depend to a great extent upon the diffusion properties of the 6Li within the matrix. Consequently knowledge od 6Li concentration gradients in the ceramic matrices is an important requirement in the continued development of the technology. In this investigation, the neutron depth profile (NDP) technique has been applied to the study of concentration profiles of 6Li in lithium aluminate ceramics, doped with 1.8%, 50% and 95% 6Li isotopic concentrations. Specimen for analysis were prepared at Battelle (PNL) as pellet discs. Samples for diffusion studies were arranged as diffusion couples in the following manner: 1.8% 6Li discs/85% 6Li powder. Experiments were performed at the Texas A&M Nuclear Science Center Reactor Building, utilizing 1 MW equivalent thermal neutron fluxes 3 × 10 11n/ m2s. The depth probed by the technique is approximately 15 μ.m. Diffusion coefficients are in the range of 2.1 × 10 -12 to 7.0 × 10 -11m2s-1 for 1.8% 6Li-doped ceramics annealed at 1200 and 1400° C, for 4 to 48-h anneal times.

  19. Deformation studies in the extremely neutron-deficient praseodymium, neodymium and promethium isotopes

    SciTech Connect

    Breitenbach, J.; Braga, R.A.; Wood, J.L. ); Semmes, P.B. . Dept. of Physics); Kormicki, J. . Dept. of Physics)

    1992-01-01

    Several experiments were performed at the UNISOR isotope separator facility at HHIRF at the Oak Ridge National Laboratory on the [beta][sup +]/EC decay of neutron-deficient rare earth isotopes. Data for the three decay chains [sup 137]Eu [yields] [sup 137]Sm [yields] [sup 137]Pm [yields] [sup 137]Nd, [sup 135]Sm [yields] [sup 135]Pm [yields] [sup 135]Nd and [sup 133]Sm [yields] [sup 133]Pm [yields] [sup 133]Nd were obtained consisting of multiscaled spectra of [gamma] rays, x rays, and conversion electrons, as well as [gamma][gamma]t, X[gamma]t, e[gamma]t and eXt coincidences. Gamma rays associated with the decay of [sup 133]Sm and [sup 133]Pm were observed for the first time. The decay of a new low-spin (1/2,3/2) isomeric state, with a half life around 70 sec was seen in [sup 133]Nd. Systematics and particle-rotor calculations are discussed.

  20. Deformation studies in the extremely neutron-deficient praseodymium, neodymium and promethium isotopes

    SciTech Connect

    Breitenbach, J.; Braga, R.A.; Wood, J.L.; Semmes, P.B.; Kormicki, J.

    1992-12-31

    Several experiments were performed at the UNISOR isotope separator facility at HHIRF at the Oak Ridge National Laboratory on the {beta}{sup +}/EC decay of neutron-deficient rare earth isotopes. Data for the three decay chains {sup 137}Eu {yields} {sup 137}Sm {yields} {sup 137}Pm {yields} {sup 137}Nd, {sup 135}Sm {yields} {sup 135}Pm {yields} {sup 135}Nd and {sup 133}Sm {yields} {sup 133}Pm {yields} {sup 133}Nd were obtained consisting of multiscaled spectra of {gamma} rays, x rays, and conversion electrons, as well as {gamma}{gamma}t, X{gamma}t, e{gamma}t and eXt coincidences. Gamma rays associated with the decay of {sup 133}Sm and {sup 133}Pm were observed for the first time. The decay of a new low-spin (1/2,3/2) isomeric state, with a half life around 70 sec was seen in {sup 133}Nd. Systematics and particle-rotor calculations are discussed.

  1. Comparisons of Neutron Cross Sections and Isotopic Composition Calculations for Fission-Product Evaluations

    NASA Astrophysics Data System (ADS)

    Kim, Do Heon; Gil, Choong-Sup; Chang, Jonghwa; Lee, Yong-Deok

    2005-05-01

    The neutron absorption cross sections for 18 fission products evaluated within the framework of the KAERI (Korea Atomic Energy Research Institute)-BNL (Brookhaven National Laboratory) international collaboration have been compared with ENDF/B-VI.7. Also, the influence of the new evaluations on the isotopic composition calculations of the fission products has been estimated through the OECD/NEA burnup credit criticality benchmarks (Phase 1B) and the LWR/Pu recycling benchmarks. These calculations were performed by WIMSD-5B with the 69-group libraries prepared from three evaluated nuclear data libraries: ENDF/B-VI.7, ENDF/B-VI.8 including the new evaluations in the resonance region covering the thermal region, and the expected ENDF/B-VII including those in the upper resonance region up to 20 MeV. For Xe-131, the composition calculated with ENDF/B-VI.8 shows a maximum difference of 5.02% compared to ENDF/B-VI.7. However, the isotopic compositions of all the fission products calculated with the expected ENDF/B-VII show no differences when compared to ENDF/B-VI.7 for the thermal reactor benchmark cases.

  2. Predictions of oxygen isotope ratios in stars and of oxygen-rich interstellar grains in meteorites

    NASA Astrophysics Data System (ADS)

    Boothroyd, Arnold I.; Sackmann, I.-Juliana; Wasserburg, G. J.

    1994-07-01

    that did NOT have the same initial 0-16/0-18 ratio. Thus one cannot assume uniform isotope ratios, even for stars of nearly solar composition. The grains 0-16/0-17 ratios, together with the Mg-26 excesses that indicate grain formation in a Al-26-rich environment, indicate that the Orgueil grain B and Murchison 83-5 grain originated in stars of roughly 1.5 solar mass, during third dredge-up on the AGB. the new Bishunpur B39 grain originated in a star of either 2 or of 4-7 solar mass.

  3. Structure of high spin state in proton-rich 74,76,78Kr isotopes: A projected shell model description

    NASA Astrophysics Data System (ADS)

    Liu, YanXin; Yu, ShaoYing; Shen, CaiWan

    2015-01-01

    The N≈ Z nuclei in the mass A˜80 region has been researched because of an abundance of nuclear structure phenomena. The projected shell model (PSM) was adopted to investigate the structure of high spin state in proton-rich 74,76,78Kr isotopes including yrast spectra, moment of inertia, electric quadrupole transitions and the behavior of single particle. The calculated results are in good agreement with available data and the shape coexistence in low-spin is also discussed.

  4. Crossover from skin mode to proton-neutron mode in E1 excitations of neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Nakada, H.; Inakura, T.; Sawai, H.

    2013-03-01

    The character of the low-energy E1 excitations is investigated by analyzing transition densities obtained from the RPA calculations in the doubly magic nuclei. We propose a decomposition method of the E1 excitations into the pn mode (i.e., oscillation between protons and neutrons) and the skin mode (i.e., oscillation of the neutron skin against the inner core) via the transition densities, by which their mixing is handled in a straightforward manner. Crossover behavior of the E1 excitations is found, from the skin mode at low energy to the pn mode at higher energy. The ratio of the skin-mode strength to the full strength turns out to be insensitive to the nuclides and to the effective interactions in the energy region of the crossover. Depending on the excitation energy, the observed low-energy E1 excitations are not necessarily dominated by the skin mode, as exemplified for 90Zr.

  5. Energy dependence of mass, charge, isotopic, and energy distributions in neutron-induced fission of 235U and 239Pu

    NASA Astrophysics Data System (ADS)

    Pasca, H.; Andreev, A. V.; Adamian, G. G.; Antonenko, N. V.; Kim, Y.

    2016-05-01

    The mass, charge, isotopic, and kinetic-energy distributions of fission fragments are studied within an improved scission-point statistical model in the reactions 235U+n and 239Pu+n at different energies of the incident neutron. The charge and mass distributions of the electromagnetic- and neutron-induced fission of 214,218Ra, 230,232,238U are also shown. The available experimental data are well reproduced and the energy-dependencies of the observable characteristics of fission are predicted for future experiments.

  6. Possibilities of production of neutron-deficient isotopes of U, Np, Pu, Am, Cm, and Cf in complete fusion reactions

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Zubov, A. S.; Scheid, W.

    2008-10-15

    Within the dinuclear system model we analyze the production of yet unknown neutron-deficient isotopes of U, Np, Pu, Am, Cm, and Cf in various complete fusion reactions. Different deexcitation channels of the excited compound nucleus are treated. The results are obtained without special adjustment to the selected evaporation channel. The fusion probability is an important ingredient of the excitation function. The results are in good agreement with the available experimental data. The alpha decay half-life times in the neutron-deficient actinides are discussed.

  7. Quantifying Gamma/Neutron Discrimination in Gadolinium-Rich Real-Time Neutron Detection Materials and Devices

    DTIC Science & Technology

    2016-05-01

    Fahrenheit ( o F) [T( o F) + 459.67]/1.8 kelvin (K) Radiation curie (Ci) [activity of radionuclides] 3.7 × 10 10 per second (s –1 ) [becquerel (Bq...experimental protocols for materials characterization and testing device radiation responses was initiated. Data was collected on usability of radiation ...neutron response which may yet hold potential for radiation detection. In addition, some baseline end-use requirements of radiation detection parameters

  8. Neutron Capture Reactions on Fe and Ni Isotopes for the Astrophysical s-process

    SciTech Connect

    Lederer, C.; Giubrone, G.; Massimi, C.; Žugec, P.; Barbagallo, M.; Colonna, N.; Domingo-Pardo, C.; Guerrero, C.; Gunsing, F.; Käppeler, F.; Tain, J.L.; Altstadt, S.; Andrzejewski, J.; Audouin, L.; Bečvář, F.; and others

    2014-06-15

    Neutron capture cross sections in the keV neutron energy region are the key nuclear physics input to study the astrophysical slow neutron capture process. In the past years, a series of neutron capture cross section measurements has been performed at the neutron time-of-flight facility n{sub T}OF at CERN focussing on the Fe/Ni mass region. Recent results and future developments in the neutron time-of-flight technique are discussed.

  9. Exploring the extended density-dependent Skyrme effective forces for normal and isospin-rich nuclei to neutron stars

    SciTech Connect

    Agrawal, B.K.; Dhiman, Shashi K.; Kumar, Raj

    2006-03-15

    We parametrize the recently proposed generalized Skyrme effective force (GSEF) containing extended density dependence. The parameters of the GSEF are determined by the fit to several properties of the normal and isospin-rich nuclei. We also include in our fit a realistic equation of state for the pure neutron matter up to high densities so that the resulting Skyrme parameters can be suitably used to model the neutron star with the 'canonical' mass ({approx}1.4M{sub {center_dot}}). For the appropriate comparison, we generate a parameter set for the standard Skyrme effective force (SSEF) using exactly the same set data as employed to determine the parameters of the GSEF. We find that the GSEF yields larger values for the neutron skin thickness which are closer to the recent predictions based on the isospin diffusion data. The Skyrme parameters so obtained are employed to compute the strength function for the isoscalar giant monopole, dipole, and quadrupole resonances. It is found that in the case of GSEF, because of the larger value of the nucleon effective mass, the values of centroid energies for the isoscalar giant resonances are in better agreement with the corresponding experimental data than those obtained using the SSEF. We also present results for some of the key properties associated with the neutron star of canonical mass and for the one with the maximum mass.

  10. 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.

  11. Isotopically uniform, 16O-depleted calcium, aluminum-rich inclusions in CH and CB carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Krot, Alexander N.; Nagashima, Kazuhide; Petaev, Michail I.

    2012-04-01

    In situ oxygen-isotope measurements of calcium-aluminum-rich inclusions (CAIs) from the metal-rich carbonaceous chondrites Isheyevo (CH/CB-like), Acfer 214 paired with Acfer 182 (CH), QUE 94411 paired with QUE 94627 (CBb), and Hammadah al Hamra 237 (CBb) revealed the presence of a common population of igneous, isotopically uniform, 16O-depleted inclusions: Δ17O (average ± 2 standard deviations) = -7 ± 4‰, -6 ± 5‰, and -8 ± 3‰, respectively. All CAIs from CBs and a significant fraction of those from CHs and Isheyevo are 16O-depleted. Most of the 16O-depleted CAIs consist of Ti-poor Al-diopside, spinel, melilite, and forsterite and surrounded by a single- and double-layered rim of forsterite ± diopside. The 16O-depleted CAIs composed of hibonite, grossite, melilite, and spinel, and surrounded by the multilayered melilite + diopside ± forsterite rims are less common. Some of the 16O-depleted refractory igneous inclusions composed of Al-diopside, forsterite, and ±spinel have chondrule-like textures (skeletal or barred). They are mineralogically most similar to Al-diopside-rich chondrules found in metal-rich carbonaceous chondrites and composed of Al-diopside, forsterite, Al-rich low-Ca pyroxene, ±glassy mesostasis, and ±spinel, suggesting there is a continuum between these objects. We suggest that (i) most of the isotopically uniform and 16O-depleted CAIs resulted from remelting of pre-existing, possibly 16O-rich refractory inclusions. The remelting may have occurred during formation of the magnesian, non-porphyritic (cryptocrystalline and skeletal) chondrules in CHs, CBs, and Isheyevo either by an unspecified, late, single-stage, highly-energetic event or in an impact-generated plume previously hypothesized for their origin; both mechanisms probably occurred in the solar nebula (i.e., in the presence of the nebula gas). The forsterite ± pyroxene rims around 16O-depleted CAIs may have resulted from evaporation-recondensation of silicon and magnesium

  12. Calcium-aluminum-rich inclusions with fractionation and unknown nuclear effects (FUN CAIs): I. Mineralogy, petrology, and oxygen isotopic compositions

    NASA Astrophysics Data System (ADS)

    Krot, Alexander N.; Nagashima, Kazuhide; Wasserburg, Gerald J.; Huss, Gary R.; Papanastassiou, Dimitri; Davis, Andrew M.; Hutcheon, Ian D.; Bizzarro, Martin

    2014-11-01

    We present a detailed characterization of the mineralogy, petrology, and oxygen isotopic compositions of twelve FUN CAIs, including C1 and EK1-4-1 from Allende (CV), that were previously shown to have large isotopic fractionation patterns for magnesium and oxygen, and large isotopic anomalies of several elements. The other samples show more modest patterns of isotopic fractionation and have smaller but significant isotopic anomalies. All FUN CAIs studied are coarse-grained igneous inclusions: Type B, forsterite-bearing Type B, compact Type A, and hibonite-rich. Some inclusions consist of two mineralogically distinct lithologies, forsterite-rich and forsterite-free/poor. All the CV FUN CAIs experienced postcrystallization open-system iron-alkali-halogen metasomatic alteration resulting in the formation of secondary minerals commonly observed in non-FUN CAIs from CV chondrites. The CR FUN CAI GG#3 shows no evidence for alteration. In all samples, clear evidence of oxygen isotopic fractionation was found. Most samples were initially 16O-rich. On a three-oxygen isotope diagram, various minerals in each FUN CAI (spinel, forsterite, hibonite, dmisteinbergite, most fassaite grains, and melilite (only in GG#3)), define mass-dependent fractionation lines with a similar slope of ∼0.5. The different inclusions have different Δ17O values ranging from ∼-25‰ to ∼-16‰. Melilite and plagioclase in the CV FUN CAIs have 16O-poor compositions (Δ17O ∼-3‰) and plot near the intercept of the Allende CAI line and the terrestrial fractionation line. We infer that mass-dependent fractionation effects of oxygen isotopes in FUN CAI minerals are due to evaporation during melt crystallization. Differences in Δ17O values of mass-dependent fractionation lines defined by minerals in individual FUN CAIs are inferred to reflect differences in Δ17O values of their precursors. Differences in δ18O values of minerals defining the mass-dependent fractionation lines in several FUN CAIs

  13. Structural characterization of titanium-doped Bioglass using isotopic substitution neutron diffraction.

    PubMed

    Martin, Richard A; Moss, Robert M; Lakhkar, Nilay J; Knowles, Jonathan C; Cuello, Gabriel J; Smith, Mark E; Hanna, John V; Newport, Robert J

    2012-12-05

    Melt quenched silicate glasses containing calcium, phosphorus and alkali metals have the ability to promote bone regeneration and to fuse to living bone. Of these glasses 45S5 Bioglass® is the most widely used being sold in over 35 countries as a bone graft product for medical and dental applications; particulate 45S5 is also incorporated into toothpastes to help remineralize the surface of teeth. Recently it has been suggested that adding titanium dioxide can increase the bioactivity of these materials. This work investigates the structural consequences of incorporating 4 mol% TiO(2) into Bioglass® using isotopic substitution (of the Ti) applied to neutron diffraction and X-ray Absorption Near Edge Structure (XANES). We present the first isotopic substitution data applied to melt quench derived Bioglass or its derivatives. Results show that titanium is on average surrounded by 5.2(1) nearest neighbor oxygen atoms. This implies an upper limit of 40% four-fold coordinated titanium and shows that the network connectivity is reduced from 2.11 to 1.97 for small quantities of titanium. Titanium XANES micro-fluorescence confirms the titanium environment is homogenous on the micron length scale within these glasses. Solid state magic angle spinning (MAS) NMR confirms the network connectivity model proposed. Furthermore, the results show the intermediate range order containing Na-O, Ca-O, O-P-O and O-Si-O correlations are unaffected by the addition of small quantities of TiO(2) into these systems.

  14. Exploring Light Neutron Rich Nuclei via the ({sup 7}Li,{sup 7}Be) Reaction

    SciTech Connect

    Cavallaro, M.; Cappuzzello, F.; Cunsolo, A.; Foti, A.; Orrigo, S. E. A.; Rodrigues, M. R. D.; Borello-Lewin, T.; Lenske, H.; Petrascu, H.; Winfield, J. S.

    2008-11-11

    A systematic study of the nuclei that can be described as an integer number of {alpha} particles plus three neutrons via the ({sup 7}Li,{sup 7}Be) reaction at about 8 MeV/u has shown the presence of Bound States Embedded in the Continuum in the energy spectra. These are experimental signatures of the dynamical correlations of an easily polarizable core with a single-particle state of the valence neutron.

  15. Cosmic-ray exposure histories of Martian meteorites studied from neutron capture reactions of Sm and Gd isotopes

    NASA Astrophysics Data System (ADS)

    Hidaka, Hiroshi; Yoneda, Shigekazu; Nishiizumi, Kunihiko

    2009-11-01

    The isotopic compositions of Sm and Gd in twelve Martian meteorites, ALH 77005, ALH 84001, DaG 735, Dhofar 019, EET 79001, Lafayette, Los Angeles, Nakhla, SaU 005, Y 000593, Y 000749 and Zagami, were determined to quantify the neutron capture records of individual meteorite specimens. Seven of these twelve samples, ALH 84001, Y 000749, DaG 735, Dhofar 019, EET 79001, SaU 005 and Zagami, showed significant isotopic shifts of 150Sm/ 149Sm and/or 158Gd/ 157Gd corresponding to neutron fluences of (0.7-3.4) × 10 15 n cm - 2 . Among these seven meteorites, the neutron fluences of ALH 84001, Y 000749, and Dhofar 019 apparently correlated with their cosmic-ray exposure ages, indicating that most of the irradiation took place while the meteoroids were small bodies in space after the ejection from Mars. However, our results suggest an accumulation of their inherited irradiation occurred on Mars. On the other hand, the exposure histories of the other four meteorites (basaltic shergottites), DaG 735, EET 79001, SaU 005, and Zagami, cannot be explained as single- or multistage irradiations in space, or as a single irradiation on the Martian surface. The mixing between basaltic lava with a significantly irradiated Martian regolith is a reasonable interpretation of the excess neutron capture records observed in these four basaltic shergottites.

  16. 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.

  17. 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.

  18. Nuclear Charge Radii of Neutron-Deficient Lead Isotopes Beyond N=104 Midshell Investigated by In-Source Laser Spectroscopy

    SciTech Connect

    Witte, H. de; Cocolios, T. E.; Dean, S.; Huyse, M.; Lesher, S. R.; Mukha, I.; Stefanescu, I.; Vel, K. van de; Walle, J. van de; Duppen, P. van; Andreyev, A. N.; Barre, N.; Roussiere, B.; Sauvage, J.; Bender, M.; Fedoseyev, V. N.; Fraile, L. M.; Jeppessen, H.

    2007-03-16

    The shape of exotic even-mass {sup 182-190}Pb isotopes was probed by measurement of optical isotope shifts providing mean square charge radii ({delta}). The experiment was carried out at the isolde (cern) on-line mass separator, using in-source laser spectroscopy. Small deviations from the spherical droplet model are observed, but when compared to model calculations, those are explained by high sensitivity of {delta} to beyond mean-field correlations and small admixtures of intruder configurations in the ground state. The data support the predominantly spherical shape of the ground state of the proton-magic Z=82 lead isotopes near neutron midshell (N=104)

  19. Schottky Mass Measurement of the {sup 208}Hg Isotope: Implication for the Proton-Neutron Interaction Strength around Doubly Magic {sup 208}Pb

    SciTech Connect

    Chen, L.; Plass, W. R.; Geissel, H.; Scheidenberger, C.; Litvinov, Yu. A.; Beckert, K.; Beller, P.; Bosch, F.; Caceres, L.; Franzke, B.; Gerl, J.; Gorska, M.; Knoebel, R.; Kozhuharov, C.; Litvinov, S. A.; Mandal, S.; Muenzenberg, G.; Nolden, F.; Saito, N.; Saito, T.

    2009-03-27

    Time-resolved Schottky mass spectrometry has been applied to uranium projectile fragments which yielded the mass value for the {sup 208}Hg (Z=80, N=128) isotope. The mass excess value of ME=-13 265(31) keV has been obtained, which has been used to determine the proton-neutron interaction strength in {sup 210}Pb, as a double difference of atomic masses. The results show a dramatic variation of the strength for lead isotopes when crossing the N=126 neutron shell closure, thus confirming the empirical predictions that this interaction strength is sensitive to the overlap of the wave functions of the last valence neutrons and protons.

  20. Photoneutron cross sections for {sup 96}Zr: A systematic experimental study of photoneutron and radiative neutron capture cross sections for zirconium isotopes

    SciTech Connect

    Utsunomiya, H.; Akimune, H.; Kondo, T.; Itoh, O.; Kamata, M.; Yamagata, T.; Goriely, S.; Harada, H.; Kitatani, F.; Goko, S.; Toyokawa, H.; Yamada, K.; Lui, Y.-W.; Hilaire, S.; Koning, A. J.

    2010-03-15

    Photoneutron cross sections were measured for {sup 96}Zr near neutron threshold with quasimonochromatic laser-Compton-scattering {gamma}-ray beams. A systematic analysis of photoneutron and radiative neutron capture data for zirconium isotopes within the statistical model calculation leads to a unified picture of low-energy {gamma}-ray strengths for zirconium isotopes that is described by the HFB + QRPA model of E1 strength supplemented with an extra {gamma} strength attributed to a giant M1 resonance. Results of the systematic analysis including radiative neutron capture cross sections for radioactive {sup 95}Zr and {sup 93}Zr nuclei are presented.

  1. 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.

  2. Precision Q-value determinations for neutron-rich rubidium isotopes at TRISTAN

    SciTech Connect

    Brenner, D.S.; Martel, M.K.; Aprahamian, A.

    1981-01-01

    Beta-ray end-point energies for Rb fission products were measured at the TRISTAN on-line mass separator using an intrinsic Ge ..beta.. spectrometer. Coincidence measurements were used to establish feeding relationships and to verify level schemes in daughter nuclides. Q/sub ..beta../ values are reported for /sup 88/ /sup 94/ /sup 96/ /sup 98/Rb and compared with results from other experiments and with predictions of mass formulae.

  3. Exploiting neutron-rich radioactive ion beams to constrain the symmetry energy

    NASA Astrophysics Data System (ADS)

    Kohley, Z.; Christian, G.; Baumann, T.; DeYoung, P. A.; Finck, J. E.; Frank, N.; Jones, M.; Smith, J. K.; Snyder, J.; Spyrou, A.; Thoennessen, M.

    2013-10-01

    The Modular Neutron Array (MoNA) and 4 Tm Sweeper magnet were used to measure the free neutrons and heavy charged particles from the radioactive ion beam induced 32Mg+9Be reaction. The fragmentation reaction was simulated with the constrained molecular dynamics model (CoMD), which demonstrated that the of the heavy fragments and free neutron multiplicities were observables sensitive to the density dependence of the symmetry energy at subsaturation densities. Through comparison of these simulations with the experimental data, constraints on the density dependence of the symmetry energy were extracted. The advantage of radioactive ion beams as a probe of the symmetry energy is demonstrated through examination of CoMD calculations for stable and radioactive-beam-induced reactions.

  4. 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.

  5. Fission barriers for neutron-rich nuclei by means of Skyrme-Hartree-Fock-Bogoliubov calculation

    SciTech Connect

    Hashizume, K.; Wada, T.; Ohta, M.; Samyn, M.; Goriely, S.

    2007-02-26

    The nuclear fission barrier height has been estimated by means of the constraint Skyrme Hartree-Fock-Bogoliubov method. The potential energy surfaces obtained by the method are analyzed with the flooding method to find several saddle points. The results for U, Np, Bk isotopes are compared with the barrier derived from the extended Thomas-Fermi plus Strutinsky integral method.

  6. Structure of Cu-As-Se glasses investigated by neutron diffraction with copper isotope substitution

    NASA Astrophysics Data System (ADS)

    Xin, Shuqin; Liu, Jian; Salmon, Philip S.

    2008-08-01

    Neutron diffraction with copper isotope substitution was used to study the structure of glassy Cu5As46.25Se48.75 , which lies at x=0.0513 on the (Cu2Se)x(AsSe)1-x pseudobinary tie line. The results are consistent with fourfold coordination of copper to matrix (As or Se) atoms at a mean distance of 2.40(2)Å and with threefold coordination of arsenic to one As and two Se atoms at a mean distance of 2.43(2)Å . A comparison is made with the structure of glassy AsSe and with the structure of a high-Cu content glass with x=0.25 . It is found that the short-range order of glassy AsSe is not changed when 5.13mol% of Cu2Se is added. However, the addition of 25mol% leads to a disruption of the intermediate-range order and to an alteration of the short-range order, which is consistent [within a scenario where arsenic remains threefold coordinated by matrix atoms at a mean distance of 2.42(2)Å ] with a substitution of As-As bonds by As-Se bonds. In the x=0.25 material, the Cu to matrix atom coordination number is ≃3 at 2.42(2)Å and the Cu-Cu nearest-neighbor coordination number is 1.0(3) at 2.70(4)Å . A comparison between (i) the measured structure of the glassy network formers AsSe and As2Se3 and (ii) the results obtained from first-principles molecular-dynamics methods points to a need for more accurate simulations in order to help elucidate the structure and properties of these materials.

  7. Superheavy Elements Production in High Intensive Neutron Fluxes

    NASA Astrophysics Data System (ADS)

    Lutostansky, Yu. S.; Lyashuk, V. I.; Panov, I. V.

    2013-06-01

    The possibility of superheavy elements production in high intensive neutron fluxes is being studied. A model of the transuranium isotopes production under conditions of pulse nucleosynthesis in a neutron flux with densities of up to ~1025 neutron/cm2 is considered. The pulse process allows us to divide it in time into two stages: the process of multiple neutron captures (with t < 10-6 s) and the subsequent β-decay of neutron-rich nuclei. The modeling of the transuranium yields takes into account the adiabatic character of the process, the probability of delayed fission, and the emission of delayed neutrons. A target with a binary composition of 238U and 239Pu, 248Cm, and 251Cf isotopes is used to predict the yields of heavy and superheavy isotopes.

  8. Iron and copper isotope fractionation during filtration and ultrafiltration of boreal organic-rich waters

    NASA Astrophysics Data System (ADS)

    Ilina, Svetlana M.; Viers, Jerome; Pokrovsky, Oleg S.; Poitrasson, Franck; Lapitsky, Sergey A.; Alekhin, Yuriy V.

    2010-05-01

    Typical feature of all boreal surface waters is high concentration of dissolved (< 0.22 µm) organic matter (DOM) and iron, notably in the form of Fe(III)-OM complexes. Organic and organo-mineral colloids are the most likely carriers of trace metals such as Cu in rivers of the boreal zone. This work addresses colloidal speciation of Cu and Fe using conventional size separation technique, on-site frontal ultrafiltration. Specifically, we aimed to test the possibility of the presence of different pools of metal having specific isotopic signatures in different colloidal fractions using stable isotope measurements. We have chosen Cu for its high affinity to colloidal DOM and Fe for its tendency to form stable organo-mineral colloids of various size. Samples of natural waters were collected from small rivers, lakes, bogs, groundwater and soil environments in the Northern Karelia (NW Russia) during summer baseflow period. Large volumes (20-40 L) of water were filtered in the field through progressively decreasing pore size filters: 20, 10, 5, 0.8, 0.45, 0.22, 0.1 µm and 100, 10 and 1 kDa (1 kDa ~ 1 nm) using nylon and regenerated cellulose membranes and frontal ultrafiltration (Millipore, Amicon) devises. The homogeneity of the sample was verified by tracing radiogenic Sr isotopes in each fraction. In all filtrates and ultrafiltrates (permeates), and in selected retentates, stable isotopic composition of Cu and Fe was measured using double focusing high resolution MC-ICP MS (Neptune). We observe rather constant Cu isotopic ratio in all filtrate series and a systematic enrichment of heavy isotope of Fe with decreasing poresize. These preliminary results can be explained by strong complexation of Cu with small-size organic ligands of fulvic nature and its partial association with organo-mineral colloids. Both Fe(III) - OM complxeation and Fe(III) oxyhydroxides precipitation can be invoked to explain Fe isotope fractionation. This work allows, for the first, time, multi-isotopic

  9. Influence of pairing correlations on the radius of neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Zhang, Ying; Chen, Ying; Meng, Jie; Ring, Peter

    2017-01-01

    The influence of pairing correlations on the neutron root mean square (rms) radius of nuclei is investigated in the framework of self-consistent Skyrme Hartree-Fock-Bogoliubov calculations. The continuum is treated appropriately by the Green's function techniques. As an example the nucleus 124Zr is treated for a varying strength of pairing correlations. We find that, as the pairing strength increases, the neutron rms radius first shrinks, reaches a minimum, and beyond this point it expands again. The shrinkage is due to the the so-called pairing antihalo effect, i.e., due to the decrease of the asymptotic density distribution with increasing pairing. However, in some cases, increasing pairing correlations can also lead to an expansion of the nucleus due to a growing occupation of so-called halo orbits, i.e., weakly bound states and resonances in the continuum with low-ℓ values. In this case, the neutron radii are extended just by the influence of pairing correlations, since these halo orbits cannot be occupied without pairing. The term "antihalo effect" is not justified in such cases. For a full understanding of this complicated interplay, self-consistent calculations are necessary.

  10. Overview of the US-Japan collaborative investigation on hydrogen isotope retention in neutron-irradiated and ion-damaged tungsten

    SciTech Connect

    Masashi Shimada; Y. Hatano; Y. Oya; T. Oda; M. Hara; G. Cao; M. Kobayashi; M. Sokolov; H. Watanabe; B. Tyburska; Y. Ueda; P. Calderoni

    2011-09-01

    Plasma-facing components (PFCs) will be exposed to 14 MeV neutrons from deuterium-tritium (D-T) fusion reactions, and tungsten, a candidate PFC for the divertor in ITER, is expected to receive a neutron dose of 0.7 displacement per atom (dpa) by the end of operation in ITER. The effect of neutron-irradiation damage has been mainly simulated using high-energy ion bombardment. While this prior database of results is quite valuable for understanding the behavior of hydrogen isotopes in PFCs, it does not encompass the full range of effects that must be considered in a practical fusion environment due to short penetration depth, damage gradient, high damage rate, and high PKA energy spectrum of the ion bombardment. In addition, neutrons change the elemental composition via transmutations, and create a high radiation environment inside PFCs, which influence the behavior of hydrogen isotope in PFCs, suggesting the utilization of fission reactors is necessary for neutron irradiation. Therefore, the effort to correlate among high-energy ions, fission neutrons, and fusion neutrons is crucial for accurately estimating tritium retention under a neutron-irradiation environment. Under the framework of the US-Japan TITAN program, tungsten samples (99.99 at. % purity from A.L.M.T. Co.) were irradiated by neutron in the High Flux Isotope Reactor (HFIR), ORNL, at 50 and 300C to 0.025, 0.3, and 1.2 dpa, and the investigation of deuterium retention in neutron-irradiation was performed in the INL Tritium Plasma Experiment (TPE), the unique high-flux linear plasma facility that can handle tritium, beryllium and activated materials. This paper reports the recent results from the comparison of ion-damaged tungsten via various ion species (2.8 MeV Fe2+, 20 MeV W2+, and 700 keV H-) with that from neutron-irradiated tungsten to identify the similarities and differences among them.

  11. A non-terrestrial 16O-rich isotopic composition for the protosolar nebula.

    PubMed

    Hashizume, Ko; Chaussidon, Marc

    2005-03-31

    The discovery in primitive components of meteorites of large oxygen isotopic variations that could not be attributed to mass-dependent fractionation effects has raised a fundamental question: what is the composition of the protosolar gas from which the host grains formed? This composition is probably preserved in the outer layers of the Sun, but the resolution of astronomical spectroscopic measurements is still too poor to be useful for comparison with planetary material. Here we report a precise determination of the oxygen isotopic composition of the solar wind from particles implanted in the outer hundreds of nanometres of metallic grains in the lunar regolith. These layers of the grains are enriched in 16O by >20 +/- 4 per thousand relative to the Earth, Mars and bulk meteorites, which implies the existence in the solar accretion disk of reactions--as yet unknown--that were able to change the 17O/16O and 18O/16O ratios in a way that was not dependent strictly on the mass of the isotope. Photochemical self-shielding of the CO gas irradiated by ultraviolet light may be one of these key processes, because it depends on the abundance of the isotopes, rather than their masses.

  12. The structure of molten CaSiO3: A neutron diffraction isotope substitution and aerodynamic levitation study.

    SciTech Connect

    Skinner, Lawrie; Benmore, Chris J; Weber, Richard; Santodonato, Louis J; Tumber, Sonia; Neuefeind, Joerg C; Lazareva, Lena; Du, Jincheng; Parise, John B

    2012-01-01

    We have performed neutron diffraction isotopic substitution experiments on aerodynamically levitated droplets of CaSiO3, to directly extract intermediate and local structural information on the Ca environment. The results show a substantial broadening of the Ca-O peak in the pair distribution function of the melt compared to the glass, which comprises primarily of 6- and 7-fold coordinated Ca-polyhedra. The broadening can be explained by a re-distribution of Ca-O bond lengths, especially towards longer distances in the liquid. The first order neutron difference function provides a rigorous test of recent molecular dynamics simulations and supports the model of the presence of short chains or channels of edge shared Ca-octahedra in the liquid state. It is suggested that the polymerization of Ca-polyhedra is responsible for the fragile viscosity behavior of the melt and the glass forming ability in CaSiO3.

  13. Isotopic ratio of 129I/127I in seaweed measured by neutron activation analysis with gamma-gamma coincidence.

    PubMed

    Toh, Y; Hatsukawa, Y; Oshima, M; Shinohara, N; Hayakawa, T; Kushita, K; Ueno, T

    2002-07-01

    129I is a long-lived (1.6 x 10(7) y) radionuclide that is produced in nature as the result of spontaneous fission of heavy elements and reaction of xenon with cosmic rays. Recently, however, artificial sources from nuclear power plants and nuclear test explosions have become a significant component of environmental radioactive iodine. Coincidence gamma-ray detection using Ge detectors makes it possible to simultaneously resolve the numerous gamma-rays produced by neutron activation. In this study, the coincidence gamma-ray detection technique was combined with neutron activation analysis to determine the radioactive iodine composition of seaweed. The ratio of 129I/127I in this common Japanese food item collected from the Ibaraki prefecture has been derived without the need for radiochemical purification. The isotopic ratio of 129I/127I in Kajime algae is 3.5(5) x 10(-10).

  14. Exploring the potential of clumped isotope thermometry on coccolith-rich sediments as a sea surface temperature proxy

    NASA Astrophysics Data System (ADS)

    Drury, Anna Joy; John, Cédric M.

    2016-10-01

    Understanding past changes in sea surface temperatures (SSTs) is crucial; however, existing proxies for reconstructing past SSTs are hindered by unknown ancient seawater composition (foraminiferal Mg/Ca and δ18O) or reflect subsurface temperatures (TEX86) or have a limited applicable temperature range (U37k'). We examine clumped isotope (Δ47) thermometry to fossil coccolith-rich material as an SST proxy, as clumped isotopes are independent of original seawater composition and applicable to a wide temperature range and coccolithophores are widespread and dissolution resistant. The Δ47-derived temperatures from <63, <20, <10, and 2-5 μm size fractions of two equatorial Pacific late Miocene-early Pliocene sediment samples (c1; c2) range between ˜18 and 29°C, with c1 temperatures consistently above c2. Removing the >63 μm fraction removes most nonmixed layer components; however, the Δ47-derived temperatures display an unexpected slight decreasing trend with decreasing size fraction. This unexpected trend could partly arise because larger coccoliths (5-12 μm) are removed during the size fraction separation process. The c1 and <63 μm c2 Δ47-derived temperatures are comparable to concurrent U37k' SSTs. The <20, <10, and 2-5 μm c2 Δ47-derived temperatures are consistently cooler than expected. The Δ47-U37k' temperature offset is probably caused by abiotic/diagenetic calcite present in the c2 2-5 μm fraction (˜53% by area), which potentially precipitated at bottom water temperatures of ˜6°C. Our results indicate that clumped isotopes on coccolith-rich sediment fractions have potential as an SST proxy, particularly in tropical regions, providing that careful investigation of the appropriate size fraction for the region and time scale is undertaken.

  15. Report of the ANS Project Feasibility Workshop for a High Flux Isotope Reactor-Center for Neutron Research Facility

    SciTech Connect

    Peretz, F.J.; Booth, R.S.

    1995-07-01

    The Advanced Neutron Source (ANS) Conceptual Design Report (CDR) and its subsequent updates provided definitive design, cost, and schedule estimates for the entire ANS Project. A recent update to this estimate of the total project cost for this facility was $2.9 billion, as specified in the FY 1996 Congressional data sheet, reflecting a line-item start in FY 1995. In December 1994, ANS management decided to prepare a significantly lower-cost option for a research facility based on ANS which could be considered during FY 1997 budget deliberations if DOE or Congressional planners wished. A cost reduction for ANS of about $1 billion was desired for this new option. It was decided that such a cost reduction could be achieved only by a significant reduction in the ANS research scope and by maximum, cost-effective use of existing High Flux Isotope Reactor (HFIR) and ORNL facilities to minimize the need for new buildings. However, two central missions of the ANS -- neutron scattering research and isotope production-were to be retained. The title selected for this new option was High Flux Isotope Reactor-Center for Neutron Research (HFIR-CNR) because of the project`s maximum use of existing HFIR facilities and retention of selected, central ANS missions. Assuming this shared-facility requirement would necessitate construction work near HFIR, it was specified that HFIR-CNR construction should not disrupt normal operation of HFIR. Additional objectives of the study were that it be highly credible and that any material that might be needed for US Department of Energy (DOE) and Congressional deliberations be produced quickly using minimum project resources. This requirement made it necessary to rely heavily on the ANS design, cost, and schedule baselines. A workshop methodology was selected because assessment of each cost and/or scope-reduction idea required nearly continuous communication among project personnel to ensure that all ramifications of propsed changes.

  16. Structures of the neutron-rich nuclei observed in fission of {sup 252}Cf

    SciTech Connect

    Ramayya, A. V.; Hamilton, J. H.; Goodin, C. J.; Brewer, N. T.; Hwang, J. K.; Luo, Y. X.; Liu, S. H.; Stone, N. J.; Daniel, A. V.; Zhu, S. J.

    2014-08-14

    Analysis of high statistics triple coincidence fission γ data from {sup 252}Cf at Gammasphere including angular correlations yielded well-expanded high-spin level schemes with more complete and reliable spin/parity assignments for {sup 82}Ge, {sup 118,120,122}Cd and {sup 114,115}Rh. Both the quasi-particle/hole couplings and quasi-rotational degrees of freedom are implied to play roles in these Cd isotopes. Evidence for triaxial shapes and octupole components in the Cd isotopes is presented. These Cd isotopes may have triaxial deformations. High-spin level schemes of {sup 114,115}Rh have been established for the first time. The existence of a relatively large signature splitting and an yrare band shows typical features of a triaxially deformed nucleus. Possible excited deformed rotational bands are observed, for the first time, in {sup 82}Ge. From the multipole mixing ratio measurement, the ground state configurations of {sup 109,111}Ru, as well as excited states in {sup 103,107}Mo and {sup 111}Ru were determined.

  17. Odd-even {sup 147-153}Pm isotopes within the neutron-proton interacting boson-fermion model

    SciTech Connect

    Barea, J.; Alonso, C. E.; Arias, J. M.

    2011-02-15

    Low-lying energy states of the {sup 147-153}Pm isotopic chain are studied within the framework of the neutron-proton interacting boson-fermion model (IBFM-2). The spectra of these isotopes show a transition from a particle coupled to a vibrational core to a particle coupled to a deformed one. The calculation reproduces this behavior. In addition, reduced transition probabilities B(E2) and B(M1) and quadrupole and magnetic moments, as well as spectroscopic factors corresponding to stripping and pickup transfer reactions, are calculated. Obtained results compare well with the available experimental data, which reinforces the reliability of the wave functions obtained within the IBFM-2 model.

  18. Some neutron and gamma radiation characteristics of plutonium cermet fuel for isotopic power sources

    NASA Technical Reports Server (NTRS)

    Neff, R. A.; Anderson, M. E.; Campbell, A. R.; Haas, F. X.

    1972-01-01

    Gamma and neutron measurements on various types of plutonium sources are presented in order to show the effects of O-17, O-18 F-19, Pu-236, age of the fuel, and size of the source on the gamma and neutron spectra. Analysis of the radiation measurements shows that fluorine is the main contributor to the neutron yields from present plutonium-molybdenum cermet fuel, while both fluorine and Pu-236 daughters contribute significantly to the gamma ray intensities.

  19. Characterization of Neutron-Induced Defects in Isotopically Enriched Lithium Tetraborate

    DTIC Science & Technology

    2011-03-01

    Electron paramagnetic resonance, electron-nuclear double resonance, pulsed anneal, and thermoluminescence studies prior to neutron irradiation concluded...that Ag doped Li2B4O7 crystals contain Ag point defects that trap both electrons and holes. Pulsed anneal and thermoluminescence studies of all...crystal types prior to neutron irradiation suggest neutron induced defects are significantly more stable than as-grown defects. Thermoluminescence may

  20. β -decay half-lives of neutron-rich nuclei at A ~ 110 on r-process path

    NASA Astrophysics Data System (ADS)

    Nishizuka, Ippei; Sumikama, Toshiyuki; Browne, Frank; Bruce, Alison; Nishimura, Shunji; Doornenbal, Pieter; Lorusso, Giuseppe; Patel, Zena; Rice, Simon; Sinclair, Laura; Soderstom, Par-Ander; Watanabe, Hiroshi; Wu, Jin; Xu, Zhengyu; Yagi, Ayumi; Eurica Collaboration

    2014-09-01

    About half of the elements heavier than iron are thought to be produced by rapid-neutron capture process (r-process). The observed natural abundance in solar system was underestimated by a theoretical model at A ~ 110 , which uses β-decay half-lives. In the present study, we measured new β half-lives of neutron-rich nuclei on r-process path at RIBF in RIKEN. The nuclei of interest were produced by in-flight fission of uranium beam in beryllium target. The WAS3ABi detector which was 5 stacked double-sided silicon strip detectors (60 × 40 × 1 mm3), was used for the implantation of ions and the detection of both the implanted ions and the subsequently-emitted β rays. It is essential to make a position correlation between the mother nucleus and the β rays. In this talk, the analysis of the position correlation will be presented in detail. Preliminary results will be also shown.

  1. Sulfur isotope fractionation during bacterial sulfate reduction in organic-rich sediments.

    PubMed

    Habicht, K S; Canfield, D E

    1997-12-01

    Isotope fractionation during sulfate reduction by natural populations of sulfate-reducing bacteria was investigated in the cyanobacterial microbial mats of Solar Lake, Sinai and the sediments of Logten Lagoon sulfuretum, Denmark. Fractionation was measured at different sediment depths, sulfate concentrations, and incubation temperatures. Rates of sulfate reduction varied between 0.1 and 37 micromoles cm-3 d-1, with the highest rates among the highest ever reported from natural sediments. The depletion of 34S during dissimilatory sulfate reduction ranged from 16% to 42%, with the largest 34S-depletions associated with the lowest rates of sulfate reduction and the lowest 34S-depletions with the highest rates. However, at high sulfate reduction rates (>10 micromoles cm-3 d-1) the lowest fractionation was 20% independent of the rates. Overall, there was a similarity between the fractionation obtained by the natural populations of sulfate reducers and previous measurements from pure cultures. This was somewhat surprising given the extremely high rates of sulfate reduction in the experiments. Our results are explained if we conclude that the fractionation was mainly controlled by the specific rate of sulfate reduction (mass cell-1 time-1) and not by the absolute rate (mass volume-1 time-1). Sedimentary sulfides (mainly FeS2) were on average 40% depleted in 34S compared to seawater sulfate. This amount of depletion was more than could be explained by the isotopic fractionations that we measured during bacterial sulfate reduction. Therefore, additional processes contributing to the fractionation of sulfur isotopes in the sediments are indicated. From both Solar Lake and Logten Lagoon we were able to enrich cultures of elemental sulfur-disproportionating bacteria. We suggest that isotope fractionation accompanying elemental sulfur disproportionation contributes to the 34S depletion of sedimentary sulfides at our study sites.

  2. Spin-polarized hydrogen and its isotopes: A rich class of quantum phases (Review Article)

    NASA Astrophysics Data System (ADS)

    Bešlić, I.; Vranješ Markić, L.; Boronat, J.

    2013-10-01

    We review the recent activity in the theoretical description of spin-polarized atomic hydrogen and its isotopes at very low temperatures. Spin-polarized hydrogen is the only system in nature that remains stable in the gas phase even in the zero temperature limit due to its small mass and weak interatomic interaction. Hydrogen and its heavier isotope tritium are bosons, the heavier mass of tritium producing a self-bound (liquid) system at zero temperature. The other isotope, deuterium, is a fermion with nuclear spin one making possible the study of three different quantum systems depending on the population of the three degenerate spin states. From the theoretical point of view, spin-polarized hydrogen is specially appealing because its interatomic potential is very accurately known making possible its precise quantum many-body study. The experimental study of atomic hydrogen has been very difficult due to its high recombination rate, but it finally led to its Bose-Einstein condensate state in 1998. Degeneracy has also been observed in thin films of hydrogen adsorbed on the 4He surface allowing for the possibility of observing the Berezinskii-Kosterlitz-Thouless superfluid transition.

  3. β-decay study of neutron-rich ^102Rb at TRIUMF-ISAC

    NASA Astrophysics Data System (ADS)

    Wang, Zhimin

    2012-10-01

    Experimental investigations of the β-decay properties of nuclei which lie along the astrophysical r-process are becoming possible with modern facilities and detection systems. In this experiment, a ^102Rb beam was produced by 500 MeV, 10 μA protons impinging on a multilayer UCx target at TRIUMF-ISAC Facility. The beam of ^102Rb ions was implanted on a movable tape at the center of the 8π spectrometer. The 20 HPGe 8π γ-ray detectors were coupled with SCEPTAR, an hemispherical array of scintillators for β-tagging and DANTE, an array of five LaBr3 detectors for fast γ-ray timing. A preliminary analysis has allowed the first identification of the 4^+ to 2^+ transition in the daughter nucleus, ^102Sr. A near identical low-lying band structure of ^102Sr with ^98, 100Sr nuclei has been observed, indicating the rigidly deformed rotational nature continues towards to the N=66 midshell. The current experimental measurements of ^102Rb β-decay half life as well as the β-delayed neutron emission branching ratio compared with reported values, the shorter β-decay half life and the larger β-delayed neutron emission branching ratio will locally reshape astrophysical r-process predictions.

  4. Crossings in alternating-parity bands of neutron-rich Ba nuclei

    SciTech Connect

    Urban, W.; Jones, M.A.; Durell, J.L.

    1995-07-22

    {sup 144}Ba and {sup 146}Ba nuclei produced in the spontaneous fission of {sup 248}Cm have been studied using the EUROGRAM II array. Spins and parities of excited levels have been deduced from triple-{gamma} angular correlation and direction-polarization correlation measurements, which is the first use of these techniques in studies of fission product nuclei. Ground-state, alternating-parity bands have been extended significantly and crossing in these bands has been found in both isotopes. For the first time alternating-parity band termination by particle alignment has been observed.

  5. Hydrogeochemical and stable isotopic investigations on CO2-rich mineral waters from Harghita Mts. (Eastern Carpathians, Romania)

    NASA Astrophysics Data System (ADS)

    Kis, Boglárka-Mercedesz; Baciu, Călin; Kármán, Krisztina; Kékedy-Nagy, Ladislau; Francesco, Italiano

    2013-04-01

    There is a worldwide interest on geothermal, mineral and groundwater as a resource for energy, drinking water supply and therapeutic needs. The increasing trend in replacing tap water with commercial bottled mineral water for drinking purposes has become an economic, hydrogeologic and medical concern in the last decades. Several investigations have been carried out worldwide on different topics related to geothermal and mineral waters, dealing with mineral water quality assessment, origin of geothermal and mineral waters, geochemical processes that influence water chemistry and water-rock interaction In Romania, the Călimani-Gurghiu-Harghita Neogene to Quaternary volcanic chain (Eastern Carpathians) is one of the most important areas from the point of view of CO2-rich mineral waters. These mineral water springs occur within other post-volcanic phenomena like dry CO2 emissions, moffettes, bubbling pools, H2S gas emissions etc. Mineral waters from this area are used for bottling, local spas and drinking purposes for local people. The number of springs, around 2000 according to literature data, shows that there is still a significant unexploited potential for good quality drinking water in this area. Within the youngest segment of the volcanic chain, the Harghita Mts., its volcaniclastic aprons and its boundary with the Transylvanian Basin, we have carried out an investigation on 23 CO2-rich mineral water springs from a hydrogeochemical and stable isotopic point of view. The mineral waters are Ca-Mg-HCO3 to Na-Cl type. Sometimes mixing between the two types can be observed. We have detected a great influence of water-rock interaction on the stable isotopic composition of the mineral waters, shown by isotopic shifts to the heavier oxygen isotope, mixing processes between shallow and deeper aquifers and local thermal anomalies. Acknowledgements: The present work was financially supported by the Romanian National Research Council, Project PN-II-ID-PCE-2011-3-0537 and by

  6. Cumulative fission yields of short-lived isotopes under natural-abundance-boron-carbide-moderated neutron spectrum

    SciTech Connect

    Finn, Erin C.; Metz, Lori A.; Greenwood, Lawrence R.; Pierson, Bruce; Wittman, Richard S.; Friese, Judah I.; Kephart, Rosara F.

    2015-04-09

    The availability of gamma spectroscopy data on samples containing mixed fission products at short times after irradiation is limited. Due to this limitation, data interpretation methods for gamma spectra of mixed fission product samples, where the individual fission products have not been chemically isolated from interferences, are not well-developed. The limitation is particularly pronounced for fast pooled neutron spectra because of the lack of available fast reactors in the United States. Samples containing the actinide isotopes 233, 235, 238U, 237Np, and 239Pu individually were subjected to a 2$ pulse in the Washington State University 1 MW TRIGA reactor. To achieve a fission-energy neutron spectrum, the spectrum was tailored using a natural abundance boron carbide capsule to absorb neutrons in the thermal and epithermal region of the spectrum. Our tailored neutron spectrum is unique to the WSU reactor facility, consisting of a soft fission spectrum that contains some measurable flux in the resonance region. This results in a neutron spectrum at greater than 0.1 keV with an average energy of 70 keV, similar to fast reactor spectra and approaching that of 235U fission. Unique fission product gamma spectra were collected from 4 minutes to 1 week after fission using single-crystal high purity germanium detectors. Cumulative fission product yields measured in the current work generally agree with published fast pooled fission product yield values from ENDF/B-VII, though a bias was noted for 239Pu. The present work contributes to the compilation of energy-resolved fission product yield nuclear data for nuclear forensic purposes.

  7. Performance of a total absorption clover detector for Qβ measurements of neutron-rich nuclei far from the β-stability line

    NASA Astrophysics Data System (ADS)

    Hayashi, H.; Shibata, M.; Asai, M.; Osa, A.; Sato, T. K.; Koizumi, M.; Kimura, A.; Oshima, M.

    2014-05-01

    To measure β-decay energies (Qβs) of neutron-rich nuclei far from the β-stability line, we have improved upon the previously described total absorption detector, composed of a clover Ge detector (80 mmϕ×90 mmL×4 crystals) and 4π BGO Compton suppressors. This detector can directly determine the Qβ from the end-point of the measured spectrum. Nuclei of interest such as new isotopes have Qβ values over 4 MeV; therefore, high detection efficiencies are needed. This total absorption detector has a through-hole (alongside its vertical axis) at the center of the four Ge crystals, and the radioactive sources can be placed in this hole to measure the total absorption spectrum. The β- and γ-rays are absorbed by the detector with almost 4π geometry while escaping radiations from the Ge detector can be detected by the 4π BGO Compton suppressors. We also developed a practical analytic procedure based on the folding method, in which response functions of γ- and β-rays were considered with an assumed decay scheme. The systematic uncertainty of the deduced Qβs was evaluated to be ±30 keV using 18 fission products whose Qβ values were precisely measured. With the detector and an on-line mass separator, we have determined the Qβ values of 166Eu and 165Gd for the first time, and have proposed more precise Qβ values for 160-165Eu and 163Gd than previously found. Owing to the especially good energy resolution of the detector, the isomeric state in 163Gd was also successfully observed for the first time through end-point analysis and analysis of the observed γ-rays. This result contributes to the determination of reliable Qβ values for 163Gd and 163Eu.

  8. Biomembranes research using thermal and cold neutrons.

    PubMed

    Heberle, F A; Myles, D A A; Katsaras, J

    2015-11-01

    In 1932 James Chadwick discovered the neutron using a polonium source and a beryllium target (Chadwick, 1932). In a letter to Niels Bohr dated February 24, 1932, Chadwick wrote: "whatever the radiation from Be may be, it has most remarkable properties." Where it concerns hydrogen-rich biological materials, the "most remarkable" property is the neutron's differential sensitivity for hydrogen and its isotope deuterium. Such differential sensitivity is unique to neutron scattering, which unlike X-ray scattering, arises from nuclear forces. Consequently, the coherent neutron scattering length can experience a dramatic change in magnitude and phase as a result of resonance scattering, imparting sensitivity to both light and heavy atoms, and in favorable cases to their isotopic variants. This article describes recent biomembranes research using a variety of neutron scattering techniques.

  9. Spectroscopy of the neutron-rich hypernucleus HeΛ7 from electron scattering

    DOE PAGES

    Gogami, T.; Chen, C.; Kawama, D.; ...

    2016-08-12

    Here, the missing mass spectroscopy of themore » $$^{7}_{\\Lambda}$$He hypernucleus was performed, using the $$^{7}$$Li$$(e,e^{\\prime}K^{+})^{7}_{\\Lambda}$$He reaction at the Thomas Jefferson National Accelerator Facility Hall C. The $$\\Lambda$$ binding energy of the ground state (1/2$$^{+}$$) was determined with a smaller error than that of the previous measurement, being $$B_{\\Lambda}$$ = 5.55 $$\\pm$$ 0.10(stat.) $$\\pm$$ 0.11(sys.) MeV. The experiment also provided new insight into charge symmetry breaking in p-shell hypernuclear systems. Finally, a peak at $$B_{\\Lambda}$$ = 3.65 $$\\pm$$ 0.20(stat.) $$\\pm$$ 0.11(sys.) MeV was observed and assigned as a mixture of 3/2$$^{+}$$ and 5/2$$^{+}$$ states, confirming the "gluelike" behavior of $$\\Lambda$$, which makes an unstable state in $$^{6}$$He stable against neutron emission.« less

  10. Spectroscopy of the neutron-rich hypernucleus He7Λ from electron scattering

    NASA Astrophysics Data System (ADS)

    Gogami, T.; Chen, C.; Kawama, D.; Achenbach, P.; Ahmidouch, A.; Albayrak, I.; Androic, D.; Asaturyan, A.; Asaturyan, R.; Ates, O.; Baturin, P.; Badui, R.; Boeglin, W.; Bono, J.; Brash, E.; Carter, P.; Chiba, A.; Christy, E.; Danagoulian, S.; De Leo, R.; Doi, D.; Elaasar, M.; Ent, R.; Fujii, Y.; Fujita, M.; Furic, M.; Gabrielyan, M.; Gan, L.; Garibaldi, F.; Gaskell, D.; Gasparian, A.; Han, Y.; Hashimoto, O.; Horn, T.; Hu, B.; Hungerford, Ed. V.; Jones, M.; Kanda, H.; Kaneta, M.; Kato, S.; Kawai, M.; Khanal, H.; Kohl, M.; Liyanage, A.; Luo, W.; Maeda, K.; Margaryan, A.; Markowitz, P.; Maruta, T.; Matsumura, A.; Maxwell, V.; Mkrtchyan, A.; Mkrtchyan, H.; Nagao, S.; Nakamura, S. N.; Narayan, A.; Neville, C.; Niculescu, G.; Niculescu, M. I.; Nunez, A.; Nuruzzaman, Okayasu, Y.; Petkovic, T.; Pochodzalla, J.; Qiu, X.; Reinhold, J.; Rodriguez, V. M.; Samanta, C.; Sawatzky, B.; Seva, T.; Shichijo, A.; Tadevosyan, V.; Tang, L.; Taniya, N.; Tsukada, K.; Veilleux, M.; Vulcan, W.; Wesselmann, F. R.; Wood, S. A.; Yamamoto, T.; Ya, L.; Ye, Z.; Yokota, K.; Yuan, L.; Zhamkochyan, S.; Zhu, L.; HKS JLab E05-115 Collaboration

    2016-08-01

    The missing mass spectroscopy of the He7Λ hypernucleus was performed using the 7Li(e ,e'K+) He7Λ reaction at the Thomas Jefferson National Accelerator Facility Hall C. The Λ -binding energy of the ground-state (1 /2+ ) was determined with a smaller error than that of the previous measurement, being BΛ=5.55 ±0 .10stat .±0 .11sys .MeV . The experiment also provided new insight into charge symmetry breaking in p -shell hypernuclear systems. Finally, a peak at BΛ=3.65 ±0 .20stat .±0 .11sys .MeV was observed and assigned as a mixture of 3 /2+ and 5 /2+ states, confirming the "gluelike" behavior of Λ , which makes an unstable state in 6He stable against neutron emission.

  11. Role of nuclear couplings in the inelastic excitation of weakly-bound neutron-rich nuclei

    SciTech Connect

    Dasso, C.H.; Lenzi, S.M.; Vitturi, A.

    1996-12-31

    Much effort is presently devoted to the study of nuclear systems far from the stability line. Particular emphasis has been placed in light systems such as {sup 11}Li, {sup 8}B and others, where the very small binding energy of the last particles causes their density distribution to extend considerably outside of the remaining nuclear core. Some of the properties associated with this feature are expected to characterize also heavier systems in the vicinity of the proton or neutron drip lines. It is by now well established that low-lying concentrations of multipole strength arise from pure configurations in which a peculiar matching between the wavelength of the continuum wavefunction of the particles and the range of the weakly-bound hole states occurs. To this end the authors consider the break-up of a weakly-bound system in a heavy-ion collision and focus attention in the inelastic excitation of the low-lying part of the continuum. They make use of the fact that previous investigations have shown that the multipole response in this region is not of a collective nature and describe their excited states as pure particle-hole configurations. Since the relevant parameter determining the strength distributions is the binding energy of the last bound orbital they find it most convenient to use single-particle wavefunctions generated by a sperical square-well potential with characteristic nuclear dimensions and whose depth has been adjusted to give rise to a situation in which the last occupied neutron orbital is loosely-bound. Spin-orbit couplings are, for the present purpose, ignored. The results of this investigation clearly indicate that nuclear couplings have the predominant role in causing projectile dissociation in many circumstances, even at bombarding energies remarkably below the Coulomb barrier.

  12. Upbend and M1 scissors mode in neutron-rich nuclei - consequences for r-process $$(n,\\gamma )$$ reaction rates

    DOE PAGES

    Larsen, A. C.; Goriely, S.; Bernstein, L. A.; ...

    2015-01-01

    An enhanced probability for low-energy γ-emission (upbend, Eγ < 3 MeV) at high excitation energies has been observed for several light and medium-mass nuclei close to the valley of stability. Also the M1 scissors mode seen in deformed nuclei increases the γ-decay probability for low-energy γ-rays (Eγ ≈ 2–3 MeV). These phenomena, if present in neutron-rich nuclei, have the potential to increase radiative neutron-capture rates relevant for the r-process. Furthermore, the experimental and theoretical status of the upbend is discussed, and preliminary calculations of (n,γ) reaction rates for neutron-rich, mid-mass nuclei including the scissors mode are shown.

  13. Upbend and M1 scissors mode in neutron-rich nuclei - consequences for r-process $(n,\\gamma )$ reaction rates

    SciTech Connect

    Larsen, A. C.; Goriely, S.; Bernstein, L. A.; Bleuel, D. L.; Bracco, A.; Brown, B. A.; Camera, F.; Eriksen, T. K.; Frauendorf, S.; Giacoppo, F.; Guttormsen, M.; Gorgen, A.; Harissopulos, S.; Leoni, S.; Liddick, S. N.; Naqvi, F.; Nyhus, H. T.; Rose, S. J.; Renstrom, T.; Schwengner, R.; Siem, S.; Spyrou, A.; Tveten, G. M.; Voinov, A. V.; Wiedeking, M.

    2015-01-01

    An enhanced probability for low-energy γ-emission (upbend, Eγ < 3 MeV) at high excitation energies has been observed for several light and medium-mass nuclei close to the valley of stability. Also the M1 scissors mode seen in deformed nuclei increases the γ-decay probability for low-energy γ-rays (Eγ ≈ 2–3 MeV). These phenomena, if present in neutron-rich nuclei, have the potential to increase radiative neutron-capture rates relevant for the r-process. Furthermore, the experimental and theoretical status of the upbend is discussed, and preliminary calculations of (n,γ) reaction rates for neutron-rich, mid-mass nuclei including the scissors mode are shown.

  14. Neutrons for biologists: a beginner's guide, or why you should consider using neutrons

    PubMed Central

    Lakey, Jeremy H.

    2009-01-01

    From the structures of isolated protein complexes to the molecular dynamics of whole cells, neutron methods can achieve a resolution in complex systems that is inaccessible to other techniques. Biology is fortunate in that it is rich in water and hydrogen, and this allows us to exploit the differential sensitivity of neutrons to this element and its major isotope, deuterium. Furthermore, neutrons exhibit wave properties that allow us to use them in similar ways to light, X-rays and electrons. This review aims to explain the basics of biological neutron science to encourage its greater use in solving difficult problems in the life sciences. PMID:19656821

  15. Neutrons for biologists: a beginner's guide, or why you should consider using neutrons.

    PubMed

    Lakey, Jeremy H

    2009-10-06

    From the structures of isolated protein complexes to the molecular dynamics of whole cells, neutron methods can achieve a resolution in complex systems that is inaccessible to other techniques. Biology is fortunate in that it is rich in water and hydrogen, and this allows us to exploit the differential sensitivity of neutrons to this element and its major isotope, deuterium. Furthermore, neutrons exhibit wave properties that allow us to use them in similar ways to light, X-rays and electrons. This review aims to explain the basics of biological neutron science to encourage its greater use in solving difficult problems in the life sciences.

  16. Study of neutron-rich nuclei near doubly magic 132Sn

    NASA Astrophysics Data System (ADS)

    Sarkar, M. Saha; Sarkar, S.

    2012-06-01

    Large basis untruncated shell-model (SM) calculations have been done for nuclei with 50 ≤Z ≤56 and 82 ≤ N ≤ 88 in the π(gdsh) ⊗ ν (hf pi) valence space above the 132Sn core using both realistic CWG and empirical SMPN (1+2)-body Hamiltonians. These neutronrich nuclei lie on or close to the path of astrophysical r-process flow. Reasons behind the similarity and dissimilarity between the results using these two interactions have been discussed. The observation and prediction of unusually depressed first excited 2+1 states in even-A semi-magic Sn isotopes having N =84-88 and the possibility of a new magic number at N = 90 above 132Sn provide motivations for reviewing the problems related to the nuclear astrophysics in general.

  17. Small angle neutron scattering modeling of copper-rich precipitates in steel

    SciTech Connect

    Spooner, S.

    1997-11-01

    The magnetic to nuclear scattering intensity ratio observed in the scattering from copper rich precipitates in irradiated pressure vessel steels is much smaller than the value of 11.4 expected for a pure copper precipitate in iron. A model for precipitates in pressure vessel steels which matches the observed scattering typically incorporates manganese, nickel, silicon and other elements and it is assumed that the precipitate is non-magnetic. In the present work consideration is given to the effect of composition gradients and ferromagnetic penetration into the precipitate on the small angle scattering cross section for copper rich clusters as distinguished from conventional precipitates. The calculation is an extension of a scattering model for micelles which consist of shells of varying scattering density. A discrepancy between recent SANS scattering experiments on pressure vessel steels was found to be related to applied magnetic field strength. The assumption of cluster structure and its relation to atom probe FIM findings as well as the effects of insufficient field for magnetic saturation is discussed.

  18. Small angle neutron scattering modeling of copper-rich precipitates in steel

    SciTech Connect

    Spooner, S.

    1997-11-01

    The magnetic-to-nuclear scattering intensity ratio observed in the scattering from copper-rich precipitates in irradiated pressure vessel steels is much smaller than the value of 11.4 expected for a pure copper precipitate in iron. A model for precipitates in pressure vessel steels which matches the observed scattering typically incorporates manganese, nickel, silicon and other elements and it is assumed that the precipitate is non-magnetic. In the present work consideration is given to the effect of composition gradients and ferromagnetic penetration into the precipitate on the small angle scattering cross section for copper-rich clusters as distinguished from conventional precipitates. The calculation is an extension of a scattering model for micelles which consist of shells of varying scattering density. A discrepancy between recent SANS scattering experiments on pressure vessel shells was found to be related to applied magnetic field strength. The assumption of cluster structure and its relation to atom probe FIM findings as well as the effects of insufficient field for magnetic saturation is discussed.

  19. Abundances in red giant stars - Nitrogen isotopes in carbon-rich molecular envelopes

    NASA Technical Reports Server (NTRS)

    Wannier, P. G.; Andersson, B.-G.; Olofsson, H.; Ukita, N.; Young, K.

    1991-01-01

    Results are presented of millimeter- and submillimeter-wave observations of HCN and HCCCN that were made of the circmustellar envelopes of eight carbon stars, including the two protoplanetary nebulae CRL 618 and CRL 2688. The observations yield a measure of the double ratio (N-14)(C-13)/(N-15)(C-12). Measured C-12/C-13 ratios are used to estimate the N-14/N-15 abundance ratio, with the resulting lower limits in all eight envelopes and possible direct determinations in two envelopes. The two determinations and four of the remaining six lower limits are found to be in excess of the terrestrial value of N-14/N-15 = 272, indicating an evolution of the nitrogen isotope ratio, which is consistent with stellar CNO processing. Observations of thermal SiO (v = 0, J = 2-1) emission show that the Si-29/Si-28 ratio can be determined in carbon stars, and further observations are indicated.

  20. Production of Samples of Individual Radioxenon Isotopes Through Neutron Irradiation of Stable Xenon Gas

    DTIC Science & Technology

    2008-09-01

    Whitney, S. C. (2006). Light-Element Neutron Depth Profiling at the University of Texas. MS Thesis, University of Texas at Austin. 2008 Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies 757

  1. Chemical and Isotopic Heterogeneities in the Deep Earth:Importance of Lower Mantle Carbonate-rich Melts

    NASA Astrophysics Data System (ADS)

    Collerson, K. D.; Williams, Q.; Murphy, D.

    2007-12-01

    Evolution of mantle chemical heterogeneity reflects a spectrum of processes. Nature of reservoirs has been inferred from radiogenic isotope and trace element systematics of mid-ocean ridge basalts (MORB) and ocean island basalts (OIB) [1]. Carbonatites, kimberlites and lamproites [2-4] also sample depleted and enriched reservoirs, however, their origin remains equivocal. Secular decrease in Th/U ratio in MORB mantle (DMM), homogeneity of Th/U inferred from Pb-isotopic data, and systematic variation in Nb/Th and Nb/U ratios in MORBs [5], show that recycled components in DMM are well mixed. Thus isotopically hererogeneous domains in DMM must be transient features and are unlikely to yield HIMU and EM chemistries. Explanations for HIMU and EM OIB chemistries include involvement of: (1) subcontinental lithospheric mantle; (2) subducted oceanic lithosphere; (3) subducted sediment; or (4) an enigmatic lower mantle (LM) "plume component". Elevated 3He/4He in OIBs and kimberlites [6] and excess 129Xe and high 40Ar/39Ar [e.g., 7-8] and solar 20Ne/22Ne [9] in carbonatites indicate that they were derived from a primitive, isolated, and less degassed source than MORB. Primordial compositions show that this reservoir escaped atmospheric contamination by Ar, Xe, and Ne and pollution by 4He-rich material (from recycled 238U) during subduction. This primitive reservoir likely exists below the depth subducted slabs obviously penetrate (ca. 1700 km) e.g., [10]. That kimberlites are deeply sourced is also shown by lower mantle inclusions in diamond, e.g., [11]. Importantly, Gp. 1 and 2 kimberlites are isotopically similar to HIMU and EM-1 OIBs [4]. We interpret Gp 1 kimberlites as mixtures of HIMU and EM sources, while Gp. 2 kimberlites (close to EM-1) are interpreted as melts of a Ca perovskite-rich reservoir, possibly from slabs in the LM. We model melting of LM phases to simulate evolution of EM1 and HIMU 87Sr/86Sr, 143Nd/144Nd, 176Hf/177Hf, 207Pb/204Pb, 206Pb/204Pb and 208Pb/204

  2. 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.

  3. 94 β -Decay Half-Lives of Neutron-Rich Cs 55 to Ho 67 : Experimental Feedback and Evaluation of the r -Process Rare-Earth Peak Formation

    NASA Astrophysics Data System (ADS)

    Wu, J.; Nishimura, S.; Lorusso, G.; Möller, P.; Ideguchi, E.; Regan, P.-H.; Simpson, G. S.; Söderström, P.-A.; Walker, P. M.; Watanabe, H.; Xu, Z. Y.; Baba, H.; Browne, F.; Daido, R.; Doornenbal, P.; Fang, Y. F.; Gey, G.; Isobe, T.; Lee, P. S.; Liu, J. J.; Li, Z.; Korkulu, Z.; Patel, Z.; Phong, V.; Rice, S.; Sakurai, H.; Sinclair, L.; Sumikama, T.; Tanaka, M.; Yagi, A.; Ye, Y. L.; Yokoyama, R.; Zhang, G. X.; Alharbi, T.; Aoi, N.; Bello Garrote, F. L.; Benzoni, G.; Bruce, A. M.; Carroll, R. J.; Chae, K. Y.; Dombradi, Z.; Estrade, A.; Gottardo, A.; Griffin, C. J.; Kanaoka, H.; Kojouharov, I.; Kondev, F. G.; Kubono, S.; Kurz, N.; Kuti, I.; Lalkovski, S.; Lane, G. J.; Lee, E. J.; Lokotko, T.; Lotay, G.; Moon, C.-B.; Nishibata, H.; Nishizuka, I.; Nita, C. R.; Odahara, A.; Podolyák, Zs.; Roberts, O. J.; Schaffner, H.; Shand, C.; Taprogge, J.; Terashima, S.; Vajta, Z.; Yoshida, S.

    2017-02-01

    The β -decay half-lives of 94 neutron-rich nuclei Cs-151144 , Ba-154146 , La-156148 , Ce-158150 , Pr-160153 , Nd-162156 , Pm-163159 , Sm-166160 , Eu-168161 , Gd-170165 , Tb-172166 , Dy-173169 , Ho-175172 , and two isomeric states Erm174 , Dym172 were measured at the Radioactive Isotope Beam Factory, providing a new experimental basis to test theoretical models. Strikingly large drops of β -decay half-lives are observed at neutron-number N =97 for Ce 58 , Pr 59 , Nd 60 , and Sm 62 , and N =105 for Eu 63 , Gd 64 , Tb 65 , and Dy 66 . Features in the data mirror the interplay between pairing effects and microscopic structure. r -process network calculations performed for a range of mass models and astrophysical conditions show that the 57 half-lives measured for the first time play an important role in shaping the abundance pattern of rare-earth elements in the solar system.

  4. 94 β-Decay Half-Lives of Neutron-Rich _{55}Cs to _{67}Ho: Experimental Feedback and Evaluation of the r-Process Rare-Earth Peak Formation.

    PubMed

    Wu, J; Nishimura, S; Lorusso, G; Möller, P; Ideguchi, E; Regan, P-H; Simpson, G S; Söderström, P-A; Walker, P M; Watanabe, H; Xu, Z Y; Baba, H; Browne, F; Daido, R; Doornenbal, P; Fang, Y F; Gey, G; Isobe, T; Lee, P S; Liu, J J; Li, Z; Korkulu, Z; Patel, Z; Phong, V; Rice, S; Sakurai, H; Sinclair, L; Sumikama, T; Tanaka, M; Yagi, A; Ye, Y L; Yokoyama, R; Zhang, G X; Alharbi, T; Aoi, N; Bello Garrote, F L; Benzoni, G; Bruce, A M; Carroll, R J; Chae, K Y; Dombradi, Z; Estrade, A; Gottardo, A; Griffin, C J; Kanaoka, H; Kojouharov, I; Kondev, F G; Kubono, S; Kurz, N; Kuti, I; Lalkovski, S; Lane, G J; Lee, E J; Lokotko, T; Lotay, G; Moon, C-B; Nishibata, H; Nishizuka, I; Nita, C R; Odahara, A; Podolyák, Zs; Roberts, O J; Schaffner, H; Shand, C; Taprogge, J; Terashima, S; Vajta, Z; Yoshida, S

    2017-02-17

    The β-decay half-lives of 94 neutron-rich nuclei ^{144-151}Cs, ^{146-154}Ba, ^{148-156}La, ^{150-158}Ce, ^{153-160}Pr, ^{156-162}Nd, ^{159-163}Pm, ^{160-166}Sm, ^{161-168}Eu, ^{165-170}Gd, ^{166-172}Tb, ^{169-173}Dy, ^{172-175}Ho, and two isomeric states ^{174m}Er, ^{172m}Dy were measured at the Radioactive Isotope Beam Factory, providing a new experimental basis to test theoretical models. Strikingly large drops of β-decay half-lives are observed at neutron-number N=97 for _{58}Ce, _{59}Pr, _{60}Nd, and _{62}Sm, and N=105 for _{63}Eu, _{64}Gd, _{65}Tb, and _{66}Dy. Features in the data mirror the interplay between pairing effects and microscopic structure. r-process network calculations performed for a range of mass models and astrophysical conditions show that the 57 half-lives measured for the first time play an important role in shaping the abundance pattern of rare-earth elements in the solar system.

  5. Production of the neutron-induced isotope, 73Ga, at the Davis Campus of the Sanford Underground Research Facility with the MAJORANA DEMONSTRATOR

    NASA Astrophysics Data System (ADS)

    Chu, Pinghan; Majorana Demonstrator Collaboration

    2016-09-01

    We report a study of the production of the neutron-induced isotope, 73Ga, in the MAJORANA DEMONSTRATOR array at the underground Davis Campus of the Sanford Underground Research Facility 4850 ft level. This isotope has a half-life time of 4.86 hours and can be generated through interactions between fast neutrons and germanium isotopes. Using its unique decay signature, we have identified three candidate events of 73Ga in the commissioning data of MAJORANA DEMONSTRATOR. Based on these three events, we estimate the corresponding neutron energy spectrum and the radioactive background generated by neutron-induced isotopes. The background from neutron-induced isotopes has been also calculated in the Region of Interest for 76Ge neutrinoless double beta decays. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics Program of the National Science Foundation, and the Sanford Underground Research Facility. We acknowledge the support of the U.S. Department of Energy through the LANL/LDRD Program. U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Award Numbers DE-AC02-05CH11231, DE-AC52-06NA25396, DE-FG02-97ER41041, DE-FG02-97ER41033, DE-FG02-97ER41042, DE-SC0012612, DE-FG02-10ER41715, DE-SC0010254, and DE-FG02-97ER4102.

  6. Method for detecting and correcting for isotope burn-in during long-term neutron dosimetry exposure

    DOEpatents

    Ruddy, Francis H.

    1988-01-01

    A method is described for detecting and correcting for isotope burn-in during-long term neutron dosimetry exposure. In one embodiment, duplicate pairs of solid state track recorder fissionable deposits are used, including a first, fissionable deposit of lower mass to quantify the number of fissions occuring during the exposure, and a second deposit of higher mass to quantify the number of atoms of for instance .sup.239 Pu by alpha counting. In a second embodiment, only one solid state track recorder fissionable deposit is used and the resulting higher track densities are counted with a scanning electron microscope. This method is also applicable to other burn-in interferences, e.g., .sup.233 U in .sup.232 Th or .sup.238 Pu in .sup.237 Np.

  7. 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.

    PubMed

    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

    2015-05-15

    The β-decay half-lives of 110 neutron-rich isotopes of the elements from _{37}Rb to _{50}Sn 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.

  8. First observation of a rotational band and the role of the proton intruder orbital π1/2+[431] in very neutron-rich odd-odd Nb106

    NASA Astrophysics Data System (ADS)

    Luo, Y. X.; Rasmussen, J. O.; Hamilton, J. H.; Ramayya, A. V.; Wang, E.; Liu, Y. X.; Jiao, C. F.; Liang, W. Y.; Xu, F. R.; Sun, Y.; Frauendorf, S.; Hwang, J. K.; Liu, S. H.; Zhu, S. J.; Brewer, N. T.; Lee, I. Y.; Ter-Akopian, G. M.; Oganessian, Yu.; Donangelo, R.; Ma, W. C.

    2014-04-01

    A rotational band was observed for the first time in Nb106 by means of γ-γ-γ and γ-γ-γ-γ measurements of prompt fission γ rays from Cf252 by using the Gammasphere multidetector array. Projected shell model and potential-energy surface calculations were performed and were compared to the experimental data of Nb106 and the previously reported Nb104. Configurations and spin-parity were assigned to the ground level, low-lying levels, and rotational bandheads of the two Nb isotopes. The new rotational band in Nb106 was interpreted as a Kπ=2- band with a configuration π1/2+[431] × ν5/2-[532]. The same spin-parity and configuration were assigned to the analogous band in Nb104. π1/2+[431] × ν5/2+[413], Kπ=3+ were assigned to the 0.66-μs isomer and explained the M2 isomeric decay to the ground in Nb106. The proton intruder orbital π1/2+[431] plays an important role in shape evolution with regard to triaxial deformation in these neutron-rich Nb isotopes.

  9. Copper isotope variations of copper-rich minerals in seafloor hydrothermal deposits and igneous rocks, measured by a femtosecond LA-MC-ICP-MS

    NASA Astrophysics Data System (ADS)

    Ikehata, K.; Ishibashi, J.; Suzuki, R.; Hirata, T.

    2013-05-01

    In recent years, the copper isotope systematics has seen an increased interest as a potential tool for understanding copper sources and geochemical processes of copper transport and deposition in ore-forming systems. The copper isotope variations of primary and secondary copper-rich minerals from modern (Mariana Trough) and ancient (Besshi-type and Kuroko-type volcanogenic massive sulfide deposits, Japan) seafloor hydrothermal deposits have been analyzed by a femtosecond-pulsed laser ablation multiple collector inductively coupled plasma mass spectrometry (fs-LA-MC-ICP-MS). The δ65Cu (where δ65Cu = [(65Cu/63Cu)sample/ (65Cu/63Cu)NIST-SRM976-1] × 1000) values of copper-rich sulfide minerals of chimney samples from active seafloor hydrothermal deposits are significantly large (δ65Cu = -0.7 to 4.0‰) compared to those of copper-rich minerals in ancient submarine hydrothermal deposits (δ65Cu = -0.3 to 0.4‰; e.g., Ikehata et al., 2011) and in igneous rocks (δ65Cu = -0.3 to 0.3‰; e.g., Ikehata et al., 2012). These large copper isotopic variations in the chimney samples are most likely explained in terms of a redox-controlled isotope fractionation during hydrothermal reworking of copper sulfides below sea floor or alteration of primary hydrothermal copper sulfides by seawater, involving the preferential incorporation of heavy copper isotopes in secondary Cu(II) solutions. These results also suggest that sub-seafloor recrystallization and metamorphic reequilibration may have reduced the original range of copper isotopes. Secondary malachite (δ65Cu = 2.6 to 3.0‰) and native copper (δ65Cu = 1.4 to 1.7‰) in the Besshi-type deposits have heavier copper isotopic values compared to precursor copper-rich minerals. These variations are mainly due to isotope fractionations during redox reactions (weathering) at low temperatures involving the preferential incorporation of heavy copper isotopes in secondary Cu(II) solutions.

  10. The subcontinental mantle beneath southern New Zealand, characterised by helium isotopes in intraplate basalts and gas-rich springs

    NASA Astrophysics Data System (ADS)

    Hoke, L.; Poreda, R.; Reay, A.; Weaver, S. D.

    2000-07-01

    New helium isotope data measured in Cenozoic intraplate basalts and their mantle xenoliths are compared with present-day mantle helium emission on a regional scale from thermal and nonthermal gas discharges on the South Island of New Zealand and the offshore Chatham Islands. Cenozoic intraplate basaltic volcanism in southern New Zealand has ocean island basalt affinities but is restricted to continental areas and absent from adjacent Pacific oceanic crust. Its distribution is diffuse and widespread, it is of intermittent timing and characterised by low magma volumes. Most of the 3He/ 4He ratios measured in fluid inclusions in mantle xenocrysts and basalt phenocrysts such as olivine, garnet, and amphibole fall within the narrow range of 8.5 ± 1.5 Ra (Ra is the atmospheric 3He/ 4He ratio) with a maximum value of 11.5 Ra. This range is characteristic of the relatively homogeneous and degassed upper MORB-mantle helium reservoir. No helium isotope ratios typical of the lower less degassed mantle (>12 Ra), such as exemplified by the modern hot-spot region of Hawaii (with up to 32 Ra) were measured. Helium isotope ratios of less than 8 Ra are interpreted in terms of dilution of upper mantle helium with a radiogenic component, due to either age of crystallisation or small-scale mantle heterogeneities caused by mixing of crustal material into the upper mantle. The crude correlation between age of samples and helium isotopes with generally lower R/Ra values in mantle xenoliths compared with host rock phenocrysts and the in general depleted Nd and Sr isotope ratios and the light rare earth element enrichment of the basalts supports derivation of melts as small melt fractions from a depleted upper mantle, with posteruptive ingrowth of radiogenic helium as a function of lithospheric age. In comparison, the regional helium isotope survey of thermal and nonthermal gas discharges of the South Island of New Zealand shows that mantle 3He anomalies in general do not show an obvious

  11. Competition between α and β decays for heavy deformed neutron-deficient Pa, U, Np, and Pu isotopes

    NASA Astrophysics Data System (ADS)

    Ni, Dongdong; Ren, Zhongzhou

    2017-01-01

    The competition between α and β decays is investigated for neutron-deficient Pa, U, Np, and Pu isotopes. β+/electron-capture (EC) decay rates are calculated within the deformed quasiparticle random-phase approximation with realistic nucleon-nucleon (N N ) interactions. Contributions from allowed Gamow-Teller and Fermi transitions as well as first-forbidden transitions are considered. α -decay calculations are performed within the generalized density-dependent cluster model. Effects of differences between neutron and proton distributions and nuclear deformation are taken into account. In the calculations, Reid-93 N N interactions are used for β+/EC decays, while Michigan three-range Yukawa effective interactions, based on the G -matrix elements of Reid N N potentials, are used for α decay. The calculated β -decay half-lives show good agreement with the experimental data over a range of magnitude from 102 to 105 s. The resulting total half-lives including α and β contributions are found to be in good agreement with the experimental data, together with the α /β -decay branching ratios.

  12. Shape coexistence in the N = 19 neutron-rich nucleus 31Mg explored by β-γ spectroscopy of spin-polarized 31Na

    NASA Astrophysics Data System (ADS)

    Nishibata, H.; Shimoda, T.; Odahara, A.; Morimoto, S.; Kanaya, S.; Yagi, A.; Kanaoka, H.; Pearson, M. R.; Levy, C. D. P.; Kimura, M.

    2017-04-01

    The structure of excited states in the neutron-rich nucleus 31Mg, which is in the region of the "island of inversion" associated with the neutron magic number N = 20, is studied by β-γ spectroscopy of spin-polarized 31Na. Among the 31Mg levels below the one neutron separation energy of 2.3 MeV, the spin values of all five positive-parity levels are unambiguously determined by observing the anisotropic β decay. Two rotational bands with Kπ = 1 /2+ and 1 /2- are proposed based on the spins and energies of the levels. Comparison on a level-by-level basis is performed between the experimental results and theoretical calculations by the antisymmetrized molecular dynamics (AMD) plus generator coordinate method (GCM). It is found that various nuclear structures coexist in the low excitation energy region in 31Mg.

  13. Inverse-kinematics one-neutron pickup with fast rare-isotope beams

    SciTech Connect

    Gade, A.; Baugher, T.; Brown, B. A.; Glasmacher, T.; McDaniel, S.; Ratkiewicz, A.; Stroberg, S. R.; Tostevin, J. A.; Bazin, D.; Campbell, C. M.; Grinyer, G. F.; Weisshaar, D.; Winkler, R.; Meierbachtol, K.; Walsh, K. A.

    2011-05-15

    Measurements and reaction model calculations are reported for single-neutron pickup reactions onto a fast {sup 22}Mg secondary beam at 84 MeV per nucleon. Measurements made on both carbon and beryllium targets, having very different structures, were used to investigate the likely nature of the pickup reaction mechanism. The measurements involve thick reaction targets and {gamma}-ray spectroscopy of the projectile-like reaction residue for final-state resolution, which permit experiments with low incident beam rates compared to traditional low-energy transfer reactions. From measured longitudinal momentum distributions we show that the {sup 12}C({sup 22}Mg,{sup 23}Mg+{gamma})X reaction largely proceeds as a direct two-body reaction, with the neutron transfer producing bound {sup 11}C target residues. The corresponding reaction on the {sup 9}Be target seems to largely leave the {sup 8}Be residual nucleus unbound at excitation energies high in the continuum. We discuss the possible use of such fast-beam one-neutron pickup reactions to track single-particle strength in exotic nuclei and also their expected sensitivity to neutron high-l (intruder) states, which are often direct indicators of shell evolution and the disappearance of magic numbers in the exotic regime.

  14. Inverse-kinematics one-neutron pickup with fast rare-isotope beams

    NASA Astrophysics Data System (ADS)

    Gade, A.; Tostevin, J. A.; Baugher, T.; Bazin, D.; Brown, B. A.; Campbell, C. M.; Glasmacher, T.; Grinyer, G. F.; McDaniel, S.; Meierbachtol, K.; Ratkiewicz, A.; Stroberg, S. R.; Walsh, K. A.; Weisshaar, D.; Winkler, R.

    2011-05-01

    Measurements and reaction model calculations are reported for single-neutron pickup reactions onto a fast Mg22 secondary beam at 84 MeV per nucleon. Measurements made on both carbon and beryllium targets, having very different structures, were used to investigate the likely nature of the pickup reaction mechanism. The measurements involve thick reaction targets and γ-ray spectroscopy of the projectile-like reaction residue for final-state resolution, which permit experiments with low incident beam rates compared to traditional low-energy transfer reactions. From measured longitudinal momentum distributions we show that the 12C(22Mg,23Mg+γ)X reaction largely proceeds as a direct two-body reaction, with the neutron transfer producing bound C11 target residues. The corresponding reaction on the Be9 target seems to largely leave the Be8 residual nucleus unbound at excitation energies high in the continuum. We discuss the possible use of such fast-beam one-neutron pickup reactions to track single-particle strength in exotic nuclei and also their expected sensitivity to neutron high-ℓ (intruder) states, which are often direct indicators of shell evolution and the disappearance of magic numbers in the exotic regime.

  15. Large negative Ti-50 anomalies in refractory inclusions from the Murchison carbonaceous chondrite - Evidence for incomplete mixing of neutron-rich supernova ejecta into the solar system

    NASA Technical Reports Server (NTRS)

    Hinton, Richard W.; Davis, Andrew M.; Scatena-Wachel, Debra E.

    1987-01-01

    An ion microprobe was used to measure Ti-50 variations in hibonite-rich inclusions from the Murchison chondrite. Both deficits and excesses of the isotope were found, depending on the inclusion being scanned. The anomalies were not correlated with the mineralogy, chemical composition, other isotopic anomalies of Ti, etc. The lack of correlations indicates that the cosmic chemical memory model (Clayton, 1981) cannot explain the observed variations. The Ti-50 concentrations may have originated when a supernova explosion triggered the collapse of a molecular cloud that formed the solar system. The solar system Ti-50 anomalies were from the cloud, not the progenitor star.

  16. Early onset of deformation in the neutron-deficient polonium isotopes

    NASA Astrophysics Data System (ADS)

    Cocolios, T. E.; Andreyev, A. N.; Antalic, S.; Barzakh, A. E.; Bastin, B.; Büscher, J.; Darby, I. G.; Dexters, W.; Fedorov, D. V.; Fedosseev, V. N.; Flanagan, K. T.; Franchoo, S.; Fritzsche, S.; Huber, G.; Huyse, M.; Keupers, M.; Köster, U.; Kudryavtsev, Yu; Mané, E.; Marsh, B. A.; Molkanov, P. L.; Page, R. D.; Seliverstov, M. D.; Sjödin, A. M.; Stefan, I.; Van de Walle, J.; Van Duppen, P.; Venhart, M.; Zemlyanoy, S. G.

    2012-09-01

    In-source laser spectroscopy has been performed at CERN-ISOLDE with the RILIS laser ion source on 191-204,206,208-211,216,218Po. New information on the β decay of 199Po were extracted in the process, challenging previous results. Large-scale atomic calculations were performed to extract the changes in the mean-square charge radius δlangler2rangle from the isotope shifts. The δlangler2rangle for the even-A isotopes reveal a large deviation from the spherical droplet model for N < 116.

  17. Carriers mobility of InAs- and InP- rich InAs-InP solid solutions irradiated by fast neutrons

    SciTech Connect

    Khutsishvili, Elza; Khomasuridze, David; Gabrichidze, Leonti; Kvirkvelia, Bella; Kekelidze, David; Guguchia, Zurab; Aliyev, Vugar; Kekelidze, Nodar

    2013-12-04

    We have studied the low temperature charge carriers mobility in bulk single crystals of InAs- and InP- rich InAs-InP solid solutions irradiated with maximum integral flux 2⋅10{sup 18} n/cm{sup 2} of fast neutrons. Influence of minor component small addition in InAs-InP solid solutions has been revealed. There are also presented data of radiation defects thermal stability.

  18. Identification of highly deformed even-even nuclei in the neutron- and proton-rich regions of the nuclear chart from the B(E2)↑ and E2 predictions in the generalized differential equation model

    NASA Astrophysics Data System (ADS)

    Nayak, R. C.; Pattnaik, S.

    2015-11-01

    We identify here the possible occurrence of large deformations in the neutron- and proton-rich (n-rich and p-rich) regions of the nuclear chart from extensive predictions of the values of the reduced quadrupole transition probability B(E2)↑ for the transition from the ground state to the first 2+ state and the corresponding excitation energy E2 of even-even nuclei in the recently developed generalized differential equation (GDE) model exclusively meant for these physical quantities. This is made possible from our analysis of the predicted values of these two physical quantities and the corresponding deformation parameters derived from them such as the quadrupole deformation β2, the ratio of β2 to the Weisskopf single-particle β2(sp) and the intrinsic electric quadrupole moment Q0, calculated for a large number of both known as well as hitherto unknown even-even isotopes of oxygen to fermium (0 to FM; Z = 8-100). Our critical analysis of the resulting data convincingly support possible existence of large collectivity for the nuclides 30,32Ne,34Mg, 60Ti, 42,62,64Cr,50,68Fe, 52,72Ni, 72,70,96Kr,74,76Sr,78,80,106,108Zr, 82,84,110,112Mo, 140Te,144Xe, 148Ba,122Ce, 128,156Nd,130,132,158,160Sm and 138,162,164,166Gd, whose values of β2 are found to exceed 0.3 and even 0.4 in some cases. Our findings of large deformations in the exotic n-rich regions support the existence of another “island of inversion” in the heavy-mass region possibly caused by breaking of the N = 70 subshell closure.

  19. 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.

  20. Biomembranes research using thermal and cold neutrons

    SciTech Connect

    Heberle, Frederick A.; Myles, Dean A. A.; Katsaras, John

    2015-08-01

    In 1932 James Chadwick discovered the neutron using a polonium source and a beryllium target (Chadwick, 1932). In a letter to Niels Bohr dated February 24, 1932, Chadwick wrote: “whatever the radiation from Be may be, it has most remarkable properties.” Where it concerns hydrogen-rich biological materials, the “most remarkable” property is the neutron’s differential sensitivity for hydrogen and its isotope deuterium. Such differential sensitivity is unique to neutron scattering, which unlike X-ray scattering, arises from nuclear forces. Consequently, the coherent neutron scattering length can experience a dramatic change in magnitude and phase as a result of resonance scattering, imparting sensitivity to both light and heavy atoms, and in favorable cases to their isotopic variants. Furthermore, this article describes recent biomembranes research using a variety of neutron scattering techniques.

  1. Biomembranes research using thermal and cold neutrons

    DOE PAGES

    Heberle, Frederick A.; Myles, Dean A. A.; Katsaras, John

    2015-08-01

    In 1932 James Chadwick discovered the neutron using a polonium source and a beryllium target (Chadwick, 1932). In a letter to Niels Bohr dated February 24, 1932, Chadwick wrote: “whatever the radiation from Be may be, it has most remarkable properties.” Where it concerns hydrogen-rich biological materials, the “most remarkable” property is the neutron’s differential sensitivity for hydrogen and its isotope deuterium. Such differential sensitivity is unique to neutron scattering, which unlike X-ray scattering, arises from nuclear forces. Consequently, the coherent neutron scattering length can experience a dramatic change in magnitude and phase as a result of resonance scattering, impartingmore » sensitivity to both light and heavy atoms, and in favorable cases to their isotopic variants. Furthermore, this article describes recent biomembranes research using a variety of neutron scattering techniques.« less

  2. Variation in Isotopic Biosignatures From Carbonate Rich, Microbial Mats in Saline, Alkaline Lakes on the Cariboo Plateau, B.C.

    NASA Astrophysics Data System (ADS)

    Brady, A.; Slater, G.; Druschel, G.; Lim, D.

    2009-05-01

    Cyanobacteria dominated, carbonate rich microbial mats found in saline, alkaline lakes on the Cariboo Plateau, B.C. represent potential analogues of the evaporative systems that might have occurred on early Earth or Mars. These evaporative lakes generally have pH values > 10, salinities of up to 33 psu and alkalinities of > 15, 000 mg CaCO3/L but differ in other geochemical parameters. The ability to understand natural variations in microbial activity and biosignatures in such modern analogues is central to our understanding of the capabilities and limits of life, the interpretation of the geologic record and potentially one day to the interpretation of astrobiological data. Phospholipid fatty acid (PLFA) profiling, voltammetry, and stable isotope analysis of organic and inorganic carbon pools highlighted the spatial and seasonal variability that exists in modern evaporative microbial mat dominated lakes. Variations in microbial PLFA distribution demonstrated that Cariboo Plateau microbial mat community composition varied seasonally and spatially. Voltammetry results showed that photosynthetic oxygen production occurred in the upper 5 mm of mats resulting in supersaturation of oxygen in surface waters. Depletion of oxygen generally occurred just below 5 mm and sulfide production began at 10 - 15 mm from the mat surface. Isotope analysis (13C) of Cariboo microbial mats showed inorganic (dissolved inorganic carbon) to organic (bulk cell) isotopic discriminations of 23-25 ‰, indicating non-CO2 limited photosynthesis. These results are in contrast to high organic content analogue mats previously reported that show evidence of CO2 limitation. Further, the Cariboo mats demonstrated significant intra- and inter-mat variations in carbonate δ13C values with respect to dissolved inorganic carbon (DIC) ranging from enrichment to 13C-depleted carbonate. In Deer Lake, isotopic enrichment of surface water DIC by 2-3 ‰ above atmospheric equilibrium indicated microbial

  3. Zinc isotope anomalies. [in Allende meteorite

    NASA Technical Reports Server (NTRS)

    Volkening, J.; Papanastassiou, D. A.

    1990-01-01

    The Zn isotope composition in refractory-element-rich inclusions of the Allende meteorite are determined. Typical inclusions contain normal Zn. A unique inclusion of the Allende meteorite shows an excess for Zn-66 of 16.7 + or - 3.7 eu (1 eu = 0.01 percent) and a deficit for Zn-70 of 21 + or - 13 eu. These results indicate the preservation of exotic components even for volatile elements in this inclusion. The observed excess Zn-66 correlates with excesses for the neutron-rich isotopes of Ca-48, Ti-50, Cr-54, and Fe-58 in the same inclusion.

  4. Chromium isotopic anomalies in the Allende meteorite

    NASA Technical Reports Server (NTRS)

    Papanastassiou, D. A.

    1986-01-01

    Abundances of the chromium isotopes in terrestrial and bulk meteorite samples are identical to 0.01 percent. However, Ca-Al-rich inclusions from the Allende meteorite show endemic isotopic anomalies in chromium which require at least three nucleosynthetic components. Large anomalies at Cr-54 in a special class of inclusions are correlated with large anomalies at Ca-48 and Ti-50 and provide strong support for a component reflecting neutron-rich nucleosynthesis at nuclear statistical equilibrium. This correlation suggests that materials from very near the core of an exploding massive star may be injected into the interstellar medium.

  5. Large negative Ti-50 anomalies in refractory inclusions from the Murchison carbonaceous chondrite - Evidence for incomplete mixing of neutron-rich supernova ejecta into the solar system

    NASA Astrophysics Data System (ADS)

    Hinton, Richard W.; Davis, Andrew M.; Scatena-Wachel, Debra E.

    1987-02-01

    The titanium isotopic compositions of several hibonite-rich inclusions from the Murchison carbonaceous chondrite have been measured using an ion microprobe. Several of these inclusions show a considerable deficit in 50Ti compared to terrestrial titanium. This result complements the recent discovery of a hibonite grain from the Murray meteorite with a 10% excess in 50Ti. There is no correlation between the magnitude or sign of the 50Ti anomaly and the mineralogy, chemical composition, inferred initial 26Al/27Al, nuclear anomalies in other isotopes of titanium or isotopic mass fractionation of magnesium, calcium, or titanium. The authors infer that at least 7% of solar system 50Ti was added shortly before formation of the solar system, probably by mixing of ≡5% supernova ejecta into the presolar cloud.

  6. Mass measurements of very neutron-deficient Mo and Tc isotopes and their impact on rp process nucleosynthesis.

    PubMed

    Haettner, E; Ackermann, D; Audi, G; Blaum, K; Block, M; Eliseev, S; Fleckenstein, T; Herfurth, F; Hessberger, F P; Hofmann, S; Ketelaer, J; Ketter, J; Kluge, H-J; Marx, G; Mazzocco, M; Novikov, Yu N; Plass, W R; Rahaman, S; Rauscher, T; Rodríguez, D; Schatz, H; Scheidenberger, C; Schweikhard, L; Sun, B; Thirolf, P G; Vorobjev, G; Wang, M; Weber, C

    2011-03-25

    The masses of ten proton-rich nuclides, including the N=Z+1 nuclides ⁸⁵Mo and ⁸⁷Tc, were measured with the Penning trap mass spectrometer SHIPTRAP. Compared to the Atomic Mass Evaluation 2003 a systematic shift of the mass surface by up to 1.6 MeV is observed causing significant abundance changes of the ashes of astrophysical x-ray bursts. Surprisingly low α separation energies for neutron-deficient Mo and Tc are found, making the formation of a ZrNb cycle in the rp process possible. Such a cycle would impose an upper temperature limit for the synthesis of elements beyond Nb in the rp process.

  7. Mass Measurements of Very Neutron-Deficient Mo and Tc Isotopes and Their Impact on rp Process Nucleosynthesis

    SciTech Connect

    Haettner, E.; Plass, W. R.; Scheidenberger, C.; Ackermann, D.; Block, M.; Eliseev, S.; Herfurth, F.; Hessberger, F. P.; Hofmann, S.; Kluge, H.-J.; Audi, G.; Blaum, K.; Ketter, J.; Fleckenstein, T.; Ketelaer, J.; Marx, G.; Schweikhard, L.; Mazzocco, M.; Novikov, Yu. N.; Vorobjev, G.

    2011-03-25

    The masses of ten proton-rich nuclides, including the N=Z+1 nuclides {sup 85}Mo and {sup 87}Tc, were measured with the Penning trap mass spectrometer SHIPTRAP. Compared to the Atomic Mass Evaluation 2003 a systematic shift of the mass surface by up to 1.6 MeV is observed causing significant abundance changes of the ashes of astrophysical x-ray bursts. Surprisingly low {alpha} separation energies for neutron-deficient Mo and Tc are found, making the formation of a ZrNb cycle in the rp process possible. Such a cycle would impose an upper temperature limit for the synthesis of elements beyond Nb in the rp process.

  8. Rubidium-rich asymptotic giant branch stars.

    PubMed

    García-Hernández, D A; García-Lario, P; Plez, B; D'Antona, F; Manchado, A; Trigo-Rodríguez, J M

    2006-12-15

    A long-debated issue concerning the nucleosynthesis of neutron-rich elements in asymptotic giant branch (AGB) stars is the identification of the neutron source. We report intermediate-mass (4 to 8 solar masses) AGB stars in our Galaxy that are rubidium-rich as a result of overproduction of the long-lived radioactive isotope (87)Rb, as predicted theoretically 40 years ago. This finding represents direct observational evidence that the (22)Ne(alpha,n)(25)Mg reaction must be the dominant neutron source in these stars. These stars challenge our understanding of the late stages of the evolution of intermediate-mass stars and would have promoted a highly variable Rb/Sr environment in the early solar nebula.

  9. Swelling of nuclei embedded in neutron-gas and consequences for fusion

    NASA Astrophysics Data System (ADS)

    Umar, A. S.; Oberacker, V. E.; Horowitz, C. J.; Reinhard, P.-G.; Maruhn, J. A.

    2015-08-01

    Fusion of very neutron rich nuclei may be important to determine the composition and heating of the crust of accreting neutron stars. We present an exploratory study of the effect of the neutron-gas environment on the structure of nuclei and the consequences for pycnonuclear fusion cross sections in the neutron drip region. We studied the formation and properties of oxygen and calcium isotopes embedded in varying neutron-gas densities. We observe that the formed isotope is the drip-line nucleus for the given effective interaction. Increasing the neutron-gas density leads to the swelling of the nuclear density. We have used these densities to study the effect of this swelling on the fusion cross sections using the São Paulo potential. At high neutron-gas densities the cross section is substantially increased but at lower densities the modification is minimal.

  10. Early Onset of Ground State Deformation in Neutron Deficient Polonium Isotopes

    NASA Astrophysics Data System (ADS)

    Cocolios, T. E.; Dexters, W.; Seliverstov, M. D.; Andreyev, A. N.; Antalic, S.; Barzakh, A. E.; Bastin, B.; Büscher, J.; Darby, I. G.; Fedorov, D. V.; Fedosseyev, V. N.; Flanagan, K. T.; Franchoo, S.; Fritzsche, S.; Huber, G.; Huyse, M.; Keupers, M.; Köster, U.; Kudryavtsev, Yu.; Mané, E.; Marsh, B. A.; Molkanov, P. L.; Page, R. D.; Sjoedin, A. M.; Stefan, I.; van de Walle, J.; van Duppen, P.; Venhart, M.; Zemlyanoy, S. G.; Bender, M.; Heenen, P.-H.

    2011-02-01

    In-source resonant ionization laser spectroscopy of the even-A polonium isotopes Po192-210,216,218 has been performed using the 6p37s S25 to 6p37p P25 (λ=843.38nm) transition in the polonium atom (Po-I) at the CERN ISOLDE facility. The comparison of the measured isotope shifts in Po200-210 with a previous data set allows us to test for the first time recent large-scale atomic calculations that are essential to extract the changes in the mean-square charge radius of the atomic nucleus. When going to lighter masses, a surprisingly large and early departure from sphericity is observed, which is only partly reproduced by beyond mean field calculations.

  11. Early Onset of Ground State Deformation in Neutron Deficient Polonium Isotopes

    SciTech Connect

    Cocolios, T. E.; Van de Walle, J.; Dexters, W.; Bastin, B.; Buescher, J.; Darby, I. G.; Huyse, M.; Keupers, M.; Kudryavtsev, Yu.; Van Duppen, P.; Seliverstov, M. D.; Andreyev, A. N.; Antalic, S.; Barzakh, A. E.; Fedorov, D. V.; Molkanov, P. L.; Fedosseyev, V. N.; Marsh, B. A.; Flanagan, K. T.; Franchoo, S.

    2011-02-04

    In-source resonant ionization laser spectroscopy of the even-A polonium isotopes {sup 192-210,216,218}Po has been performed using the 6p{sup 3}7s {sup 5}S{sub 2} to 6p{sup 3}7p {sup 5}P{sub 2} ({lambda}=843.38 nm) transition in the polonium atom (Po-I) at the CERN ISOLDE facility. The comparison of the measured isotope shifts in {sup 200-210}Po with a previous data set allows us to test for the first time recent large-scale atomic calculations that are essential to extract the changes in the mean-square charge radius of the atomic nucleus. When going to lighter masses, a surprisingly large and early departure from sphericity is observed, which is only partly reproduced by beyond mean field calculations.

  12. The effect of pressure, isotopic (H/D) substitution, and other variables on miscibility in polymer-solvent systems. The nature of the demixing process; dynamic light scattering and small angle neutron scattering studies. Final report

    SciTech Connect

    Van Hook, W.A.

    2000-01-01

    A research program examining the effects of pressure, isotope substitution and other variables on miscibility in polymer solvent systems is described. The techniques employed included phase equilibrium measurements and dynamic light scattering and small angle neutron scattering.

  13. 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

    SciTech Connect

    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.

  14. Isotopic Measurements in CAIs with the Nanosims: Implications to the understanding of the Formation process of Ca, Al-Rich Inclusions

    NASA Technical Reports Server (NTRS)

    Ito, M.; Messenger, S.; Walker, Robert M.

    2007-01-01

    Ca, Al-rich Inclusions (CAIs) preserve evidence of thermal events that they experienced during their formation in the early solar system. Most CAIs from CV and CO chondrites are characterized by large variations in O-isotopic compositions of primary minerals, with spinel, hibonite, and pyroxene being more O-16-rich than melilite and anorthite, with delta 17, O-18 = approx. -40%o (DELTA O-17 = delta O-17 - 0.52 x delta O-18 = approx. - 20%o ). These anomalous compositions cannot be accounted for by standard mass dependent fractionation and diffusive process of those minerals. It requires the presence of an anomalous oxygen reservoir of nucleosynthetic origin or mass independent fractionations before the formation of CAIs in the early solar system. The CAMECA NanoSIMS is a new generation ion microprobe that offers high sensitivity isotopic measurements with sub 100 nm spatial resolution. The NanoSIMS has significantly improved abilities in the study of presolar grains in various kind of meteorites and the decay products of extinct nuclides in ancient solar system matter. This instrument promises significant improvements over other conventional ion probes in the precision isotopic characterization of sub-micron scales. We report the results of our first O isotopic measurements of various CAI minerals from EK1-6-3 and 7R19-1(a) utilizing the JSC NanoSIMS 50L ion microprobe. We evaluate the measurement conditions, the instrumental mass fractionation factor (IMF) for O isotopic measurement and the accuracy of the isotopic ratio through the analysis of a San Carlos olivine standard and CAI sample of 7R19-1(a).

  15. Neutron removal cross section as a measure of neutron skin

    SciTech Connect

    Fang, D. Q.; Ma, Y. G.; Cai, X. Z.; Tian, W. D.; Wang, H. W.

    2010-04-15

    We study the relation between neutron removal cross section (sigma{sub -N}) and neutron skin thickness for finite neutron-rich nuclei using the statistical abrasion ablation model. Different sizes of neutron skin are obtained by adjusting the diffuseness parameter of neutrons in the Fermi distribution. It is demonstrated that there is a good linear correlation between sigma{sub -N} and the neutron skin thickness for neutron-rich nuclei. Further analysis suggests that the relative increase of neutron removal cross section could be used as a quantitative measure for neutron skin thickness in neutron-rich nuclei.

  16. Examining the stability of thermally fissile Th and U isotopes

    NASA Astrophysics Data System (ADS)

    Kumar, Bharat; Biswal, S. K.; Singh, S. K.; Patra, S. K.

    2015-11-01

    The properties of recently predicted thermally fissile Th and U isotopes are studied within the framework of the relativistic mean-field approach using the axially deformed basis. We calculate the ground, first intrinsic excited state for highly neutron-rich thorium and uranium isotopes. The possible modes of decay such as α decay and β decay are analyzed. We found that neutron-rich isotopes are stable against α decay, however, they are very unstable against β decay. The lifetime of these nuclei is predicted to be tens of seconds against β decay. If these nuclei are utilized before their decay time, a lot of energy can be produced with the help of multifragmentation fission. Also, these nuclei have great implications from the astrophysical point of view. In some cases, we found that the isomeric states with energy range from 2 to 3 MeV and three maxima in the potential energy surface of Th-230228 and U-234228 isotopes.

  17. Relevance of single-particle and collective excitations in zirconium isotopes populated by neutron transfer reactions in the {sup 90}Zr+{sup 208}Pb system

    SciTech Connect

    Pajtler, M. Varga; Szilner, S.; Malenica, D. Jelavić; Mijatović, T.; Soić, N.; Corradi, L.; Angelis, G. de; Fioretto, E.; Montanari, D.; Stefanini, A. M.; Valiente-Dobón, J. J.; Gadea, A.; Haas, F.; Lunardi, S.; Mengoni, D.; Montagnoli, G.; Recchia, F.; Scarlassara, F.; Märginean, N.; Pollarolo, G.; and others

    2015-10-15

    Multineutron transfer reaction {sup 90}Zr+{sup 208}Pb has been studied at the energy close to the Coulomb barrier energy by using the PRISMA + CLARA set-up. In this fragment-γ coincidence measurement, the selective properties of the reaction mechanism in the population of the specific states have been discussed. Based on the observed γ transitions of neutron transfer channels, namely {sup 89–94}Zr isotopes, their level schemes have been constructed and updated.

  18. Study of neutron-deficient isotopes of Fl in the 239Pu, 240Pu + 48Ca reactions

    NASA Astrophysics Data System (ADS)

    Voinov, A. A.; Utyonkov, V. K.; Brewer, N. T.; Oganessian, Yu Ts; Rykaczewski, K. P.; Abdullin, F. Sh; Dmitriev, S. N.; Grzywacz, R. K.; Itkis, M. G.; Miernik, K.; Polyakov, A. N.; Roberto, J. B.; Sagaidak, R. N.; Shirokovsky, I. V.; Shumeiko, M. V.; Tsyganov, Yu S.; Subbotin, V. G.; Sukhov, A. M.; Sabelnikov, A. V.; Vostokin, G. K.; Hamilton, J. H.; Stoyer, M. A.; Strauss, S. Y.

    2016-07-01

    The results of the experiments aimed at the synthesis of Fl isotopes in the 239Pu + 48Ca and 240Pu + 48Ca reactions are presented. The experiment was performed using the Dubna gas-filled recoil separator at the U400 cyclotron. In the 239Pu+48Ca experiment one decay of spontaneously fissioning 284Fl was detected at 245-MeV beam energy. In the 240Pu+48Ca experiment three decay chains of 285Fl were detected at 245 MeV and four decays were assigned to 284Fl at the higher 48Ca beam energy of 250 MeV. The α-decay energy of 285Fl was measured for the first time and decay properties of its descendants 281Cn, 277Ds, 273Hs, 269Sg, and 265Rf were determined more precisely. The cross section of the 239Pu(48Ca,3n)284Fl reaction was observed to be about 20 times lower than those predicted by theoretical models and 50 times less than the value measured in the 244Pu+48Ca reaction. The cross sections of the 240Pu(48Ca,4-3n)284,285Fl at both 48Ca energies are similar and exceed that observed in the reaction with lighter isotope 239Pu by a factor of 10. The decay properties of the synthesized nuclei and their production cross sections indicate rapid decrease of stability of superheavy nuclei with departing from the neutron number N=184 predicted to be the next magic number.

  19. Descriptions of carbon isotopes within the energy density functional theory

    SciTech Connect

    Ismail, Atef; Cheong, Lee Yen; Yahya, Noorhana; Tammam, M.

    2014-10-24

    Within the energy density functional (EDF) theory, the structure properties of Carbon isotopes are systematically studied. The shell model calculations are done for both even-A and odd-A nuclei, to study the structure of rich-neutron Carbon isotopes. The EDF theory indicates the single-neutron halo structures in {sup 15}C, {sup 17}C and {sup 19}C, and the two-neutron halo structures in {sup 16}C and {sup 22}C nuclei. It is also found that close to the neutron drip-line, there exist amazing increase in the neutron radii and decrease on the binding energies BE, which are tightly related with the blocking effect and correspondingly the blocking effect plays a significant role in the shell model configurations.

  20. Calcium-aluminum-rich inclusions with fractionation and unidentified nuclear effects (FUN CAIs): II. Heterogeneities of magnesium isotopes and 26Al in the early Solar System inferred from in situ high-precision magnesium-isotope measurements

    NASA Astrophysics Data System (ADS)

    Park, Changkun; Nagashima, Kazuhide; Krot, Alexander N.; Huss, Gary R.; Davis, Andrew M.; Bizzarro, Martin

    2017-03-01

    Calcium-aluminum-rich inclusions with isotopic mass fractionation effects and unidentified nuclear isotopic anomalies (FUN CAIs) have been studied for more than 40 years, but their origins remain enigmatic. Here we report in situ high precision measurements of aluminum-magnesium isotope systematics of FUN CAIs by secondary ion mass spectrometry (SIMS). Individual minerals were analyzed in six FUN CAIs from the oxidized CV3 carbonaceous chondrites Axtell (compact Type A CAI Axtell 2271) and Allende (Type B CAIs C1 and EK1-4-1, and forsterite-bearing Type B CAIs BG82DH8, CG-14, and TE). Most of these CAIs show evidence for excess 26Mg due to the decay of 26Al. The inferred initial 26Al/27Al ratios [(26Al/27Al)0] and the initial magnesium isotopic compositions (δ26Mg0) calculated using an exponential law with an exponent β of 0.5128 are (3.1 ± 1.6) × 10-6 and 0.60 ± 0.10‰ (Axtell 2271), (3.7 ± 1.5) × 10-6 and -0.20 ± 0.05‰ (BG82DH8), (2.2 ± 1.1) × 10-6 and -0.18 ± 0.05‰ (C1), (2.3 ± 2.4) × 10-5 and -2.23 ± 0.37‰ (EK1-4-1), (1.5 ± 1.1) × 10-5 and -0.42 ± 0.08‰ (CG-14), and (5.3 ± 0.9) × 10-5 and -0.05 ± 0.08‰ (TE) with 2σ uncertainties. We infer that FUN CAIs recorded heterogeneities of magnesium isotopes and 26Al in the CAI-forming region(s). Comparison of 26Al-26Mg systematics, stable isotope (oxygen, magnesium, calcium, and titanium) and trace element studies of FUN and non-FUN igneous CAIs indicates that there is a continuum among these CAI types. Based on these observations and evaporation experiments on CAI-like melts, we propose a generic scenario for the origin of igneous (FUN and non-FUN) CAIs: (i) condensation of isotopically normal solids in an 16O-rich gas of approximately solar composition; (ii) formation of CAI precursors by aggregation of these solids together with variable abundances of isotopically anomalous grains-possible carriers of unidentified nuclear (UN) effects; and (iii) melt evaporation of these precursors

  1. Coordinated Isotopic and Mineral Characterization of Highly Fractionated 18O-Rich Silicates in the Queen Alexandra Range 99177 CR3 Chondrite

    NASA Technical Reports Server (NTRS)

    Nguyen, A. N.; Keller, L. P.; Messenger, S.; Rahman, Z.

    2016-01-01

    Carbonaceous chondrites contain a mixture of solar system condensates, pre-solar grains, and primitive organic matter. Each of these materials record conditions and processes in different regions of the solar nebula, on the meteorite parent body, and beyond the solar system. Oxygen isotopic studies of meteorite components can trace interactions of distinct oxygen isotopic reservoirs in the early solar system and secondary alteration processes. The O isotopic compositions of the earliest solar system condensates fall along a carbonaceous chondrite anhydrous mineral (CCAM) line of slope approximately 1 in a plot of delta 17O against delta 18O. This trend is attributed to mixing of material from 16O-poor and 16O-rich reservoirs. Secondary processing can induce mass-dependent fractionation of the O isotopes, shifting these compositions along a line of slope approximately 0.52. Substantial mass-dependent fractionation of O isotopes has been observed in secondary minerals in CAIs, calcite, and FUN inclusions. These fractionations were caused by significant thermal or aqueous alteration. We recently reported the identification of four silicate grains with extremely fractionated O isotopic ratios (delta 18O equals 37 - 55 per mille) in the minimally altered CR3 chondrite QUE 99177. TEM analysis of one grain indicates it is a nebular condensate that did not experience substantial alteration. The history of these grains is thus distinct from those of the aforementioned fractionated materials. To constrain the origin of the silicate grains, we conducted further Mg and Fe isotopic studies and TEM analyses of two grains.

  2. Rotational bands in odd-A Cm and Cf isotopes: Exploring the highest neutron orbitals

    SciTech Connect

    Tandel, S. K.; Chowdhury, P.; Lakshmi, S.; Tandel, U. S.; Ahmad, I.; Carpenter, M. P.; Gros, S.; Janssens, R. V. F.; Khoo, T. L.; Kondev, F. G.; Greene, J. P.; Lauritsen, T.; Lister, C. J.; Peterson, D.; Robinson, A.; Seweryniak, D.; Zhu, S.; Hartley, D. J.

    2010-10-15

    Rotational bands have been identified up to high spins ({approx_equal}28({h_bar}/2{pi})) in the odd-A nuclei {sup 247,249}Cm and {sup 249}Cf through inelastic excitation and transfer reactions around the Z=100 region where stability results from shell effects. The [620]1/2 Nilsson configuration in {sup 249}Cm is the highest-lying neutron orbital, from above the N=164 spherical subshell gap, for which high-spin rotational behavior has been established. The data allow for an unambiguous experimental assignment of configurations to the observed bands, unusual for odd-A nuclei near Z=100. The high-spin properties are described in terms of Woods-Saxon cranking calculations.

  3. In-beam gamma-ray spectroscopy of very neutron-rich nuclei: excited states in 46S and 48Ar.

    PubMed

    Gade, A; Adrich, P; Bazin, D; Brown, B A; Cook, J M; Diget, C Aa; Glasmacher, T; McDaniel, S; Ratkiewicz, A; Siwek, K; Weisshaar, D

    2009-05-08

    We report on the first in-beam gamma-ray spectroscopy study of the very neutron-rich nucleus 46S. The N=30 isotones 46S and 48Ar were produced in a novel way in two steps that both necessarily involve nucleon exchange and neutron pickup reactions 9Be(48Ca,48K)X followed by 9Be(48K,48Ar+gamma)X at 85.7 MeV/u midtarget energy and 9Be(48Ca,46Cl)X followed by 9Be(46Cl,46S+gamma)X at 87.0 MeV/u midtarget energy, respectively. The results are compared to large-scale shell-model calculations in the sd-pf shell using the SDPF-NR effective interaction and Z-dependent modifications.

  4. In-Beam {gamma}-Ray Spectroscopy of Very Neutron-Rich Nuclei: Excited States in {sup 46}S and {sup 48}Ar

    SciTech Connect

    Gade, A.; Brown, B. A.; Cook, J. M.; Glasmacher, T.; McDaniel, S.; Ratkiewicz, A.; Siwek, K.; Adrich, P.; Bazin, D.; Diget, C. A.; Weisshaar, D.

    2009-05-08

    We report on the first in-beam {gamma}-ray spectroscopy study of the very neutron-rich nucleus {sup 46}S. The N=30 isotones {sup 46}S and {sup 48}Ar were produced in a novel way in two steps that both necessarily involve nucleon exchange and neutron pickup reactions {sup 9}Be({sup 48}Ca,{sup 48}K)X followed by {sup 9}Be({sup 48}K,{sup 48}Ar+{gamma})X at 85.7 MeV/u midtarget energy and {sup 9}Be({sup 48}Ca,{sup 46}Cl)X followed by {sup 9}Be({sup 46}Cl,{sup 46}S+{gamma})X at 87.0 MeV/u midtarget energy, respectively. The results are compared to large-scale shell-model calculations in the sd-pf shell using the SDPF-NR effective interaction and Z-dependent modifications.

  5. d{sub 5/2} proton hole strength in neutron-rich {sup 43}P: Shell structure and nuclear shapes near N=28

    SciTech Connect

    Riley, L. A.; Baugher, T. R.; Hosier, K. E.; Adrich, P.; Bazin, D.; Diget, C. A.; Weisshaar, D.; Brown, B. A.; Cook, J. M.; Gade, A.; Garland, D. A.; Glasmacher, T.; Ratkiewicz, A.; Siwek, K. P.; Cottle, P. D.; Kemper, K. W.; Otsuka, T.; Rae, W. D. M.; Tostevin, J. A.; Utsuno, Y.

    2008-07-15

    We report on the use of the one-proton knockout reaction from {sup 44}S to determine the location of d{sub 5/2} proton strength in neutron-rich {sup 43}P. The results are used to test two shell-model frameworks with different pictures of the evolution of single-proton energies along the N=28 isotones near the neutron dripline. We observe a concentration of d{sub 5/2} proton hole strength near 1 MeV in excitation energy. This result favors the recent shell-model interaction of Utsuno et al. [Eur. Phys. J. Spec. Top. 150, 187 (2007)] and provides additional evidence for an oblate shape for {sup 42}Si.

  6. Systematical study of high-spin rotational bands in neutron-deficient Kr isotopes by the extended projected shell model

    NASA Astrophysics Data System (ADS)

    Wu, Xin-Yi; Ghorui, S. K.; Wang, Long-Jun; Kaneko, K.; Sun, Yang

    2017-01-01

    We analyze the high-spin structure of the even-even 72-80Kr isotopes using the Projected Shell Model (PSM). With the help of the Pfaffian formulas, we have vigorously extended the quasi-particle (qp) basis of the PSM code and applied in this mass region for the first time. We consider a sufficiently large multi-qp configuration space in order to describe high-spin rotational behavior. The results show that the calculation can reproduce most of the known rotational bands with positive- or negative-parity. Moreover, some side bands appearing in the near-yrast region are predicted. The main structure for each band is discussed in terms of multi-qp configurations. The variations in moment of inertia with spin are explained in terms of successive band crossings among the 2-qp, 4-qp, 6-qp, and 8-qp states. The B (E 2) transition probabilities in these bands are also calculated. To further understand the high-spin behavior of these neutron-deficient nuclei and to confirm predictions of the present work, good high-spin data, especially for B (E 2) transitions, are called for.

  7. Search for unknown isotopes using the JAERI-ISOL

    NASA Astrophysics Data System (ADS)

    Ichikawa, S.; Tsukada, K.; Oura, Y.; Iimura, H.; Nishinaka, I.; Hatsukawa, Y.; Nagame, Y.; Asai, M.; Osa, A.; Kojima, Y.; Hirose, T.; Kawade, K.; Ohyama, T.; Sueki, K.

    1996-04-01

    A search for unknown neutron-rich rare-earth isotopes and neutron-deficient americium isotopes was carried out using a gas-jet coupled thermal ion source installed in the JAERI on-line isotope separator (JAERI-ISOL). New isotopes b166Tb and d165Gd produced in the proton-induced fission of 238U were identified. The half-lives were 21+/-6 s for b166Tb and 10.3+/-1.6 s for d.165Gd. Pu KX-rays associated with EC decays of americium isotopes produced in heavy-ion induced reactions were observed in the X/γ-ray spectra for the mass separated fraction of 237 and 236.

  8. Spectroscopy of 36Mg: interplay of normal and intruder configurations at the neutron-rich boundary of the "island of inversion".

    PubMed

    Gade, A; Adrich, P; Bazin, D; Bowen, M D; Brown, B A; Campbell, C M; Cook, J M; Ettenauer, S; Glasmacher, T; Kemper, K W; McDaniel, S; Obertelli, A; Otsuka, T; Ratkiewicz, A; Siwek, K; Terry, J R; Tostevin, J A; Utsuno, Y; Weisshaar, D

    2007-08-17

    We report on the first spectroscopy study of the very neutron-rich nucleus (36)(12)Mg24 using the direct two-proton knockout reaction 9Be(38Si,36Mg+gamma)X at 83 MeV/nucleon. The energy of the first excited 2+ state of 36Mg, E(2+(1)=660(6) keV, was measured. The magnitude of the partial cross sections to the ground state and the 2+(1) state is indicative of strong intruder admixtures in the lowest-lying states as suggested by Monte Carlo shell-model calculations.

  9. Exotic Structure of Carbon Isotopes

    NASA Astrophysics Data System (ADS)

    Suzuki, Toshio; Sagawa, Hiroyuki; Hagino, Kouichi

    2003-12-01

    Ground state properties of C isotopes, deformation and elecromagnetic moments, as well as electric dipole transition strength are investigated. We first study the ground state properties of C isotopes using a deformed Hartree-Fock (HF) + BCS model with Skyrme interactions. Isotope dependence of the deformation properties is investigated. Shallow deformation minima are found in several neutron-rich C isotopes. It is also shown that the deformation minima appear in both the oblate and the prolate sides in 17C and 19C having almost the same binding energies. Next, we carry out shell model calculations to study electromagnetic moments and electric dipole transitions of C isotopes. We point out the clear configuration dependence of the quadrupole and magnetic moments in the odd C isotopes, which will be useful to find out the deformation and spin-parities of the ground states of these nuclei. Electric dipole states of C isotopes are studied focusing on the interplay between low energy Pigmy strength and giant dipole resonances. Low peak energies, two-peak structure and large widths of the giant resonances show deformation effects. Calculated transition strength below dipole giant resonance in heavier C isotopes than 15C is found to exhaust 12 ~ 15% of the Thomas-Reiche-Kuhn sum rule value and 50 ~ 80% of the cluster sum rule value.

  10. Different carbon reservoirs of auriferous fluids in African Archean and Proterozoic gold deposits? Constraints from stable carbon isotopic compositions of quartz-hosted CO2-rich fluid inclusions

    NASA Astrophysics Data System (ADS)

    Lüders, Volker; Klemd, Reiner; Oberthür, Thomas; Plessen, Birgit

    2015-04-01

    Stable carbon (and when present, nitrogen) isotope ratios of fluid inclusions in quartz from selected gold deposits in Ghana and Zimbabwe have been analyzed using a crushing device interfaced to an isotopic ratio mass spectrometer (IRMS) in order to constrain possible sources of the auriferous fluids. The study revealed a striking difference in stable carbon isotopic compositions of CO2 in quartz-hosted fluid inclusions from Archean and Paleoproterozoic orogenic gold deposits and points to diverse sources of CO2 in the studied deposits. Whether this finding can be generalized for other Archean and Proterozoic orogenic gold deposits worldwide remains open. However, a significant CO2 contribution by mantle degassing can be ruled out for every deposit studied. Devolatilization of greenstone belt rocks is the most likely source for CO2 in some Archean Au deposits in Zimbabwe, whereas CO2 in Proterozoic vein-type Au deposits in the West African Craton is most likely derived from Corg-bearing metasedimentary rocks. The δ13CCO2 values of high-density CO2-rich, water-poor inclusions hosted in quartz pebbles from the world-class Au-bearing conglomerate deposits at Tarkwa (Ghana) differ considerably from the δ13CCO2 values of similar high-density CO2-rich inclusions in vein quartz from the giant Ashanti deposit (Ghana) and disprove the idea of derivation of the Tarkwaian quartz (and gold?) from an older equivalent to the Ashanti vein-type gold deposit.

  11. Use of Isotope Abundance of 15NO3-N in a Nitrate Rich Stream Below a Wastewater Treatment Plant to Evaluate Denitrification

    NASA Astrophysics Data System (ADS)

    Lofton, D.; Hershey, A. E.

    2005-05-01

    Using natural isotope abundances of nitrate-nitrogen, in conjunction with nitrate concentrations along a stream transect, can provide information about nitrate input versus downstream export and losses due to denitrification. Given that denitrifying microbes prefer the lighter isotope, isotopic fractionation should occur in nitrate rich streams resulting in enrichment of 15NO3-N if denitrification is an important process resulting in an inverse relationship between nitrate and δ 15NO3-N. Conversely, if the relationship between 15NO3-N and δ 15N is not inversely proportional, denitrification is likely of minor importance in the reach. Variable nonlinear patterns could be indicative of 15NO3-N rich input from groundwater, tributaries or concentrations in excess of microbial demand leading to massive downstream export. We measured stream 15NO3-N concentrations in an urban stream receiving high nitrogen inputs from a wastewater treatment plant. Although observed NO3-N concentrations varied from 3-6 mg L-1 in the stream reach, the relationship between ln NO3 and δ 15NO3-N was very weak, suggesting limited importance of denitrification.

  12. High sulfur isotope fractionation associated with anaerobic oxidation of methane in a low sulfate, iron rich environment

    NASA Astrophysics Data System (ADS)

    Weber, Hannah; Thamdrup, Bo; Habicht, Kirsten

    2016-06-01

    Sulfur isotope signatures provide key information for the study of microbial activity in modern systems and the evolution of the Earth surface redox system. Microbial sulfate reducers shift sulfur isotope distributions by discriminating against heavier isotopes. This discrimination is strain-specific and often suppressed at sulfate concentrations in the lower micromolar range that are typical to freshwater systems and inferred for ancient oceans. Anaerobic oxidation of methane (AOM) is a sulfate-reducing microbial process with a strong impact on global sulfur cycling in modern habitats and potentially in the geological past, but its impact on sulfur isotope signatures is poorly understood, especially in low sulfate environments. We investigated sulfur cycling and 34S fractionation in a low-sulfate freshwater sediment with biogeochemical conditions analogous to Early Earth environments. The zone of highest AOM activity was associated in situ with a zone of strong 34S depletions in the pool of reduced sulfur species, indicating a coupling of sulfate reduction and AOM at sulfate concentrations < 50 µmol L-1. In slurry incubations of AOM-active sediment, the addition of methane stimulated sulfate reduction and induced a bulk sulfur isotope effect of ~29 ‰. Our results imply that sulfur isotope signatures may be strongly impacted by AOM even at sulfate concentrations two orders of magnitude lower than at present oceanic levels. Therefore, we suggest that sulfur isotope fractionation during AOM must be considered when interpreting 34S signatures in modern and ancient environment.

  13. Signature inversion in odd-odd {sup 114}Rh: First identification of high-spin states in very neutron-rich {sup 114}Rh and application of the triaxial projected shell model

    SciTech Connect

    Liu, S. H.; Chen, Y. S.; Gao, Z. C.; Zhu, S. J.; Gu, L.; Yeoh, E. Y.; Luo, Y. X.; Rasmussen, J. O.; Ma, W. C.; Batchelder, J. C.; Ter-Akopian, G. M.; Oganessian, Yu. Ts.; Gelberg, A.

    2011-06-15

    High-spin excited states in the very neutron-rich nucleus {sup 114}Rh have been studied by examining the prompt {gamma} rays emitted in the spontaneous fission of {sup 252}Cf with the Gammasphere detector array. A high-spin level scheme of {sup 114}Rh has been established for the first time with 13 new levels. The level scheme is proposed to be built on a 7{sup -} state. The existence of a relatively large signature splitting and an yrare band show features which may indicate triaxial deformation. The phenomenon of signature inversion has been observed in {sup 114}Rh at I=12 ({h_bar}/2{pi}). The observed signature inversion of {sup 114}Rh is interpreted successfully in terms of the triaxial projected shell model. Theoretical calculations suggest that the negative-parity, yrast band of {sup 114}Rh has the two-quasi-particle configuration of {pi}g{sub 9/2} x {nu}h{sub 11/2}, consistent with the systematics of odd-odd Rh isotopes. The signature inversion at spin 12 ({h_bar}/2{pi}) may be attributed to the change of rotational mode, from quasi-particle aligned rotation at low spins to collective rotation at high spins.

  14. Isotopic yield measurement in the heavy mass region for {sup 239}Pu thermal neutron induced fission

    SciTech Connect

    Bail, A.; Serot, O.; Mathieu, L.; Litaize, O.; Materna, T.; Koester, U.; Faust, H.; Letourneau, A.; Panebianco, S.

    2011-09-15

    Despite the huge number of fission yield data available in the different evaluated nuclear data libraries, such as JEFF-3.1.1, ENDF/B-VII.0, and JENDL-4.0, more accurate data are still needed both for nuclear energy applications and for our understanding of the fission process itself. It is within the framework of this that measurements on the recoil mass spectrometer Lohengrin (at the Institut Laue-Langevin, Grenoble, France) was undertaken, to determine isotopic yields for the heavy fission products from the {sup 239}Pu(n{sub th},f) reaction. In order to do this, a new experimental method based on {gamma}-ray spectrometry was developed and validated by comparing our results with those performed in the light mass region with completely different setups. Hence, about 65 fission product yields were measured with an uncertainty that has been reduced on average by a factor of 2 compared to that previously available in the nuclear data libraries. In addition, for some fission products, a strongly deformed ionic charge distribution compared to a normal Gaussian shape was found, which was interpreted as being caused by the presence of a nanosecond isomeric state. Finally, a nuclear charge polarization has been observed in agreement, with the one described on other close fissioning systems.

  15. Rhenium and osmium isotopes in black shales and Ni-Mo-PGE-rich sulfide layers, Yukon Territory, Canada, and Hunan and Guizhou provinces, China

    USGS Publications Warehouse

    Horan, M.F.; Morgan, J.W.; Grauch, R.I.; Coveney, R.M.; Murowchick, J.B.; Hulbert, L.J.

    1994-01-01

    Rhenium and osmium abundances and osmium isotopic compositions were determined by negative thermal ionization mass spectrometry for samples of Devonian black shale and an associated Ni-enriched sulfide layer from the Yukon Territory, Canada. The same composition information was also obtained for samples of early Cambrian Ni-Mo-rich sulfide layers hosted in black shale in Guizhou and Hunan provinces, China. This study was undertaken to constrain the origin of the PGE enrichment in the sulfide layers. Samples of the Ni sulfide layer from the Yukon Territory are highly enriched in Re, Os, and other PGE, with distinctly higher Re/192Os but similar Pt/Re, compared to the black shale host. Re-Os isotopic data of the black shale and the sulfide layer are approximately isochronous, and the data plot close to reference isochrons which bracket the depositional age of the enclosing shales. Samples of the Chinese sulfide layers are also highly enriched in Re, Os, and the other PGE. Re/192Os are lower than in the Yukon sulfide layer. Re-Os isotopic data for the sulfide layers lie near a reference isochron with an age of 560 Ma, similar to the depositional age of the black shale host. The osmium isotopic data suggest that Re and PGE enrichment of the brecciated sulfide layers in both the Yukon Territory and in southern China may have occurred near the time of sediment deposition or during early diagenesis, during the middle to late Devonian and early Cambrian, respectively. ?? 1994.

  16. Beta-delayed proton emission in neutron-deficient lanthanide isotopes

    SciTech Connect

    Wilmarth, P.A.

    1988-09-30

    Forty-two ..beta..-delayed proton precursors with 56less than or equal toZless than or equal to71 and 63less than or equal toNless than or equal to83 were produced in heavy-ion reactions at the Lawrence Berkeley Laboratory SuperHILAC and their radioactive decay properties studied at the on-line mass separation facility OASIS. Twenty-five isotopes and eight delayed proton branches were identified for the first time. Delayed proton energy spectra and proton coincident ..gamma..-ray and x-ray spectra were measured for all precursors. In a few cases, proton branching ratios were also determined. The precursor mass numbers were determined by the separator, while the proton coincident x-ray energies provided unambiguous Z identifications. The proton coincident ..gamma..-ray intensities were used to extract final state branching ratios. Proton emission from ground and isomeric states was observed in many cases. The majority of the delayed proton spectra exhibited the smooth bell-shaped distribution expected for heavy mass precursors. The experimental results were compared to statistical model calculations using standard parameter sets. Calculations using Nilsson model/RPA ..beta..-strength functions were found to reproduce the spectral shapes and branching ratios better than calculations using either constant or gross theory ..beta..-strength functions. Precursor half-life predictions from the Nilsson model/RPA ..beta..-strength functions were also in better agreement with the measured half-lives than were gross theory predictions. The ratios of positron coincident proton intensities to total proton intensities were used to determine Q/sub EC/-B/sub p/ values for several precursors near N=82. The statistical model calculations were not able to reproduce the experimental results for N=81 precursors. 154 refs., 82 figs., 19 tabs.

  17. Vacancy enhanced formation and phase transition of Cu-rich precipitates in α - iron under neutron irradiation

    NASA Astrophysics Data System (ADS)

    Lv, G. C.; Zhang, H.; He, X. F.; Yang, W.; Su, Y. J.

    2016-04-01

    In this paper, we employed both molecular statics and molecular dynamics simulation methods to investigate the role of vacancies in the formation and phase transition of Cu-rich precipitates in α-iron. The results indicated that vacancies promoted the diffusion of Cu atoms to form Cu-rich precipitates. After Cu-rich precipitates formed, they further trapped vacancies. The supersaturated vacancy concentration in the Cu-rich precipitate induced a shear strain, which triggered the phase transition from bcc to fcc structure by transforming the initial bcc (110) plane into fcc (111) plane. In addition, the formation of the fcc-twin structure and the stacking fault structure in the Cu-rich precipitates was observed in dynamics simulations.

  18. Distinction between elastic scattering of weakly bound proton- and neutron-rich nuclei: The case of 8B and 11Be

    NASA Astrophysics Data System (ADS)

    Yang, Y. Y.; Liu, X.; Pang, D. Y.

    2016-09-01

    Experimental data show that the elastic scattering cross sections of the neutron-rich nucleus 11Be are greatly reduced by the coupling effects from the breakup channels, while those of the proton-rich nucleus 8B are not. Such difference is found to persist in results of systematic calculations of 8B elastic scattering from 208Pb at 60 and 170.3 MeV and from 64Zn at 32 and 86 MeV, and 11Be elastic scattering from 208Pb at 55 and 143 MeV and from 64Zn at 29 and 66 MeV with the continuum-discretized coupled channel (CDCC) method. The Coulomb and centrifugal barriers experienced by the valence proton in the ground state of 8B, which do not exist for the valence neutron in the ground state of 11Be, are found to be the reason for such differences in the angular distributions of elastic scattering cross sections of these two weakly bound nuclei.

  19. Description of C isotopes within RMF+BCS approach

    SciTech Connect

    Saxena, G.; Singh, D.; Kaushik, M.

    2013-06-03

    In the present investigations we have employed relativistic mean-field plus BCS (RMF + BCS) approach to carry out a systematic study for the ground state properties of even-even C Isotopes. One of the prime reason of this study has been to look into the role of low lying states in neutron rich reason near neutron drip line. It is found that irrespective of whether any resonant state exists or not, the occupancy of weakly bound neutron single particle states having low orbital angular momentum, (l = 0 or 1), with a well spread wave function due to the absence or very small strength of centrifugal barrier, helps to cause the occurrence of nuclei with widely extended neutron density. Such nuclei are found to have characteristically very small two-neutron separation energy and large neutron rms radius akin to that observed in weakly bound systems.

  20. Geochemical and stable isotopic constraints on the generation and passive treatment of acidic, Fe-SO4 rich waters.

    PubMed

    Matthies, Romy; Aplin, Andrew C; Boyce, Adrian J; Jarvis, Adam P

    2012-03-15

    Reducing and Alkalinity Producing Systems (RAPS) remediate net-acidic metalliferous mine drainage by creating anoxic conditions in which bacterial sulfate reduction (BSR) raises alkalinity and drives the precipitation of iron and other chalcophilic elements as sulfides. We report chemical and stable isotopic data from a study monitoring the biogeochemical processes involved in the generation of mine waters and their remediation by two RAPS. Sulfur isotopes show that sulfate in all mine waters has a common source (pyrite oxidation), whilst oxygen isotopes show that oxidation of pyritic sulfur is mediated by Fe(III)(aq). The isotopic composition of dissolved sulfide, combined with the sulfur and oxygen isotopic composition of sulfate in RAPS effluents, proves BSR and details its dual isotope systematics. The occurrence and isotopic composition of solid phase iron sulfides indicate the removal of reduced sulfur within the RAPS, with significant amounts of elemental sulfur indicating reoxidation steps. However, only 0 to 9% of solid phase iron occurs as Fe sulfides, with approximately 70% of the removed iron occurs as Fe(III) (hydr)oxides. Some of the (hydr)oxide is supplied to the wetland as solids and is simply filtered by the wetland substrate, playing no role in alkalinity generation or proton removal. However, the majority of iron is supplied as dissolved Fe(II), indicating that acid generating oxidation and hydrolysis reactions dominate iron removal. The overall contribution of BSR to the sulfur geochemistry in the RAPS is limited and sulfate retention is dominated by sulfate precipitation, comparable to aerobic treatment systems, and show that the proton acidity resulting from iron oxidation and hydrolysis must be subsequently neutralised by calcite dissolution and/or BSR deeper in the RAPS sediments. BSR is not as important as previously thought for metal removal in RAPS. The results have practical consequences for the design, treatment performance and long

  1. Geochemistry and oxygen isotope composition of main-group pallasites and olivine-rich clasts in mesosiderites: Implications for the "Great Dunite Shortage" and HED-mesosiderite connection

    NASA Astrophysics Data System (ADS)

    Greenwood, Richard C.; Barrat, Jean-Alix; Scott, Edward R. D.; Haack, Henning; Buchanan, Paul C.; Franchi, Ian A.; Yamaguchi, Akira; Johnson, Diane; Bevan, Alex W. R.; Burbine, Thomas H.

    2015-11-01

    Evidence from iron meteorites indicates that a large number of differentiated planetesimals formed early in Solar System history. These bodies should have had well-developed olivine-rich mantles and consequentially such materials ought to be abundant both as asteroids and meteorites, which they are not. To investigate this "Great Dunite Shortage" we have undertaken a geochemical and oxygen isotope study of main-group pallasites and dunitic rocks from mesosiderites. Oxygen isotope analysis of 24 main-group pallasites (103 replicates) yielded a mean Δ17O value of -0.187 ± 0.016‰ (2σ), which is fully resolved from the HED Δ17O value of -0.246 ± 0.014 (2σ) obtained in our earlier study and demonstrates that both groups represent distinct populations and were derived from separate parent bodies. Our results show no evidence for Δ17O bimodality within the main-group pallasites, as suggested by a number of previous studies. Olivine-rich materials from the Vaca Muerta, Mount Padbury and Lamont mesosiderites, and from two related dunites (NWA 2968 and NWA 3329), have Δ17O values within error of the mesosiderite average. This indicates that these olivine-rich materials are co-genetic with other mesosiderite clasts and are not fragments from an isotopically distinct pallasite-like impactor. Despite its extreme lithologic diversity the mesosiderite parent body was essentially homogeneous with respect to Δ17O, a feature best explained by an early phase of large-scale melting (magma ocean), followed by prolonged igneous differentiation. Based on the results of magma ocean modeling studies, we infer that Mg-rich olivines in mesosiderites formed as cumulates in high-level chambers and do not represent samples of the underlying mantle. By analogy, recently documented Mg-rich olivines in howardites may have a similar origin. Although the Dawn mission did not detect mesosiderite-like material on Vesta, evidence linking the mesosiderites and HEDs includes: (i) their nearly

  2. Mg-O isotopes trace the origin of Mg-rich fluids in the deeply subducted continental crust of Western Alps

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Xiang; Schertl, Hans-Peter; Zheng, Yong-Fei; Huang, Fang; Zhou, Kun; Gong, Ying-Zeng

    2016-12-01

    Fluids are important for mass transfer at the slab-mantle interface in subduction zones. However, it is usually difficult to trace fluids from specific sources in a subducting slab, especially those derived from dehydration of serpentinite. Coesite-bearing whiteschist at Dora-Maira in the Western Alps is characterized by strong Mg enrichment relative to the country rocks, which requires infiltration of Mg-rich fluids into the supracrustal rock. In order to constrain the origin of such Mg-rich fluids, we have performed an integrated study of whole-rock Mg and O isotopes, zircon U-Pb ages and O isotopes for the whiteschist and related rocks. Zircons in the whiteschist show two groups of U-Pb ages at ∼262 Ma and ∼34 Ma, respectively, for relict and newly grown domains. The Permian U-Pb ages of relict magmatic domains are consistent with the protolith age of host metagranite, suggesting that their common protolith is the Permian granite. The Tertiary U-Pb ages occur in coesite-bearing metamorphic domains, consistent with the known age for ultrahigh-pressure metamorphism. The metamorphic domains have δ18O values of 5.8- 6.8 ‰, whereas the relict magmatic domains have high δ18O values of ∼ 10 ‰. Such high δ18O values are also characteristic of the metagranite, indicating that the whiteschist protolith underwent metasomatism by metamorphic fluids with low δ18O value of ∼ 2- 4 ‰. The whiteschist mostly has whole-rock δ26Mg values of -0.07 to 0.72‰, considerably higher than country-rock δ26Mg values of -0.54 to - 0.11 ‰. Thus, the metamorphic fluids are not only rich in Mg but also heavy in Mg isotopes. They were probably derived from the breakdown of Mg-rich hydrous minerals such as talc and antigorite in serpentinite at the slab-mantle interface in the subduction channel. Therefore, the dehydration of mantle wedge serpentinite during the subduction and exhumation of continental crust can provide the Mg-rich fluids responsible for the metasomatism

  3. Probing the neutron skin thickness in collective modes of excitation

    NASA Astrophysics Data System (ADS)

    Paar, N.; Horvat, A.

    2014-03-01

    Nuclear collective motion provides valuable constraint on the size of neutron-skin thickness and the properties of nuclear matter symmetry energy. By employing relativistic nuclear energy density functional (RNEDF) and covariance analysis related to χ2 fitting of the model parameters, relevant observables are identified for dipole excitations, which strongly correlate with the neutron-skin thickness (rnp), symmetry energy at saturation density (J) and slope of the symmetry energy (L). Using the RNEDF framework and experimental data on pygmy dipole strength (68Ni, 132Sn, 208Pb) and dipole polarizability (208Pb), it is shown how the values of J, and L, and rnp are constrained. The isotopic dependence of moments associated to dipole excitations in 116-136Sn shows that the low-energy dipole strength and polarizability in neutron-rich nuclei display strong sensitivity to the symmetry energy parameter J, more pronounced than in isotopes with moderate neutron-to-proton number ratios.

  4. Distinguishing Mantle Components by Sr and Nd Isotope Analysis of Single Melt Inclusions: Case Study on Italian Potassium-rich Lavas

    NASA Astrophysics Data System (ADS)

    Koornneef, J.; Nikogosian, I.; van Bergen, M.; Smeets, R.; Bouman, C.; Schwieters, J. B.; Davies, G. R.

    2014-12-01

    Melt inclusions record more extreme isotopic variability than their bulk host lavas and offer the potential to better constrain mantle components that contribute to magmatism. Isotopic analyses of melt inclusions are, however, challenging because of their limited size. To date, Sr and Pb isotope data have been obtained for oceanic islands by application of in situ analysis techniques, either by SIMS or LA-(MC)-ICPMS. Comprehensive studies of inclusions from other settings have yet to be performed. Here, we report the first combined Sr and Nd isotope data on individual melt inclusions from Pliocene-Quaternary K-rich lavas from mainland Italy, obtained using wet chemistry techniques and TIMS analysis. We use newly developed 1013 Ohm resistors mounted in the feedback loop of Faraday cup amplifiers. Compared to default 1011 Ohm resistors, use of 1013 Ohm resistors results in a 10-fold improvement of the signal-to-noise ratio and more precise data when analysing small ion beams (< 20 mV). Twenty-one olivine hosted (85 - 92 mol % Fo) melt inclusions from seven volcanic centres along the Italian peninsula were analysed. Inclusions were homogenised and analysed for trace elements prior to isotopic analysis. 87Sr/86Sr ratios in the melt inclusions range from 0.70508 to 0.71543; 143Nd/144Nd ratios from 0.51175 to 0.51268. Significant differences in 87Sr/86Sr and 143Nd/144Nd were found between melt inclusions and host lavas indicating distinct evolution paths for the lava groundmasses and the primitive melts that were trapped in the phenocrysts. The isotopic variability is interpreted to be the result of (1) mixing of melts derived from a heterogeneous mantle modified by subduction-related metasomatism, (2) mingling of distinct batches of olivine-bearing magma within a plumbing system, and (3) local assimilation of crustal material. These preliminary data suggest that combined analysis of individual melt inclusions for trace elements and Sr-Nd isotope ratios is a promising

  5. {alpha}-decay of the new isotope {sup 187}Po: Probing prolate structures beyond the neutron mid-shell at N = 104

    SciTech Connect

    Andreyev, A.N.; Antalic, S.

    2006-04-15

    The new neutron-deficient isotope {sup 187}Po has been identified in the complete fusion reaction {sup 46}Ti+{sup 144}Sm{yields}{sup 187}Po+3n at the velocity filter SHIP. Striking features of the {sup 187}Po {alpha} decay are the strongly-hindered decay to the spherical ground state and unhindered decay to a surprisingly low-lying deformed excited state at 286 keV in the daughter nucleus {sup 183}Pb. Based on the potential energy surface calculations, the {sup 187}Po ground state and the 286 keV excited state in {sup 183}Pb were interpreted as being of prolate origin. The systematic deviation of the {alpha}-decay properties in the lightest odd-A Po isotopes relative to the smooth behavior in the even-A neighbors is discussed. Improved data for the decay of {sup 187}Bi{sup m,g} were also obtained.

  6. Dose-dependent response of nitrogen stable isotope ratio to proportion of legumes in diet to authenticate lamb meat produced from legume-rich diets.

    PubMed

    Devincenzi, T; Delfosse, O; Andueza, D; Nabinger, C; Prache, S

    2014-01-01

    This study investigated the dose-dependent response in lamb meat of stable nitrogen isotope ratio to the dietary proportion of legumes, and the ability of the nitrogen isotope signature of the meat to authenticate meat produced from legume-rich diets. Four groups of nine male Romane lambs grazing a cocksfoot pasture were supplemented with different levels of fresh alfalfa forage to obtain four dietary proportions of alfalfa (0%, 25%, 50% and 75%) for 98 days on average before slaughter (groups L0, L25, L50 and L75). We measured the stable nitrogen isotope ratio in the forages and in the longissimus thoracis muscle. The δ(15)N value of the meat decreased linearly with the dietary proportion of alfalfa. The distribution of the δ(15)N values of the meat discriminated all the L0 lambs from the L75 lambs, and gave a correct classification score of 85.3% comparing lambs that ate alfalfa with those that did not.

  7. Stable Carbon Isotope Fractionation during Bacterial Acetylene Fermentation: Potential for Life Detection in Hydrocarbon-Rich Volatiles of Icy Planet(oid)s

    PubMed Central

    Baesman, Shaun M.; Oremland, Ronald S.

    2015-01-01

    Abstract We report the first study of stable carbon isotope fractionation during microbial fermentation of acetylene (C2H2) in sediments, sediment enrichments, and bacterial cultures. Kinetic isotope effects (KIEs) averaged 3.7 ± 0.5‰ for slurries prepared with sediment collected at an intertidal mudflat in San Francisco Bay and 2.7 ± 0.2‰ for a pure culture of Pelobacter sp. isolated from these sediments. A similar KIE of 1.8 ± 0.7‰ was obtained for methanogenic enrichments derived from sediment collected at freshwater Searsville Lake, California. However, C2H2 uptake by a highly enriched mixed culture (strain SV7) obtained from Searsville Lake sediments resulted in a larger KIE of 9.0 ± 0.7‰. These are modest KIEs when compared with fractionation observed during oxidation of C1 compounds such as methane and methyl halides but are comparable to results obtained with other C2 compounds. These observations may be useful in distinguishing biologically active processes operating at distant locales in the Solar System where C2H2 is present. These locales include the surface of Saturn's largest moon Titan and the vaporous water- and hydrocarbon-rich jets emanating from Enceladus. Key Words: Acetylene—Fermentation—Isotope fractionation—Enceladus—Life detection. Astrobiology 15, 977–986. PMID:26539733

  8. Sulphur and oxygen isotope analysis to identify sources of sulphur in gypsum-rich black crusts developed on granites.

    PubMed

    Rivas, T; Pozo, S; Paz, M

    2014-06-01

    We describe the results of sulphur and oxygen isotope analyses used to identify sources of the gypsum present in black crusts that grow on the granite of historical buildings. The crusts were sampled at various locations in and near the city of Vigo (NW Spain) and were analysed for their sulphur content and δ(34)S and δ(18)O isotope ratios. Sampled crusts had δ(34)S values of 7.3‰ to 12.9‰ and δ(18)O values of 6.56‰ to 12.51‰. Sampled as potential sulphur sources were bulk depositions, seawater, foundation, ashlar and construction materials and combustion residues. The results indicated marine and, to a lesser extent, anthropogenic, origins for the sulphur and ruled out the contribution of sub-soil sulphates by capillary rise from building foundations. Isotope analyses would indicate that cement and mortar were enriched in sulphur after their application in buildings. The fact that facade orientation (towards the sea or fossil fuel pollution sources) was correlated with sulphur isotope distribution pointed to various contributions to black crust formation.

  9. Zinc isotope anomalies in Allende meteorite inclusions

    NASA Technical Reports Server (NTRS)

    Loss, R. D.; Lugmair, G. W.

    1990-01-01

    The isotopic compositions of Zn, Cr, Ti, and Ca have been measured in a number of CAIs from the Allende meteorite. The aim was to test astrophysical models which predict large excesses of Zn-66 to accompany excesses in the neutron-rich isotopes of Ca, Ti, Cr, and Ni. Some of the CAIs show clearly resolved but small excesses for Zn-66 which are at least an order of magnitude smaller than predicted. This result may simply reflect the volatility and chemical behavior of Zn as compared to the other (more refractory) anomalous elements found in these samples. Alternatively, revision of parameters and assumptions used for the model calculations may be required.

  10. Shell-model Monte Carlo studies of neutron-rich nuclei in the 1s-0d-1p-0f shells

    NASA Astrophysics Data System (ADS)

    Dean, D. J.; Ressell, M. T.; Hjorth-Jensen, M.; Koonin, S. E.; Langanke, K.; Zuker, A. P.

    1999-05-01

    We demonstrate the feasibility of realistic shell-model Monte Carlo (SMMC) calculations spanning multiple major shells, using a realistic interaction whose bad saturation and shell properties have been corrected by a newly developed general prescription. Particular attention is paid to the approximate restoration of translational invariance. The model space consists of the full sd-pf shells. We include in the study some well-known T=0 nuclei and several unstable neutron-rich ones around N=20,28. The results indicate that SMMC calculations can reproduce binding energies, B(E2) transitions, and other observables with an interaction that is practically parameter free. Some interesting insight is gained into the nature of deep correlations. The validity of previous studies is confirmed.

  11. Spectroscopy of {sup 36}Mg: Interplay of Normal and Intruder Configurations at the Neutron-Rich Boundary of the 'Island of Inversion'

    SciTech Connect

    Gade, A.; Bowen, M. D.; Brown, B. A.; Campbell, C. M.; Cook, J. M.; Glasmacher, T.; McDaniel, S.; Ratkiewicz, A.; Siwek, K.; Terry, J. R.; Adrich, P.; Bazin, D.; Ettenauer, S.; Obertelli, A.; Weisshaar, D.; Kemper, K. W.; Otsuka, T.; Tostevin, J. A.; Utsuno, Y.

    2007-08-17

    We report on the first spectroscopy study of the very neutron-rich nucleus {sub 12}{sup 36}Mg{sub 24} using the direct two-proton knockout reaction {sup 9}Be({sup 38}Si,{sup 36}Mg+{gamma})X at 83 MeV/nucleon. The energy of the first excited 2{sup +} state of {sup 36}Mg, E(2{sub 1}{sup +})=660(6) keV, was measured. The magnitude of the partial cross sections to the ground state and the 2{sub 1}{sup +} state is indicative of strong intruder admixtures in the lowest-lying states as suggested by Monte Carlo shell-model calculations.

  12. Order of [6]Ti4+ in a Ti-rich calcium amphibole from Kaersut, Greenland: a combined X-ray and neutron diffraction study

    NASA Astrophysics Data System (ADS)

    Diego Gatta, G.; McIntyre, Garry J.; Oberti, Roberta; Hawthorne, Frank C.

    2016-10-01

    In order to characterize the role of Ti in the crystal structure of calcium amphiboles with high or even dominant oxo-component, the crystal structure of a Ti-rich calcium amphibole from a gabbro at Kaersut, Greenland, has been refined with single-crystal MoKα X-ray intensity data to an R 1(F) index of ~0.025, and with single-crystal Laue neutron intensity data to an R 1(F) index of ~0.053. The crystal used for X-ray structure refinement was characterized by electron- and ion-microprobe analysis. The site populations of the C-group cations Mg, Fe and Ti were calculated from the refined site-scattering values for the M(1), M(2) and M(3) sites derived by both X-ray and neutron diffraction. Ti is distributed among all the three sixfold coordinated M sites, with a strong preference for the M(1) and M(3) sites, where its main role is maintaining electroneutrality at the deprotonated O(3) site. The pattern of distortion of the M(1), M(2) and M(3) octahedra differs from that in F-free deprotonated or partly deprotonated amphiboles, where Ti4+ does not occur at the M(3) site. The neutron structure refinement provides also a clear picture of the environment of the proton, anisotropic displacement behaviour and potential hydrogen-bonding arrangements. A trifurcated hydrogen-bonding configuration has been identified, with two O(6) and one O(7) oxygen atoms as acceptors of weak hydrogen-bonds.

  13. Order of [6]Ti4+ in a Ti-rich calcium amphibole from Kaersut, Greenland: a combined X-ray and neutron diffraction study

    NASA Astrophysics Data System (ADS)

    Diego Gatta, G.; McIntyre, Garry J.; Oberti, Roberta; Hawthorne, Frank C.

    2017-02-01

    In order to characterize the role of Ti in the crystal structure of calcium amphiboles with high or even dominant oxo-component, the crystal structure of a Ti-rich calcium amphibole from a gabbro at Kaersut, Greenland, has been refined with single-crystal Mo Kα X-ray intensity data to an R 1( F) index of 0.025, and with single-crystal Laue neutron intensity data to an R 1( F) index of 0.053. The crystal used for X-ray structure refinement was characterized by electron- and ion-microprobe analysis. The site populations of the C-group cations Mg, Fe and Ti were calculated from the refined site-scattering values for the M(1), M(2) and M(3) sites derived by both X-ray and neutron diffraction. Ti is distributed among all the three sixfold coordinated M sites, with a strong preference for the M(1) and M(3) sites, where its main role is maintaining electroneutrality at the deprotonated O(3) site. The pattern of distortion of the M(1), M(2) and M(3) octahedra differs from that in F-free deprotonated or partly deprotonated amphiboles, where Ti4+ does not occur at the M(3) site. The neutron structure refinement provides also a clear picture of the environment of the proton, anisotropic displacement behaviour and potential hydrogen-bonding arrangements. A trifurcated hydrogen-bonding configuration has been identified, with two O(6) and one O(7) oxygen atoms as acceptors of weak hydrogen-bonds.

  14. Particle-hole intruder levels in 67Cu, collectivity, monopole shifts, and the hockey-stick behaviour of ell - 1/2 5/2- levels in neutron-rich odd-mass Cu nuclei

    NASA Astrophysics Data System (ADS)

    Walters, W. B.; Chiara, C. J.

    2011-01-01

    A new sequence of gamma rays with energies of 572, 499, 585, and 674 keV has been identified in 67Cu populating the 7/2- level at 2362 keV. Owing to the strong population of the 2362-keV level via an ell = 3 proton pickup reaction, that level is assigned to be an f7/2-1 2-particle-1-hole "intruder" proton configuration, and the new levels are found to form a sequence consistent with intruder sequences in the adjacent odd-mass Cu isotopes and in the odd-mass Sb isotopes. The changing position of the intruder sequence in the odd-mass Cu isotopes is discussed and related to the onset of collectivity associated with the presence of g9/2 neutrons beyond N = 40. The increase in collectivity is also discussed for a number of isotonic and isotopic chains as more protons or neutrons, respectively, are added beyond an oscillator shell boundary. For most of these systems, the ell -1/2 levels show a systematic "hockey-stick-like" behaviour with a sharp decrease in energy with the addition of the first protons or neutrons, owing to both the added collectivity and the tensor interaction, and then a lower slope when collectivity changes are diminished and only the tensor interaction is influencing the changes in level positions.

  15. Neutronics Simulations of 237Np Targets to Support Safety-Basis and 238Pu Production Assessment Efforts at the High Flux Isotope Reactor

    SciTech Connect

    Chandler, David; Ellis, Ronald James

    2015-01-01

    Fueled by two highly enriched uranium-bearing fuel elements surrounded by a large concentric ring of beryllium reflector, the High Flux Isotope Reactor (HFIR) provides one of the highest neutron fluxes in the world and is used to produce unique isotopes like plutonium-238. The National Aeronautics and Space Administration use radioisotope thermoelectric generators powered by 238Pu for deep-space missions. As part of the US Department of Energy s task to reestablish the domestic production of 238Pu, a technology demonstration sub-project has been initiated to establish a new 238Pu supply chain. HFIR safety-basis neutronics calculations are being performed to ensure the target irradiations have no adverse impacts on reactor performance and to calculate data required as input to follow-on thermal-structural, thermal-hydraulic and radionuclide/dose analyses. Plutonium-238 production assessments are being performed to estimate the amount of 238Pu that can be produced in HFIR s permanent beryllium reflector. It is estimated that a total of 0.96 1.12 kg 238Pu (~1.28 1.49 kg PuO2 at 85% 238Pu/Pu purity) could be produced per year in HFIR s permanent beryllium reflector irradiation facilities if they are all utilized.

  16. Direct lead isotope analysis in Hg-rich sulfides by LA-MC-ICP-MS with a gas exchange device and matrix-matched calibration.

    PubMed

    Zhang, Wen; Hu, Zhaochu; Günther, Detlef; Liu, Yongsheng; Ling, Wenli; Zong, Keqing; Chen, Haihong; Gao, Shan

    2016-12-15

    In situ Pb isotope data of sulfide samples measured by LA-MC-ICP-MS provide valuable geochemical information for studies of the origin and evolution of ore deposits. However, the severe isobaric interference of (204)Hg on (204)Pb and the lack of matrix-matched sulfide reference materials limit the precision of Pb isotopic analyses for Hg-rich sulfides. In this study, we observe that Hg forms vapor and can be completely removed from sample aerosol particles produced by laser ablation using a gas exchange device. Additionally, this device does not influence the signal intensities of Pb isotopes. The within-run precision, the external reproducibility and the analytical accuracy are significantly improved for the Hg-rich sulfide samples using this mercury-vapor-removing device. Matrix effects are observed when using silicate glass reference materials as the external standards to assess the relationship of mass fractionation factors between Tl and Pb in sulfide samples, resulting in a maximum deviation of ∼0.20% for (20x)Pb/(204)Pb. Matrix-matched reference materials are therefore required for the highly precise and accurate Pb isotope analyses of sulfide samples. We investigated two sulfide samples, MASS-1 (the Unites States Geological Survey reference materials) and Sph-HYLM (a natural sphalerite), as potential candidates. Repeated analyses of the two proposed sulfide reference materials by LA-MC-ICP-MS yield good external reproducibility of <0.04% (RSD, k = 2) for (20x)Pb/(206)Pb and <0.06% (RSD, k = 2) for (20x)Pb/(204)Pb with the exception of (20x)Pb/(204)Pb in MASS-1, which provided an external reproducibility of 0.24% (RSD, k = 2). Because the concentration of Pb in MASS-1 (76 μg g(-1)) is ∼5.2 times lower than that in Sph-HYLM (394 ± 264 μg g(-1)). The in situ analytical results of MASS-1 and Sph-HYLM are consistent with the values obtained by solution MC-ICP-MS, demonstrating the reliability and robustness of our analytical protocol.

  17. Reach-scale isotope tracer experiment to quantify denitrification and related processes in a nitrate-rich stream, midcontinent United States

    USGS Publications Warehouse

    Böhlke, J.K.; Harvey, J.W.; Voytek, M.A.

    2004-01-01

    We conducted an in-stream tracer experiment with Br and 15N-enriched NO3- to determine the rates of denitrification and related processes in a gaining NO3--rich stream in an agricultural watershed in the upper Mississippi basin in September 2001. We determined reach-averaged rates of N fluxes and reactions from isotopic analyses of NO3-, NO 2-, N2, and suspended particulate N in conjunction with other data in a 1.2-km reach by using a forward time-stepping numerical simulation that included groundwater discharge, denitrification, nitrification, assimilation, and air-water gas exchange with changing temperature. Denitrification was indicated by a systematic downstream increase in the ??15N values of dissolved N2. The reach-averaged rate of denitrification of surface-water NO3- indicated by the isotope tracer was approximately 120 ?? 20 ??mol m-2 h-1 (corresponding to zero- and first-order rate constants of 0.63 ??mol L-1 h-1 and 0.009 h -1, respectively). The overall rate of NO3- loss by processes other than denitrification (between O and about 200 ??mol m-2 h-1) probably was less than the denitrification rate but had a large relative uncertainty because the NO3- load was large and was increasing through the reach. The rates of denitrification and other losses would have been sufficient to reduce the stream NO 3- load substantially in the absence of NO 3- sources, but the losses were more than offset by nitrification and groundwater NO3- inputs at a combined rate of about 500-700 ??mol m-2 h-1. Despite the importance of denitrification, the overall mass fluxes of N2 were dominated by discharge of denitrified groundwater and air-water gas exchange in response to changing temperature, whereas the flux of N2 attributed to denitrification was relatively small. The in-stream isotope tracer experiment provided a sensitive direct reach-scale measurement of denitrification and related processes in a NO3--rich stream where other mass-balance methods were not suitable because

  18. Transuranium isotopes

    SciTech Connect

    Hoffman, D.C.

    1985-12-01

    The needs of the research community for the production of transuranium isotopes, the quantities required, the continuity of production desired, and what a new steady state neutron source would have to provide to satisfy these needs are discussed. Examples of past frontier research which need these isotopes as well as an outline of the proposed Large Einsteinium Activation Program, LEAP, which requires roughly ten times the current production of /sup 254/Es are given. 15 refs., 5 figs., 4 tabs.

  19. Radiative neutron capture: Hauser Feshbach vs. statistical resonances

    NASA Astrophysics Data System (ADS)

    Rochman, D.; Goriely, S.; Koning, A. J.; Ferroukhi, H.

    2017-01-01

    The radiative neutron capture rates for isotopes of astrophysical interest are commonly calculated on the basis of the statistical Hauser Feshbach (HF) reaction model, leading to smooth and monotonically varying temperature-dependent Maxwellian-averaged cross sections (MACS). The HF approximation is known to be valid if the number of resonances in the compound system is relatively high. However, such a condition is hardly fulfilled for keV neutrons captured on light or exotic neutron-rich nuclei. For this reason, a different procedure is proposed here, based on the generation of statistical resonances. This novel technique, called the "High Fidelity Resonance" (HFR) method is shown to provide similar results as the HF approach for nuclei with a high level density but to deviate and be more realistic than HF predictions for light and neutron-rich nuclei or at relatively low sub-keV energies. The MACS derived with the HFR method are systematically compared with the traditional HF calculations for some 3300 neutron-rich nuclei and shown to give rise to significantly larger predictions with respect to the HF approach at energies of astrophysical relevance. For this reason, the HF approach should not be applied to light or neutron-rich nuclei. The Doppler broadening of the generated resonances is also studied and found to have a negligible impact on the calculated MACS.

  20. Neutron matter, symmetry energy and neutron stars

    NASA Astrophysics Data System (ADS)

    Gandolfi, S.; Steiner, A. W.

    2016-01-01

    Recent progress in quantum Monte Carlo with modern nucleon-nucleon interactions have enabled the successful description of properties of light nuclei and neutron- rich matter. Of particular interest is the nuclear symmetry energy, the energy cost of creating an isospin asymmetry, and its connection to the structure of neutron stars. Combining these advances with recent observations of neutron star masses and radii gives insight into the equation of state of neutron-rich matter near and above the saturation density. In particular, neutron star radius measurements constrain the derivative of the symmetry energy.