Shell closures, loosely bound structures, and halos in exotic nuclei

Energy Technology Data Exchange (ETDEWEB)

Saxena, G., E-mail: gauravphy@gmail.com [Govt. Women Engineering College, Department of Physics (India); Singh, D. [University of Rajasthan, Department of Physics (India)

2013-04-15

Inspired by the recent experiments indicating doubly magic nuclei that lie near the drip-line and encouraged by the success of our relativistic mean-field (RMF) plus state-dependent BCS approach to the description of the ground-state properties of drip-line nuclei, we develop this approach further, across the entire periodic table, to explore magic nuclei, loosely bound structures, and halo formation in exotic nuclei. In our RMF+BCS approach, the single-particle continuum corresponding to the RMF is replaced by a set of discrete positive-energy states for the calculations of pairing energy. Detailed analysis of the single-particle spectrum, pairing energies, and densities of the nuclei predict the unusual proton shell closures at proton numbers Z = 6, 14, 16, 34, and unusual neutron shell closures at neutron numbers N = 6, 14, 16, 34, 40, 70, 112. Further, in several nuclei like the neutron-rich isotopes of Ca, Zr, Mo, etc., the gradual filling of lowlying single-particle resonant state together with weakly bound single-particle states lying close to the continuum threshold helps accommodate more neutrons but with an extremely small increase in the binding energy. This gives rise to the occurrence of loosely bound systems of neutron-rich nuclei with a large neutron-to-proton ratio. In general, the halo-like formation, irrespective of the existence of any resonant state, is seen to be due to the large spatial extension of the wave functions for the weakly bound single-particle states with low orbital angular momentum having very small or no centrifugal barriers.

Sensitivity of the halo nuclei-12C elastic scattering at incident nucleon energy 800 MeV to the halo density distribution

Science.gov (United States)

Hassan, M. A. M.; Nour El-Din, M. S. M.; Ellithi, A.; Hosny, H.; Salama, T. N. E.

2017-10-01

In the framework of Glauber optical limit approximation where Coulomb effect is taken into account, the elastic scattering differential cross section for halo nuclei with {}^{12}{C} at 800 MeV/N has been calculated. Its sensitivity to the halo densities and the root mean square of the core and halo is the main goal of the current study. The projectile nuclei are taken to be one-neutron and two-neutron halo. The calculations are carried out for Gaussian-Gaussian, Gaussian-Oscillator and Gaussian-2 s phenomenological densities for each considered projectile in the mass number range 6-29. Also included a comparison between the obtained results of phenomenological densities and the results within the microscopic densities LSSM of {}6{He} and {}^{11}{Li} and microscopic densities GCM of {}^{11}{Be} where the density of the target nucleus {}^{12}{C} obtained from electron-{}^{12}{C} scattering is used. The zero range approximation is considered in the calculations. We found that the sensitivity of elastic scattering differential cross section to the halo density is clear if the nucleus appears as two clear different clusters, core and halo.

Structure of neutron-rich nuclei

International Nuclear Information System (INIS)

Nazarewicz, W.

2000-01-01

Complete text of publication follows. The uncharted regions of the (N,Z) plane contain information that can answer many questions of fundamental importance for science: How many protons and neutrons can be clustered together by the strong interaction to form a bound nucleus? What are the proton and neutron magic numbers of the exotic nuclei? What are the properties of very short-lived exotic nuclei with extreme neutron-to-proton ratios? What is the effective nucleon-nucleon interaction in a nucleus that has a very large neutron excess? Nuclear life far from stability is different from that around the stability line; the promised access to completely new combinations of proton and neutron numbers offers prospects for new structural phenomena. The main objective of this talk is to discuss some of the challenges and opportunities of research with exotic nuclei. The covered topics will include: Theoretical challenges; Skins and halos in heavy nuclei; Shape coexistence in exotic nuclei; Beta-decays of neutron-rich nuclei. (author)

Reactions with fast radioactive beams of neutron-rich nuclei

Energy Technology Data Exchange (ETDEWEB)

Aumann, T. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany)

2005-11-01

The neutron dripline has presently been reached only for the lightest nuclei up to the element oxygen. In this region of light neutron-rich nuclei, scattering experiments are feasible even for dripline nuclei by utilizing high-energy secondary beams produced by fragmentation. In the present article, reactions of high-energy radioactive beams will be exemplified using recent experimental results mainly derived from measurements of breakup reactions performed at the LAND and FRS facilities at GSI and at the S800 spectrometer at the NSCL. Nuclear and electromagnetically induced reactions allow probing different aspects of nuclear structure at the limits of stability related to the neutron-proton asymmetry and the weak binding close to the dripline. Properties of the valence-neutron wave functions are studied in the one-neutron knockout reaction, revealing the changes of shell structure when going from the beta-stability line to more asymmetric loosely bound neutron-rich systems. The vanishing of the N=8 shell gap for neutron-rich systems like {sup 11}Li and {sup 12}Be, or the new closed N=14, 16 shells for the oxygen isotopes are examples. The continuum of weakly bound nuclei and halo states can be studied by inelastic scattering. The dipole response, for instance, is found to change dramatically when going away from the valley of stability. A redistribution of the dipole strength towards lower excitation energies is observed for neutron-rich nuclei, which partly might be due to a new collective excitation mode related to the neutron-proton asymmetry. Halo nuclei in particular show strong dipole transitions to the continuum at the threshold, being directly related to the ground-state properties of the projectile. Finally, an outlook on future experimental prospects is given. (orig.)

Reactions with fast radioactive beams of neutron-rich nuclei

International Nuclear Information System (INIS)

Aumann, T.

2005-11-01

The neutron dripline has presently been reached only for the lightest nuclei up to the element oxygen. In this region of light neutron-rich nuclei, scattering experiments are feasible even for dripline nuclei by utilizing high-energy secondary beams produced by fragmentation. In the present article, reactions of high-energy radioactive beams will be exemplified using recent experimental results mainly derived from measurements of breakup reactions performed at the LAND and FRS facilities at GSI and at the S800 spectrometer at the NSCL. Nuclear and electromagnetically induced reactions allow probing different aspects of nuclear structure at the limits of stability related to the neutron-proton asymmetry and the weak binding close to the dripline. Properties of the valence-neutron wave functions are studied in the one-neutron knockout reaction, revealing the changes of shell structure when going from the beta-stability line to more asymmetric loosely bound neutron-rich systems. The vanishing of the N=8 shell gap for neutron-rich systems like 11 Li and 12 Be, or the new closed N=14, 16 shells for the oxygen isotopes are examples. The continuum of weakly bound nuclei and halo states can be studied by inelastic scattering. The dipole response, for instance, is found to change dramatically when going away from the valley of stability. A redistribution of the dipole strength towards lower excitation energies is observed for neutron-rich nuclei, which partly might be due to a new collective excitation mode related to the neutron-proton asymmetry. Halo nuclei in particular show strong dipole transitions to the continuum at the threshold, being directly related to the ground-state properties of the projectile. Finally, an outlook on future experimental prospects is given. (orig.)

Momentum distributions in light halo nuclei and structure constraints

Directory of Open Access Journals (Sweden)

Souza L. A.

2016-01-01

Full Text Available The core recoil momentum distribution of neutron-rich isotopes of light exotic nuclei is studied within a three-body model, where the nuclei are described by a core and two neutrons, with interactions dominated by the s-wave channel. In our framework, the two-body subsystems should have large scattering lengths in comparison with the interaction range allowing to use a three-body model with a zero-range force. The ground-state halo wave functions in momentum space are obtained by using as inputs the two-neutron separation energy and the energies of the singlet neutron-neutron and neutron-core virtual states. Within our model, we obtain the momentum probability densities for the Borromean exotic nuclei 11Li and 22C. In the case of the core recoil momentum distribution of 11Li, a fair reproduction of the experimental data was obtained, without free parameters, considering only the two-body low-energies. By analysing the obtained core momentum distribution in face of recent experimental data, we verify that such data are constraining the 22C two-neutron separation energy to a value between 100 and 400 keV.

Isospin quantum number and structure of the excited states in halo nuclei. Halo-isomers

International Nuclear Information System (INIS)

Izosimov, I.N.

2015-01-01

It has been shown that isobar-analog (IAS), double isobar-analog (DIAS), configuration (CS), and double configuration states (DCS) can simultaneously have n-n, n-p, and p-p halo components in their wave functions. Differences in halo structure of the excited and ground states can result in the formation of isomers (halo-isomers). Both the Borromean and tango halo types can be observed for n-p configurations of atomic nuclei. The structure of the ground and excited states with different isospin quantum number in halo-like nuclei is discussed. B(Mλ) and B(Eλ) for γ-transitions in 6-8 Li, 8-10 Be, 8,10,11 B, 10-14 C, 13-17 N, 15-17,19 O, and 17 F are analyzed. Special attention is given to nuclei whose ground state does not exhibit halo structure, but the excited state may have one.

Penning Trap Experiments with the Most Exotic Nuclei on Earth: Precision Mass Measurements of Halo Nuclei

Science.gov (United States)

Brodeur, M.; Brunner, T.; Ettenauer, S.; Lapierre, A.; Ringle, R.; Delheij, P.; Dilling, J.

2009-05-01

Exotic nuclei are characterized with an extremely unbalanced protons-neutrons ratio (p/n) where for instance, the halo isotopes of He and Li have up to 3X more n than p (compared to p/n = 1 in ^12C). The properties of these exotic halo nuclei have long been recognized as the most stringent tests of our understanding of the strong force. ^11Li belongs to a special category of halos called Borromean, bound as a three-body family, while the two-body siblings, ^10Li and 2 n, are unbound as separate entities. Last year, a first mass measurement of the radioisotope ^11Li using a Penning trap spectrometer was carried out at the TITAN (Triumf's Ion Trap for Atomic and Nuclear science) facility at TRIUMF-ISAC. Penning traps are proven to be the most precise device to make mass measurements, yet until now they were unable to reach these nuclei. At TRIUMF we managed to measure the mass of ^11Li to an unprecedented precision of dm/m = 60 ppb, which is remarkable since it has a half-life of only 8.8 ms which it the shortest-lived nuclide to be measured with this technique. Furthermore, new and improved masses for the 2 and 4 n halo ^6,8He, as well has the 1 n halo ^11Be have been performed. An overview of the TITAN mass measurement program and its impact in understanding the most exotic nuclei will be given.

Investigations of the neutron halo by radioactive beam experiments

International Nuclear Information System (INIS)

Mueller, A.C.

1993-01-01

Recently, a new tool has become available to study the behaviour of nuclei at the limits of particle stability. Heavy-ion projectile fragmentation, in combination with efficient recoil spectrometers, allows to prepare 'exotic' beams which can be used to induce secondary nuclear reactions. First experiments have revealed surprising features in the reactions of the most neutron-rich light nuclei. There is now conclusive evidence that the observed effects are due to long-tail matter distributions ('neutron halo') which occur for the last, very weakly bound neutrons. The results of some recent radioactive beam experiments, made by means of the spectrometer LISE3 at GANIL, are presented. (author) 24 refs.; 7 figs

Structure study in the 19C halo

International Nuclear Information System (INIS)

Angelique, J.C.; Le Brun, C.; Liegard, E.; Marques, F.M.; Orr, N.A.

1997-01-01

The halo nuclei are nuclei which have one or more neutrons (or protons) with very weak binding energy what results in a spatial extension beyond the core containing the other nucleons. This important spatial extension is related via the Heisenberg principle to a narrow momentum distribution which signs the halo structure of the nucleus under consideration. To extend our understanding of this phenomenon an experiment has been carried out with the DEMON multidetector in the frame of the collaboration E133. The subject was the study of 19 C, a nucleus susceptible of having a neutron halo due to the low binding energy of its last neutron (S n = 240 ± 100 keV). The 19 C secondary beam was produced by fragmentation of a primary 40 Ar beam in a carbon target between the two solenoids of SISSI and than directed to a GANIL experimental room. A silicon detector telescope was used to detect the charged particles issued from the reaction of 19 C nuclei with the tantalum target while the DEMON detection modular assembly separated by four meters from the target allowed the neutron detection between 0 and 42 degrees. The first results of this analysis are favorable to a halo structure for this nucleus for the reaction channel in which the 18 C core is destroyed. We have compared the angular distribution of the neutrons of 19 C with those obtained from the breakup reactions of other exotic nuclei ( 21 N, 22 O and 24 F) but having no halo structure. A net different behavior of these nuclei indicate a clear difference in structure. Actually, the 19 C distribution corresponds to the superposition of a broad distribution and narrow distribution. The last one having width of 42 ± 12 MeV/c, compatible with an important spatial extension, corresponds to neutrons coming from the halo. It is argued that the model in which the halo neutron moves on a s orbital cannot described the structure of 19 C halo. A more adequate description would be a mixture of s and d orbitals which would also

Effect of a neutron skin on collective dipoles modes in nuclei

International Nuclear Information System (INIS)

Warner, D.D.; Van Isacker, P.; Nagarajan, M.A.

1992-01-01

One of the principal motivations for accelerated radioactive beams is to probe nuclear structure at the limits of nuclear stability. For neutron-rich nuclei, an indication of the new phenomena which may occur has already appeared, in the guise of the neutron halo discovered in very light nuclei. More generally, a steadily increasing neutron skin thickness is expected as the neutron excess increases. The presence of such a mantle of dominantly neutron matter will then particularly affect the properties of collective modes involving the out-of-phase motion of neutrons and protons. This paper explores the effect of the neutron skin thickness on the isovector M1 and E1 modes in medium and heavy mass nuclei. A simple model is used, couched in terms of classical oscillations of neutron and proton densities. The treatment includes the open-quotes pygmyclose quotes E1 mode, which corresponds to motion of the core against the loosely-bound neutrons in the mantle and predicts a significant lowering of this mode, even at relatively modest values of the skin thickness

Study of Neutron Halo Structure in Interaction of 6He with Nuclei of Photoemulsion

International Nuclear Information System (INIS)

Belovitsky, G.; Konobeevski, E.; Stepanov, A.; Zavarzina, V.; Zuyev, S.; Polukhina, N.; Rusetsky, A.; Starkov, N.; Lukyanov, S.; Sobolev, Yu.

2008-01-01

To investigate the structure of halo of Borromean nuclei, we propose an experimental method of studying quasi-free scattering of proton by the constituents of halo-nuclei in photo emulsion. The experimental study of 6 He + 1 H interaction is performed using 6 He beam of Flerov Laboratory of Nuclear Reactions (JINR, Dubna) at energy of about 10 MeV/u and technique of nuclear photo emulsions. Searching for events of quasi-free scattering and their processing is performed using the PAVICOM-setup at P.N. Lebedev Physical institute

Neutron momentum distributions from ''core break-up'' reactions of halo nuclei

International Nuclear Information System (INIS)

Nilsson, T.; Blaich, T.; Borege, M.J.G.

1995-01-01

Neutron angular distributions from violent break-up reactions of 11 Li and 11 Be have been measured at 28 MeV/u and 280 MeV/u and at 41 MeV/u and 460 MeV/u, respectively. The derived neutron momentum distributions show a narrow component in transverse momentum that is within uncertainties independent of beam energy and target charge. This component is suggested to be simply related to the momentum distribution of the loosely bound halo neutron(s) in the projectiles. (orig.)

Giant halos in medium nuclei within modified relativistic mean field (MRMF) model

Energy Technology Data Exchange (ETDEWEB)

Nugraha, A. M., E-mail: alpi.mahisha@gmail.com; Sulaksono, A. [Departemen Fisika, FMIPA, Universitas Indonesia, Kampus UI Depok (Indonesia); Sumaryada, T. [Department of Physics, Bogor Agricultural University, Jalan Meranti Kampus IPB Dramaga Bogor 16680 (Indonesia)

2016-04-19

The large number of neutrons in a region beyond a closed shell core indicates the presence of giant halos in nuclei. In this work, by using the Rotival method within a modified relativistic mean field (MRMF) model, we predict theoretically the formation of giant halos in Cr and Zr isotopes. The MRMF model is a modification of standard RMF model augmented with isoscalar and isovector tensor terms, isovector-isoscalar vector cross coupling term and electromagnetic exchange term for Coulomb interaction in local density approximation (LDA).

Total dissociation cross section of halo nuclei

Energy Technology Data Exchange (ETDEWEB)

Formanek, J. [Karlova Univ., Prague (Czech Republic). Fakulta Matematicko-Fyzikalni; Lombard, R.J. [Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire

1996-10-01

Calculations of the total dissociation cross section is performed in the impact parameter representation. The case of {sup 11}Be and {sup 11}Li loosing one and two neutron(s), respectively, by collision on a {sup 12}C target, which remains in its ground state are discussed. The results are found to depend essentially on the rms radius of the halo wave function. (author). 12 refs.

Influence of neutron halo in the interaction of 6He nucleus of 35 MeV/nucleon with 197Au and 238U

International Nuclear Information System (INIS)

Perier, Yann

1997-01-01

In this study, we have attempted to answer some of the questions still open concerning neutron halo nuclei. The interest of the latter lies in their very peculiar structure. The analysis of the kinematical features of the halo nucleus fragments originating from the dissociation following the interaction with a target nucleus is an essential tool for probing this structure. We studied the 6 He + Au, U at 35 A.MeV system with a new method. Simultaneous measurements of the halo nucleus core, the halo neutrons and the excitation energy deposited in the target nucleus assessed with ORION allowed us to obtain information about the formation of the 5 He nucleus and about the partial validity of the sudden approximation at moderate bombarding energy. The study of the core nucleus and neutron angular distributions confirmed that it is difficult to extract information on the internal structure at the halo neutrons from their widths. The halo neutron longitudinal momentum distributions were studied. Their widths were found to increase as the impact parameter decreases. The 4 He - core parallel momentum distributions were also investigated. The widths are weakly dependent on the excitation energy deposited in the target nucleus, but increase with the 4 He emission angle as for the halo neutrons. The ratio between one- and two-neutron stripping cross sections seems to indicate that the two halo neutrons are strongly correlated with a large dineutron component, as ascertained by a calculation in the framework of the Serber model. (author)

Influence of neutron halo in the interaction of {sup 6}He nucleus of 35 MeV/nucleon with {sup 197}Au and {sup 238}U; Influence du halo de neutrons dans l`interaction du noyau {sup 6}He de 35 MeV/nucleon avec {sup 197}Au et {sup 238}U

Energy Technology Data Exchange (ETDEWEB)

Perier, Yann [Grand Accelerateur National d`Ions Lourds (GANIL), 14 - Caen (France)

1997-10-27

In this study, we have attempted to answer some of the questions still open concerning neutron halo nuclei. The interest of the latter lies in their very peculiar structure. The analysis of the kinematical features of the halo nucleus fragments originating from the dissociation following the interaction with a target nucleus is an essential tool for probing this structure. We studied the {sup 6}He + Au, U at 35 A.MeV system with a new method. Simultaneous measurements of the halo nucleus core, the halo neutrons and the excitation energy deposited in the target nucleus assessed with ORION allowed us to obtain information about the formation of the {sup 5}He nucleus and about the partial validity of the sudden approximation at moderate bombarding energy. The study of the core nucleus and neutron angular distributions confirmed that it is difficult to extract information on the internal structure at the halo neutrons from their widths. The halo neutron longitudinal momentum distributions were studied. Their widths were found to increase as the impact parameter decreases. The {sup 4}He - core parallel momentum distributions were also investigated. The widths are weakly dependent on the excitation energy deposited in the target nucleus, but increase with the {sup 4}He emission angle as for the halo neutrons. The ratio between one- and two-neutron stripping cross sections seems to indicate that the two halo neutrons are strongly correlated with a large dineutron component, as ascertained by a calculation in the framework of the Serber model. (author) 84 refs., 98 figs., 17 tabs.

Double folding model analysis of elastic scattering of halo nucleus ...

Indian Academy of Sciences (India)

carried out which provide valuable insight for improving our understanding of nuclear reactions. One of the interesting aspects is to understand the effect of the halo structure, on elastic scattering cross-sections at near-Coulomb barrier energies in reactions induced by neutron halo nuclei and weakly bound radioactive ...

Exclusive measurement of breakup reactions with the one-neutron halo nucleus sup 1 sup 1 Be

CERN Document Server

Palit, R; Aumann, T; Boretzky, K; Carlson, B V; Cortina-Gil, D; Elze, T W; Emling, H; Geissel, H; Hellström, M; Jones, K L; Kratz, J V; Kulessa, R; Leifels, Y; Leistenschneider, A; Münzenberg, G; Nociforo, C; Reiter, P; Simon, H; Sümmerer, K; Walús, W

2003-01-01

Electromagnetic and nuclear inelastic scattering of the halo nucleus sup 1 sup 1 Be have been investigated by a measurement of the one-neutron removal channel, utilizing a secondary sup 1 sup 1 Be beam with an energy of 520 MeV/nucleon impinging on lead and carbon targets. All decay products, i.e. sup 1 sup 0 Be fragments, neutrons, and gamma-rays have been detected in coincidence. Partial cross sections for the population of ground and excited states in sup 1 sup 0 Be were determined for nuclear diffractive breakup as well as for electromagnetically induced breakup. The partial cross sections for ground-state transitions have been differentiated further with respect to excitation energy, and the dipole-strength function associated solely with transitions of the halo 2s sub 1 sub / sub 2 neutron to the continuum has been derived. The extracted dipole strength integrated from the neutron threshold up to 6.1 MeV excitation energy amounts to 0.90(6) e sup 2 fm sup 2. A spectroscopic factor for the nu 2s sub 1 su...

Pre-asymptotic behavior of single-particle overlap integrals of non-Borromean two-neutron halos

International Nuclear Information System (INIS)

Timofeyuk, N.K.; Tostevin, J.A.; Blokhintsev, L.D.

2003-01-01

For non-Borromean two-neutron halo nuclei, modifications to the behavior of single-particle overlap integrals will arise due to the correlations of the two interacting nucleons in the halo. An additional contribution to the overlap integral can be obtained using the Feynman diagram approach. This additional term is modeled using a simple local potential model. We show that these modifications may play a role in detailed interpretations of experimental results from single-nucleon knockout, transfer, and other reactions that probe the single-nucleon overlap functions

Decay Properties of the Halo Nucleus $^{11}$Li

CERN Multimedia

2002-01-01

During the past years a considerable experimental effort has been devoted to the production and study of nuclei close to the neutron and proton drip-lines. The most spectacular phenomenon encountered is the occurrence of neutron halos in the loosely bound neutron rich nuclei. \\\\ \\\\ Another interesting feature, observed at ISOLDE, which most likely is connected to the halo structure, is the very strong (super-allowed) Gamow-Teller $\\beta$- transitions to highly excited states which are systematically observed for the lightest neutron rich drip-line nuclei. These transitions might be viewed as arising from the quasi-free $\\beta$ -decay of the halo neutrons. It is proposed to make a detailed study of the $\\beta$- strength function for $^{11}$Li, a nuclide having a half-life of 8.2 ms and a Q $\\beta$-value of 20.73~MeV. \\\\ \\\\ So far only a lower limit of the Gamow-Teller transition rate to highly excited states ($\\approx$~18.5~MeV) in the daughter nucleus has been obtained from measurements of $\\beta$-delayed tri...

Projectile fragmentation of neutron-rich nuclei on light target (momentum distribution and nucleon-removal cross section)

International Nuclear Information System (INIS)

Kobayashi, T.; Tanihata, I.; Suzuki, T.

1992-01-01

Transverse momentum distributions of the projectile fragments from β-unstable nuclei have been measured with various projectile and target combinations. The momentum correlation of two neutrons in the neutron halo is extracted from the P c t distribution of 9 Li and hat of the neutrons. It is found that the two neutrons are moving in the same direction on average and thus strongly suggests the formation of a di-neutron in 11 Li. (Author)

Existence of halo-structure for the first excited levels of both the 13C-13N and the 17O-17F nuclei

International Nuclear Information System (INIS)

Gridnev, K.A.; Novatskij, B.G.

2003-01-01

From calculated the Coulomb shifts difference for the carbon and oxygen isotopes analog levels the valent nucleons the orbit radius values R C and the density parameter r 0 are presented. It is shown that the density parameter values are slightly varying for the all analog nuclear pairs. The exception constitutes the first excited states of the 13 C- 13 N and the 17 O- 17 F nuclei, whose valent nucleons populate the 2s-shell (L=0). These states one can to consider as structures with brightly distinguished of the ( 13 C * , 17 O * ) neutron halo and the( 13 N * , 17 F * ) proton halo

Reaction Mechanism and Structure Interplay for Proton Elastic Scattering from Halo Nuclei

International Nuclear Information System (INIS)

Crespo, R.; Johnson, R.C.

1999-01-01

The aim of this work is to clarify what properties of the projectile w.f. are relevant to describe elastic scattering of halo nuclei from stable nuclei. In particular, we examine how far elastic scattering observables probe correlation effects among projectile nucleons. Our treatment is based on a multiple scattering expansion of the proton-projectile transition amplitude in a form which is well adapted to the weakly bound cluster picture of halo nuclei. In the specific case of 11 Li scattering from protons at 800 MeV/u we show that because core recoil effects are significant, scattering cross sections can not, in general, be deduced from knowledge of the total matter density alone. We advocate that the optical potential concept for the scattering of halo nuclei on protons should be avoided and that the multiple scattering series for the full transition amplitude should be used instead

Reaction mechanism and structure interplay for proton elastic scattering from halo nuclei

International Nuclear Information System (INIS)

Crespo, R.; Johnson, R. C.

1999-01-01

The aim of this work is to clarify what properties of the projectile w.f. are relevant to describe elastic scattering of halo nuclei from stable nuclei. In particular, we examine how far elastic scattering observables probe correlation effects among projectile nucleons. Our treatment is based on a multiple scattering expansion of the proton-projectile transition amplitude in a form which is well adapted to the weakly bound cluster picture of halo nuclei. In the specific case of 11 Li scattering from protons at 800 MeV/u we show that because core recoil effects are significant, scattering crosssections cannot, in general, be deduced from knowledge of the total matter density alone. We advocate that the optical potential concept for the scattering of halo nuclei on protons should be avoided and that the multiple scattering series for the full transition amplitude should be used instead

Probing the density tail of radioactive nuclei with antiprotons

CERN Document Server

Obertelli, Alexandre; Uesaka, Tomohiro; Corsi, Anna; Pollacco, Emmanuel; Flavigny, Freddy

2017-01-01

We propose an experiment to determine the proton and neutron content of the radial density tail in short-lived nuclei. The objectives are to (i) to evidence new proton and neutron halos, (ii) to understand the development of neutron skins in medium-mass nuclei, (iii) to provide a new observable that characterises the density tail of short-lived nuclei.

Momentum profile analysis in one-neutron knockout from Borromean nuclei

Energy Technology Data Exchange (ETDEWEB)

Aksyutina, Yu. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, ExtreMe Matter Institute, EMMI, D-64291 Darmstadt (Germany); Aumann, T. [Institut fuer Kernphysik, Technische Universitaet, D-64289 Darmstadt (Germany); Boretzky, K. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, ExtreMe Matter Institute, EMMI, D-64291 Darmstadt (Germany); Borge, M.J.G. [Instituto Estructura de la Materia, CSIC, E-28006 Madrid (Spain); Caesar, C.; Chatillon, A. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, ExtreMe Matter Institute, EMMI, D-64291 Darmstadt (Germany); Chulkov, L.V. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, ExtreMe Matter Institute, EMMI, D-64291 Darmstadt (Germany); Kurchatov Institute, RU-123182 Moscow (Russian Federation); Cortina-Gil, D. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, ExtreMe Matter Institute, EMMI, D-64291 Darmstadt (Germany); University of Santiago de Compostela, 15706 Santiago de Compostela (Spain); Datta Pramanik, U. [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Emling, H. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, ExtreMe Matter Institute, EMMI, D-64291 Darmstadt (Germany); Fynbo, H.O.U. [Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark); Geissel, H.; Ickert, G. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, ExtreMe Matter Institute, EMMI, D-64291 Darmstadt (Germany); Johansson, H.T. [Fundamental Fysik, Chalmers Tekniska Hoegskola, S-412 96 Goeteborg (Sweden); and others

2013-01-29

One-neutron knockout reactions from Borromean nuclei are analyzed using a profile function analysis technique. The profile function, which is derived as the square root of the variance of the measured fragment + neutron momenta as a function of their relative energy, is shown to be very sensitive to the angular momentum of the knocked out neutron. Three cases are studied here: {sup 7}He, where the profile function analysis shows a presence of (s{sub 1/2}){sup 2} component in the {sup 8}He ground-state wave-function, {sup 10}Li, where the presence of a 11(2)% d-wave contribution to the relative energy spectrum above 1.5 MeV is found and, finally, the presence of a major s contribution around 0.5 MeV relative energy in the {sup 13}Be case and that the observed decay to the {sup 12}Be 2{sup +} state originates in a d state in {sup 13}Be.

Structure of neutron-rich nuclei

International Nuclear Information System (INIS)

Nazarewicz, W.; Oak Ridge National Lab., TN; Warsaw Univ.

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

Studies of exotic nuclei

International Nuclear Information System (INIS)

Angelique, J.C.; Orr, N.A.

1997-01-01

The study of the nuclei far off stability valley is of much interest for testing the nuclear models established for the stable nuclei but also for astrophysics to understand the nucleosynthesis. Experiments aim to measure the mass and lifetime, to build the decay schemes and also to study the structure and the properties of these nuclei. The radioactive beam group focused its research on light neutron-rich nuclei having a halo neutron structure. Mass measurements in N ∼ Z nuclei namely in A ∼ 60-80 proton-rich nuclei, important for understanding the rp process, are mentioned, as well as in nuclei in the 100 Sn region. In the newly obtained 26 O and 28 O nuclei the lifetimes, the probabilities of emission of one for more neutrons were determined. The data analysis has permitted to determine also for the first time the lifetimes of 27,29 F and 30 Ne. Studies of nuclei in the 100 Sn region, near the proton drip line in the ground and isomeric states are now under way. The spectroscopy (energy levels, gamma emissions, etc.) of the neutron-rich nuclei produced by the 36 S fragmentation has been carried out in 31 Ne, 17 B and 29 F. Studies by Coulomb excitation of the 2 + excited states and associated probability B (E2) in O, Ne, Ni and Zn are now analysed

Exclusive and restricted inclusive reactions involving the 11Be one-neutron halo

International Nuclear Information System (INIS)

Anne, R.; Emling, H.; Hansen, P.G.; Hornshoj, P.; Bimbot, R.; Dogny, S.

1993-01-01

Reactions of a 41 MeV/u beam of the radioactive halo nucleus 11 Be have been studied with a counter telescope coupled to an array of neutron detectors. The technique allows to determine single-neutron inclusive and exclusive angular distributions. The targets (Be, Ti and Au) were chosen to illustrate the relative roles played by nuclear and Coulomb mechanisms. It is shown that for the dissociation process it is possible to account almost quantitatively for the integral, single- and double-differential cross-sections from models without free parameters including the Coulomb, Serber and Glauber (diffraction dissociation) mechanisms. (K.A.). 56 refs., 11 figs., 1 tab

Lessons from two paradigmatic developments; Rutherford's nuclear atom and halo nuclei

International Nuclear Information System (INIS)

Vaagen, J S; Ershov, S N; Zhukov, M V

2012-01-01

In its initial 1911 version, underpinned by discoveries in alpha-scattering experiments, Rutherford's atom model made a gross separation of neutral matter; A veil of light negative matter surrounding a tiny impenetrable heavy positive core. The model had however little to say about the atomic (electronic) architecture and dynamics, hence did not make it straight to the catwalk of physics of those days. Three quarters of a century later, in 1985, new discoveries in collision experiments revealed existence of abnormally large light nuclei, but could say less about the nuclear architecture. History sometimes repeats itself: Like Bohr's ad hoc planetary model (1913) changed the fate of Rutherford's discovery, again Scandinavian inspired ideas on architecture, this time nuclear halos, changed our paradigm for the heart of matter. We comment on the need for a concerted Rutherfordian effort between theory and increasingly complete reaction experiments if further ground-breaking progress is going to be made in halo physics, and physics in vicinities of neutron and proton driplines, and generally in the more widely growing field of many-body open quantum systems, where structure and reactions come together.

Relativistic exotic nuclei as projectile beams. New perspectives of studies on the properties of nuclei

International Nuclear Information System (INIS)

Geissel, H.

1997-03-01

Examinations of the production cross-sections and the kinematics permitted refinement of model concepts of the peripheral reactions in exotic nuclei at energies from 100 to 1000 A MeV. Due to the strong selectivity and resolution achieved it was possible to discover a large number of novel isotopes at the fragment separator FRS, despite the relatively low projectile beam intensities of the SIS. The two twice magic nuclei found, Ni 78 and Sn 100, are particularly interesting, as they could not be measured so far with other experimental systems. Fission of relativistic uranium ions proved to be a particularly successful process yielding many medium-heavy, neutron-rich nuclei. Insight into the structure of light neutron halos could be improved. The superlarge spatial dimensions of the nuclear halos is discussed. (orig./CB) [de

Sub-Coulomb fusion with halo nuclei

International Nuclear Information System (INIS)

Fekou-Youmbi, V.; Sida, J.L.; Alamanos, N.; Auger, F.; Bazin, D.; Borcea, C.; Cabot, C.; Cunsolo, A.; Foti, A.; Gillibert, A.; Lepine, A.; Lewitowicz, M.; Liguori-Neto, R.; Mittig, W.; Pollacco, E.; Roussel-Chomaz, P.; Volant, C.; Yong Feng, Y.

1995-01-01

The nuclear structure of halo nuclei may have strong influence on the fusion cross section at sub-barrier energies. The actual theoretical debate is briefly reviewed and sub-barrier fusion calculations for the system 11 Be+ 238 U are presented. An experimental program on sub-barrier fusion for the systems 7,9,10,11 Be+ 238 U is underway at GANIL. First results with 9 Be and 11 Be beams were obtained using the F.U.S.ION detector. Relative fission cross sections are presented. ((orig.))

Exotic nuclei: Halos

Energy Technology Data Exchange (ETDEWEB)

Orr, Nigel [Lab. de Physique Corpusculaire, Caen Univ., 14 (France); Collaboration: La Direction des Sciences de la Matiere du CEA (FR); Le Fonds National de la Recherche Scientifique de Belgique (BE)

1998-12-31

A brief overview of the nuclear halo is presented. Following some historical remarks the general characteristics of the halo systems are discussed with reference to a simple model. The conditions governing the formation of halos are also explored, as are two subjects of current interest - low-lying resonances of halo nucleon correlations. (author) 54 refs., 16 figs., 1 tabs.

Investigation of halo structure of He by hyperspherical three-body ...

Indian Academy of Sciences (India)

Abstract. Hyperspherical harmonics expansion method is applied to a three-body model of two neutron halo nuclei. Convergence of the expansion has been ensured. A repulsive part is introduced in the interaction between the core and the extra-core neutron, to simulate Pauli principle. Two neutron separation energy ...

Fusion reaction around the Coulomb barrier with neutron-rich nuclei

Energy Technology Data Exchange (ETDEWEB)

Yoshida, Atsushi [Institute of Physical and Chemical Research, Wako, Saitama (Japan)

1997-07-01

Two fusion reactions with neutron-rich nuclei are reported in this work. On the first reaction: {sup 9,10,11}Be+{sup 209}Bi, the fusion cross sections around the coulomb barrier were measured by determing {alpha} disintegration from compound nucleus Fr. In the field of 10-100 mb, the same total fusion cross sections were obtained. The phenomenon {sup 11}Be(neutron halo nucleus) alone increased and decreased was not observed. The fusion cross sections of {sup 27,29,31}Al+{sup 197}Au system were determined by using 130 kcps and 30 kcps of beam strength of {sup 29,31}Al, respectively. The value of {sup 27}Al was reproduced by calculation, but that of {sup 29}Al increased around barrier which could not be explained by CCDEF calculation. (S.Y.)

Physics of the continuum of borromean nuclei

Energy Technology Data Exchange (ETDEWEB)

Vaagen, J S; Rogde, T [Dept. of Physics, Univ. of Bergen (Norway); Danilin, B V [RRC The Kurchatov Inst., Kurchatov, Moscow (Russian Federation); Ershov, S N [JINR, Dubna, Moscow (Russian Federation); Thompson, I J [Dept. of Physics, Univ. of Surrey, Guildford (United Kingdom); Zhukov, M V [Chalmers Univ. of Technology and Goeteborg Univ., Goeteborg (Sweden); RNBT Collaboration

1998-06-01

The continuum states of two-neutron halo nuclei are calculated in the method of hyperspherical harmonics. Using DWIA theory appropriate for dilute halo matter we have probed the structure of the low-lying {sup 6}He continuum via calculations of charge-exchange and inelastic scattering. (orig.)

Coulomb Excitation of Neutron-Rich $A\\approx$140 Nuclei

CERN Multimedia

Van duppen, P L E

2002-01-01

Investigating the isospin dependence of the product between the B( E2; 0$_{1}^{+} \\rightarrow 2_{1}^{+}$)-value and the 2$_{1}^{+}$-excitation energy E$_{2^{+}}$ in even-even nuclei around $A\\!\\approx$140 one observes a rather smooth trend close to the valley of stability but clear indication for a reduction from the extrapolated B(E2)-values by one order of magnitude for some very neutron-rich nuclei. While close to the valley of stability the strong neutron-proton interaction results in an equilibration of the neutron and proton deformations with a predominate isoscalar character of the collective 2$^{+}$ excitation, it is conceivable that more loosely bound neutrons cannot polarize a close-to-magic proton core that well any more. This might result in a decoupling of the shape of the outer neutrons from the core and in a strong isovector admixture to the lowest lying 2$^{+}$ level. In this way the 2$^{+}$ -energies could be further lowered in neutron-rich nuclei, while the quadrupole moments of the proton c...

Two-proton radioactivity with 2p halo in light mass nuclei A=18–34

Directory of Open Access Journals (Sweden)

G. Saxena

2017-12-01

Full Text Available Two-proton radioactivity with 2p halo is reported theoretically in light mass nuclei A=18–34. We predict 19Mg, 22Si, 26S, 30Ar and 34Ca as promising candidates of ground state 2p-radioactivity with S2p0. Observation of extended tail of spatial charge density distribution, larger charge radius and study of proton single particle states, Fermi energy and the wave functions indicate 2p halo like structure which supports direct 2p emission. The Coulomb and centrifugal barriers in experimentally identified 2p unbound 22Si show a quasi-bound state that ensures enough life time for such experimental probes. Our predictions are in good accord with experimental and other theoretical data available so far. Keywords: Relativistic mean-field theory, Nilson Strutinsky approach, Two-proton radioactivity, One- and two-proton separation energy, Halo nuclei, Proton drip-lines

Nuclear-physical investigations with oriented nuclei and polarized neutrons

International Nuclear Information System (INIS)

Alfimenkov, V.P.; Pikel'ner, L.B.; Sharapov, Eh.I.

1980-01-01

Several experiments with oriented nuclei and polarized neutrons are considered, as well as some methods of polarization of neutrons and nuclei. Experiments on the study of spin dependence of neutron cross sections for fissionable and nonfissionable nuclei interaction of polarized neutrons with polarized nuclei as well as measurement of magnetic momenta of compound-states of rare-earth nuclei. Described are some investigations with thermal neutrons: study on spin dependence of neutron scattering length with nuclei and gamma radiation of neutron radiation capture. Difficulties of production of high-intensive polarized neutron beams and construction of oriented targets are noted. Neutron polarization by transmission of them through a polarized proton target is the most universal method (out of existing methods) in the energy range under consideration [ru

Reaction cross section measurements of neutron-rich exotic nuclei in the vicinity of closed shells N=20 and N=28

International Nuclear Information System (INIS)

Khouaja, A.

2003-12-01

Using the direct method, the mean energy integrated reaction cross section was investigated for a wide range of neutron-rich nuclei (N → Ar) at GANIL. Using the parametrisation of S. Kox, 19 new radii measurements (reaction cross sections) were obtained. By the isotopic, isotonic and isospin dependence, the evolution of the strong reduced radius was studied according to the excess of neutrons. New halo effect is proposed to the nuclei of Mg 35 and S 44 . A quadratic parametrization is also proposed for the nuclear radius as a function of the isospin in the region of closed shells N=8 and N=28. In addition, we used a modified version of the Glauber model for studying the tail and matter distribution of nuclei. Indeed, using our new data the effects of the nuclear size (root mean square radii) and the matter distribution (diffusivity) were de-convoluted for each isotope. The root mean square radii of Na and Mg isotopes obtained so far were consistent with the ones from literature. (author)

Special role of neutron-halo nucleus on the momentum dissipation in heavy ion collisions

International Nuclear Information System (INIS)

Xing Yongzhong; Tianshui Normal Univ., Tianshui; Liu Jianye; Tianshui Normal Univ., Tianshui; Chinese Academy of Sciences, Lanzhou; Zuo Wei; Li Xiguo; Chinese Academy of Sciences, Lanzhou

2005-01-01

The special role of neutron-halo nucleus 19 B on the momentum dissipation was investigated by using isospin dependent quantum molecular dynamics. In order to compare and protrude the special role of neutron-halo-nucleus 19 B, the momentum dissipation induced by a same mass stable nucleus 19 F was investigated under the same incident channel condition. It is found that the weak bound neutron-halo structure of 19 B weakens the momentum dissipation process compared to those induced by stable nucleus 19 F in the lower energy region. However the nuclear stopping of colliding system with the neutron-halo nucleus 19 B decreases gradually with the increasing beam energy. For all of mass targets and impact parameters the neutron-halo nucleus 19 B weakens the momentum dissipation process. (authors)

Neutron-capture reactions by stable and unstable neutron-rich nuclei and their relevance for nucleosynthesis in hot and explosive astrophysical scenarios

International Nuclear Information System (INIS)

Hofinger, R.

1997-10-01

This thesis deals on the one hand with neutron-capture reactions by carbon-, nitrogen-, oxygen- and sulfur-isotopes, and on the other hand with the two-step processes 4 He(2n, γ) 6 He and 9 Li(2n, γ) 11 Li. Some of the involved carbon-, nitrogen- and oxygen-isotopes possess neutron-halos characterized by the unexpected large radial extension of the nuclear matter density distribution. Special attention is paid to the halo properties in the calculation of the direct neutron capture cross section. For the determination of the nuclear structure, models are used, when no experimental information is available. The results for the reaction rates are compared to previously used rates. The rates obtained in this work are partly orders of magnitude higher than the previously used reaction rates. The reaction rates for the two-step processes are on the one hand calculated assuming a two-step process, on the other hand from genuine three-body models for the process of photodisintegration of the nuclei 6 He and 11 Li. It turns out that the calculations assuming a trio-step process underestimate the reaction rates by orders of magnitude. The influence of the reaction rate for the reaction 4 He(2n, γ) 6 He and the formation of 12 C is examined in a nuclear reaction network under conditions which are typical for the α- process in supernovae of type II. It turns out that under these conditions the influence of the reaction 4 He(2n, γ) 6 He is negligible on the formation of 12 C. (author)

New excitation modes in halo nuclei

International Nuclear Information System (INIS)

Sagawa, H.

1992-01-01

Multipole resonances in exotic neutron-rich nuclei are addressed on the basis of microscopic calculations, i.e., in the framework of the self-consistent H-F + RPA theory. A bunch of resonances with multipoles J π = 0 + , 1 - and 2 + is found near the particle threshold E x ∼ 1 MeV in 10 He having significant portions of the sum rule values and narrow widths. The long tail of the loosely-bound neutrons is the cause of the threshold anomaly of these resonances

Neutron rich nuclei

International Nuclear Information System (INIS)

Foucher, R.

1979-01-01

If some β - emitters are particularly interesting to study in light, medium, and heavy nuclei, another (and also) difficult problem is to know systematically the properties of these neutron rich nuclei far from the stability line. A review of some of their characteristics is presented. How far is it possible to be objective in the interpretation of data is questioned and implications are discussed

Investigation of correlations in light neutron-rich nuclei

International Nuclear Information System (INIS)

Normand, G.

2004-10-01

Correlations play a crucial role in understanding the structure of light nuclei at and beyond the neutron drip-line. In this context, the two-neutron halo nucleus He 6 and the unbound systems H 5 , He 7,9 and Li 10 have been studied via measurements of the breakup of beams of He 6 and Be 11,12 . The CHARISSA and DEMON detector arrays were employed. The interpretation was facilitated by a simulation code (SILLAGE) which provided for the setup. In the case of He 7 , the existence of an excited state with E r ∼ 1 MeV and gamma ∼ 0.75 MeV was confirmed. The virtual character of the s-wave ground state of Li 10 was also confirmed and a scattering length of as ∼ -16 fm deduced. The results obtained for He 9 suggest that a virtual s-wave state may exist just above threshold. The study of the three-body breakup of He 6 found that the decay of the first 2+ state is essentially direct, while the decay of the remaining continuum strength is sequential - passage via He 5 . Using the technique of intensity interferometry an rms separation between the halo neutrons of 7.7 +- 0.8 fm was derived. This result was confirmed by a complementary method utilizing Dalitz plots. In the case of H 5 , the invariant mass spectrum was found to exhibit a broad (gamma ∼ 2 MeV) structure some 1.8 MeV above threshold. Comparison with recent three-body model calculations suggest that this corresponds to the predicted 1/2+ ground state. An rms valence neutron separation of some 5.5 fm was estimated. A search was also carried out for the 4n system using the Be 12* (2 alpha + Xn decay channel). No signal was observed beyond that expected on the basis of the known background processes. (author)

Neutron rich nuclei around 132Sn

International Nuclear Information System (INIS)

Bhattacharya, Sarmishtha

2016-01-01

The neutron rich nuclei with few particles or holes in 132 Sn have various experimental and theoretical interest to understand the evolution of nuclear structure around the doubly magic shell closure Z=50 and N=82. Some of the exotic neutron rich nuclei in this mass region are situated near waiting points in the r-process path and are of special astrophysical interest. Neutron rich nuclei near 132 Sn have been studied using fission fragment spectroscopy. The lifetime of low lying isomeric states have been precisely measured and the beta decay from the ground and isomeric states have been characterized using gamma-ray spectroscopy

A realistic solvable model for the Coulomb dissociation of neutron halo nuclei

International Nuclear Information System (INIS)

Baur, G.; Hencken, K.; Trautmann, D.

2003-01-01

As a model of a neutron halo nucleus we consider a neutron bound to an inert core by a zero range force. We study the breakup of this simple nucleus in the Coulomb field of a target nucleus. In the post-form DWBA (or, in our simple model CWBA (''Coulomb wave born approximation'')) an analytic solution for the T-matrix is known. We study limiting cases of this T-matrix. As it should be, we recover the Born approximation for weak Coulomb fields (i.e., for the relevant Coulomb parameters much smaller than 1). For strong Coulomb fields, high beam energies, and scattering to the forward region we find a result which is very similar to the Born result. It is only modified by a relative phase (close to 0) between the two terms and a prefactor (close to 1). A similar situation exists for bremsstrahlung emission. This formula can be related to the first order semiclassical treatment of the electromagnetic dissociation. Since our CWBA model contains the electromagnetic interaction between the core and the target nucleus to all orders, this means that higher order effects (including postacceleration effects) are small in the case of high beam energies and forward scattering. Our model also predicts a scaling behavior of the differential cross section, that is, different systems (with different binding energies, beam energies and scattering angles) show the same dependence on two variables x and y. (orig.)

Comparison of halo of 11Be, 15C, and 19C

Science.gov (United States)

Kharab, R.; Kumar, R.; Singh, P.; Sharma, H. C.

2007-12-01

We have compared the halo of 11Be, 15C, and 19C nuclei by analyzing the one-neutron stripping reaction data on the Be target at 60-, 54-, and 57-MeV/ A beam energies, respectively, within the framework of the eikonal approximation approach. The determination of effective range through the comparison of the total cross section data and prediction has revealed that the halo of 19C is the well developed, while that of 15C is the least and that of 11Be lies in between these two. The longitudinal momentum distribution data also strengthen these observations.

Elastic scattering, fusion, and breakup of light exotic nuclei

Energy Technology Data Exchange (ETDEWEB)

Kolata, J.J. [University of Notre Dame, Physics Department, Notre Dame, IN (United States); Guimaraes, V. [Universidade de Sao Paulo, Instituto de Fisica, Sao Paulo, SP (Brazil); Aguilera, E.F. [Instituto Nacional de Investigaciones Nucleares, Departamento de Aceleradores, Mexico, Distrito Federal (Mexico)

2016-05-15

The present status of fusion reactions involving light (A< 20) radioactive projectiles at energies around the Coulomb barrier (E<10 MeV per nucleon) is reviewed, emphasizing measurements made within the last decade. Data on elastic scattering (providing total reaction cross section information) and breakup channels for the involved systems, demonstrating the relationship between these and the fusion channel, are also reviewed. Similarities and differences in the behavior of fusion and total reaction cross section data concerning halo nuclei, weakly-bound but less exotic projectiles, and strongly-bound systems are discussed. One difference in the behavior of fusion excitation functions near the Coulomb barrier seems to emerge between neutron-halo and proton-halo systems. The role of charge has been investigated by comparing the fusion excitation functions, properly scaled, for different neutron- and proton-rich systems. Possible physical explanations for the observed differences are also reviewed. (orig.)

Role of neutrons in the fusion of nuclei

International Nuclear Information System (INIS)

Zagrebaev, V. I.; Samarin, V. V.

2007-01-01

The problem of a quantum-mechanical description of a near-barrier fusion of heavy nuclei under conditions of a strong coupling of their relative motion to neutron degrees of freedom is studied. New mutually complementing efficient models employing the multidimensional time-dependent Schroedinger equation and methods for numerically solving the problems in question within these models are proposed. This makes it possible to study the evolution of wave functions for outer neutrons and to calculate nucleon transfer probabilities and occupation numbers for quasimolecular states over the entire energy range, including that of deep-subbarrier energies. It is shown that the valence-neutron wave functions extend over the volumes of both colliding nuclei before their surfaces come into contact and even before these nuclei overcome the Coulomb barrier (collectivization of outer nucleons). This gives rise to a substantial neutron-transfer effect on the fusion of nuclei and, in particular, to a sizable increase in the probability of subbarrier fusion for specific combinations of nuclei

Study of Beta-Delayed Neutron Emission by Neutron-Rich Nuclei and Analysis of the Nuclear Reaction Mechanism responsible for the Yields of these Nuclei

International Nuclear Information System (INIS)

Bazin, D.

1987-07-01

Among the nuclear mechanisms used for the production of nuclei far from stability, the projectile fragmentation process has recently proved its efficiency. However, at Fermi energies, one has to take into account some collective and relaxation effects which drastically modify the production cross-sections. The spectroscopic study of very neutron-rich nuclei is very dependent of these production rates. A study of beta-delayed neutron emission which leads to new measurements of half-lives and neutron delayed emission probabilities is achieved with a liquid scintillator detector. The results which are then compared to different theories are of interest for the understanding of natural production of heavy elements (r processus) [fr

Relativistic mean field calculations in neutron-rich nuclei

Energy Technology Data Exchange (ETDEWEB)

Gangopadhyay, G.; Bhattacharya, Madhubrata [Department of Physics, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Roy, Subinit [Saha Institute of Nuclear Physics, Block AF, Sector 1, Kolkata- 700 064 (India)

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.

Nuclei in a neutron star

International Nuclear Information System (INIS)

Oyamatsu, K.; Yamada, M.

1994-01-01

We report on the recent progress in understanding the matter in the crust of a neutron star. For nuclides in the outer crust, recently measured masses of neutron-rich nuclei enable us to determine more accurately the stable nuclide as a function of the matter density. In the inner crust, the compressible liquid-drop model predicts successive change of the nuclear shape, from sphere to cylinder, slab, cylindrical hole and spherical hole at densities just before the transition to uniform matter. In order to go beyond the liquiddrop model, we performed the Thomas-Fermi calculation paying special attention to the surface diffuseness, and have recently calculated the shell energies of the non-spherical nuclei. We have found from these studies that all these non-spherical nuclei exist stably in the above order even if we include the surface diffuseness and shell energies. (author)

Charge Radius Measurement of the Halo Nucleus $^{11}$Li

CERN Multimedia

Kluge, H-J; Kuehl, T; Simon, H; Wang, Haiming; Zimmermann, C; Onishi, T; Tanihata, I; Wakasugi, M

2002-01-01

%IS385 %title\\\\ \\\\The root-mean-square charge radius of $^{11}$Li will be determined by measuring the isotope shift of a suitable atomic transition in a laser spectroscopic experiment. Comparing the charge radii of the lithium isotopes obtained by this nuclear-model-independent method with the relevant mass radii obtained before will help to answer the question whether the proton distribution in halo nuclei at the neutron drip-line is decoupled to the first order from their neutron distribution. The necessary experimental sensitivity requires the maximum possible rate of $^{11}$Li nuclei in a beam of low emittance which can only be provided by ISOLDE.

Beta decay rates of neutron-rich nuclei

International Nuclear Information System (INIS)

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

2015-01-01

Heavy element nucleosynthesis models involve various properties of thousands of nuclei in order to simulate the intricate details of the process. By necessity, as most of these nuclei cannot be studied in a controlled environment, these models must rely on the nuclear structure models for input. Of all the properties, the beta-decay half-lives are one of the most important ones due to their direct impact on the resulting abundance distributions. 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

Beta decay rates of neutron-rich nuclei

Energy Technology Data Exchange (ETDEWEB)

Marketin, Tomislav, E-mail: marketin@phy.hr [Department of Physics, Faculty of Science, University of Zagreb, 10000 Zagreb (Croatia); Huther, Lutz [Institut für Kernphysik (Theoriezentrum), Technische Universität Darmstadt, 64289 Darmstadt (Germany); Martínez-Pinedo, Gabriel [Institut für Kernphysik (Theoriezentrum), Technische Universität Darmstadt, 64289 Darmstadt (Germany); GSI Helmholtzzentrum für Schwerioneneforschung, Planckstraße 1, 64291 Darmstadt (Germany)

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.

Studies with radioactive beams - properties of neutron halo

International Nuclear Information System (INIS)

Tanihata, I.

1992-01-01

Interaction cross sections σ I and 9 Li transverse momentum distributions of 11 Li reactions were measured using p, d, Be and C targets at 800 A and 400 A MeV. The density distribution of 11 Li nucleus has been determined, for the first time, combining the interaction cross sections with various targets and energies. It was confirmed that only the distribution with long tail describe the observed data. The momentum correlation of two neutrons in the neutron halo is extracted from the P T distribution of 9 Li and that of neutron. It is found that the two neutrons are moving in the same direction in average and thus strongly suggests a formation of di-neutron in 11 Li

Puzzle of the folding potential on the nuclear halo reactions

International Nuclear Information System (INIS)

Ismail, Atef; Lee, Yen Cheong; Mahmoud, Z.M.M.

2015-01-01

Folding potentials of the elastic scattering drip-line nuclei at various incident energies is one method to study nuclear matter density distributions and nuclear radii. The nuclei with density distributions consisting of a bulk (core) and an outer layer (halo), dilute and spatially extended are called the halo nuclei caused for the weak particle binding. Several halo nuclei are studied and many potential candidates are identified. All the cross-sections of the elastic scattering for the drip-line nuclei 11 Be and 6 He, are calculated to understand the exotic properties of these nuclei starting from its structure, extended radius, nuclear size till the large total reaction cross-sections for these nuclei when it interacts with a stable target 12 C. (author)

Two-proton knockout on neutron-rich nuclei

International Nuclear Information System (INIS)

Bazin, D.; Brown, B.A.; Campbell, C.M.; Church, J.A.; Dinca, D.C.; Enders, J.; Gade, A.; Glasmacher, T.; Hansen, P.G.; Mueller, W.F.; Olliver, H.; Perry, B.C.; Sherrill, B.M.; Terry, J.R.; Tostevin, J.A.

2004-01-01

Two-proton knockout reactions on neutron-rich nuclei [Phys. Rev. Lett. 91 (2003) 012501] have been studied in inverse kinematics at intermediate energy. Strong evidence that the two-proton removal from a neutron-rich system proceeds as a direct reaction is presented, together with a preliminary theoretical discussion of the partial cross sections based on eikonal reaction theory and the many-body shell model. They show that this reaction can be used to characterize the wave functions of the projectiles and holds great promise for the study of neutron-rich nuclei

Symmetry energy and surface properties of neutron-rich exotic nuclei

Energy Technology Data Exchange (ETDEWEB)

Gaidarov, M. K.; Antonov, A. N. [Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Sofia 1784 (Bulgaria); Sarriguren, P. [Instituto de Estructura de la Materia, IEM-CSIC, Serrano 123, E-28006 Madrid (Spain); Moya de Guerra, E. [Departamento de Fisica Atomica, Molecular y Nuclear, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain)

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.

Beta decay rates of neutron-rich nuclei

Science.gov (United States)

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

2016-06-01

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

Beta decay rates of neutron-rich nuclei

International Nuclear Information System (INIS)

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

2016-01-01

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

Beta decay rates of neutron-rich nuclei

Energy Technology Data Exchange (ETDEWEB)

Marketin, Tomislav, E-mail: marketin@phy.hr; Petković, Jelena; Paar, Nils [Department of Physics, Faculty of Science, University of Zagreb, 10000 Zagreb (Croatia); Huther, Lutz [Institut für Kernphysik (Theoriezentrum), Technische Universität Darmstadt, 64289 Darmstadt (Germany); Martínez-Pinedo, Gabriel [Institut für Kernphysik (Theoriezentrum), Technische Universität Darmstadt, 64289 Darmstadt (Germany); GSI Helmholtzzentrum für Schwerioneneforschung, Planckstraße 1, 64291 Darmstadt (Germany)

2016-06-21

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

Two-neutron “halo” from the low-energy limit of neutron–neutron interaction: Applications to drip-line nuclei 22C and 24O

Directory of Open Access Journals (Sweden)

Toshio Suzuki

2016-02-01

Full Text Available The formation of two-neutron “halo”, a low-density far-extended surface of weakly-bound two neutrons, is described using the neutron–neutron (nn interaction fixed at the low-energy nn scattering limit. This method is tested for loosely-bound two neutrons in 24O, where a good agreement with experimental data is found. It is applied to halo neutrons in 22C in two ways: with the 20C core being closed or correlated (due to excitations from the closed core. This nn interaction is shown to be strong enough to produce a two-neutron halo in both cases, locating 22C on the drip line, while 21C remains unbound. A unique relation between the two neutron separation energy, S2n, and the radius of neutron halo is presented. New predictions for S2n and the radius of neutron halo are given for 22C. The appearance of Efimov states is also discussed.

Properties of Lithium-11 and Carbon-22 at leading order in halo effective field theory

Directory of Open Access Journals (Sweden)

Acharya Bijaya

2016-01-01

Full Text Available We study the 11Li and 22C nuclei at leading order (LO in halo effective field theory (Halo EFT. Using the value of the 22C rms matter radius deduced in Ref. [1] as an input in a LO calculation, we simultaneously constrain the values of the two-neutron (2n separation energy of 22C and the virtual-state energy of the 20C−neutron system (hereafter denoted 21C. The 1−σ uncertainty of the input rms matter radius datum, along with the theory error estimated from the anticipated size of the higher-order terms in the Halo EFT expansion, gives an upper bound of about 100 keV for the 2n separation energy. We also study the electric dipole excitation of 2n halo nuclei to a continuum state of two neutrons and the core at LO in Halo EFT. We first compare our results with the 11Li data from a Coulomb dissociation experiment and obtain good agreement within the theoretical uncertainty of a LO calculation. We then obtain the low-energy spectrum of B(E1 of this transition at several different values of the 2n separation energy of 22C and the virtual-state energy of 21C. Our predictions can be compared to the outcome of an ongoing experiment on the Coulomb dissociation of 22C to obtain tighter constraints on the two- and three-body energies in the 22C system.

Nuclear halo and its related reactions

International Nuclear Information System (INIS)

Zhang Huanqiao

2005-01-01

In order to search proton halo, the reaction cross sections of 27,28 P, 29 S and the corresponding isotones on Si target were measured at intermediate energies. The measured reaction cross sections of the N=12 and 13 isotones show an abrupt increase at Z=15. The experimental results for the isotones with Z=14 as well as 28 P can be well described by the modified Glauber theory of the optical limit approach. The enhancement of the reaction cross sections for 28 P could be explained in the modified Glauber theory with an enlarged core. Theoretical analysis with the modified Glauber theory of the optical limit and few-body approaches underpredicted the experimental data of 27 P. Our theoretical analysis shows that an enlarged core together with proton halo is probably the mechanism responsible for the enhancement of the cross sections for the reaction of 27 P+ 28 Si. In addition, we find from the experimental results that 29 S may have a moderate proton halo structure. Except the nuclei near or at drop-lines, halo may appear in the excited states of stable nuclei. By means of the asymptotic normalization coefficients (ANC's) extracted from transfer reactions of 11 B(d, p) 12 B, 12 C(d, p) 13 C, and H( 6 He, n) 6 Li, we have verified that the second ( Jπ = 2 - ) and third (Jπ = 1 - ) excited states in 12 B and the first (Jπ =1/2 + ) excited state in 13 C are the neutron halo states, while the second excited state (3.56 MeV, Jπ = 0 + ) in 6 Li is a proton-neutron halo state. We have proposed a procedure to extract the probability for valence particle being out of the binding potential from the measured nuclear asymptotic normalization coefficients. With this procedure, available data regarding the nuclear halo candidates are systematically analyzed and a number of halo nuclei are confirmed. Based on these results we have got a much relaxed condition for nuclear halo occurrence. Furthermore, we have presented the scaling laws for the dimensionless quantity 2 >/R 2 of

Concluding remarks of the International symposium on structure and reactions of unstable nuclei

International Nuclear Information System (INIS)

Mueller, A.C.

1991-01-01

A brief history of unstable beams is given, followed by a short description of the experimental facilities. The structure and reaction of unstable nuclei is discussed, and the neutron-halo nuclei are studied. Some considerations are given related to exotic-beam facilities. (K.A.) 14 refs., 2 figs

Properties of neutron-rich nuclei studied by fission product nuclear chemistry

International Nuclear Information System (INIS)

Meyer, R.A.; Henry, E.A.; Griffin, H.C.; Lien, O.G. III; Lane, S.M.; Stevenson, P.C.; Yaffe, R.P.; Skarnemark, G.

1979-09-01

A review is given of the properties of neutron-rich nuclei studied by fission product nuclear chemistry and includes the techniques used in elemental isolation and current research on the structure of nuclei near 132 Sn, particle emission, and coexisting structure in both neutron-poor and neutron-rich nuclei. 35 references

Symmetry energy, unstable nuclei and neutron star crusts

Energy Technology Data Exchange (ETDEWEB)

Iida, Kei [Kochi University, Department of Natural Science, Kochi (Japan); RIKEN Nishina Center, Saitama (Japan); Oyamatsu, Kazuhiro [RIKEN Nishina Center, Saitama (Japan); Aichi Shukutoku University, Department of Human Informatics, Aichi (Japan)

2014-02-15

The phenomenological approach to inhomogeneous nuclear matter is useful to describe fundamental properties of atomic nuclei and neutron star crusts in terms of the equation of state of uniform nuclear matter. We review a series of researches that we have developed by following this approach. We start with more than 200 equations of state that are consistent with empirical masses and charge radii of stable nuclei and then apply them to describe matter radii and masses of unstable nuclei, proton elastic scattering and total reaction cross sections off unstable nuclei, and nuclei in neutron star crusts including nuclear pasta. We finally discuss the possibility of constraining the density dependence of the symmetry energy from experiments on unstable nuclei and even observations of quasi-periodic oscillations in giant flares of soft gamma-ray repeaters. (orig.)

Interaction cross section study of the two-neutron halo nucleus 22C

Directory of Open Access Journals (Sweden)

Y. Togano

2016-10-01

Full Text Available The interaction cross sections (σI of the very neutron-rich carbon isotopes 19C, 20C and 22C have been measured on a carbon target at 307, 280, and 235 MeV/nucleon, respectively. A σI of 1.280±0.023 b was obtained for 22C, significantly larger than for 19,20C, supporting the halo character of 22C. A 22C root-mean-squared matter radius of 3.44±0.08 fm was deduced using a four-body Glauber reaction model. This value is smaller than an earlier estimate (of 5.4±0.9 fm derived from a σI measurement on a hydrogen target at 40 MeV/nucleon. These new, higher-precision σI data provide stronger constraints for assessing the consistency of theories describing weakly bound nuclei.

Neutron halo in 14B studied via reaction cross sections

International Nuclear Information System (INIS)

Fukuda, M.; Tanaka, M.; Iwamoto, K.; Wakabayashi, S.; Yaguchi, M.; Ohno, J.; Morita, Y.; Kamisho, Y.; Mihara, M.; Matsuta, K.; Nishimura, D.; Suzuki, S.; Nagashima, M.; Ohtsubo, T.; Ogura, T.; Abe, K.; Kikukawa, N.; Sakai, T.; Sera, D.; Takechi, M.; Izumikawa, T.; Suzuki, T.; Yamaguchi, T.; Sato, K.; Furuki, H.; Miyazawa, S.; Ichihashi, N.; Kohno, J.; Yamaki, S.; Kitagawa, A.; Sato, S.; Fukuda, S.

2014-01-01

Reaction cross sections (σ R ) for the neutron-rich nucleus 14 B on Be, C, and Al targets have been measured at several energies in the intermediate energy range of 45-120 MeV/nucleon. The present experimental σ R show a significant enhancement relative to the systematics of stable nuclei. The nucleon density distribution was deduced through the fitting procedure with the modified Glauber calculation. The necessity of a long tail in the density distribution was found, which is consistent with the valence neutron in 2s 1/2 orbital with the small empirical one-neutron separation energy in 14 B. (authors)

Pair correlations in nuclei

International Nuclear Information System (INIS)

Shimizu, Yoshifumi

2009-01-01

Except for the closed shell nuclei, almost all nuclei are in the superconducting state at their ground states. This well-known pair correlation in nuclei causes various interesting phenomena. It is especially to be noted that the pair correlation becomes weak in the excited states of nuclei with high angular momentum, which leads to the pair phase transition to the normal state in the high spin limit. On the other hand, the pair correlation becomes stronger in the nuclei with lower nucleon density than in those with normal density. In the region of neutron halo or skin state of unstable nuclei, this phenomenon is expected to be further enhanced to be observed compared to the ground state of stable nuclei. An overview of those interesting aspects caused via the pair correlation is presented here in the sections titled 'pair correlations in ground states', pair correlations in high spin states' and 'pair correlations in unstable nuclei' focusing on the high spin state. (S. Funahashi)

Reactions and single-particle structure of nuclei near the drip lines

International Nuclear Information System (INIS)

Hansen, P.G.; Sherrill, B.M.

2001-01-01

The techniques that have allowed the study of reactions of nuclei situated at or near the neutron or proton drip line are described. Nuclei situated just inside the drip line have low nucleon separation energies and, at most, a few bound states. If the angular momentum in addition is small, large halo states are formed where the wave function of the valency nucleon extends far beyond the nuclear radius. We begin with examples of the properties of nuclear halos and of their study in radioactive-beam experiments. We then turn to the continuum states existing above the particle threshold and also discuss the possibility of exciting them from the halo states in processes that may be thought of as 'collateral damage'. Finally, we show that the experience from studies of halo states has pointed to knockout reactions as a new way to perform spectroscopic studies of more deeply bound non-halo states. Examples are given of measurements of l values and spectroscopic factors

Shell gap reduction in neutron-rich N=17 nuclei

International Nuclear Information System (INIS)

Obertelli, A.; Gillibert, A.; Alamanos, N.; Alvarez, M.; Auger, F.; Dayras, R.; Drouart, A.; France, G. de; Jurado, B.; Keeley, N.; Lapoux, V.; Mittig, W.; Mougeot, X.; Nalpas, L.; Pakou, A.; Patronis, N.; Pollacco, E.C.; Rejmund, F.; Rejmund, M.; Roussel-Chomaz, P.; Savajols, H.; Skaza, F.; Theisen, Ch.

2006-01-01

The spectroscopy of 27 Ne has been investigated through the one-neutron transfer reaction 26 Ne(d,p) 27 Ne in inverse kinematics at 9.7 MeV/nucleon. The results strongly support the existence of a low-lying negative parity state in 27 Ne, which is a signature of a reduced sd-fp shell gap in the N=16 neutron-rich region, at variance with stable nuclei

Model calculations for the airborne Fast Ice Nuclei CHamber FINCH-HALO

Science.gov (United States)

Nillius, B.; Bingemer, H.; Bundke, U.; Jaenicke, R.; Reimann, B.; Wetter, T.

2009-04-01

Ice nuclei (IN) initiate the formation of primary ice in tropospheric clouds. In mixed phase clouds the primary ice crystals can grow very fast by the Bergeron-Findeisen process (Findeisen, 1938) at the expense of evaporating water droplets, and form precipitation. Thus, IN are essential for the development of precipitation in mixed phase clouds in the middle latitude. However, the role of IN in the development of clouds is still poorly understood and needs to be studied (Levin and Cotton, 2007). A Fast Ice Nuclei CHamber (FINCH-HALO) for airborne operation on the High And LOng Range research aircraft (HALO) is under development at the Institute for Atmosphere and Environment University Frankfurt. IN particles are activated within the chamber at certain ice super-saturation and temperature by mixing three gas flows, a warm moist, a cold dry, and an aerosol flow. After activation the particles will grow within a processing chamber. In an optical depolarisation detector droplets and ice crystals are detected separately. The setup of the new FINCH-HALO instrument is based on the ground based IN counter FINCH (Bundke, 2008). In FINCH-HALO a new cooling unit is used. Thus, measurements down to -40°C are possible. Furthermore minor changes of the inlet section where the mixing occurs were done. The contribution will present 3D model calculations with FLUENT of the flow conditions in the new inlet section for different pressure levels during a flight typical for HALO. Growth rates of ice crystals in the chamber at different temperature and super-saturation will be shown. References: Bundke U., B. Nillius, R. Jaenicke, T. Wetter, H. Klein, H. Bingemer, (2008). The Fast Ice Nucleus Chamber FINCH, Atmospheric Research, doi:10.1016/j.atmosres.2008.02.008 Findeisen, R., (1938). Meteorologisch-physikalische Begebenheiten der Vereisung in der Atmosphäre. Hauptversammlung 1938 der Lilienthal-Gesellschaft. Levin, Z., W. Cotton, (2007). Aerosol pollution impact on precipitation

Reaction cross section measurements of neutron-rich exotic nuclei in the vicinity of closed shells N=20 and N=28; Mesures de section efficace de reaction de noyaux exotiques riches en neutrons dans la zone de fermeture des couches N=20 et N=28

Energy Technology Data Exchange (ETDEWEB)

Khouaja, A

2003-12-01

Using the direct method, the mean energy integrated reaction cross section was investigated for a wide range of neutron-rich nuclei (N {yields} Ar) at GANIL. Using the parametrisation of S. Kox, 19 new radii measurements (reaction cross sections) were obtained. By the isotopic, isotonic and isospin dependence, the evolution of the strong reduced radius was studied according to the excess of neutrons. New halo effect is proposed to the nuclei of Mg{sup 35} and S{sup 44}. A quadratic parametrization is also proposed for the nuclear radius as a function of the isospin in the region of closed shells N=8 and N=28. In addition, we used a modified version of the Glauber model for studying the tail and matter distribution of nuclei. Indeed, using our new data the effects of the nuclear size (root mean square radii) and the matter distribution (diffusivity) were de-convoluted for each isotope. The root mean square radii of Na and Mg isotopes obtained so far were consistent with the ones from literature. (author)

Maris polarization in neutron-rich nuclei

Directory of Open Access Journals (Sweden)

Shubhchintak

2018-03-01

Full Text Available We present a theoretical study of the Maris polarization effect and its application in quasi-free reactions to assess information on the structure of exotic nuclei. In particular, we explore the dependence of the polarization effect on neutron excess and neutron-skin thickness. We discuss the uncertainties in the calculations of triple differential cross sections and of analyzing powers due the choices of various nucleon–nucleon interactions and optical potentials and the limitations of the method. Our study implies that polarization variables in (p, 2p reactions in inverse kinematics can be an effective probe of single-particle structure of nuclei in radioactive-beam facilities.

Maris polarization in neutron-rich nuclei

Science.gov (United States)

Shubhchintak; Bertulani, C. A.; Aumann, T.

2018-03-01

We present a theoretical study of the Maris polarization effect and its application in quasi-free reactions to assess information on the structure of exotic nuclei. In particular, we explore the dependence of the polarization effect on neutron excess and neutron-skin thickness. We discuss the uncertainties in the calculations of triple differential cross sections and of analyzing powers due the choices of various nucleon-nucleon interactions and optical potentials and the limitations of the method. Our study implies that polarization variables in (p, 2p) reactions in inverse kinematics can be an effective probe of single-particle structure of nuclei in radioactive-beam facilities.

Exotic nuclei: another aspect of nuclear structure

International Nuclear Information System (INIS)

Dobaczewski, J.; Blumenfeld, Y.; Flocard, H.; Garcia Borge, M.J.; Nowacki, F.; Rombouts, S.; Theisen, Ch.; Marques, F.M.; Lacroix, D.; Dessagne, P.; Gaeggeler, H.

2002-01-01

This document gathers the lectures made at the Joliot Curie international summer school in 2002 whose theme that year was exotic nuclei. There were 11 contributions whose titles are: 1) interactions, symmetry breaking and effective fields from quarks to nuclei; 2) status and perspectives for the study of exotic nuclei: experimental aspects; 3) the pairing interaction and the N = Z nuclei; 4) borders of stability region and exotic decays; 5) shell structure of nuclei: from stability to decay; 6) variational approach of system with a few nucleons; 7) from heavy to super-heavy nuclei; 8) halos, molecules and multi-neutrons; 9) macroscopic approaches for fusion reactions; 10) beta decay: a tool for spectroscopy; 11) the gas phase chemistry of super-heavy elements

Modeling a neutron rich nuclei source

Energy Technology Data Exchange (ETDEWEB)

Mirea, M.; Bajeat, O.; Clapier, F.; Ibrahim, F.; Mueller, A.C.; Pauwels, N.; Proust, J. [Institut de Physique Nucleaire, IN2P3/CNRS, 91 - Orsay (France); Mirea, M. [Institute of Physics and Nuclear Engineering, Tandem Lab., Bucharest (Romania)

2000-07-01

The deuteron break-up process in a suitable converter gives rise to intense neutron beams. A source of neutron rich nuclei based on the neutron induced fission can be realised using these beams. A theoretical optimization of such a facility as a function of the incident deuteron energy is reported. The model used to determine the fission products takes into account the excitation energy of the target nucleus and the evaporation of prompt neutrons. Results are presented in connection with a converter-target specific geometry. (author000.

Modeling a neutron rich nuclei source

International Nuclear Information System (INIS)

Mirea, M.; Bajeat, O.; Clapier, F.; Ibrahim, F.; Mueller, A.C.; Pauwels, N.; Proust, J.; Mirea, M.

2000-01-01

The deuteron break-up process in a suitable converter gives rise to intense neutron beams. A source of neutron rich nuclei based on the neutron induced fission can be realised using these beams. A theoretical optimization of such a facility as a function of the incident deuteron energy is reported. The model used to determine the fission products takes into account the excitation energy of the target nucleus and the evaporation of prompt neutrons. Results are presented in connection with a converter-target specific geometry. (authors)

Possibility of a crossed-beam experiment involving slow-neutron capture by unstable nuclei - ``rapid-process tron''

Science.gov (United States)

Yamazaki, T.; Katayama, I.; Uwamino, Y.

1993-02-01

The possibility of a crossed beam facility of slow neutrons capturing unstable nuclei is examined in connection with the Japanese Hadron Project. With a pulsed proton beam of 50 Hz repetition and with a 100 μA average beam current, one obtains a spallation neutron source of 2.4 × 10 8 thermal neutrons/cm 3/spill over a 60 cm length with a 3 ms average duration time by using a D 2O moderator. By confining radioactive nuclei of 10 9 ions in a beam circulation ring of 0.3 MHz revolution frequency, so that nuclei pass through the neutron source, one obtains a collision luminosity of 3.9 × 10 24/cm 2/s. A new research domain aimed at studying rapid processes in nuclear genetics in a laboratory will be created.

Investigation of correlations in light neutron-rich nuclei; Etude des correlations dans les noyaux legers riches en neutrons

Energy Technology Data Exchange (ETDEWEB)

Normand, G

2004-10-01

Correlations play a crucial role in understanding the structure of light nuclei at and beyond the neutron drip-line. In this context, the two-neutron halo nucleus He{sup 6} and the unbound systems H{sup 5}, He{sup 7,9} and Li{sup 10} have been studied via measurements of the breakup of beams of He{sup 6} and Be{sup 11,12}. The CHARISSA and DEMON detector arrays were employed. The interpretation was facilitated by a simulation code (SILLAGE) which provided for the setup. In the case of He{sup 7}, the existence of an excited state with E{sub r} {approx} 1 MeV and gamma {approx} 0.75 MeV was confirmed. The virtual character of the s-wave ground state of Li{sup 10} was also confirmed and a scattering length of as {approx} -16 fm deduced. The results obtained for He{sup 9} suggest that a virtual s-wave state may exist just above threshold. The study of the three-body breakup of He{sup 6} found that the decay of the first 2+ state is essentially direct, while the decay of the remaining continuum strength is sequential - passage via He{sup 5}. Using the technique of intensity interferometry an rms separation between the halo neutrons of 7.7 +- 0.8 fm was derived. This result was confirmed by a complementary method utilizing Dalitz plots. In the case of H{sup 5}, the invariant mass spectrum was found to exhibit a broad (gamma {approx} 2 MeV) structure some 1.8 MeV above threshold. Comparison with recent three-body model calculations suggest that this corresponds to the predicted 1/2+ ground state. An rms valence neutron separation of some 5.5 fm was estimated. A search was also carried out for the 4n system using the Be{sup 12*} (2 alpha + Xn decay channel). No signal was observed beyond that expected on the basis of the known background processes. (author)

Studies of the neutron single-particle structure of exotic nuclei at the HRIBF

International Nuclear Information System (INIS)

Thomas, J.S.; Bardayan, D.W.; Blackmon, J.C.; Cizewski, J.A.; 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.

2004-01-01

The study of neutron single-particle strengths in neutron-rich nuclei is of interest for nuclear structure and nuclear astrophysics. The distribution of single-particle strengths constrains the effective Hamiltonian and pairing interactions and determines neutron interaction rates that are crucial for understanding the synthesis of heavy nuclei in supernovae via the rapid neutron capture process. Particularly important are the neutron single-particle levels in nuclei near closed neutron shells. Radioactive ion beams from the Holifield Radioactive Ion Beam Facility have been used to study (d,p) reactions in inverse kinematics in order to probe neutron single-particle states in exotic nuclei. The results of a measurement with a 82 Ge beam will be presented

Shape evolution in neutron-rich A ~ 140 nuclei beyond the doubly-magic nucleus 132Sn

Science.gov (United States)

Odahara, Atsuko; Eurica Collaboration

2014-09-01

Study for the shape evolution enables us to disentangle competition between spherical (single-particle like) shape and deformed (collective-like) shape as a function of neutron number. Neutron-rich nuclei in the northeast region of the doubly-magic 132Sn locates in one of the best mass region where a variety of collective modes, not only prolate deformation but also octupole collectivity, are expected to appear. These neutron-rich A ~140 nuclei were produced by using in-flight fission reaction of the 345 MeV/u 238U86+ beam at RIKEN RI Beam Factory. This experiment was performed in the framework of the EURICA (EUroball RIken Cluster Array) project based on the highly-efficient β- and isomer-decay spectroscopy methods. Around 20 extremely neutron-rich nuclei with Z=51--55 have been studied in this work. New isomers with half lives of longer than hundreds ns were found in some nuclei, such as the neutron-rich Cs isotopes. Also, preliminary results for the β decay of neutron-rich I and Xe isotopes have been obtained. Systematic change of the shape evolution for these neutron-rich isotopes will be discussed.

Fusion reaction using low energy neutron-excess nucleus beam

International Nuclear Information System (INIS)

Fukuda, Tomokazu

1994-01-01

The present state and the plan of the experiment of measuring the fusion reaction near barriers by using neutron-excess nucleus beam, which has been advanced at RIKEN are reported. One of the purposes of this experiment is the feasibility investigation of the fusion reaction by using neutron-excess nuclei, which is indispensable for synthesizing superheavy elements. It is intended to systematically explore some enhancing mechanism in the neutron-excess nuclei which are unfavorable in beam intensity. This research can become the good means to prove the dynamic behavior of the neutrons on the surfaces of nuclei in reaction. The fusion reaction of 27 Al + Au was measured by using the stable nucleus beam of 27 Al, and the results are shown. In order to know the low energy fusion reaction of 11 Li and 11 Be which are typical halo nuclei, the identification by characteristic α ray of composite nuclei is carried out in 7,9,11 Li + 209 Bi and 9,10,11 Be + 208 Pb. A new detector having high performance, New MUSIC, is being developed. As the experiment by using this detector, the efficient measurement of the fusion reaction by using heavy neutron-excess nuclei up to Ni is considered. An example of 8 Li + α → 11 B + n reaction for celestial body physics is mentioned. (K.I.)

Symmetry structure in neutron deficient xenon nuclei

International Nuclear Information System (INIS)

Govil, I. M.

1998-01-01

The paper describes the measurements of the lifetimes of the excited states in the ground state band of the Neutron deficient Xe nuclei ( 122,124 Xe) by recoil Distance Method (RDM). The lifetimes of the 2 + state in 122 Xe agrees with the RDM measurements but for 124 Xe it does not agree the RDM measurements but agrees with the earlier Coulomb-excitation experiment. The experimental results are compared with the existing theories to understand the changes in the symmetry structure of the Xe-nuclei as the Neutron number decreases from N=76( 130 Xe) to N=64( 118 Xe)

Symmetry structure in neutron deficient xenon nuclei

Science.gov (United States)

Govil, I. M.

1998-12-01

The paper describes the measurements of the lifetimes of the excited states in the ground state band of the Neutron deficient Xe nuclei (122,124Xe) by recoil Distance Method (RDM). The lifetimes of the 2+ state in 122Xe agrees with the RDM measurements but for 124Xe it does not agree the RDM measurements but agrees with the earlier Coulomb-excitation experiment. The experimental results are compared with the existing theories to understand the changes in the symmetry structure of the Xe-nuclei as the Neutron number decreases from N=76(130Xe) to N=64(118Xe).

Isospin Conservation in Neutron Rich Systems of Heavy Nuclei

Science.gov (United States)

Jain, Ashok Kumar; Garg, Swati

2018-05-01

It is generally believed that isospin would diminish in its importance as we go towards heavy mass region due to isospin mixing caused by the growing Coulomb forces. However, it was realized quite early that isospin could become an important and useful quantum number for all nuclei including heavy nuclei due to neutron richness of the systems [1]. Lane and Soper [2] also showed in a theoretical calculation that isospin indeed remains quite good in heavy mass neutron rich systems. In this paper, we present isospin based calculations [3, 4] for the fission fragment distributions obtained from heavy-ion fusion fission reactions. We discuss in detail the procedure adopted to assign the isospin values and the role of neutron multiplicity data in obtaining the total fission fragment distributions. We show that the observed fragment distributions can be reproduced rather reasonably well by the calculations based on the idea of conservation of isospin. This is a direct experimental evidence of the validity of isospin in heavy nuclei, which arises largely due to the neutron-rich nature of heavy nuclei and their fragments. This result may eventually become useful for the theories of nuclear fission and also in other practical applications.

ISINN-5. 5. International seminar on interaction of neutrons with nuclei. Neutron spectroscopy, nuclear structure, related topics

International Nuclear Information System (INIS)

1997-01-01

The materials submitted at the fifth in a series of annual international seminar on interaction of neutrons with nuclei Neutron Spectroscopy, Nuclear Structure, Related Topics (ISINN-5) are given. The Seminar is organized by the Frank Laboratory of Neutron Physics of the Joint Institute for Nuclear Research and took place in Dubna on May 14-17, 1997. About 130 specialists from Belgium, China, Germany, France, Japan, Korea, Latvia, Netherlands, Ukraine, 7 Russian research institutes and a number of JINR laboratories took part in the Seminar. The scope of the problems discussed is traditionally wide. It includes the problems of violation of fundamental symmetries in the interaction of neutrons with nuclei, the properties of the neutron as the fundamental particle, nonstatistical aspects of the radiation capture of neutrons by nuclei, topical problems of the theory of nucleus, and the fission mechanism of heavy nuclei. The latest results obtained with ultracold neutrons (UCN), in particular, different approaches to understanding of the cause of UCN anomalous leakage through the walls of the trap are considered as well. The wide spectrum of methodological aspects of neutron-aided experiments is also discussed in details

Bookshelf (''Neutrons, Nuclei and Matter'', by J. Byrne)

Energy Technology Data Exchange (ETDEWEB)

Hansen, P. G.

1994-09-15

Time was when a neophyte wanting to do experiments with neutrons would be told first to read D.J. Hughes' classic ''Pile Neutron Research'' (1952). The book by J. Byrne is in many respects a modern equivalent, although if you were to send your student away with it, you will risk not seeing him or her again for a considerable time. What is immediately striking is that the book, rich in information and quite long, is cross-disciplinary and touches essentially all the main areas of modern physics. It covers parts of particle physics, such as the internal structure of the neutron, time-reversal violation as revealed by the (still hypothetical) electric dipole moment of the neutron, and the coupling constants for the weak interaction. From the field of basic quantum physics there are chapters on neutron optics, wave phenomena with neutrons and on the applications of these in solid-state physics. Other chapters again delve deeply into nuclear structure, nuclear reaction theory, as well as their applications: nuclear reactors and nuclear energy. At a time with specialization rampant and many physicists tending to believe that venturing outside their own cloisters is uninteresting and even dangerous, it is a pleasure to come across a book that is basically just about physics. J. Byrne of Sussex has for long been active in neutron research at the British-French-German Institut Laue-Langevin (ILL) research reactor in Grenoble, where he has worked on subjects such as weak interactions and fundamental symmetries. He has clearly intended ''Neutrons, Nuclei and Matter'' as a vade-mecum that will allow the practitioner to find the necessary information and formulas. But I believe that many others not directly engaged in neutron research will gain new insight from its many examples. To take just one case, I had not been aware of the simple physical principles that permit cold neutrons to be stored in a bottle. (The main point is that a medium containing nuclei with positive

The resonance neutron fission on heavy nuclei

International Nuclear Information System (INIS)

Kopach, Yu.N.; Popov, A.B.; Furman, V.I.; Alfimenkov, V.P.; Lason', L.; Pikel'ner, L.B.; ); Gonin, N.N.; Kozlovskij, L.K.; Tambovtsev, D.I.; Gagarskij, A.M.; Petrov, G.A.; Sokolov, V.E.

2001-01-01

A new approach to the description of the fission, similar to the well-known reaction theory and based on the helicity representation for the exit fission channels, is briefly summarized. This approach allows one to connect the multimodal fission representation with A. Bohr's concept of the fission transition states and to obtain formulae for the partial and differential fission cross sections. The formulae are used for analysis of the angular anisotropy of fragments in the neutron resonance induced fission of aligned 235 U nuclei and of the P-even angular forward-backward and right-left correlations of fragments oe the P-odd correlations caused by the interference of s- and p-wave neutron resonances [ru

Structure of halo nuclei - overview of theoretical status

International Nuclear Information System (INIS)

Al-Khalili, J.S.

2003-01-01

The past decade has seen an explosion of theoretical interest in the structure and dynamics of halo nuclei. Their basic defining features of weak binding and large radial extent due to the extended tail in their densities is now well-described within few-body models. This has led to impressive advances in few-body reaction theories which crucially take into account this few-body nature. This paper will review some of the recent advances in both structure and reaction studies, and will focus on the issues currently of interest along with possible directions for future advances. On the structure side, improvements to few-body models are being explored to take into account the role of antisymmetrization more accurately and the importance of core polarization and excitation. The successes of fully microscopic approaches will also be reviewed. (orig.)

Enrichment of r-Process Elements by Neutron Star Mergers through the Sub-Halo Clustering

Science.gov (United States)

Ishimaru, Yuhri; Ojima, Takuya; Wanajo, Shinya; Prantzos, Nikos

Neutron star mergers (NSMs) are suggested to be the most plausible site of r-process by nucleosynthesis studies, while previous chemical evolution models pointed out that the long lifetimes of NS binaries are in conflict with the observed [r/Fe] of the Galactic halo stars. We attempt to solve this problem, assuming the Galactic halo was formed from merging sub-halos. We find that [r/Fe] start increasing at [Fe/H] < -3, if the star formation efficiencies are smaller for less massive sub-halos. We also show that small numbers of NSMs for least massive sub-halos could cause the large enhancement of [r/Fe]. Our results support NSMs as the major site of r-process.

New aspects of the neutron capture in light nuclei

Energy Technology Data Exchange (ETDEWEB)

Mengoni, A. [Institute of Physical and Chemical Research, Wako, Saitama (Japan)

1997-03-01

Several neutron capture cross sections of light nuclei (A {<=} 40) for neutron energies up to the MeV region have been recently calculated. Examples are (target nuclei): {sup 12}C, {sup 13}C, {sup 16}O and {sup 10}Be. The results of these calculations will be shown together with a comparison with the most recent experimental data. In the case of n + {sup 10}Be case, the cross section of the inverse process (Coulomb dissociation of {sup 11}Be) is considered and compared with the measurement. A discussion on the relevant nuclear structure information required for the evaluation of nuclear data of light nuclei is given. (author)

Orientation of nuclei excited by polarized neutrons

International Nuclear Information System (INIS)

Lifshits, E.P.

1986-01-01

Polarization and radiation angular distribution of oriented nuclei in inelastic scattering of polarized neutrons were investigated. Nucleus orientation in the final state was described by polarization density matrix (PDM). If PDM is known, angular distributions, linear and circular polarization of γ-quanta emitted by a nucleus can be determined. Analytical expression for PDM, conditions of its diagonalization in the case of direct nucleus excitation and excitation by the stage of compound nucleus were obtained. Orientation of 12 C nuclei in the excited state 4.439 MeV, 2 + at energy of incident neutrons in the laboratory system from 4.8 MeV (excitation threshold) upt to 9 MeV was calculated as an example. Neutrons in initial state are completely polarized along Z axis. Calculations showed that excitation proceeds mainly by the stage of compound nucleus formation and 12 C nucleus is highly polarized in excited state

Nucleon-nucleon momentum correlation function for light nuclei

International Nuclear Information System (INIS)

Ma, Y.G.; Cai, X.Z.; Chen, J.G.; Fang, D.Q.; Guo, W.; Liu, G.H.; Ma, C.W.; Ma, E.J.; Shen, W.Q.; Shi, Y.; Su, Q.M.; Tian, W.D.; Wang, H.W.; Wang, K.; Wei, Y.B.; Yan, T.Z.

2007-01-01

Nucleon-nucleon momentum correlation function have been presented for nuclear reactions with neutron-rich or proton-rich projectiles using a nuclear transport theory, namely Isospin-Dependent Quantum Molecular Dynamics model. The relationship between the binding energy of projectiles and the strength of proton-neutron correlation function at small relative momentum has been explored, while proton-proton correlation function shows its sensitivity to the proton density distribution. Those results show that nucleon-nucleon correlation function is useful to reflect some features of the neutron- or proton-halo nuclei and therefore provide a potential tool for the studies of radioactive beam physics

Spectroscopic information on light halo - nuclei within the framework of multiparticle shell model

International Nuclear Information System (INIS)

Khaydarov, R.R.

2004-09-01

Aim of the inquiry: to develop the potential approach within the framework of multiparticle shell model; to obtain analytical expressions for a wave function and equations for widths off sub-barrier resonance states; to apply the theoretical approach for obtaining properties of 5 He, 5 Li, 8 B and 11 N nuclei; to estimate values of root-mean-square radiuses, radial density of nucleons, magnetic dipole and electrical quadrupole moments and spectroscopic information for 8 B and 8 Li with use of a method of expansion on functions of Storm - Liouville; to estimate the contribution of 2p - shell of 13 C and process of exchange replacement to the astrophysical S-factor of 13 C (α, n) 16 O reaction. Method of the research: theoretical approaches within the framework of multiparticle shell model. Achieved results and their novelty: new theoretical approach allowing to describe correctly the experimental static characteristics of sub-barrier one-particle resonance states in of 5 He, 5 Li, 8 B and 11 N light nuclei has been developed. Structure of 8 B and 8 Li light mirror nuclei with use of the approach for the description of one-particle resonance states based on the method of expansion on functions of Storm - Liouville has been investigated; The spectroscopic information for proton halo in 8 B and values of the magnetic dipole and electric quadrupole moments of 8 B and 8 Li with use of technique of genealogical coefficients have been obtained. The contribution of 2p - shell of 13 C (α, n) 16 O reaction has been estimated. (author)

Study of 19C by One-Neutron Knockout

Directory of Open Access Journals (Sweden)

Hwang Jongwon

2016-01-01

Full Text Available The spectroscopic structure of 19C, a prominent one-neutron halo nucleus, has been studied with a 20C secondary beam at 290 MeV/nucleon and a carbon target. Neutron-unbound states populated by the one-neutron knockout reaction were investigated by means of the invariant mass method. The preliminary relative energy spectrum and parallel momentum distribution of the knockout residue, 19C*, were reconstructed from the measured four momenta of the 18C fragment, neutron, and beam. Three resonances were observed in the spectrum, which correspond to the states at Ex = 0.62(9, 1.42(10, and 2.89(10 MeV. The parallel momentum distributions for the 0.62-MeV and 2.89-MeV states suggest spin-parity assignments of 5/2+ and 1/2−, respectively. The 1.42-MeV state is in line with the reported 5/22+ state.

Statistical properties of warm nuclei: Investigating the low-energy enhancement in the $\\gamma$- strength function of neutron-rich nuclei

CERN Multimedia

We propose to start a program to study the $\\gamma$-ray strength function of neutron rich nuclei in inverse kinematics with radioactive beams at HIE-ISOLDE. An unexpected increase in the $\\gamma$-strength function at low energy has been observed in several stable nuclei using the Oslo method. This year these results were confirmed with a different experimental technique and model independent analysis developed by iThemba/Livermore. If this enhancement of the $\\gamma$-strength function is also present in neutron-rich nuclei, it will strongly affect the neutron capture cross sections, which are important input in stellar models of synthesis of heavier elements in stars. We propose to start with an experiment using a $^{66}$Ni beam of 5.5 MeV /u, where the data will be analyzed using both methods independently, and we are sure to get enough statistics, before moving to more neutron-rich nuclei. When/if neutron-rich Ti, Fe or Mo beams will be available at ISOLDE, we will submit additional proposals.

GALS – setup for production and study of heavy neutron rich nuclei

Directory of Open Access Journals (Sweden)

Zemlyanoy Sergey

2015-01-01

Full Text Available 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 below 208Pb 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.

GALS – setup for production and study of heavy neutron rich nuclei

CERN Document Server

Zemlyanoy, Sergey; Kozulin, Eduard; Kudryavtsev, Yury; Fedosseev, Valentin; Bark, Robert; Janas, Zenon; Othman, Hosam

2015-01-01

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 below ^208Pb 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.

Neutron scattering on deformed nuclei

International Nuclear Information System (INIS)

Hansen, L.F.; Haight, R.C.; Pohl, B.A.; Wong, C.; Lagrange, C.

1984-09-01

Measurements of neutron elastic and inelastic differential cross sections around 14 MeV for 9 Be, C, 181 Ta, 232 Th, 238 U and 239 Pu have been analyzed using a coupled channel (CC) formalism for deformed nuclei and phenomenological global optical model potentials (OMP). For the actinide targets these results are compared with the predictions of a semi-microscopic calculation using Jeukenne, Lejeune and Mahaux (JLM) microscopic OMP and a deformed ground state nuclear density. The overall agreement between calculations and the measurements is reasonable good even for the very light nuclei, where the quality of the fits is better than those obtained with spherical OMP

Neutron induced reaction of light nuclei and its role in nuclear astrophysics

International Nuclear Information System (INIS)

Nagai, Y.

2000-01-01

Recently, much interest has arisen in the abundance of the s-process isotopes in stars of various metallicity to construct models of the chemical evolution of the Galaxy. Efforts involving both observations and yield estimations of these isotopes are being made for a wide range of metallicities and stellar masses to compare the chemical evolution models with the observational data. So far, in the models of the chemical evolution of the s-isotopes the yields of the isotopes versus the abundance of either 56 Fe (seed) nuclei or 16 O (source) nuclei have been suggested to be linear. However, it has now been shown to be nonlinear for low-metallicity massive stars. The nonlinearity was due to neutron poison by abundant light nuclei. Namely, if the neutron capture cross sections of the light nuclei would be large, the yields of heavier s-isotopes would decrease; the relationship of the yields versus the abundance of either 56 Fe (seed) or 16 O (source) nuclei becomes nonlinear; furthermore, the yields of p-process nuclei would decrease, since the s-process nuclei are the immediate predecessors of the p-nuclei. Therefore, in order to construct models to predict the s- and p-isotope productions as functions of the metallicity and stellar mass, it is necessary to know the neutron capture cross sections of light nuclei at stellar neutron energy. In the lecture, I discuss detailed motive of the study, together with results recently obtained. (author)

Curves and tables of neutron cross sections of fission product nuclei in JENDL-3

Energy Technology Data Exchange (ETDEWEB)

Nakagawa, Tsuneo [ed.

1992-06-15

Neutron cross sections of 172 nuclei in the fission product region stored in JENDL-3 are shown in graphs and tables. The evaluation work of these nuclei was made by the Fission Product Nuclear Data Working Group of the Japanese Nuclear Data Committee, in the neutron energy region from 10{sup {minus}5} eV to 20 MeV. Almost of the cross section data reproduced in graphs in this report. The cross section averaged over 38 energy intervals are listed in a table. Shown in order tables are thermal cross sections, resonance integrals, Maxwellian neutron flux average cross sections, fission spectrum average cross sections, 14-MeV cross sections, one group average cross sections in neutron flux of typical types of fission reactors and average cross sections in the 30-keV Maxwellian spectrum.

Curves and tables of neutron cross sections of fission product nuclei in JENDL-3

International Nuclear Information System (INIS)

Nakagawa, Tsuneo

1992-06-01

Neutron cross sections of 172 nuclei in the fission product region stored in JENDL-3 are shown in graphs and tables. The evaluation work of these nuclei was made by the Fission Product Nuclear Data Working Group of the Japanese Nuclear Data Committee, in the neutron energy region from 10 -5 eV to 20 MeV. Almost all the cross section data are reproduced in graphs in this report. The cross section averaged over 38 energy intervals are listed in a table. Shown in other tables are thermal cross sections, resonance integrals, Maxwellian neutron flux average cross sections, fission spectrum average cross sections, 14-MeV cross sections, one group average cross sections in neutron flux of typical types of fission reactors and average cross sections in the 30-keV Maxwellian spectrum. (author)

Direct mass measurements of light neutron-rich nuclei using fast recoil spectrometers

International Nuclear Information System (INIS)

Vieira, D.J.; Wouters, J.M.

1987-01-01

Extensive new mass measurement capabilities have evolved with the development of recoil spectrometers. In the Z = 3 to 9 neutron-rich region alone, 12 neutron-rich nuclei have been determined for the first time by the fast-recoil direct mass measurement method. A recent experiment using the TOFI spectrometer illustrates this technique. A systematic investigation of nuclei that lie along or near the neutron-drip line has provided a valuable first glimpse into the nuclear structure of such nuclei. No evidence for a large single-particle energy gap at N = 14 is observed; however, a change in the two-neutron separation model calculations, and is interpreted in terms of the smaller 1s/sub 1/2/ - 1s/sub 1/2/ interaction compared to that of the 0d/sub 5/2/ - 0d/sub 5/2/ neutron-neutron interaction. 18 refs., 7 figs., 1 tab

Study of the Unbound Nuclei $^{10}$Li and $^{7}$He at REX ISOLDE

CERN Multimedia

2002-01-01

% IS367\\\\ \\\\ We propose to study the two unbound nuclei $^{10}$Li and $^{7}$He produced in simple one-neutron pick-up reactions induced by intense beams of $^{9}$Li and $^{6}$He from REX ISOLDE in $^{9}$Be and CD$_{2}$ targets.\\\\ \\\\The unbound nucleus $^{10}$Li is a binary subsystem of the two-neutron halo nucleus $^{11}$Li and its structure is of key importance for theoretical investigations of the halo structure. We propose two different reactions, which together would give an unambiguous determination of lowest $\\textit{s-}$ and $\\textit{p-}$wave resonances in the ($^{9}$Li+n) system.\\\\ \\\\Similarly $^{7}$He plays an important role in the dissociation of $^{8}$He, a drip-line nucleus with an $\\alpha$+4n five-body structure. The aim of our investigation is to search for an excited 1/2$^{-}$ state above the $^{7}$He 3/2$^{-}$ ground state in order to investigate its cluster structure. \\\\ \\\\

Measurement of total reaction cross sections of exotic neutron rich nuclei

International Nuclear Information System (INIS)

Mittig, W.; Chouvel, J.M.; Wen Long, Z.

1987-01-01

Total reaction cross-sections of neutron rich nuclei from C to Mg in a thick Si-target have been measured using the detection of the associated γ-rays in a 4Π-geometry. This cross-section strongly increases with neutron excess, indicating an increase of as much as 15% of the reduced strong absorption radius with respect to stable nuclei

Microscopic theories of effective interaction with an application to halo nuclei

International Nuclear Information System (INIS)

Kuo, T.T.S.

1997-01-01

The effective interaction used in shell model calculations plays a central role in nuclear structure calculations. We review here several microscopic methods for deriving such effective interactions, starting from the free NN potential. For a chosen model space, there are formal methods for obtaining a model-space effective hamiltonian H eff which can reproduce certain physical properties of the original hamiltonian. These methods are briefly discussed. Among them, the Q-box folded diagram method initially developed by Kuo-Lee-Ratcliff is relatively more convenient for numerical calculations. To apply this method to nuclear structure calculations, a first step is perform a partial summation of certain Q-box diagrams so as to express the Q-box in terms of G-matrix interactions. Accurate calculation of the G-matrix for finite nuclei is now feasible. For a given Q-box the folded-diagram series for the effective interaction can be summed up to all orders using iterative methods, such as the Lee-Suzuki method and the Krenciglowa-Kuo method. For the Q-box, however, it seems that one has to adopt some low-order, in the G-matrix, approximation. A highly desirable situation seems to be provided by halo nuclei where the valence nucleons are weakly attached to those of the inner core. In this case the effect of core-polarization is largely weakened, and the Q-box may be accurately calculated by including only few low-order G-matrix diagrams. (orig.)

Neutron resonance spins of 159Tb from experiments with polarized neutrons and polarized nuclei

International Nuclear Information System (INIS)

Alfimenkov, V.P.; Ivanenko, A.I.; Lason', L.; Mareev, Yu.D.; Ovchinnikov, O.N.; Pikel'ner, L.B.; Sharapov, Eh.I.

1976-01-01

Spins of 27 neutron resonances of 159 Tb with energies up to 114 eV have been measured using polarized neutrons and nuclei beams in the modernized time-of-flight spectrometer of the IBR-30 pulse reator. The direct measurements of the terbium resonances spins performed using polarized neutrons reaffirm the conclusion that there are no unstationary effects in the behaviour of 159 Tb neutron resonances in the energy range

The pygmy dipole resonance in neutron-rich nuclei

International Nuclear Information System (INIS)

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

2016-01-01

The pygmy dipole resonance (PDR), which has been observed via the enhancement of the electric dipole strength E 1 of atomic nuclei, is studied within a microscopic collective model. The latter employs the Hartree-Fock (HF) method with effective nucleon-nucleon interactions of the Skyrme types plus the random-phase approximation (RPA). The results of the calculations obtained for various even-even nuclei such as "1"6"-"2"8O, "4"0"-"5"8Ca, "1"0"0"-"1"2"0Sn, and "1"8"2"-"2"1"8Pb show that the PDR is significantly enhanced when the number of neutrons outside the stable core of the nucleus is increased, that is, in the neutron-rich nuclei. As the result, the relative ratio between the energy weighted sum of the strength of the PDR and that of the GDR (giant dipole resonance) does not exceed 4%. The collectivity of the PDR and GDR states will be also discussed. (paper)

Testing two-nucleon transfer reaction mechanism with elementary modes of excitation in exotic nuclei

CERN Document Server

Broglia, R A; Idini, A; Barranco, F; Vigezzi, E

2015-01-01

Nuclear Field Theory of structure and reactions is confronted with observations made on neutron halo dripline nuclei, resulting in the prediction of a novel (symbiotic) mode of nuclear excitation, and on the observation of the virtual effect of the halo phenomenon in the apparently non-halo nucleus $^7$Li. This effect is forced to become real by intervening the virtual process with an external (t,p) field which, combined with accurate predictive abilities concerning the absolute differential cross section, reveals an increase of a factor 2 in the cross section due to the presence of halo ground state correlations, and is essential to reproduce the value of the observed $d \\sigma(^7$Li(t,p)$^9$Li)/d$\\Omega$.

Quest of halo in 31Ne using Glauber model formalism with deformed relativistic mean field density

International Nuclear Information System (INIS)

Sharma, Mahesh K.; Patra, S.K.

2012-01-01

The advancement of radio active ion beam (RIB) explored the structure of exotic nuclei, which are away from the β stability line. Such nuclei with weak binding lie at the limit of stability and exhibit some fascinating phenomena. One of them is the formation of one or more nucleon halo structure. It is well established that the interaction cross section of halo nuclei like 11 Li, 11 Be and 19 C show anomalously large interaction cross sections and matter radius than that of their neighboring nuclei. Some recent investigations for 31 Ne predict that has a halo nature. The first experimental evidence also suggests 31 Ne as a halo candidate. The isotope 31 Ne having N=21, which breaks the shell closer structure as a consequence of deformation associated with the strong intruder configuration and having special interest, because it lie at island of inversion. Here we apply the well known Glauber approach with conjunction of deformed relativistic mean field densities of projectile and target nuclei. It is to be noted that Panda et al has done the similar calculation using a spherical density

Calculation of the radii of neutron rich light exotic nuclei

International Nuclear Information System (INIS)

Charagi, S.K.; Gupta, S.K.

1991-01-01

The interaction cross section of a few unstable neutron rich nuclei have been measured using exotic isotope beams produced through the projectile fragmentation process in high energy heavy-ion collisions. Interaction cross section of He, Li, Be and B isotope projectiles with Be, C and Al targets have thus been measured at 790 MeV/nucleon. We have made a comprehensive analysis of the data on the interaction cross section, to extract the radii of these neutron rich light nuclei. 7 refs., 1 fig., 3 tabs

SU(3) symmetries in exotic neutron-rich nuclei

International Nuclear Information System (INIS)

Hayes, A.C.

1991-01-01

We examine the structure of the exotic neutron-rich nucleus 11 Li with an emphasis on understanding the origin of the soft E1 resonance and the neuron halo. The similarities and differences between shell model and di-neutron cluster model descriptions of the system are displayed using the Hecht expansion techniques. We find that the ground state 11 Li as described in large shell model calculations is well approximated by the di-neutron cluster state. In contrast to the ground state, the soft E1 model of 11 Li appears to have a more complicated structure and the E1 strength of this resonance is very sensitive to cancellations between p→s and p→d contributions to the dipole matrix elements. 12 refs., 6 figs., 3 tabs

Fast neutron scattering on actinide nuclei

International Nuclear Information System (INIS)

1982-01-01

More and more sophisticated neutron experiments have been carried out with better samples in several laboratories and it was necessary to intercompare them. In this respect, let us quote for example (n,n'e) and (n,n'#betta#) measurements. Moreover, high precision (p,p), (p,p') and (p,n) measurements have been made, thus supplementing neutron experiments in the determination of the parameters of the optical model, still widely used to describe the neutron-nucleus interaction. The optical model plays a major role and it is therefore essential to know it well. The spherical optical model is still very useful, especially because of its simplicity and of the relatively short calculation times, but is obviously insufficient to treat deformed nuclei such as actinides. For accurate calculations about these nuclei, it is necessary to use a deformed potential well and solve a set of coupled equations, hence long computational times. The importance of compound nucleus formation at low energy requires also a good knowledge of the statistical model together with that of all the reaction mechanisms which are involved, including fission for which an accurate barrier is necessary and, of course, well-adjusted level densities. The considerations form the background of the Scientific Programme set up by a Programme Committee whose composition is given further on in this book

Neutron spin precession in samples of polarised nuclei and neutron spin phase imaging

Energy Technology Data Exchange (ETDEWEB)

Piegsa, Florian Michael

2009-07-09

The doublet neutron-deuteron (nd) scattering length b{sub 2,d}, which is at present only known with an accuracy of 5%, is particularly well suited to fix three-body forces in novel effective field theories at low energies. The understanding of such few-nucleon systems is essential, e.g. for predictions of element abundances in the big-bang and stellar fusion. b{sub 2,d} can be obtained via a linear combination of the spin-independent nd scattering length b{sub c,d} and the spin-dependent one, b{sub i,d}. The aim of this thesis was to perform a high-accuracy measurement of the latter to improve the relative accuracy of b{sub 2,d} below 1%. The experiment was performed at the fundamental neutron physics beam line FUNSPIN at the Paul Scherrer Institute in Switzerland. It utilises the effect that the spin of a neutron passing through a target with polarised nuclei performs a pseudomagnetic precession proportional to the spin-dependent scattering length of the nuclei. An ideal method to measure this precession angle very accurately is Ramsey's atomic beam technique, adapted to neutrons. The most crucial part of the experimental setup is the so-called frozen spin target, which consists of a specially designed dilution refrigerator and contains a sample with dynamically polarised nuclear spins. The polarisation of the sample is determined by nuclear magnetic resonance (NMR) techniques. It turned out that the relaxation of the nuclear spins during the necessary ''cross-calibration'' of the two employed NMR systems is ultimately limiting the achievable accuracy of b{sub i,d}. During the extensive use of the Ramsey resonance method in the neutron-deuteron experiment, an idea emerged that the applied technique could be exploited in a completely different context, namely polarised neutron radiography. Hence, the second part of the thesis covers the development of a novel neutron radiography technique, based on the spin-dependent interaction of the

Neutron spin precession in samples of polarised nuclei and neutron spin phase imaging

International Nuclear Information System (INIS)

Piegsa, Florian Michael

2009-01-01

The doublet neutron-deuteron (nd) scattering length b 2,d , which is at present only known with an accuracy of 5%, is particularly well suited to fix three-body forces in novel effective field theories at low energies. The understanding of such few-nucleon systems is essential, e.g. for predictions of element abundances in the big-bang and stellar fusion. b 2,d can be obtained via a linear combination of the spin-independent nd scattering length b c,d and the spin-dependent one, b i,d . The aim of this thesis was to perform a high-accuracy measurement of the latter to improve the relative accuracy of b 2,d below 1%. The experiment was performed at the fundamental neutron physics beam line FUNSPIN at the Paul Scherrer Institute in Switzerland. It utilises the effect that the spin of a neutron passing through a target with polarised nuclei performs a pseudomagnetic precession proportional to the spin-dependent scattering length of the nuclei. An ideal method to measure this precession angle very accurately is Ramsey's atomic beam technique, adapted to neutrons. The most crucial part of the experimental setup is the so-called frozen spin target, which consists of a specially designed dilution refrigerator and contains a sample with dynamically polarised nuclear spins. The polarisation of the sample is determined by nuclear magnetic resonance (NMR) techniques. It turned out that the relaxation of the nuclear spins during the necessary ''cross-calibration'' of the two employed NMR systems is ultimately limiting the achievable accuracy of b i,d . During the extensive use of the Ramsey resonance method in the neutron-deuteron experiment, an idea emerged that the applied technique could be exploited in a completely different context, namely polarised neutron radiography. Hence, the second part of the thesis covers the development of a novel neutron radiography technique, based on the spin-dependent interaction of the neutron with ferromagnetic samples and magnetic fields

Neutron emission study after muon capture by nuclei

International Nuclear Information System (INIS)

Bouyssy, Alain.

1974-01-01

Muon capture by nuclei, used in the beginning for checking the weak interaction, is now a method of investigation of nuclear structure. Study of spectrum, asymmetry and polarization of emitted neutrons after polarized muon capture has been done in three directions: weak coupling constants, final state interaction, nuclear wave functions. The neutron intensity and helicity are very dependent of the neutron - residual nucleus interaction, while the asymmetry is sensitive to the wave functions used for the proton. Moreover if the induced tensor coupling constant is different from zero the asymmetry is increased. Longitudinal polarization experiments, with those for neutron intensity, would be of great interest to give informations on neutron asymmetry [fr

Studies of isovector excitations in nuclei by neutron-induced reactions

International Nuclear Information System (INIS)

Nilsson, L.

1987-01-01

In this paper isovector excitations in nuclei, in particular the giant isovector quadrupole resonance in spherical nuclei, will be discussed. Several methods to investigate this excitation have been used, e.g. inelastic electron scattering and charge-exchange reactions. An alternative method to study isovector E2 resonances in nuclei, based on the radiative capture of fast neutrons, will be presented. Results from such experiments performed at the tandem accelerator laboratories in Los Alamos and Uppsala will be presented and discussed in terms of the direct-semidirect capture model. As a separate issue, the preparations being undertaken at Uppsala for studies of isovector excitations in nuclei by means of the (n,p) reaction will be described. A schematic lay-out of the experiment will be presented together with some relevant neutron beam parameters. Among isovector excitations to be studied by this method are the isovector monopole resonance and the Gamow-Teller resonance. 54 references, 6 figures, 1 table

Total reaction cross sections and neutron-removal cross sections of neutron-rich light nuclei measured by the COMBAS fragment-separator

Science.gov (United States)

Hue, B. M.; Isataev, T.; Erdemchimeg, B.; Artukh, A. G.; Aznabaev, D.; Davaa, S.; Klygin, S. A.; Kononenko, G. A.; Khuukhenkhuu, G.; Kuterbekov, K.; Lukyanov, S. M.; Mikhailova, T. I.; Maslov, V. A.; Mendibaev, K.; Sereda, Yu M.; Penionzhkevich, Yu E.; Vorontsov, A. N.

2017-12-01

Preliminary results of measurements of the total reaction cross sections σR and neutron removal cross section σ-xn for weakly bound 6He, 8Li, 9Be and 10Be nuclei at energy range (20-35) A MeV with 28Si target is presented. The secondary beams of light nuclei were produced by bombardment of the 22Ne (35 A MeV) primary beam on Be target and separated by COMBAS fragment-separator. In dispersive focal plane a horizontal slit defined the momentum acceptance as 1% and a wedge degrader of 200 μm Al was installed. The Bρ of the second section of the fragment-separator was adjusted for measurements in energy range (20-35) A MeV. Two-neutron removal cross sections for 6He and 10Be and one -neutron removal cross sections 8Li and 9Be were measured.

A large-area, position-sensitive neutron detector with neutron/γ-ray discrimination capabilities

International Nuclear Information System (INIS)

Zecher, P.D.; Galonsky, A.; Kruse, J.J.; Gaff, S.J.; Ottarson, J.; Wang, J.; Seres, Z.; Ieki, K.; Iwata, Y.; Schelin, H.

1997-01-01

To further study neutron-rich halo nuclei, we have constructed a neutron detector array. The array consists of two separate banks of detectors, each of area 2 x 2 m 2 and containing 250 l of liquid scintillator. Each bank is position-sensitive to better than 10 cm. For neutron time-of-flight measurements, the time resolution of the detector has been demonstrated to be about 1 ns. By using the scintillator NE-213, we are able to distinguish between neutron and γ-ray signals above 1 MeV electron equivalent energy. Although the detector array was constructed for a particular experiment it has also been used in a number of other experiments. (orig.)

Nuclear transition moment measurements of neutron rich nuclei

Science.gov (United States)

Starosta, Krzysztof

2009-10-01

The Recoil Distance Method (RDM) and related Doppler Shift Attenuation Method (DSAM) are well-established tools for lifetime measurements following nuclear reactions near the Coulomb barrier. Recently, the RDM was implemented at National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University using NSCL/K"oln plunger device and a unique combination of the state-of-the-art instruments available there. Doppler-shift lifetime measurements following Coulomb excitation, knock-out, and fragmentation at intermediate energies of ˜100 MeV/u hold the promise of providing lifetime information for excited states in a wide range of unstable nuclei. So far, the method was used to investigate the collectivity of the neutron-rich ^16,18,20C, ^62,64,66Fe, ^70,72Ni, ^110,114Pd isotopes and also of the neutron-deficient N=Z ^64Ge. A significant fraction of these experiments was performed using NSCL's Segmented Germanium Array instrumented with the Digital Data Acquisition System which enables gamma-ray tracking. The impact of GRETINA and gamma-ray tracking on RDM and DSAM studies of neutron-rich nuclei will be discussed.

Nuclear symmetry energy and the neutron skin in neutron-rich nuclei

NARCIS (Netherlands)

Dieperink, AEL; Dewulf, Y; Van Neck, D; Waroquier, M; Rodin, [No Value

2003-01-01

The symmetry energy for nuclear matter and its relation to the neutron. skin in finite nuclei is discussed. The symmetry energy as a function of density obtained in a self-consistent Green function approach is presented and compared to the results of other recent theoretical approaches. A partial

Spectroscopy of 9Be and observation of neutron halo structure in the states of positive parity rotational band

Directory of Open Access Journals (Sweden)

Demyanova A.S.

2014-03-01

Full Text Available The differential cross sections of the 9Be + α inelastic scattering at 30 MeV were measured at the tandem of Tsukuba University. All the known states of 9Be up to energies ~ 12 MeV were observed and decomposed into three rotational bands, each of them having a cluster structure consisting of a 8Be core plus a valence neutron in one of the sub-shells: p3/2−, s1/2+ and p1/2−. Existence of a neutron halo in the positive parity states was confirmed.

Pseudomagic nuclei

International Nuclear Information System (INIS)

Scharff-Goldhaber, G.

1979-01-01

It was shown previously that, below a critical angular momentum, yrast bands of nonmagic nuclei are well described by the two-parameter variable moment of inertia model. Some striking exceptions to this rule are found in nuclei which have the same mass number as doubly magic nuclei but possess either one (or two) proton pairs beyond a magic number and one (or two) neutron hole pairs, or vice versa. Yrast bands in these pseudomagic nuclei resemble those in magic nuclei. 17 references

Shell and isotopic effects in neutron interaction with nuclei. [Optical model and nucleus asymmetry correlations

Energy Technology Data Exchange (ETDEWEB)

Pasechnik, M V

1978-01-01

Major results of investigations into the shell structure of deformed nuclei with the number of neutrons of approximately 100, as well as new isotopic effects in the inelastic scattering of fast neutrons with nuclei are reported. The experiments conducted at the WWR-M research reactor have shown a substantial dependence of the nuclear excited energy-level density on the mass number and the number of neutrons. The fact resulted in a conclusion that the deformed nuclei possess filled shells, that was an incentive to revise the whole nuclear shell concept. In particular it was established that the property of magicity rests not only on the sphericity of nuclei but it may be also observed in strongly deformed nuclei. The isotope-spin dependence of the nuclear potential was studied at the AG-5 pulse electrostatic generator. The parameters of the potential were determined by comparing the experimental data on inelastic scattering and polarization of fast neutrons by nuclei from /sup 48/Ti to /sup 209/Bi with the calculations in terms of the optical model. Simple correlations were established between the optical potential and the nucleus asymmetry parameter ..cap alpha..=N-Z/A in wide ranges of mass numbers and neutron energy.

Nuclear structure for the crust of neutron stars and exotic nuclei

International Nuclear Information System (INIS)

Goegelein, Peter

2007-01-01

In this work the Skyrme Hartree-Fock and Relativistic Hartree--Fock approaches have been considered to describe the structure of nuclear systems ranging from finite nuclei, structures in the crust of neutron stars to homogeneous matter. Effects of pairing correlations and finite temperature are also taken into account. The numerical procedure in the cubic box is described for the Skyrme Hartree-Fock as well as the relativistic Hartree-Fock approach. And finally, results for the crust of neutron stars and exotic nuclei are presented and discussed. (orig.)

Nuclear structure for the crust of neutron stars and exotic nuclei

Energy Technology Data Exchange (ETDEWEB)

Goegelein, Peter

2007-07-01

In this work the Skyrme Hartree-Fock and Relativistic Hartree--Fock approaches have been considered to describe the structure of nuclear systems ranging from finite nuclei, structures in the crust of neutron stars to homogeneous matter. Effects of pairing correlations and finite temperature are also taken into account. The numerical procedure in the cubic box is described for the Skyrme Hartree-Fock as well as the relativistic Hartree-Fock approach. And finally, results for the crust of neutron stars and exotic nuclei are presented and discussed. (orig.)

Ground-state properties of neutron magic nuclei

Energy Technology Data Exchange (ETDEWEB)

Saxena, G., E-mail: gauravphy@gmail.com [Govt. Women Engineering College, Department of Physics (India); Kaushik, M. [Shankara Institute of Technology, Department of Physics (India)

2017-03-15

A systematic study of the ground-state properties of the entire chains of even–even neutron magic nuclei represented by isotones of traditional neutron magic numbers N = 8, 20, 40, 50, 82, and 126 has been carried out using relativistic mean-field plus Bardeen–Cooper–Schrieffer approach. Our present investigation includes deformation, binding energy, two-proton separation energy, single-particle energy, rms radii along with proton and neutron density profiles, etc. Several of these results are compared with the results calculated using nonrelativistic approach (Skyrme–Hartree–Fock method) along with available experimental data and indeed they are found with excellent agreement. In addition, the possible locations of the proton and neutron drip-lines, the (Z, N) values for the new shell closures, disappearance of traditional shell closures as suggested by the detailed analyzes of results are also discussed in detail.

Examining the possibility to observe neutron dark decay in nuclei

Science.gov (United States)

Pfützner, M.; Riisager, K.

2018-04-01

As proposed recently by Fornal and Grinstein, neutrons can undergo a dark matter decay mode which has not yet been observed. Such a decay could explain the existing discrepancy between two different methods of neutron lifetime measurements. If such neutron decay is possible, then it should occur also in nuclei with sufficiently low neutron binding energy. We examine a few nuclear candidates for the dark neutron decay and we consider the possibilities of their experimental identification. In more detail we discuss the case of 11Be which appears as the most promising nucleus for the observation of neutron dark decay.

Examining the possibility to observe neutron dark decay in nuclei

DEFF Research Database (Denmark)

Pfutzner, M.; Riisager, K.

2018-01-01

also in nuclei with sufficiently low neutron binding energy. We examine a few nuclear candidates for the dark neutron decay and we consider the possibilities of their experimental identification. In more detail we discuss the case of Be-11 which appears as the most promising nucleus for the observation......As proposed recently by Fornal and Grinstein, neutrons can undergo a dark matter decay mode which has not yet been observed. Such a decay could explain the existing discrepancy between two different methods of neutron lifetime measurements. If such neutron decay is possible, then it should occur...... of neutron dark decay....

Neutron-proton mass difference in finite nuclei and the Nolen-Schiffer anomaly

International Nuclear Information System (INIS)

Meissner, U.G.; Rakhimov, A.M.; Wirzba, A.; Yakhshiev, U.T.

2008-01-01

The neutron-proton mass difference in finite nuclei is studied in the framework of a medium-modified Skyrme model. The possible interplay between the effective nucleon mass in finite nuclei and the Nolen-Schiffer anomaly is discussed. In particular, we find that a correct description of the properties of mirror nuclei leads to a stringent restriction of possible modifications of the nucleon's effective mass in nuclei. (orig.)

Halo structure of strange particles in nuclei

International Nuclear Information System (INIS)

Akaishi, Yoshinori; Yamazaki, Toshimitsu.

1997-01-01

Some characteristic behaviors of hyperons in nuclei which have recently been revealed experimentally and theoretically are discussed with the emphasis on the repulsive part of the hyperon-nucleus interaction. The observed Σ 4 He nucleus is a bound state with J π = 0 + and T ≅ 1/2. Its nucleus-Σ potential derived from a realistic ΣN interaction is characterized by inner repulsion and a strong Lane term, which play important roles in forming the Σ-hypernuclear bound state. In 208 Pb a typical Coulomb-assisted bound state is expected, where Σ is trapped in the surface region by the nucleus-Σ potential with the aid of Coulomb and centrifugal interactions. In the double-strangeness (S=-2) sector, there is a possibility that the lightest double-Λ hypernucleus ΛΛ 4 H is abundantly populated by stopping Ξ - on 4 He. Its formation branching amounts to about 15%. A stopped Ξ - on 9 Be will also produce efficiently a variety of double-Λ hyperfragments. Discrete spectra of weak-decay pions from the fragments will provide a means of mass spectroscopy of double-Λ hypernuclei. In the S=-2 five-body system an excited state Ξ 5 H is predicted to appear with 'strangeness halo' and the ground state ΛΛ 5 H with almost pure ΛΛ component. (author)

The NSCL neutron wall facility

International Nuclear Information System (INIS)

Zecher, P.; Galonsky, A.; Kruse, J.

1995-01-01

The authors have constructed and installed a large-area, high-efficiency neutron detector at the NSCL. The motivation behind the detector's design was provided by their desire to improve a previous experiment, where they measured the soft-dipole-resonance parameters and ground state n-n correlations in 11 Li, and to perform similar experiments on other neutron-rich halo nuclei. The detector consists of two planes of liquid scintillator, each 4 square meters in area; it is position sensitive and is capable of neutron-γ-ray discrimination. A general overview of the detector's design and measurements of its performance in test experiments will be presented

Pairing in exotic neutron-rich nuclei near the drip line and in the crust of neutron stars

Science.gov (United States)

Pastore, A.; Margueron, J.; Schuck, P.; Viñas, X.

2013-09-01

Exotic and drip-line nuclei as well as nuclei immersed in a low-density gas of neutrons in the inner crust of neutron stars are systematically investigated with respect to their neutron pairing properties. This is done using Skyrme density-functional and different pairing forces such as a density-dependent contact interaction and a separable form of a finite-range Gogny interaction. Hartree-Fock-Bogoliubov (HFB) and Bardeen-Cooper-Schrieffer (BCS) theories are compared. It is found that neutron pairing is reduced towards the drip line while overcast by strong shell effects. Furthermore, resonances in the continuum can have an important effect counterbalancing the tendency of reduction and leading to a persistence of pairing at the drip line. It is also shown that in these systems the difference between HFB and BCS approaches can be quantitatively large.

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

International Nuclear Information System (INIS)

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

1981-01-01

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

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

Directory of Open Access Journals (Sweden)

Leoni S.

2016-01-01

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

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

Science.gov (United States)

Leoni, S.

2016-05-01

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

The analysis of the elastic scattering of 11Be and 6Li by adiabatic approximation

International Nuclear Information System (INIS)

Takagi, S.

2000-01-01

The unstable nuclei, particularly, the neutron halo nuclei which exist near by the neutron dripline, are recently one of the interesting topics in the nuclear physics. By the adiabatic approximation, R. C. Jhonson et al. have reproduced the experimental differential cross-section of the elastic scattering of the neutron halo nucleus 11 Be (+ l2 C) [1]. We have applied their method to the elastic scattering of another nucleus 6 Li which is not a halo nucleus but has the cluster structure as 11 Be. But it couldn't reproduce the experimental data, so that the method of Johnson et al. is poor in the case of 6 Li. (author)

$\\gamma$ and fast-timing spectroscopy of the doubly magic $^{132}$Sn and its one- and two-neutron particle/hole neighbours

CERN Multimedia

We propose to use fast-timing and spectroscopy to study five nuclei including the doubly magic $^{132}$Sn and its four neighbours: two-neutron hole $^{130}$Sn, one-neutron hole $^{131}$Sn, one-neutron particle $^{133}$Sn and two-neutron particle $^{134}$Sn. There is an increasing interest in these nuclei since they serve to test nuclear models using state-of-the-art interactions and many body approaches, and they provide information relevant to deduce single particle states. In addition properties of these nuclei are very important to model the astrophysical $\\textit{r-process}$. The present ISOLDE facility provides unique capabilities to study these Sn nuclei populated in the $\\beta$-decay of In isomers, produced from a UCx target unit equipped with neutron converter and ionized with RILIS, capable of selective isomer ionization. The increased production yields for $^{132}$In are estimated to be 200 larger than in the previous work done at OSIRIS. We will use the recently commissioned Isolde Decay Station (I...

Test of Symmetries with Neutrons and Nuclei

International Nuclear Information System (INIS)

Paul, Stephan

2009-01-01

Precision experiments at low energies probing weak interaction are a very promising and complementary tool for investigating the structure of the electro-weak sector of the standard model, and for searching for new phenomena revealing signs for an underlaying new symmetry. With the advent of new technologies in particle trapping and production of beams for exotic nuclei as well as ultracold neutrons, we expect one or two orders of magnitude gain in precision. This corresponds to the progress expected by new high luminosity B-factories or the LHC. Domains studied are β-decays where decay correlations, partial or total decay rates may reveal the nature of the left-right structure of the interaction and the investigation of discrete symmetries. Here the search for a finite electric dipole moment which, due to its CP-violating nature were sensational by itself, could shed light on the structure of the vacuum at very small distances. Last but not least ideas of a mirror world can be extended to the sector of baryons which can be studied with neutrons.

Lifetime measurement in neutron-rich A ∝ 100 nuclei

Energy Technology Data Exchange (ETDEWEB)

Ansari, Saba; Jolie, Jan; Regis, Jean-Marc; Saed-Samii, Nima; Warr, Nigel [Institute for Nuclear Physics, University of Cologne, Cologne (Germany); Collaboration: EXILL-FATIMA-Collaboration

2016-07-01

Rapid shape changes are observed in the region of neutron rich nuclei with a mass around A=100. Precise lifetime measurements are a key ingredient in the systematic study of the evolution of nuclear deformation and the degree of collectivity in this region. Nuclear lifetimes of excited states can be obtained using the fast-timing technique with LaBr{sub 3}(Ce)-scintillators. We used neutron induced fission of {sup 241}Pu in order to study lifetimes of excited states of fission fragments in the A∝100 region. The EXILL-FATIMA array located at the PF1B cold neutron beam line at the Institut Laue-Langevin comprises of 8 BGO-shielded EXOGAM clover detectors and 16 very fast LaBr{sub 3}(Ce)-scintillator detectors, which were installed around the fission target. We have studied the lifetimes of low lying states for the nuclei {sup 98}Zr, {sup 100}Zr and {sup 102}Zr by applying the generalized centroid difference method. In this contribution we report on the used fast-timing setup and present preliminary results for the studied isotopes.

Study of subshell gap around N = 70 for neutron-rich nuclei

International Nuclear Information System (INIS)

Hemalatha, M.

2011-01-01

The study and search for new regions of shell closure for nuclei away from stability is a topic of current interest both experimentally and theoretically. There have been few studies predicting a weak spherical subshell gap of 110 Zr (N = 70), for example. This is supported by a recent study indicating that the spherical N = 70 shell gap may not have a large effect at N = 68 for Zr isotopes. It would be, therefore, interesting to know whether there is a subshell closure at N = 70 in the neutron rich region and also for the very neutron-rich nuclei, 110 Zr

Neutron skin studies of medium and heavy nuclei

Directory of Open Access Journals (Sweden)

Thiel M.

2014-06-01

Full Text Available The recent PREX experiment at JLab has demonstrated the sensitivity of parity violating electron scattering to the neutron density, meanwhile outlining its major experimental challenges. On the other side, intermediate energy photons are an ideal probe for studying the properties of strongly interacting matter from the nuclear scale down to the sub-nuclear components of the nucleus. Among others coherent pion photoproduction can provide information on the existence and nature of neutron skins in nuclei. The simultaneous combination of different techniques allows a systematic determination across the periodic table thus benchmarking modern calculation. Recently a systematic investigation of the latter method has been exploited at MAMI (Mainz. At MESA the same setup as in the measurement of the weak mixing angle can be used to determine the parity-violating asymmetry for polarized electrons scattered on heavy nuclei with a 1% resolution. Status and prospects of the projects are presented.

Exotic nuclei: another aspect of nuclear structure; Les noyaux exotiques: un autre regard sur la structure nucleaire

Energy Technology Data Exchange (ETDEWEB)

Dobaczewski, J [Warsaw Univ., Institute of Theoretical Physics (Poland); Blumenfeld, Y; Flocard, H; Garcia Borge, M J; Nowacki, F; Rombouts, S; Theisen, Ch; Marques, F M; Lacroix, D; Dessagne, P; Gaeggeler, H

2002-07-01

This document gathers the lectures made at the Joliot Curie international summer school in 2002 whose theme that year was exotic nuclei. There were 11 contributions whose titles are: 1) interactions, symmetry breaking and effective fields from quarks to nuclei; 2) status and perspectives for the study of exotic nuclei: experimental aspects; 3) the pairing interaction and the N = Z nuclei; 4) borders of stability region and exotic decays; 5) shell structure of nuclei: from stability to decay; 6) variational approach of system with a few nucleons; 7) from heavy to super-heavy nuclei; 8) halos, molecules and multi-neutrons; 9) macroscopic approaches for fusion reactions; 10) beta decay: a tool for spectroscopy; 11) the gas phase chemistry of super-heavy elements.

Bookshelf (''Neutrons, Nuclei and Matter'', by J. Byrne)

International Nuclear Information System (INIS)

Hansen, P.G.

1994-01-01

Time was when a neophyte wanting to do experiments with neutrons would be told first to read D.J. Hughes' classic ''Pile Neutron Research'' (1952). The book by J. Byrne is in many respects a modern equivalent, although if you were to send your student away with it, you will risk not seeing him or her again for a considerable time. What is immediately striking is that the book, rich in information and quite long, is cross-disciplinary and touches essentially all the main areas of modern physics. It covers parts of particle physics, such as the internal structure of the neutron, time-reversal violation as revealed by the (still hypothetical) electric dipole moment of the neutron, and the coupling constants for the weak interaction. From the field of basic quantum physics there are chapters on neutron optics, wave phenomena with neutrons and on the applications of these in solid-state physics. Other chapters again delve deeply into nuclear structure, nuclear reaction theory, as well as their applications: nuclear reactors and nuclear energy. At a time with specialization rampant and many physicists tending to believe that venturing outside their own cloisters is uninteresting and even dangerous, it is a pleasure to come across a book that is basically just about physics. J. Byrne of Sussex has for long been active in neutron research at the British-French-German Institut Laue-Langevin (ILL) research reactor in Grenoble, where he has worked on subjects such as weak interactions and fundamental symmetries. He has clearly intended ''Neutrons, Nuclei and Matter'' as a vade-mecum that will allow the practitioner to find the necessary information and formulas. But I believe that many others not directly engaged in neutron research will gain new insight from its many examples. To take just one case, I had not been aware of the simple physical principles that permit cold neutrons to be stored in a bottle. (The main point is that a

Neutron moderation theory with thermal motion of the moderator nuclei

Energy Technology Data Exchange (ETDEWEB)

Rusov, V.D.; Tarasov, V.A.; Chernezhenko, S.A.; Kakaev, A.A.; Smolyar, V.P. [Odessa National Polytechnic University, Department of Theoretical and Experimental Nuclear Physics, Odessa (Ukraine)

2017-09-15

In this paper we present the analytical expression for the neutron scattering law for an isotropic source of neutrons, obtained within the framework of the gas model with the temperature of the moderating medium as a parameter. The obtained scattering law is based on the solution of the general kinematic problem of elastic scattering of neutrons on nuclei in the L-system. Both the neutron and the nucleus possess arbitrary velocities in the L-system. For the new scattering law we obtain the flux densities and neutron moderation spectra as functions of temperature for the reactor fissile medium. The expressions for the moderating neutrons spectra allow reinterpreting the physical nature of the underlying processes in the thermal region. (orig.)

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

Energy Technology Data Exchange (ETDEWEB)

Kimura, M. [Hokkaido University, Department of Physics, Sapporo (Japan); Hokkaido University, Nuclear Reaction Data Centre, Faculty of Science, Sapporo (Japan); Suhara, T. [Matsue College of Technology, Matsue (Japan); Kanada-En' yo, Y. [Kyoto University, Department of Physics, Kyoto (Japan)

2016-12-15

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 3α 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. (orig.)

The role of neutron star mergers in the chemical evolution of the Galactic halo

Science.gov (United States)

Cescutti, G.; Romano, D.; Matteucci, F.; Chiappini, C.; Hirschi, R.

2015-05-01

Context. The dominant astrophysical production site of the r-process elements has not yet been unambiguously identified. The suggested main r-process sites are core-collapse supernovae and merging neutron stars. Aims: We explore the problem of the production site of Eu. We also use the information present in the observed spread in the Eu abundances in the early Galaxy, and not only its average trend. Moreover, we extend our investigations to other heavy elements (Ba, Sr, Rb, Zr) to provide additional constraints on our results. Methods: We adopt a stochastic chemical evolution model that takes inhomogeneous mixing into account. The adopted yields of Eu from merging neutron stars and from core-collapse supernovae are those that are able to explain the average [Eu/Fe]-[Fe/H] trend observed for solar neighbourhood stars, the solar abundance of Eu, and the present-day abundance gradient of Eu along the Galactic disc in the framework of a well-tested homogeneous model for the chemical evolution of the Milky Way. Rb, Sr, Zr, and Ba are produced by both the s- and r-processes. The r-process yields were obtained by scaling the Eu yields described above according to the abundance ratios observed in r-process rich stars. The s-process contribution by spinstars is the same as in our previous papers. Results: Neutron star binaries that merge in less than 10 Myr or neutron star mergers combined with a source of r-process generated by massive stars can explain the spread of [Eu/Fe] in the Galactic halo. The combination of r-process production by neutron star mergers and s-process production by spinstars is able to reproduce the available observational data for Sr, Zr, and Ba. We also show the first predictions for Rb in the Galactic halo. Conclusions: We confirm previous results that either neutron star mergers on a very short timescale or both neutron star mergers and at least a fraction of Type II supernovae have contributed to the synthesis of Eu in the Galaxy. The r

Formation of halo-structures in oxygen isotopes through change of occupancy of levels near Fermi surface

International Nuclear Information System (INIS)

Bhattacharya, Rupayan

2000-01-01

Recently a new parametrisation of Skyrme interaction has been formulated in order to study the level inversions of A=9 isobars. The role of occupancy of 2s 1/2 level in determining the halo structures of O, N, C, B and Be nuclei was shown. A thorough investigation on the binding energies, rms charge, neutron and matter distribution and occupation probabilities of levels near the Fermi surface has been done in the present work

The analysis of the elastic scattering of {sup 11}Be and {sup 6}Li by adiabatic approximation

Energy Technology Data Exchange (ETDEWEB)

Takagi, S. [Osaka City Univ. (Japan). Dept. of Physics

2000-01-01

The unstable nuclei, particularly, the neutron halo nuclei which exist near by the neutron dripline, are recently one of the interesting topics in the nuclear physics. By the adiabatic approximation, R. C. Jhonson et al. have reproduced the experimental differential cross-section of the elastic scattering of the neutron halo nucleus {sup 11}Be (+{sup l2}C) [1]. We have applied their method to the elastic scattering of another nucleus {sup 6}Li which is not a halo nucleus but has the cluster structure as {sup 11}Be. But it couldn't reproduce the experimental data, so that the method of Johnson et al. is poor in the case of {sup 6}Li. (author)

Relativistic exotic nuclei as projectile beams. New perspectives of studies on the properties of nuclei; Relativistische exotische Kerne als Projektilstrahlen. Neue Perspektiven zum Studium der Kerneigenschaften

Energy Technology Data Exchange (ETDEWEB)

Geissel, H

1997-03-01

Examinations of the production cross-sections and the kinematics permitted refinement of model concepts of the peripheral reactions in exotic nuclei at energies from 100 to 1000 A MeV. Due to the strong selectivity and resolution achieved it was possible to discover a large number of novel isotopes at the fragment separator FRS, despite the relatively low projectile beam intensities of the SIS. The two twice magic nuclei found, Ni 78 and Sn 100, are particularly interesting, as they could not be measured so far with other experimental systems. Fission of relativistic uranium ions proved to be a particularly successful process yielding many medium-heavy, neutron-rich nuclei. Insight into the structure of light neutron halos could be improved. The superlarge spatial dimensions of the nuclear halos is discussed. (orig./CB) [Deutsch] Die Untersuchungen der Produktionsquerschnitte und der Kinematik fuehr ten zu einer Verfeinerung der Modellvorstellungen der peripheren Kernr eaktionen an exotischen Kernen bei Energien im Bereich von 100- 1000 A MeV. Die hohe Selektivitaet und Aufloesung waren die Voraussetzung, da ss schon bei den vergleichsweise niedrigen Projektilstrahlintensitaete n des SIS eine grosse Anzahl von neuen Isotopen am Fragmentseparator F RS entdeckt werden konnten. Besonders erwaehnenswert sind die beiden d oppelt magischen Kerne Ni 78 und Sn 100, die mit anderen experimentel len Anlagen vorher nicht zugaenglich waren.Die Spaltung relativistisch er Uranionen hat sich als eine besonders ergiebige Quelle fuer mittels chwere neutronenreiche Kerne erwiesen. Die Kenntnisse der Struktur lei chter Neutronen- Halokerne konnten erweitert werden. Die uebergrosse r aeumliche Ausdehnung der Halokerne wurde aufgezeigt.

The number of degrees of freedom for statistical distribution of s wave reduced neutron width for several nuclei

International Nuclear Information System (INIS)

Zhixiang, Z.

1983-01-01

The least squares fit has been performed using chi-squared distribution function for all available evaluated data for s-wave reduced neutron width of several nuclei. The number of degrees of freedom and average value have been obtained. The missing levels of weak s-wave resonances and extra p-wave levels have been taken into account, if any. For 75 As and 103 Rh, s-wave population has been separated by Bayes' theorem before making fit. The results thus obtained are consistent with Porter-Thomas distribution, i.e., chi-squared distribution with γ=1, as one would expect. It has not been found in this work that the number of degrees of freedom for the distribution of s-wave reduced neutron width might be greater than one as reported by H.C.Sharma et al. (1976) at the international conference on interactions of neutrons with nuclei. (Auth.)

Neutron optical potentials in unstable nuclei and the equation of state of asymmetric nuclear matter

International Nuclear Information System (INIS)

Oyamatsu, K.; Iida, K.

2003-01-01

Neutron single particle potential is one of the basic macroscopic properties to describe structure and reactions of nuclei in nuclear reactors and in the universe. However, the potential is quite uncertain for unstable nuclei primarily because the equation of state (EOS) of asymmetric nuclear matter is not known well. The present authors studied systematically the empirical EOS of asymmetric nuclear matter using a macroscopic nuclear model; about two hundred EOS's having empirically allowed values of L (symmetry energy density derivative coefficient) and K 0 (incompressibility) were obtained from the fittings to masses and radii of stable nuclei. It was suggested that the L value could be determined from global (Z, A) dependence of nuclear radii. In the present study, the single particle potential is examined assuming kinetic energies of non-interacting Fermi gases. The potential in a nucleus can be calculated easily, once the density distribution is solved using the effective nuclear interaction (EOS). Neutron and proton single particle potentials are calculated systematically for 80 Ni using the two hundred EOS's. It is found that the neutron-proton potential difference has clear and appreciable L dependence, while the potential for each species does not show such simple dependence on L. (author)

Clustering and correlations at the neutron drip-line

Energy Technology Data Exchange (ETDEWEB)

Orr, N.A.; Marques, F.M

2003-03-01

Some recent experimental studies of clustering and correlations within very neutron-rich light nuclei are reviewed. In particular, the development of the novel probes of neutron-neutron interferometry and Dalitz-plot analyses is presented through the example of the dissociation of the two-neutron halo system {sup 14}Be. The utility of high-energy proton radiative capture is illustrated using a study of the {sup 6}He(p,{gamma}) reaction. A new approach to the production and detection of bound neutron clusters is also described, and the observation of events with the characteristics expected for tetraneutrons ({sup 4}n) liberated in the breakup of {sup 14}Be is discussed. The prospects for future work, including systems beyond the neutron drip-line, are briefly outlined. (authors)

Hot nuclei studied with high efficiency neutron detectors

International Nuclear Information System (INIS)

Galin, J.

1990-01-01

We have shown the invaluable benefit that a high efficiency 4π neutron detector can bring to the study of reaction mechanisms following collisions of heavy nuclei at intermediate energy. Analysis requires Monte-Carlo simulations for comparison between experimental data and any emission model. In systematic measurements with projectiles of velocity corresponding to energies between 27 and 77 MeV/u, where both the influence of beam velocity and mass have been investigated separately, it has been shown that the projectile-target mass asymmetry, much more than velocity, has a decisive influence on energy dissipation. The closer the projectile mass to the target mass, the more energy is dissipated per unit mass of the considered projectile plus target system. The latter presents all the characteristics of a thermalized system, evaporating a copious number of light particles: up to about 40 neutrons (after efficiency correction) and 11 light charged particles in the most dissipative collisions between Kr+Au, and 90 neutrons for Pb+U with a yet unknown number of l.c.p. In the Kr experiment, these particles are isotropically emitted in the frame of a fused system, excited with 1.2 GeV. Moreover, l.c.p. exhibit Maxwellian energy distributions as in any standard evaporation process. We are now eager to better characterize the properties of the Pb+Au (U) systems for which about 1/3 of the neutrons are freed in a rather large fraction of all collisions. The thermalized energy should then approach very closely the total binding energy of the two interacting nuclei

Blazars with arcminute-scale radio halos

International Nuclear Information System (INIS)

Ulvestad, J.S.; Antonucci, R.R.J.; Space Telescope Science Institute, Baltimore, MD)

1986-01-01

About 10-arcsec resolution 20-cm wavelength maps are presented for three nearby BL Lac objects: Mkn 180, whose halo has a linear size of 85 kpc, 2155-304, with a halo about 375 kpc across, and 1727 + 502, whose one-sided diffuse emission extends to a distance of about 145 kpc from its radio core. Little evidence is found for strong radio variability in the cores of the three blazars; these and other results obtained are consistent with the assertion that the three objects should be classified as normal low luminosity double radio galaxies with optically dull nuclei, if seen from other directions. 20 references

Low-lying dipole strength of neutron-rich 'island of inversion' nuclei around n ∼ 20

International Nuclear Information System (INIS)

Datta Pramanik, U.; Chakraborty, S.; Ray, I.

2009-01-01

Magic numbers are the basic building blocks of nuclear structure since last fifty years. Recently, through various experimental results using Radioactive Ion Beam (RIB) facilities, it has been observed that those long cherished magic numbers are not valid anymore in the neutron rich nuclei like 32 Mg etc. The breakdown of magic number was hinted in the late 1980 's by Thibault et. al. in sodium nuclei ( 31,32 Na). Motobayashi et. al. showed large deformation for 32 Mg which leads to the failure of magic number at N = 20. Exploration into the cause of this breakdown shows the filling of higher pf orbitals rather than the pure lower sd orbitals in the ground state of the neutron-rich nuclei like Ne, Na, Mg in the region N∼20. Thus there is obviously an inversion in nuclear orbitals and hence the so called name 'island of inversion'. This year, we have performed an experiment at GSI, Darmstadt. The measurement of dipole threshold strength of neutron-rich nucleus (N∼20) through electromagnetic excitation was done using LAND-FRS setup. Through this dipole strength, we would like to probe directly the quantum numbers of the valence neutrons in neutron rich nuclei like 31-33 Mg, 33-35 Al, 29-30 Na, 25-27 Ne, 24 F etc.

Cluster-transfer reactions with radioactive beams: a spectroscopic tool for neutron-rich nuclei

CERN Document Server

AUTHOR|(CDS)2086156; Raabe, Riccardo; Bracco, Angela

In this thesis work, an exploratory experiment to investigate cluster-transfer reactions with radioactive beams in inverse kinematics is presented. The aim of the experiment was to test the potential of cluster-transfer reactions at the Coulomb barrier, as a possible mean to perform $\\gamma$ spectroscopy studies of exotic neutron-rich nuclei at medium-high energies and spins. The experiment was performed at ISOLDE (CERN), employing the heavy-ion reaction $^{98}$Rb + $^{7}$Li at 2.85 MeV/A. Cluster-transfer reaction channels were studied through particle-$\\gamma$ coincidence measurements, using the MINIBALL Ge array coupled to the charged particle Si detectors T-REX. Sr, Y and Zr neutron-rich nuclei with A $\\approx$ 100 were populated by either triton- or $\\alpha$ transfer from $^{7}$Li to the beam nuclei and the emitted complementary charged fragment was detected in coincidence with the $\\gamma$ cascade of the residues, after few neutrons evaporation. The measured $\\gamma$ spectra were studied in detail and t...

RMF+BCS description of some traditional neutron magic isotones

International Nuclear Information System (INIS)

Saxena, G.; Singh, D.; Kaushik, M.

2014-01-01

The traditional neutron magic nuclei with N = 8, 20, 28, 50, 82 and 126, and those with neutron sub-magic number N = 40 are investigated within the relativistic mean-field plus BCS (RMF+BCS) approach. The results indicate appearance of new proton magic numbers as well as the disappearance of conventional magic numbers for nuclei with extreme isospin values. The calculated energies and densities do not indicate any tendency for the proton halo formations in any of the proton rich isotones due to Coulomb interaction and different single particle spectra. However, the potential barrier provided by the Coulomb interaction and that due to the centrifugal force may cause a long delay in the actual decay of proton rich nucleus resulting in the extended drip line. (authors)

Experiments with relativistic exotic nuclei at the FRS

International Nuclear Information System (INIS)

Geissel, H.

1994-11-01

The concept and experimental programme of the secondary nuclear beam facility BRENDA at GSI is presented. The central part of BRENDA is the magnetic spectrometer FRS providing spatially separated monoisotopic exotic beams of all elements up to uranium. The FRS as a versatile magnetic spectrometer for experiments with heavy ions in the energy range of (0.1-2) A.GeV has been used to study peripheral nuclear collisions from oxygen up to uranium projectiles. In the uranium experiments we discovered that projectile fission is a powerful tool to investigate new neutron-rich fission fragments. In the medium mass region we have identified the doubly magic nucleus 100 Sn and measured its half-life. Light halo nuclei have been studied in kinematically complete experiments with the FRS in combination with the dipole magnet ALADIN, and the neutron detector LAND. The FRS combined with the storage and cooler ring ESR offers new precision experiments, e.g., direct mass measurements, decay studies of highly-charged nuclei, or nuclear structure studies in inverse kinematics. (orig.)

Study of neutron-proton pairing in N=Z unstable nuclei through transfer reactions

International Nuclear Information System (INIS)

Le Crom, B.

2016-01-01

A nucleus is described as a set of independent neutrons and protons linked by a mean-field potential. However, in order to have a better description one needs to take into account some residual interactions such as pairing. Neutron-neutron and proton-proton pairings are well-studied but neutron-proton pairing is not well-known. np pairing can be isovector pairing such as nn and pp pairing or isoscalar which is yet unknown. Over-binding of N=Z nuclei could be a manifestation of np pairing. We have studied np pairing through transfer reactions. In this case, the cross-section of np pair transfer is expected to be enhanced in the presence of important np pairing. np pairing is expected to be important in N=Z nuclei with high J orbitals. Since the development of radioactive beam facilities, such beams are only available. The experiment was performed at GANIL with an efficient set-up so as to detect products from the (p, 3 He) transfer reaction. This reaction is affected by isovector and isoscalar np pairing. We used 56 Ni and 52 Fe beams so as to see the effect of the occupancy of 0f 7/2 shell on the np pairing. First, we analysed the data from the 56 Ni(p,d) 55 Ni reaction and we compared the results with the literature to validate analysis procedure. After analysing data from the 56 Ni(p, 3 He) 54 Co reaction and extracting the population of the various states of 54 Co, we obtained information about the relative intensity between isoscalar and isovector np pairing in 56 Ni showing the predominance of isovector np pairing in this nucleus. Moreover, in the framework of developing a new charged particle detector, research on the discrimination of light nuclei using pulse shape analysis was performed and is also presented. (author)

Mean field theory of nuclei and shell model. Present status and future outlook

International Nuclear Information System (INIS)

Nakada, Hitoshi

2003-01-01

Many of the recent topics of the nuclear structure are concerned on the problems of unstable nuclei. It has been revealed experimentally that the nuclear halos and the neutron skins as well as the cluster structures or the molecule-like structures can be present in the unstable nuclei, and the magic numbers well established in the stable nuclei disappear occasionally while new ones appear. The shell model based on the mean field approximation has been successfully applied to stable nuclei to explain the nuclear structure as the finite many body system quantitatively and it is considered as the standard model at present. If the unstable nuclei will be understood on the same model basis or not is a matter related to fundamental principle of nuclear structure theories. In this lecture, the fundamental concept and the framework of the theory of nuclear structure based on the mean field theory and the shell model are presented to make clear the problems and to suggest directions for future researches. At first fundamental properties of nuclei are described under the subtitles: saturation and magic numbers, nuclear force and effective interactions, nuclear matter, and LS splitting. Then the mean field theory is presented under subtitles: the potential model, the mean field theory, Hartree-Fock approximation for nuclear matter, density dependent force, semiclassical mean field theory, mean field theory and symmetry, Skyrme interaction and density functional, density matrix expansion, finite range interactions, effective masses, and motion of center of mass. The subsequent section is devoted to the shell model with the subtitles: beyond the mean field approximation, core polarization, effective interaction of shell model, one-particle wave function, nuclear deformation and shell model, and shell model of cross shell. Finally structure of unstable nuclei is discussed with the subtitles: general remark on the study of unstable nuclear structure, asymptotic behavior of wave

Study of neutron rich nuclei by delayed neutron decay using the Tonnerre multidetector; Etude de la decroissance par neutrons retardes de noyaux legers riches en neutrons avec le multidetecteur tonnerre

Energy Technology Data Exchange (ETDEWEB)

Timis, C.N

2001-07-01

A new detection array for beta delayed neutrons was built. It includes up to 32 plastic scintillation counters 180 cm long located at 120 cm from the target. Neutron energy spectra are measured by time-of-flight in the 300 keV-15 MeV range with good energy resolution. The device was tested with several known nuclei. Its performances are discussed in comparison with Monte Carlo simulations. They very high overall detection efficiency on the TONNERRE array made it possible to study one and two neutron emission of {sup 11}Li. A complete decay scheme was obtained. The {sup 33}Mg and {sup 35}Al beta decays were investigated for the first time by neutron and gamma spectroscopy. Complete decay schemes were established and compared to large scale shell-model calculations. (authors)

An Antiproton Ion Collider (AIC) for Measuring Neutron and Proton Distributions in Stable and Radioactive Nuclei

International Nuclear Information System (INIS)

Kienle, Paul

2005-01-01

An antiproton-ion collider is proposed to independently determine mean square radii for protons and neutrons in stable and short lived nuclei by means of antiproton absorption at medium energies. The experiment makes use of the electron ion collider complex (ELISE) of the GSI FAIR project with appropriate modifications of the electron ring to store, cool and collide antiprotons of 30 MeV energy with 740A MeV energy ions.The total absorption cross-section of antiprotons by the stored ions will be measured by detecting their loss by means of the Schottky noise spectroscopy method. Cross sections for the absorption on protons and neutrons, respectively, will be studied by detection of residual nuclei with A-1 either by the Schottky method or by analysing them in recoil detectors after the first dipole stage of the NESR following the interaction zone. With a measurement of the A-1 fragment momentum distribution, one can test the momentum wave functions of the annihilated neutron and proton, respectively. Furthermore by changing the incident ion energy the tails of neutron and proton distribution can be measured.The absorption cross section is at asymptotic energies in leading order proportional to the mean square radius of the nucleus. Predicted cross sections and luminosities show that the method is applicable to nuclei with production rates of about 105 s-1 or lower, depending on the lifetime of the ions in the NESR, and for half-lives down to 1 second

New relativistic effective interaction for finite nuclei, infinite nuclear matter, and neutron stars

Science.gov (United States)

Kumar, Bharat; Patra, S. K.; Agrawal, B. K.

2018-04-01

We carry out the study of finite nuclei, infinite nuclear matter, and neutron star properties with the newly developed relativistic force, the Institute of Physics Bhubaneswar-I (IOPB-I). Using this force, we calculate the binding energies, charge radii, and neutron-skin thickness for some selected nuclei. From the ground-state properties of superheavy nuclei (Z =120 ), it is noticed that considerable shell gaps appear at neutron numbers N =172 , 184, and 198, manifesting the magicity at these numbers. The low-density behavior of the equation of state for pure neutron matter is compatible with other microscopic models. Along with the nuclear symmetry energy, its slope and curvature parameters at the saturation density are consistent with those extracted from various experimental data. We calculate the neutron star properties with the equation of state composed of nucleons and leptons in β -equilibrium, which are in good agreement with the x-ray observations by Steiner [Astrophys. J. 722, 33 (2010), 10.1088/0004-637X/722/1/33] and Nättilä [Astron. Astrophys. 591, A25 (2016), 10.1051/0004-6361/201527416]. Based on the recent observation of GW170817 with a quasi-universal relation, Rezzolla et al. [Astrophys. J. Lett. 852, L25 (2018), 10.3847/2041-8213/aaa401] have set a limit for the maximum mass that can be supported against gravity by a nonrotating neutron star in the range 2.01 ±0.04 ≲M (M⊙)≲2.16 ±0.03 . We find that the maximum mass of the neutron star for the IOPB-I parametrization is 2.15 M⊙ . The radius and tidal deformability of a canonical neutron star of mass 1.4 M⊙ are 13.2 km and 3.9 ×1036g cm2s2 , respectively.

Comparison of the Porter-Thomas distribution with neutron resonance data of even-even nuclei

International Nuclear Information System (INIS)

Camarda, H.S.

1994-01-01

The low-energy neutron resonance data of the even-even nuclei 152 Sm, 158 Gd, 162 Dy, 166,168 Er, 182 W, 232 Th, and 236,238 U have been examined in order to test the validity of the Porter-Thomas distribution of the reduced neutron widths---a chi-squared distribution with one degree of freedom (v=1). In an attempt to circumvent the ever-present problems of missed or spurious s wave levels as well as extra p wave levels, a maximum likelihood statistic was employed which used only measured widths greater than some minimum value. A Bayes-theory test applied to the data helped to ensure that p wave contamination of the s wave level population was not significant. The error-weighted value of the number of degrees of freedom for the nine nuclei studied, left-angle v right-angle=0.98±0.10, is consistent with the theoretical expectation of v=1

Cluster models of light nuclei and the method of hyperspherical harmonics: Successes and challenges

International Nuclear Information System (INIS)

Danilin, B. V.; Shul'gina, N. B.; Ershov, S. N.; Vaagen, J. S.

2009-01-01

Hyperspherical-harmonics method to investigate the lightest nuclei having three-cluster structure is discussed together with recent experiments. Properties of bound states and methods to explore three-body continuum are presented. The challenges created by large neutron excess and halo phenomena are highlighted. Astrophysical aspects of the 7 Li + n → 8 Li + γ reaction and the solar-boron-neutrinos problem are analyzed. Three-cluster structure of highly excited states in 8 Be is shown to be responsible for extreme isospin mixing. Progress in studies of 6 He- and 11 Li-induced inclusive and exclusive nuclear reactions is demonstrated, providing information on the nature of continuum structures of Borromean nuclei.

Neutron-Proton Mass Difference in Nuclear Matter and in Finite Nuclei and the Nolen-Schiffer Anomaly

Directory of Open Access Journals (Sweden)

Yakhshiev U.T.

2010-04-01

Full Text Available The neutron-proton mass difference in (isospin asymmetric nuclear matter and finite nuclei is studied in the framework of a medium-modified Skyrme model. The proposed effective Lagrangian incorporates both the medium influence of the surrounding nuclear environment on the single nucleon properties and an explicit isospin-breaking effect in the mesonic sector. Energy-dependent charged and neutral pion optical potentials in the s- and p-wave channels are included as well. The present approach predicts that the neutron-proton mass difference is mainly dictated by its strong part and that it markedly decreases in neutron matter. Furthermore, the possible interplay between the effective nucleon mass in finite nuclei and the Nolen-Schiffer anomaly is discussed. In particular, we find that a correct description of the properties of mirror nuclei leads to a stringent restriction of possible modifications of the nucleon’s effective mass in nuclei.

Is neutron evaporation from highly excited nuclei a poisson random process

International Nuclear Information System (INIS)

Simbel, M.H.

1982-01-01

It is suggested that neutron emission from highly excited nuclei follows a Poisson random process. The continuous variable of the process is the excitation energy excess over the binding energy of the emitted neutrons and the discrete variable is the number of emitted neutrons. Cross sections for (HI,xn) reactions are analyzed using a formula containing a Poisson distribution function. The post- and pre-equilibrium components of the cross section are treated separately. The agreement between the predictions of this formula and the experimental results is very good. (orig.)

Microscopic description of quadrupole collectivity in neutron-rich nuclei across the N = 126 shell closure

Science.gov (United States)

Rodríguez-Guzmán, R.; Robledo, L. M.; Sharma, M. M.

2015-06-01

The quadrupole collectivity in Nd, Sm, Gd, Dy, Er, Yb, Hf and W nuclei with neutron numbers 122 ≤ N ≤ 156 is studied, both at the mean field level and beyond, using the Gogny energy density functional. Besides the robustness of the N = 126 neutron shell closure, it is shown that the onset of static deformations in those isotopic chains with increasing neutron number leads to an enhanced stability and further extends the corresponding two-neutron drip lines far beyond what could be expected from spherical calculations. Independence of the mean-field predictions with respect to the particular version of the Gogny energy density functional employed is demonstrated by comparing results based on the D1S and D1M parameter sets. Correlations beyond mean field are taken into account in the framework of the angular momentum projected generator coordinate method calculation. It is shown that N = 126 remains a robust neutron magic number when dynamical effects are included. The analysis of the collective wave functions, average deformations and excitation energies indicate that, with increasing neutron number, the zero-point quantum corrections lead to dominant prolate configurations in the 0{1/+}, 0{2/+}, 2{1/+} and 2{2/+} states of the studied nuclei. Moreover, those dynamical deformation effects provide an enhanced stability that further supports the mean-field predictions, corroborating a shift of the r-process path to higher neutron numbers. Beyond mean-field calculations provide a smaller shell gap at N = 126 than the mean-field one in good agreement with previous theoretical studies. However, the shell gap still remains strong enough in the two-neutron drip lines.

Polarised nuclei for neutron science: recent applications and perspectives

International Nuclear Information System (INIS)

Glaettli, Hans

2004-01-01

Neutron scattering on nuclei is spin dependent, particularly strongly for 1 H. The means to achieve large nuclear polarisations and its use for structure analysis or as spin-handling device are reviewed. High resolution (diffraction) as well as low resolution (SANS) measurements can benefit from polarised nuclei by changing selectively the form factors of Bragg reflections or the contrasts (the scattering length density profiles) in SANS. The internal structure of ribosomes and the conformation of polymers in solution have been investigated by this method. A numerical simulation is presented to show the influence of steady-state polarisation of protons on the scattering from a protein-ARN model complex. In addition, a more recent technique, time-resolved SANS is described. It makes use of spatial polarisation gradients created around paramagnetic centres at the onset of nuclear polarisation. Such polarisation domains can enhance considerably the scattering amplitude of free radicals and thus contribute to determine their positions inside a complex protein. Examples of possible future experiments are proposed which combine simultaneously the selectivity of solid-state NMR techniques and neutron scattering

Halos and related structures

DEFF Research Database (Denmark)

Riisager, Karsten

2013-01-01

The halo structure originated from nuclear physics but is now encountered more widely. It appears in loosely bound, clustered systems where the spatial extension of the system is significantly larger than that of the binding potentials. A review is given on our current understanding of these stru......The halo structure originated from nuclear physics but is now encountered more widely. It appears in loosely bound, clustered systems where the spatial extension of the system is significantly larger than that of the binding potentials. A review is given on our current understanding...... of these structures, with an emphasis on how the structures evolve as more cluster components are added and on the experimental situation concerning halo states in light nuclei....

Incident energy and target dependence of interaction cross sections and density distribution of neutron drip-line nuclei

International Nuclear Information System (INIS)

Shimoura, S.

1992-01-01

The relation between nuclear density distribution and interaction cross section is discussed in terms of Glauber model. Based on the model, density distribution of neutron drip-line nucleus 11 Be and 11 Li is determined experimentally from incident energy dependence of interaction cross sections of 11 Be and 11 Li on light targets. The obtained distributions have long tails corresponding to neutron halos of loosely bound neutrons. (Author)

Systematic study of even-even nuclei with Hartree-Fock+BCS method using Skyrme SIII force

Energy Technology Data Exchange (ETDEWEB)

Tajima, Naoki; Takahara, Satoshi; Onishi, Naoki [Tokyo Univ. (Japan). Coll. of Arts and Sciences

1997-03-01

We have applied the Hartree-Fock+BCS method with Skyrme SIII force formulated in a three-dimensional Cartesian-mesh representation to even-even nuclei with 2 {<=} Z {<=} 114. We discuss the results concerning the atomic masses, the quadrupole (m=0, 2) and hexadecapole (m=0, 2, 4) deformations, the skin thicknesses, and the halo radii. We also discuss the energy difference between oblate and prolate solutions and the shape difference between protons and neutrons. (author)

Neutron emission in fission of highly excited californium nuclei (E*=76 MeV)

International Nuclear Information System (INIS)

Blinov, M.V.; Bordyug, V.M.; Kozulin, Eh.M.; Mozhaev, A.N.; Levitovich, M.; Muzychka, Yu.A.; Penionzhkevich, Yu.Eh.; Pustyl'nik, B.I.

1990-01-01

The differential cross sections for neutron production in the fission of highly excited californium nuclei formed in the 238 U+ 12 C (105 MeV) reaction have been measured. From the analysis of the experimental data is follows that the number of pre-fission neutrons substantially exceeds the value obtained in the framework of the standard statistical model. The saddle-to-scission time of the excited nucleus is estimated on the basis of the neutron multiplicity. The dependences of the neutron number and neutron average energies upon the fragment mass are determined

Multiple sampling ionization chamber (MUSIC) for investigation of fusion induced by halo nuclei

International Nuclear Information System (INIS)

Petrascu, H.; Kumagai, H.; Tanihata, I.; Fueloep, Zs.; Petrascu, M.

1999-01-01

A high resolution MUSIC for low and medium energy ions up to ∼ 20 AMeV, for investigation of fusion processes induced by halo nuclei, has been achieved. The chamber was used in the first experiments, aiming at investigating fusion processes induced by 9,11 Li with light targets. In these experiments MUSIC was used for the identification of the inclusive evaporation residues produced in the Si detector target, mounted inside the chamber. By using MUSIC it was possible to separate the inclusive spectra corresponding to the fusion processes, from the background due to the energy degraded beam particles. In principle such a chamber could be also used for investigation of particular fusion channels produced in the entrance window. In this case one could obtain the fusion product trajectory angle with the horizontal plane, by coupling each anode pad to a TDC. The chamber was also provided by a position grid, mounted between the Frisch grid and the anode pads. The energy loss distribution widths were measured using α particles. The chamber was filled with P-10 gas at pressures between 200 and 300 torr. The obtained resolution corresponding to a single pad, is close to the limit derived from the theory of Badhwar. (authors)

Program package for calculation of cross sections of neutron scattering on deformed nuclei by the coupled-channel method

International Nuclear Information System (INIS)

Kloss, Yu.Yu.

1985-01-01

Program package and numerical solution of the problem for a system of coupled equations used in optical model to solve a problem on low and mean energy neutron scattering on deformed nuclei, is considered. With these programs differnet scattering cross sections depending on the incident neutron energy on even-even and even-odd nuclei were obtained. The programm permits to obtain different scattering cross sections (elastic, inelastic), excitation cross sections of the first three energy levels of rotational band depending on the energy, angular distributions and neutron polarizations including excited channels. In the program there is possibility for accounting even-even nuclei octupole deformation

Structure and reactions of quantum halos

International Nuclear Information System (INIS)

Jensen, A.S.; Riisager, K.; Fedorov, D.V.; Garrido, E.

2004-01-01

This article provides an overview of the basic principles of the physics of quantum halo systems, defined as bound states of clusters of particles with a radius extending well into classically forbidden regions. Exploiting the consequences of this definition, the authors derive the conditions for occurrence in terms of the number of clusters, binding energy, angular momentum, cluster charges, and excitation energy. All these quantities must be small. The article discusses the transitions between different cluster divisions and the importance of thresholds for cluster or particle decay, with particular attention to the Efimov effect and the related exotic states. The pertinent properties can be described by the use of dimensionless variables. Then universal and specific properties can be distinguished, as shown in a series of examples selected from nuclear, atomic, and molecular systems. The neutron dripline is especially interesting for nuclei and negative ions for atoms. For molecules, in which the cluster division comes naturally, a wider range of possibilities exists. Halos in two dimensions have very different properties, and their states are easily spatially extended, whereas Borromean systems are unlikely and spatially confined. The Efimov effect and the Thomas collapse occur only for dimensions between 2.3 and 3.8 and thus not for 2. High-energy reactions directly probe the halo structure. The authors discuss the reaction mechanisms for high-energy nuclear few-body halo breakup on light, intermediate, and heavy nuclear targets. For light targets, the strong interaction dominates, while for heavy targets, the Coulomb interaction dominates. For intermediate targets these processes are of comparable magnitude. As in atomic and molecular physics, a geometric impact-parameter picture is very appropriate. Finally, the authors briefly consider the complementary processes involving electroweak probes available through beta decay, electromagnetic transitions, and

Effective neutron-proton interaction in rare earth odd-odd nuclei

International Nuclear Information System (INIS)

Boisson, Jean-Paul.

1975-01-01

The effective neutron-proton interaction V(np) in the rare earth odd-odd deformed nuclei is studied. The parameters of the effective interaction are determined from least square fits of calculated matrix elements compared to the ones extracted from experiment. These fits show the existence of a long range repulsive component as well the importance of the even term of the tensor part of V(np). Some informations are obtained concerning the influence of the choice of the sample of experimental data, of the average field and finally, of the radial shape of the effective interaction. Some predictions are made concerning as yet unconfirmed V(np) matrix elements [fr

Study of fusion mechanism of halo nuclear 11Be+208Pb by applying QMD model

International Nuclear Information System (INIS)

Wang Ning; Li Zhuxia

2001-01-01

The authors have studied the fusion reaction for 11 Be + 208 Pb near barrier by applying QMD model, and find that in t he fusion reaction induced by halo nuclei there simultaneously exist two mechanisms competing with each other. On one hand, 11 Be is a weakly bound nuclear system and is easily broke up caused by the interaction with target, when it approaches to target, so the fusion cross section is suppressed. On the other hand, several neutrons of 11 Be transfer into 208 Pb and interact with 208 Pb to cause the local radius of 208 Pb increase and result in an enhancement of fusion cross section. The fusion cross sections calculated show an enhancement near barrier, and the calculated results agree with the experimental data reasonably well

Study of the elastic scattering and of the (p,n) charge exchange reaction with neutron-rich light exotic beams; Etude de la diffusion elastique et de la reaction d`echange de charge (p,n) avec des faisceaux exotiques legers riches en neutrons

Energy Technology Data Exchange (ETDEWEB)

Cortina Gil, D.

1996-07-05

We have measured at GANIL, with the high resolution spectrometer SPEG, the elastic scattering of several neutron rich secondary beams ({sup 6}He, {sup 10}Be and {sup 11}Be) on a polypropylene target and the charge exchange reaction p({sup 6}He, {sup 6}Li)n. These exotic beams were produced by nuclear fragmentation and re-focalized with the SISSI device (superconducting solenoids). The signature of a halo structure in these nuclei has been analysed. Special attention has been paid to several aspects of the associated calculations namely, the proton and neutron density distributions and the small binding energy for the last nucleons in these exotic nuclei. Break-up mechanisms are seen to play an important role in these nuclei. 100 refs.

Interrelation between the isoscalar octupole phonon and the proton-neutron mixed-symmetry quadrupole phonon in near-spherical nuclei

International Nuclear Information System (INIS)

Smirnova, N.A.; Van Isacker, P.; Smirnova, N.A; Pietralla, N.; Yale Univ., New Haven, CT; Mizusaki, T.

2000-01-01

The interrelation between the octupole phonon and the low-lying proton-neutron mixed-symmetry quadrupole in near-spherical nuclei is investigated. The one-phonon states decay by collective E3 and E2 transitions to the ground state and by relatively strong E1 and M1 transitions to the isoscalar 2 + 1 state. We apply the proton-neutron version of the Interacting Boson Model including quadrupole and octupole bosons (sdf-IBM-2). Two F-spin symmetric dynamical symmetry limits of the model, namely the vibrational and the γ-unstable ones, are considered. We derived analytical formulae for excitation energies as well as B(E1), B(M1), B(E2), and B(E3) values for a number of transitions between low-lying states. The model well reproduces many known transition strengths in the near spherical nuclei 142 Ce and 94 Mo. (authors)

Interrelation between the isoscalar octupole phonon and the proton-neutron mixed-symmetry quadrupole phonon in near-spherical nuclei

Energy Technology Data Exchange (ETDEWEB)

Smirnova, N.A.; Van Isacker, P. [Grand Accelerateur National d' Ions Lourds (GANIL), 14 - Caen (France); Smirnova, N.A [Paris-11 Univ., 91 - Orsay (France). Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse]|[Institute for Nuclear Physics, Moscow State University (Russian Federation); Pietralla, N. [Institut fur Kernphysik, Universitat zu Koln (Germany)]|[Yale Univ., New Haven, CT (United States). Wright Nuclear Structure Lab; Mizusaki, T. [Tokyo Univ. (Japan). Dept. of Physics

2000-07-01

The interrelation between the octupole phonon and the low-lying proton-neutron mixed-symmetry quadrupole in near-spherical nuclei is investigated. The one-phonon states decay by collective E3 and E2 transitions to the ground state and by relatively strong E1 and M1 transitions to the isoscalar 2{sup +}{sub 1} state. We apply the proton-neutron version of the Interacting Boson Model including quadrupole and octupole bosons (sdf-IBM-2). Two F-spin symmetric dynamical symmetry limits of the model, namely the vibrational and the {gamma}-unstable ones, are considered. We derived analytical formulae for excitation energies as well as B(E1), B(M1), B(E2), and B(E3) values for a number of transitions between low-lying states. The model well reproduces many known transition strengths in the near spherical nuclei {sup 142}Ce and {sup 94}Mo. (authors)

Exotic light nuclei and nuclei in the lead region

International Nuclear Information System (INIS)

Poppelier, N.A.F.M.

1989-01-01

Three methods are discussed for modifying, or renormalizing, a truncated nuclear hamiltonian such that the wave functions obtained by diagonalizing this modified or effective hamiltoniandescribe the nucleus as well as possible: deriving the hamiltonian directly from a realistic nucleon-nucleon interaction between free nucleons; parametrizing the hamiltonian in terms of a number of parameters and determining these parameters from a least-squares fit of calculated properties to experimental data; approximating the nucleon-nucleon (NN) interaction between two nucleons in a nucleus by a simple analytic expression. An effective hamiltonian derived following the second method is applied in a theoretical study of exotic nuclei in the region of Z=2-9 and A=4-30 and the problem of the neutron halo in 11 Li is discussed. Results of shell-model calculations of 20i Pb and nuclei in its neighbourhood are presented in which an effective hamiltonian was employed derived with the last method. The quenching of M1 strength in 208 Pb, and the spectroscopic factors measured in proton knock-out reactions could be described quite satisfactory. Finally, a method is presented for deriving the effective hamiltonian directly from the realistic NN interaction with algebraic techniques. (H.W.). 114 refs.; 34 figs.; 12 tabs.; schemes

Neutron emission in fission of highly excited californium nuclei (E* = 76 MeV)

International Nuclear Information System (INIS)

Blinov, M.V.; Bordyug, V.M.; Kozulin, E.M.; Levitovich, M.; Mozhaev, A.N.; Muzychka, Yu.A.; Penionzhkevich, Yu.E.; Pustyl'nik, B.I.

1990-01-01

Differential cross sections for neutron production have been measured in fission of excited californium nuclei produced in the reaction 238 U + 12 C (105 MeV). It follows from analysis of the experimental results that the number of neutrons emitted before fission considerably exceeds the number obtained in the framework of the standard statistical model. On the basis of the multiplicity of neutrons they authors have estimated the time of fission of the excited nucleus. The dependence of the number of neutrons and their average energies on the mass of the fragments is determined

Decay spectroscopy of neutron-rich nuclei with the CAITEN detector

Energy Technology Data Exchange (ETDEWEB)

Steiger, Konrad [Physik-Department E12, Technische Universitaet Muenchen (Germany); Collaboration: CAITEN-Collaboration

2012-07-01

An experiment in fall 2010 at the RIBF (Radioactive Ion Beam Factory at RIKEN, Japan) investigated the neutron-rich nuclei in the neighborhood of {sup 30}Ne and {sup 36}Mg. These nuclei were produced by relativistic projectile fragmentation of a 345 AMeV {sup 48}Ca primary beam which was delivered from the superconducting ring cyclotron SRC with an average intensity of 70 pnA. The secondary cocktail beam was separated and identified with the BigRIPS fragment separator and the ZeroDegree spectrometer. The unambiguous particle identification was achieved by measuring the energy loss, time of flight and magnetic rigidity event-by-event. The identified fragments were implanted in the CAITEN detector (Cylindrical Active Implantation Target for Efficient Nuclear-decay study). The main part of this detector is a 4 x 10{sup 4}-fold segmented plastic scintillator with the shape of a hollow cylinder. To reduce background events the scintillator was moved continuously in axial and vertical direction (similar to a tape-transporting system). Implantations and decays were correlated in time and space. {gamma}-rays were detected with three germanium clover detectors. For the first time {beta}-delayed gammas were measured in the neutron-rich isotopes {sup 36-38}Si. The status of the analysis and preliminary results including new half-life values and tentative level schemes for these very exotic nuclei are presented.

Production and identification of new, neutron-rich nuclei in the 208Pb region

International Nuclear Information System (INIS)

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

1998-01-01

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

Study of the N=28 shell closure by one neutron transfer reaction: astrophysical application and {beta}-{gamma} spectroscopy of neutron rich nuclei around N=32/34 and N=40; Etude de la fermeture de couche N=28 autour du noyau {sub 18}{sup 46}Ar{sub 28} par reaction de transfert d'un neutron: application a l'astrophysique et Spectroscopie {beta}-{gamma} de noyaux riches en neutrons de N=32/34 et N=40

Energy Technology Data Exchange (ETDEWEB)

Gaudefroy, L

2005-09-15

The study of the N=28 shell closure has been presented as well as its astrophysical implications. Moreover the structure of neutron rich nuclei around N=32/34 and 40 was studied. The N=28 shell closure has been studied trough the one neutron transfer reaction on {sup 44,46}Ar nuclei. Excitation energies of states in {sup 45,47}Ar nuclei have been obtained, as well as their angular momenta and spectroscopic factors. These results were used to show that N=28 is still a good magic number in the argon isotopic chain. We interpreted the evolution of the spin-orbit partner gaps in terms of the tensor monopolar proton-neutron interaction. Thanks to this latter, we showed it is not necessary to summon up a reduction of the intensity of the spin-orbit force in order to explain this evolution in N=29 isotopes from calcium to argon chains. The neutron capture rates on {sup 44,46}Ar have been determined thanks to the results of the transfer reaction. Their influence on the nucleosynthesis of {sup 46,48}Ca was studied. We proposed stellar conditions to account for the abnormal isotopic ratio observed in the Allende meteorite concerning {sup 46,48}Ca isotopes. The beta decay and gamma spectroscopy of neutron rich nuclei in the scandium to cobalt region has been studied. We showed that beta decay process is dominated by the {nu}f{sub 5/2} {yields} {pi}f{sub 7/2} Gamow-Teller transition. Moreover, we demonstrated that the {nu}g{sub 9/2} hinders this process in the studied nuclei, and influences their structure, by implying the existence of isomers. Our results show that N=34 is not a magic number in the titanium chain and the superior ones. (author)

Study of induced reactions by a secondary beam of 11Be in Be, Ti and Au targets

International Nuclear Information System (INIS)

Dogny, S.

1992-01-01

In the last decade, new phenomena arised from nuclear reaction studies of neutron-rich light nuclei produced by projectile fragmentation. In this work, first we will recall briefly some aspects of these studies, in particular the two-neutron halo for nuclei whose binding energy of the two last neutrons is low. Secondly, we will describe the experiment which aims to study 11 Be reactions on Be, Ti and Be targets. The results of this experiment show the presence of a one-neutron halo, corresponding to a high dissociation cross-section for the three targets. We will show that three mechanisms, Coulomb dissociation for heavy targets, diffraction-and absorption-dissociation for light targets, account satisfactorily for reactions leading to 10 Be

Study on the systematics of two-neutron high spin states in fp shell nuclei by means of the (α,2He) reaction

International Nuclear Information System (INIS)

Wienands, U.

1983-05-01

The (α, 2 He)-reaction was studied at 56-57 MeV incident energy at the target nuclei sup(58,60,62,64)Ni. In a laboratory angular range from 15 0 -37.5 0 the angular distributions of the absolute differential cross section were taken up. The measurements were performed with the position resolving 2 He detector developed in Bonn. By means of DWBA calculations for the first time in all final nuclei states with the configurations (fsub(5/2), gsub(9/2)) 7 -(gsub(9/2)) 8 2 +, and (gsub(9/2), dsub(5/2)) 6 + could be identified; these were except the Jsup(π)=7 - states in 60 Ni hitherto not known. The two-neutron binding energies of these states were under inclusion of further states known from literature compared with shell model calculations according to the weak coupling method of Bansal and French. By a set of 4 parameters both the two-neutron binding energies of the (fsub(5/2), gsub(9/2)) 7 - and (gsub(9/2)) 2 sub(8+) states and the one-particle binding energies of the f - sub(5/2) and g + sub(5/2) one-neutron states over a large number of nuclei could very well be reproduced. For calculations on the states with the configuration (gsub(9/2), dsub(5/2)) 6 + the present data set is not yet sufficient. The found agreement of the calculations with the experimental data shows that two-neutron high spin states in the fp shell nuclei can be correctly described by this simple picture. (orig.) [de

On the difference between proton and neutron spin-orbit splittings in nuclei

International Nuclear Information System (INIS)

Isakov, V.I.; Erokhina, K.I.; Mach, H.; Sanchez-Vega, M.; Fogelberg, B.

2002-01-01

The latest experimental data on nuclei at 132 Sn permit us for the first time to determine the spin-orbit splittings of neutrons and protons in identical orbits in this neutron-rich doubly magic region and compare the case to that of 208 Pb. Using the new results, which are now consistent for the two neutron-rich doubly magic regions, a theoretical analysis defines the isotopic dependence of the mean-field spin-orbit potential and leads to a simple explicit expression for the difference between the spin-orbit splittings of neutrons and protons. The isotopic dependence is explained in the framework of different theoretical approaches. (orig.)

Nuclei with exotic constituents

International Nuclear Information System (INIS)

Yamazaki, Toshimitsu.

1990-08-01

We discuss various interesting features in the behavior of exotic constituents of nuclei such as hyperons and mesons, in particular, with emphases on the aspect of exotic halos which are formed in general by short-range repulsion and long-range attraction. Specifically, Λ and Σ hypernuclei and pionic nuclei are discussed. (author)

Angular Distributions of Neutrons from (p,n)-Reactions in some Mirror Nuclei

Energy Technology Data Exchange (ETDEWEB)

Stroemberg, L G; Wiedling, T; Holmqvist, B

1964-04-15

The angular distributions of neutrons from the reactions {sup 13}C (p,n) {sup 13}N and {sup 19}F (p, n) {sup 19}Ne have been measured for some energies close to the reactions threshold. For the reaction {sup 9}B (p, n) {sup 9}C angular distributions have been measured at several proton energies below the reaction threshold of the neutrons to the first excited state in {sup 11}C . A 5.5 MeV Van de Graaff has been used for the experiments. The neutrons were detected with a long counter. The measurements were carried out for 16 energies for the B (p,n) reaction, 3 energies for the C (p, n) reaction, and for 7 energies for the F 19(p, n) reaction. One of the main reasons for investigating these (p, n) reactions was to check whether the direct reaction process is important at low proton energies as well as close to reaction thresholds in nuclei consisting of closed shells of neutrons and protons either with an extra nucleon outside the closed shell or a nucleon hole. Comparisons with a theory proposed by Bloom, Glendenning, and Moszkowski have been performed.

Clusters in Nuclei. Vol. 2

International Nuclear Information System (INIS)

Beck, Christian

2012-01-01

Following the pioneering discovery of alpha clustering and of molecular resonances, the field of nuclear clustering is today one of those domains of heavy-ion nuclear physics that faces the greatest challenges, yet also contains the greatest opportunities. After many summer schools and workshops, in particular over the last decade, the community of nuclear molecular physicists has decided to collaborate in producing a comprehensive collection of lectures and tutorial reviews covering the field. This second volume follows the successful Lect. Notes Phys. 818 (Vol.1), and comprises six extensive lectures covering the following topics: - Microscopic cluster models - Neutron halo and break-up reactions - Break-up reaction models for two- and three-cluster projectiles - Clustering effects within the di-nuclear model - Nuclear alpha-particle condensates - Clusters in nuclei: experimental perspectives By promoting new ideas and developments while retaining a pedagogical style of presentation throughout, these lectures will serve as both a reference and an advanced teaching manual for future courses and schools in the fields of nuclear physics and nuclear astrophysics. (orig.)

Clusters in Nuclei. Vol. 2

Energy Technology Data Exchange (ETDEWEB)

Beck, Christian (ed.) [Strasbourg Univ. (France). Inst. Pluridiciplinaire Hubert Curien

2012-07-01

Following the pioneering discovery of alpha clustering and of molecular resonances, the field of nuclear clustering is today one of those domains of heavy-ion nuclear physics that faces the greatest challenges, yet also contains the greatest opportunities. After many summer schools and workshops, in particular over the last decade, the community of nuclear molecular physicists has decided to collaborate in producing a comprehensive collection of lectures and tutorial reviews covering the field. This second volume follows the successful Lect. Notes Phys. 818 (Vol.1), and comprises six extensive lectures covering the following topics: - Microscopic cluster models - Neutron halo and break-up reactions - Break-up reaction models for two- and three-cluster projectiles - Clustering effects within the di-nuclear model - Nuclear alpha-particle condensates - Clusters in nuclei: experimental perspectives By promoting new ideas and developments while retaining a pedagogical style of presentation throughout, these lectures will serve as both a reference and an advanced teaching manual for future courses and schools in the fields of nuclear physics and nuclear astrophysics. (orig.)

Observation of the one- to six-neutron transfer reactions at sub-barrier energies

Energy Technology Data Exchange (ETDEWEB)

Jiang, C.L.; Rehm, K.E.; Gehring, J. [and others

1995-08-01

It was suggested many years ago that when two heavy nuclei are in contact during a grazing collision, the transfer of several correlated neutron-pairs could occur. Despite considerable experimental effort, however, so far only cross sections for up to four-neutron transfers have been uniquely identified. The main difficulties in the study of multi-neutron transfer reactions are the small cross sections encountered at incident energies close to the barrier, and various experimental uncertainties which can complicate the analysis of these reactions. We have for the first time found evidence for multi-neutron transfer reactions covering the full sequence from one- to six-neutron transfer reactions at sub-barrier energies in the system {sup 58}Ni + {sup 100}Mo.

The angular clustering of WISE-selected active galactic nuclei: Different halos for obscured and unobscured active galactic nuclei

Energy Technology Data Exchange (ETDEWEB)

Donoso, E. [Instituto de Ciencias Astronómicas, de la Tierra, y del Espacio (ICATE), 5400 San Juan (Argentina); Yan, Lin [Infrared Processing and Analysis Center, Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Stern, D.; Assef, R. J. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

2014-07-01

We calculate the angular correlation function for a sample of ∼170,000 active galactic nuclei (AGNs) extracted from the Wide-field Infrared Survey Explorer (WISE) catalog, selected to have red mid-IR colors (W1 – W2 > 0.8) and 4.6 μm flux densities brighter than 0.14 mJy). The sample is expected to be >90% reliable at identifying AGNs and to have a mean redshift of (z) = 1.1. In total, the angular clustering of WISE AGNs is roughly similar to that of optical AGNs. We cross-match these objects with the photometric Sloan Digital Sky Survey catalog and distinguish obscured sources with r – W2 > 6 from bluer, unobscured AGNs. Obscured sources present a higher clustering signal than unobscured sources. Since the host galaxy morphologies of obscured AGNs are not typical red sequence elliptical galaxies and show disks in many cases, it is unlikely that the increased clustering strength of the obscured population is driven by a host galaxy segregation bias. By using relatively complete redshift distributions from the COSMOS survey, we find that obscured sources at (z) ∼ 0.9 have a bias of b = 2.9 ± 0.6 and are hosted in dark matter halos with a typical mass of log (M/M {sub ☉} h {sup –1}) ∼ 13.5. In contrast, unobscured AGNs at (z) ∼ 1.1 have a bias of b = 1.6 ± 0.6 and inhabit halos of log (M/M {sub ☉} h {sup –1}) ∼ 12.4. These findings suggest that obscured AGNs inhabit denser environments than unobscured AGNs, and they are difficult to reconcile with the simplest AGN unification models, where obscuration is driven solely by orientation.

Spectroscopy of neutron rich nuclei using cold neutron induced fission of actinide targets at the ILL: the EXILL campaign

Directory of Open Access Journals (Sweden)

de France G.

2014-03-01

Full Text Available A combination of germanium detectors has been installed at the PF1B neutron guide of the ILL to perform the prompt spectroscopy of neutron-rich nuclei produced in the neutron-capture induced-fission of 235U and 241Pu. In addition LaBr3 detectors from the FATIMA collaboration have been installed in complement with the EXOGAM clovers to measure lifetimes of low-lying excited states. The measured characteristics and online spectra indicate very good performances of the overall setup.

Relation between proton and neutron asymptotic normalization coefficients for light mirror nuclei and its relevance for nuclear astrophysics)

International Nuclear Information System (INIS)

Timofeyuk, N.K.; Johnson, R.C.; Descouvemont, P.

2005-01-01

In this talk, relation between proton and neutron Asymptotic Normalization Coefficients (ANCs) for light mirror nuclei will be discussed. This relation follows from charge symmetry of nucleon-nucleon interactions and is given by a simple approximate analytical formula which involves proton and neutron separation energies, charges of residual nuclei and the range of their strong interaction with the last nucleon. This relation is valid both for particle-bound mirror nuclear levels and for mirror pairs in which one of the levels is a narrow resonance. In the latter case, the width of this resonance is related to the ANC of its mirror particle-stable analog. Our theoretical study of mirror ANCs for several light nuclei within a framework of microscopic two-, three- and four-cluster models, have shown that the ratio of mirror ANCs changes as predicted by the simple approximate analytical formula. We will also compare the results from our microscopic calculations to the predictions of the single-particle model and discuss mirror symmetry of spectroscopic factors and single-particle ANCs. (author)

Fifth International Conference on Fission and Properties of Neutron-Rich Nuclei

CERN Document Server

Ramayya, A V; ICFN5

2014-01-01

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

Neutron diffraction experiments on ordered silver nuclei at Picokelvin temperatures

International Nuclear Information System (INIS)

Annila, A.J.; Hakonen, P.J.; Lounasmaa, O.V.; Nummila, K.K.; Oja, A.S.; Tuoriniemi, J.T.; Clausen, K.N.; Lindgaard, P.-A.; Siemensmeyer, K.; Steiner, M.; Weinfurter, H.; Viertioe, H.E.

1990-08-01

Nuclear spins in silver constitute an ideal antiferromagnetic spin - 1/2 model system in an fcc lattice. The nuclei are well localized and the interactions coupling the spins can be calculated from first principles. Strong quantum effects are expected owing to spin - 1/2. The magnetic phase diagram of the system has been investigated by several theoretical methods. In the present study the feasibility of neutron diffraction experiments on nuclear magnetic order in silver is discussed. The requirements for cryogenics and for neutron equipment are based on experience with current NMR measurements on sivler and with neutron diffraction work on copper. It is concluded that an experiment using an isotopically enriched specimen of either 107 Ag or 109 Ag is feasible but difficult. (author) 1 tab., 16 ills., 38 refs

Particle-number fluctuations and neutron-proton pairing effects on proton and neutron radii of even-even N Almost-Equal-To Z nuclei

Energy Technology Data Exchange (ETDEWEB)

Douici, M.; Allal, N. H.; Fellah, M.; Benhamouda, N.; Oudih, M. R. [Laboratoire de Physique Theorique, Faculte de Physique, USTHB BP 32 El-Alia, 16111 Bab-Ezzouar, Alger (Algeria) and Institut des Sciences et Technologie, Centre Universitaire de Khemis Miliana, Route de Theniet-El-Had, 44225 Khemis-Milia (Algeria); Laboratoire de Physique Theorique, Faculte de Physique, USTHB BP 32 El-Alia, 16111 Bab-Ezzouar, Alger (Algeria) and Centre de Recherche Nucleaire d' Alger, COMENA, BP399 Alger-Gare, Alger (Algeria); Laboratoire de Physique Theorique, Faculte de Physique, USTHB BP 32 El-Alia, 16111 Bab-Ezzouar, Alger (Algeria)

2012-10-20

The particle-number fluctuation effect on the root-mean-square (rms) proton and neutron radii of even-even N Almost-Equal-To Z nuclei is studied in the isovector neutron-proton (np) pairing case using an exact particle-number projection method and the Woods-Saxon model.

Evaluation of the total gamma-ray production cross-sections for nonelastic interaction of fast neutrons with iron nuclei

International Nuclear Information System (INIS)

Savin, M.V.; Nefedov, Yu.Ya; Livke, A.V.; Zvenigorodskij, A.G.

2001-01-01

Experimental data on the total gamma-ray production cross-sections for inelastic interaction of fast neutrons with iron nuclei were analysed. The total gamma-ray production cross-sections, grouped according to E γ , were evaluated in the neutron energy range 0.5-19 MeV. The statistical spline approximation method was used to evaluate the experimental data. Evaluated data stored in the ENDF, JENDL, BROND, and other libraries on gamma-ray production spectra and cross-sections for inelastic interaction of fast neutrons with iron nuclei, were analysed. (author)

Odd-odd neutron-excess nuclei from the magicity region close to 132Sn

International Nuclear Information System (INIS)

Erokhina, K.I.; Isakov, V.I.

1994-01-01

This is the second publication in a series devoted to theoretical study of neutron-excess nuclei close to the doubly magic nuclide 132 Sn. Odd-odd nuclei from this region are considered by using the quasi-boson approximation. Energy level spectra, electromagnetic transition probabilities, and β-decay properties of nuclei are analyzed. Among other things, the renormalization of the axial-vector constant in the nucleus is determined. Numerical calculations are made for 134 Sb, 130 In, 132 Sb, and 132 In nuclides. Whenever possible, the results are compared with experimental data. 33 refs., 11 figs., 1 tab

Second proton and neutron alignments in the doubly-odd nuclei 154,156Tb

International Nuclear Information System (INIS)

Hartley, D.J.; Allen, J.L.; Brown, T.B.; Kondev, F.G.; Pfohl, J.; Riley, M.A.; Fischer, S.M.; Janssens, R.V.; Nisius, D.T.; Fallon, P.; Ma, W.C.; Simpson, J.

1999-01-01

High-spin states in the doubly-odd nuclei 154,156 Tb have been populated in two separate experiments using the 36 S+ 124 Sn reaction at different beam energies (160 and 175 MeV). The yrast structures of both nuclei were extended to much higher spin (I≤48ℎ) than previously known and several quasiparticle alignments have been identified. These include the second neutron alignment and a clear delineation of the second proton crossing in 156 Tb. Systematics of these crossings for odd-Z nuclei and comparisons with results of cranked shell model calculations are discussed. thinsp copyright 1999 The American Physical Society

Cluster structures in light nuclei

International Nuclear Information System (INIS)

Horiuchi, H.

2000-01-01

Complete text of publication follows. Clustering in neutron-rich nuclei is discussed. To understand the novel features (1,2,3) of the clustering in neutron-rich nuclei, the basic features of the clustering in stable nuclei (4) are briefly reviewed. In neutron-rich nuclei, the requirement of the stability of clusters is questioned and the threshold rule is no more obeyed. Examples of clustering in Be and B isotopes (4,5) are discussed in some detail. Possible existence of novel type of clustering near neutron dripline is suggested (1). (author)

Neutron matter, neutron pairing, and neutron drops based on chiral effective field theory interactions

Energy Technology Data Exchange (ETDEWEB)

Krueger, Thomas

2016-10-19

The physics of neutron-rich systems is of great interest in nuclear and astrophysics. Precise knowledge of the properties of neutron-rich nuclei is crucial for understanding the synthesis of heavy elements. Infinite neutron matter determines properties of neutron stars, a final stage of heavy stars after a core-collapse supernova. It also provides a unique theoretical laboratory for nuclear forces. Strong interactions are determined by quantum chromodynamics (QCD). However, QCD is non-perturbative at low energies and one presently cannot directly calculate nuclear forces from it. Chiral effective field theory circumvents these problems and connects the symmetries of QCD to nuclear interactions. It naturally and systematically includes many-nucleon forces and gives access to uncertainty estimates. We use chiral interactions throughout all calculation in this thesis. Neutron stars are very extreme objects. The densities in their interior greatly exceed those in nuclei. The exact composition and properties of neutron stars is still unclear but they consist mainly of neutrons. One can explore neutron stars theoretically with calculations of neutron matter. In the inner core of neutron stars exist very high densities and thus maybe exotic phases of matter. To investigate whether there exists a phase transition to such phases even at moderate densities we study the chiral condensate in neutron matter, the order parameter of chiral symmetry breaking, and find no evidence for a phase transition at nuclear densities. We also calculate the more extreme system of spin-polarised neutron matter. With this we address the question whether there exists such a polarised phase in neutron stars and also provide a benchmark system for lattice QCD. We find spin-polarised neutron matter to be an almost non-interacting Fermi gas. To understand the cooling of neutron stars neutron pairing is of great importance. Due to the high densities especially triplet pairing is of interest. We

The neutron-proton pairing and the moments of inertia of the rare earth even-even nuclei

International Nuclear Information System (INIS)

Calik, A. E.; Deniz, C.; Gerceklioglu, M.

2009-01-01

In this study, the possible effect of the neutron-proton pairing interaction in the heavy nuclei has been investigated in the framework of the BCS model by making a simple approximation. This effect has been searched realistically by calculating the moments of inertia of deformed even-even nuclei. Calculations show that the moments of inertia of rare earth nuclei changed dramatically and approached the experimental values.

Investigation of the core-halo structure of the neutron-rich nuclei 6He and 8He by intermediate-energy elastic proton scattering at high momentum transfer

International Nuclear Information System (INIS)

Aksouh, F.

2002-12-01

The elastic proton scattering from the halo nuclei 6 He and 8 He was investigated in inverse kinematics at energies around 700 MeV/u with the aim to deduce the differential cross sections for the region of high momentum transfer, covering the first diffraction minimum. For this purpose, a liquid-hydrogen target was specially developed and used for the first time allowing to obtain low-background data as compared to commonly used targets made from C-H compounds. Previous data taken in the region of small momentum transfer were sensitive to the size and the peripheral shape of the total nuclear matter density distribution but not to the inner part. The present data allow for a more detailed insight in the structure of the alike core in 6,8 He through a better determination of the matter density distributions. Several density distributions calculated from different microscopic models were used to derive elastic scattering cross sections which are compared with the obtained data. (author)

Cross section measurements of fissile nuclei for slow neutrons; Mesures de sections efficaces de noyaux fissiles pour les neutrons lents

Energy Technology Data Exchange (ETDEWEB)

Auclair, J M; Hubert, P; Joly, R; Vendryes, G; Jacrot, B; Netter, F [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Galula, M [Centre National de la Recherche Scientifique (CNRS), 91 - Gif-sur-Yvette (France)

1955-07-01

It presents the experimental measurements of cross section of fissile nuclei for slow neutrons to improve the understanding of some heavy nuclei of great importance in the study of nuclear reactors. The different experiments are divided in three categories. In the first part, it studied the variation with energy of the cross sections of natural uranium, {sup 233}U, {sup 235}U and {sup 239}Pu. Two measurement techniques are used: the time-of-flight spectrometer and the crystal spectrometer. In a second part, the fission cross sections of {sup 233}U and {sup 239}Pu for thermal neutrons are compared using a neutron flux from EL-2 going through a double fission chamber. The matter quantity contained in each source is measured by counting the {alpha} activity with a solid angle counter. Finally, the average cross section of {sup 236}U for a spectra of neutrons from the reactor is measured by studying the {beta} activity of {sup 237}U formed by the reaction {sup 236}U (n, {gamma}) {sup 237}U in a sample of {sup 236}U irradiated in the Saclay reactor (EL-2). (M.P.)

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

Directory of Open Access Journals (Sweden)

Jia Jie Li

2016-02-01

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

Analyzing powers and interference between one- and multi-step processes in (polarized p, t) reactions on medium-mass vibrational nuclei

International Nuclear Information System (INIS)

Yagi, K.; Kunori, S.; Aoki, Y.; Nagano, K.; Tagishi, Y.

1978-01-01

A neutron-number (N) dependence of analyzing powers A (theta) has been observed for the first time in (polarized p, t) reactions leading to the quadrupole vibrational states (2 1 + ) in 98 Ru, sup(102,108)Pd, 114 Cd, 116 Sn, and sup(120,126)Te. Although analyzing powers for the ground-state transitions A(theta,0 sub(g)sup(+)) are very similar to each other, those for the 2 1 + transitions A(theta,2 1 + ) for the nuclei belonging to the beginning of the N = 50 - 82 shell are markedly different, having almost opposite signs, from A(theta,2 1 + ) for nuclei belonging to the latter half of the major shell. The difference is explained as a result of a sign change of the interference between one- and inelastic multi-step processes in two-neutron pickup reactions. Nuclear structure effects on such an interference are discussed on the basis of the microscopic description of collective quadrupole oscillation of nuclei. (author)

Neutron and Proton Diffusion in Fusion Reactions for the Synthesis of Superheavy Nuclei

International Nuclear Information System (INIS)

Ming-Hui, Huang; Zai-Guo, Gan; Zhao-Qing, Feng; Xiao-Hong, Zhou; Jun-Qing, Li

2008-01-01

The restriction of the one dimensional (1D) master equation (ME) with the mass number of the projectile-like fragment as a variable is studied, and a two-dimensional (2D) master equation with the neutron and proton numbers as independent variables is set up, and solved numerically. Our study showed that the 2D ME can describe the fusion process well in all projectile-target combinations. Therefore the possible channels to synthesize super-heavy nuclei can be studied correctly in wider possibilities. The available condition for employing 1D ME is pointed out

Importance of nuclear triaxiality for electromagnetic strength, level density and neutron capture cross sections in heavy nuclei

CERN Document Server

Grosse, Eckart; Massarczyk, Ralph

2014-01-01

Cross sections for neutron capture in the range of unresolved resonances are predicted simultaneously to level distances at the neutron threshold for more than 100 spin-0 target nuclei with A >70. Assuming triaxiality in nearly all these nuclei a combined parameterization for both, level density and photon strength is presented. The strength functions used are based on a global fit to IVGDR shapes by the sum of three Lorentzians adding up to the TRK sum rule and theory-based predictions for the A-dependence of pole energies and spreading widths. For the small spins reached by capture level densities are well described by only one free global parameter; a significant collective enhancement due to the deviation from axial symmetry is observed. Reliable predictions for compound nuclear reactions also outside the valley of stability as expected from the derived global parameterization are important for nuclear astrophysics and for the transmutation of nuclear waste.

Neutron-rich isotopes around the r-process 'waiting-point' nuclei 2979Cu50 and 3080Zn50

International Nuclear Information System (INIS)

Kratz, K.L.; Gabelmann, H.; Pfeiffer, B.; Woehr, A.

1991-01-01

Beta-decay half-lives (T 1/2 ) and delayed-neutron emission probabilities (P n ) of very neutron-rich Cu to As nuclei have been measured, among them the new isotopes 77 Cu 48 , 79 Cu 50 , 81 Zn 51 and 84 Ga 53 . With the T 1/2 and P n -values of now four N≅50 'waiting-point' nuclei known, our hypothesis that the r-process has attained a local β-flow equilibrium around A≅80 is further strengthened. (orig.)

HIGH ENERGY NEUTRINOS PRODUCED IN THE ACCRETION DISKS BY NEUTRONS FROM NUCLEI DISINTEGRATED IN THE AGN JETS

Energy Technology Data Exchange (ETDEWEB)

Bednarek, W., E-mail: bednar@uni.lodz.pl [Department of Astrophysics, The University of Lodz, 90-236 Lodz, ul. Pomorska 149/153 (Poland)

2016-12-20

We investigate the consequences of acceleration of nuclei in jets of active galaxies not far from the surface of an accretion disk. The nuclei can be accelerated in the re-connection regions in the jet and/or at the jet boundary, between the relativistic jet and its cocoon. It is shown that the relativistic nuclei can efficiently fragment onto specific nucleons in collisions with the disk radiation. Neutrons, directed toward the accretion disk, take a significant part of energy from the relativistic nuclei. These neutrons develop a cascade in the dense accretion disk. We calculate the neutrino spectra produced in such a hadronic cascade within the accretion disk. We propose that the neutrinos produced in such a scenario, from the whole population of super-massive black holes in active galaxies, can explain the extragalactic neutrino background recently measured by the IceCube neutrino detector, provided that a 5% fraction of galaxies have an active galactic nucleus and a few percent of neutrons reach the accretion disk. We predict that the neutrino signals in the present neutrino detectors, produced in terms of such a model, will not be detectable even from the nearby radio galaxies similar to M87.

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

Energy Technology Data Exchange (ETDEWEB)

Rykaczewski, K. [Oak Ridge National Lab., TN (United States). Physics Div.]|[ISOLDE-CERN, Geneva (Switzerland)]|[Univ. of Warsaw (Poland); Kurpeta, J.; Plochocki, A. [Univ. of Warsaw (Poland)] [and others

1998-11-01

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

Relativistic Hartree-Bogoliubov description of the halo nuclei

Energy Technology Data Exchange (ETDEWEB)

Meng, J.; Ring, P. [Universitaet Muenchen, Garching (Germany)

1996-12-31

Here the authors report the development of the relativistic Hartree-Bogoliubov theory in coordinate space. Pairing correlations are taken into account by both density dependent force of zero range and finite range Gogny force. As a primary application the relativistic HB theory is used to describe the chain of Lithium isotopes reaching from {sup 6}Li to {sup 11}Li. In contrast to earlier investigations within a relativistic mean field theory and a density dependent Hartree Fock theory, where the halo in {sup 11}Li could only be reproduced by an artificial shift of the 1p{sub 1/2} level close to the continuum limit, the halo is now reproduced in a self-consistent way without further modifications using the scattering of Cooper pairs to the 2s{sub 1/2} level in the continuum. Excellent agreement with recent experimental data is observed.

Neutron-induced cross sections of short-lived nuclei via the surrogate reaction method

Directory of Open Access Journals (Sweden)

Morel P.

2011-10-01

Full Text Available The measurement of neutron-induced cross sections of short-lived nuclei is extremely difficult due to the radioactivity of the samples. The surrogate reaction method is an indirect way of determining cross sections for nuclear reactions that proceed through a compound nucleus. This method presents the advantage that the target material can be stable or less radioactive than the material required for a neutron-induced measurement. We have successfully used the surrogate reaction method to extract neutron-induced fission cross sections of various short-lived actinides. In this work, we investigate whether this technique can be used to determine neutron-induced capture cross sections in the rare-earth region.

Neutron-induced cross sections of short-lived nuclei via the surrogate reaction method

Directory of Open Access Journals (Sweden)

Tassan-Got L.

2012-02-01

Full Text Available The measurement of neutron-induced cross sections of short-lived nuclei is extremely difficult due to the radioactivity of the samples. The surrogate reaction method is an indirect way of determining cross sections for nuclear reactions that proceed through a compound nucleus. This method presents the advantage that the target material can be stable or less radioactive than the material required for a neutron-induced measurement. We have successfully used the surrogate reaction method to extract neutron-induced fission cross sections of various short-lived actinides. In this work, we investigate whether this technique can be used to determine neutron-induced capture cross sections in the rare-earth region.

Study of very neutron-rich nuclei produced by means of a 48Ca beam

International Nuclear Information System (INIS)

Lewitowicz, M.; Artukh, A.G.

1991-01-01

The results of experiments with a 48 Ca beam performed at GANIL are presented and discussed. More than 30 very neutron-rich isotopes were identified or studied for the first time. The evidence for particle-unstable character of the 26 O isotope is reported. Half-life measurements for light neutron rich nuclei are compared with different theoretical predictions. (author) 14 refs.; 6 figs.; 1 tab

New mass analysis and results for neutron rich nuclei performed with isochronous mass spectrometry

Energy Technology Data Exchange (ETDEWEB)

Diwisch, Marcel [Justus-Liebig-Universitaet Giessen, Giessen (Germany); Knoebel, Ronja; Geissel, Hans; Plass, Wolfgang; Scheidenberger, Christoph [Justus-Liebig-Universitaet Giessen, Giessen (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Patyk, Zygmunt [Soltan Institute for Nuclear Studies, Warsaw (Poland); Weick, Helmut [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany)

2015-07-01

The Isochronous Mass Spectrometry (IMS) allows to measure masses of rare exotic nuclei in a storage ring in a timescale of tens of μs. The ring is operated in an isochronous mode, i.e. such that particles with different velocities but same mass-to-charge ratio (m/q) travel different paths in the ring arcs (faster ions travel longer paths whereas slower ions travel shorter paths). This means that for each m/q a fix revolution time exists and can be measured by a time-of-flight (TOF) detector which then yields the masses of the nuclei for known charge states. A new analysis approach of IMS data with a correlation matrix method allowed combining data with different quality. The latest production run was using an additional determination of the magnetic rigidity which increased the resolving power of the experiment. Combining this experiment with previous experiments one can increase the statistics and accuracy of the overall mass determination. It was possible to deduce mass values of neutron rich isotopes which have not been measured before. One of those isotopes is {sup 130}Cd which is a very important nuclei involved in the r-process. Those mass values and a comparison to theoretical predictions will be presented in the poster.

Semi-empirical neutron tool calibration (one and two-group approximation)

International Nuclear Information System (INIS)

Czubek, J.A.

1988-01-01

The physical principles of the new method of calibration of neutron tools for the rock porosity determination are given. A short description of the physics of neutron transport in the matter is presented together with some remarks on the elementary interactions of neutrons with nuclei (cross sections, group cross sections etc.). The definitions of the main integral parameters characterizing the neutron transport in the rock media are given. The three main approaches to the calibration problem: empirical, theoretical and semi-empirical are presented with some more detailed description of the latter one. The new semi-empirical approach is described. The method is based on the definition of the apparent slowing down or migration length for neutrons sensed by the neutron tool situated in the real borehole-rock conditions. To calculate this apparent slowing down or migration lengths the ratio of the proper space moments of the neutron distribution along the borehole axis is used. Theoretical results are given for one- and two-group diffusion approximations in the rock-borehole geometrical conditions when the tool is in the sidewall position. The physical and chemical parameters are given for the calibration blocks of the Logging Company in Zielona Gora. Using these data the neutron parameters of the calibration blocks have been calculated. An example, how to determine the calibration curve for the dual detector tool applying this new method and using the neutron parameters mentioned above together with the measurements performed in the calibration blocks, is given. The most important advantage of the new semi-empirical method of calibration is the possibility of setting on the unique calibration curve all experimental calibration data obtained for a given neutron tool for different porosities, lithologies and borehole diameters. 52 refs., 21 figs., 21 tabs. (author)

Neutron roton pairing effect on some even ven rare-earth proton-rich nuclei

International Nuclear Information System (INIS)

Mokhtari, D.

2004-01-01

The neutron roton pairing effect on some even ven rare-earth proton-rich nuclei is studied. It is taken into account, in the isovector case, within the framework of the generalized Bogoliubov-Valatin transformation, using Woods-Saxon single-particle energies. (author)

Hot nuclei studies with a 4 π-Neutron detector

International Nuclear Information System (INIS)

Galin, J.; Crema, E.; Doubre, H.; Guerreau, D.; Jiang, D.X.; Morjean, M.; Piasecki, E.; Pouthas, J.; Saint-Laurent, F.; Sokolov, A.; Wang, X.D.; Charvet, J.L.; Frehaut, J.; Lott, B.; Magnago, C.; Patin, Y.; Gatty, B.; Jacquet, D.; Lott, B.

1989-01-01

When studying the behavior of hot nuclei, the challenge is twofold: how are they formed in nucleus-nucleus collisions and how do they decay Systematic studies have been undertaken at GANIL by bombarding heavy targets (Au, Th) with intermediate energy projectiles (27, 35, 44 and 77 MeV/u Ar and 32 MeV/u Kr). For such neutron rich systems the thermalized energy can be roughly evaluated simply by measuring the multiplicity of evaporated neutrons using a 4 π Gd loaded, liquid scintillator detector. The influence of the bombarding energy and projectile mass on the energy dissipation has been investigated for different exit channels and special emphasis has been put in the study of the most dissipative collisions. The thermal energy, derived by summing the energy removed by both evaporated neutrons and light charged particles is shown to saturate at E * ≅ 650 MeV in the Ar induced reactions between 27 and 77 MeV/u, in good consistency with the predictions of semi-classical Landau-Vlasov calculations

The Excursion Set Theory of Halo Mass Functions, Halo Clustering, and Halo Growth

Science.gov (United States)

Zentner, Andrew R.

I review the excursion set theory with particular attention toward applications to cold dark matter halo formation and growth, halo abundance, and halo clustering. After a brief introduction to notation and conventions, I begin by recounting the heuristic argument leading to the mass function of bound objects given by Press and Schechter. I then review the more formal derivation of the Press-Schechter halo mass function that makes use of excursion sets of the density field. The excursion set formalism is powerful and can be applied to numerous other problems. I review the excursion set formalism for describing both halo clustering and bias and the properties of void regions. As one of the most enduring legacies of the excursion set approach and one of its most common applications, I spend considerable time reviewing the excursion set theory of halo growth. This section of the review culminates with the description of two Monte Carlo methods for generating ensembles of halo mass accretion histories. In the last section, I emphasize that the standard excursion set approach is the result of several simplifying assumptions. Dropping these assumptions can lead to more faithful predictions and open excursion set theory to new applications. One such assumption is that the height of the barriers that define collapsed objects is a constant function of scale. I illustrate the implementation of the excursion set approach for barriers of arbitrary shape. One such application is the now well-known improvement of the excursion set mass function derived from the "moving" barrier for ellipsoidal collapse. I also emphasize that the statement that halo accretion histories are independent of halo environment in the excursion set approach is not a general prediction of the theory. It is a simplifying assumption. I review the method for constructing correlated random walks of the density field in the more general case. I construct a simple toy model to illustrate that excursion set

Fast neutron scattering from soft nuclei: coupled-channel formalism and illustrations

International Nuclear Information System (INIS)

Delaroche, J.P.

1986-01-01

Spectra of most of the even-even nuclei have a character which is neither that of a pure vibrator nor that of a pure rotor. Instead, the nuclear spectra display very often both characters. Therefore, improvements in the analysises of nucleon scattering and reaction cross sections require that appropriate collective models of nuclear structure be used. A selection of these models is reviewed, and suggestions are given as to how to extend the familiar coupled-channel formalism to incorporate these enriched collective pictures. These extensions are primarily intended to describe inelastic scattering from levels belonging to β - , γ - and octupole bands. Illustrations are given for neutron and proton scattering off various nuclei [fr

Monte Carlo simulations with MENATE program in order to determine the characteristics of neutron multidetector

International Nuclear Information System (INIS)

Petrascu, M.; Isbasescu, Alina; Constantinescu, A.; Serban, S.; Stoica, I.V.

2004-01-01

The neutron multidetector consists of 81 detectors, made of 4x4x12 cmc BC-400 crystals mounted on XP2972 phototubes. This detector placed in the forward direction at 138 cm from the target, was used to detect the correlated neutrons in the fusion of Li11 halo nuclei with Si targets. To verify the criterion for selecting the true coincidences against cross-talk ( a spurious effect in which the same neutron is registered by two or more detectors) and to establish the optimal distance between adjacent detectors, the program MENATE ( written by P.Desesquelles, IPN - Orsay) was used to generate Monte Carlo neutrons and their interactions in multidetector. The results were analysed with PAW (from CERN Library). (authors)

$\\beta$ - decay asymmetry in mirror nuclei: A = 9

CERN Multimedia

Axelsson, L E; Smedberg, M

2002-01-01

Investigations of light nuclei close to the drip lines have revealed new and intriguing features of the nuclear structure. The occurrence of halo structures in loosely bound systems has had a great impact on the nuclear physics research in the last years. As intriguing but not yet solved is the nature of transitions with very large $\\beta$ - strength. \\\\ \\\\We report here on the investigation of this latter feature by an accurate measurement of the $\\beta$ - decay asymmetry between the mirror nuclei in the A=9 mass chain.\\\\ \\\\The possible asymmetry for the decay to the states around 12 MeV is interesting not only due to the fact that the individual B$_{GT}$ values are large (with large overlap in wave-functions, an unambiguous interpretation is much easier made), but also due to the special role played by this transition for the $^{9}$Li decay. It seems to belong to a class of high-B$_{GT}$ transitions observed at the neutron drip line and has been suggested to be due either to a lowering of the giant Gamow-Te...

The astrophysical r-process and its dependence on properties of nuclei far from stability: Beta strength functions and neutron capture rates

International Nuclear Information System (INIS)

Klapdor, H.V.; Metzinger, J.; Oda, T.; Thielemann, F.K.; Hillebrandt, W.

1981-01-01

The question of the astrophysical site of the rapid neutron capture (r-) process which is believed to be responsible for the production of the heavy elements in the universe has been a problem in astrophysics for more than two decades. The solution of this problem is not only dependent on the development of realistic astrophysical supernova models, i.e. correct treatment of the hydrodynamics of gravitational collapse and supernova explosion and the equation of state of hot and dense matter, but is shown in this paper to be very sensitive also to 'standard' nuclear physics properties of nuclei far from stability such as beta decay properties and neutron capture rates. For both of the latter, strongly oversimplifying assumptions, not applying the development in nuclear physics during the last decade, have been made in almost all r-process calculations performed up to now. A critical discussion of the state of the art of such calculations seems therefore to be indicated. In this paper procedures are described which allow one to obtain: 1) β-decay properties (decay rates, β-delayed neutron emissions and fission rates); 2) neutron capture rates for neutron-rich nuclei considerably improved over what has been used up to now. The beta strength functions are calculated for approx. equal to6000 nuclei between beta stability line and neutron drip line. By hydrodynamical supernova explosion calculations using realistic stellar models it is shown that as a consequence of the improved β-rates explosive He burning is a convincing alternative site to the 'classical' r-process whose existence still is questionable. The new β-rates will be important also for the investigation of further astrophysical sites producing heavy elements such as the r(n)-processes in explosive C or Ne burning. (orig.)

Neutron-skin thickness of finite nuclei in relativistic mean-field models with chiral limits

International Nuclear Information System (INIS)

Jiang Weizhou; Li Baoan; Chen Liewen

2007-01-01

We study several structure properties of finite nuclei using relativistic mean-field Lagrangians constructed according to the Brown-Rho scaling due to the chiral symmetry restoration at high densities. The models are consistent with current experimental constraints for the equations of state of symmetric matter at both normal and supranormal densities and of asymmetric matter at subsaturation densities. It is shown that these models can successfully describe the binding energies and charge radii of finite nuclei. Compared to calculations with usual relativistic mean-field models, these models give a reduced thickness of neutron skin in 208 Pb between 0.17 fm and 0.21 fm. The reduction of the predicted neutron skin thickness is found to be due to not only the softening of the symmetry energy but also the scaling property of ρ meson required by the partial restoration of chiral symmetry

Interaction of polarized neutrons with polarized La nuclei and the structure of the cross section at energies up to 20 eV

International Nuclear Information System (INIS)

Alfimenkov, V.P.; Mareev, Yu.D.; Novitskii, V.V.; Pikel'ner, L.B.; Skoi, V.R.

1994-01-01

Properties of lanthanum are investigated in an experiment on the interaction of polarized neutrons with polarized La nuclei. The total cross section for lanthanum is measured for neutron energies ranging from 0.4 to 10 eV. It is shown that one strong level below the neutron binding energy is sufficient for obtaining a good description of the lanthanum cross section in this energy range. The results on the cross section for the interaction of polarized projectiles on a polarized target confirm this conclusion. The spin of the 138 La neutron resonance at 3.0 eV is found to be J = 11 / 2 . 13 refs., 3 figs

Evolution of collectivity in neutron-rich nuclei in the 132Sn region

International Nuclear Information System (INIS)

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

2006-01-01

Motivated by the observed regularity in the energy spectra and the structure of the shell model wave functions for the levels of 137 Te and 137 I, a few weakly and moderately deformed neutron-rich odd-A nuclei above the doubly magic nucleus 132 Sn 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

High-energy neutron yields in interactions of carbon ions with 114Sn and 124Sn nuclei

International Nuclear Information System (INIS)

Blinov, M.B.; Gavrilov, B.P.; Kovalenko, S.S.; Kozulin, Eh.M.; Mozhaev, A.N.; Oganesyan, Yu.Ts.; Penionzhkevich, Yu.Eh.

1984-01-01

The measurements of the yields of neutrons (energy more than 5 MeV) emitted in the interactions of carbon-12 ions (9 MeV/nucl.) with nuclei of two tin isotopes are conducted. The results obtained prove the effect of nucleon composition of a nucleus on the process of formation of high-energy neutrons. To clarify the concrete interaction mechanism it is necessary to perform systematic research for a number of isotopes differing in the relation of the number of neutrons and protons and binding energies of the last neutron

First delayed neutron emission measurements at ALTO with the neutron detector TETRA

International Nuclear Information System (INIS)

Testov, D.; Ancelin, S.; Bettane, J.; Ibrahim, F.; Kolos, K.; Mavilla, G.; Niikura, M.; Verney, D.; Wilson, J.; Kuznetsova, E.; Penionzhkevich, Yu.; Smirnov, V.; Sokol, E.

2013-01-01

Beta-decay properties are among the easiest and, therefore, the first ones to be measured to study new neutron-rich isotopes. Eventually, a very small number of nuclei could be sufficient to estimate their lifetime and neutron emission probability. With the new radioactive beam facilities which have been commissioned recently (or will be constructed shortly) new areas of neutron-rich isotopes will become reachable. To study beta-decay properties of such nuclei at IPN (Orsay) in the framework of collaboration with JINR (Dubna), a new experimental setup including the neutron detector of high efficiency TETRA was developed and commissioned

Charged particles produced in neutron reactions on nuclei from beryllium to gold

International Nuclear Information System (INIS)

Haight, R.C.

1997-01-01

Charged-particle production in reactions of neutrons with nuclei has been studied over the past several years with the spallation source of neutrons from 1 to 50 MeV at the Los Alamos Neutron Science Center (LANSCE). Target nuclides include 9Be, C, 27Al, Si, 56Fe, 59Co, 58,60Ni, 93Nb and 197Au. Proton, deuteron, triton, 3He and 4He emission spectra, angular distributions and production cross sections have been measured. Transitions from the compound nuclear reaction mechanism to precompound reactions are clearly seen in the data. The data are compared with data from the literature where available, with evaluated nuclear data libraries, and with calculations where the selection of the nuclear level density prescription is of great importance. Calculations normalized at En = 14 MeV can differ from the present data by a factor of 2 for neutron energies between 5 and 10 MeV

Manifestation of the halo structure in momentum distributions from {sup 6}He fragmentation

Energy Technology Data Exchange (ETDEWEB)

Aumann, T. [Mainz Univ. (Germany). Inst. fuer Kernchemie; Chulkov, L.V.; Pribora, V.N. [Rossijskij Nauchnyj Tsentr ``Kurchatovskij Inst.``, Moscow (Russian Federation); Smedberg, M.H. [Chalmers Univ. of Technology, Goeteborg (Sweden)

1998-03-01

Experimental data on momentum distribution in the fragmentation of a 240 MeV/u {sup 6}He beam on a carbon target are compared with several models of the {sup 6}He nucleus based on different physical assumptions. It is shown that a lack of a strict theoretical description of the fragmentation mechanism and, in particular, of the final state interaction prevents from any contra or versa arguments for these models. The requirement of a fragment ({sup 5}He) survival or spatial localization of a fragment in the {sup 6}He wave function is an essential point in the reaction mechanism. The analysis of the {sup 5}He momentum (sum of the neutron and the {alpha}-particle momenta) distribution is free from the effect of final state interaction and thus more promising. It is shown that due to the requirement of fragment survival this distribution is determined mainly by the asymptotic of the {sup 6}He wave function. Large sensitivity to the outer part of the halo structure gives a unique possibility to estimate the admixture of s-waves in the ground states of {sup 11}Li and {sup 14}Be directly from the momentum distribution of {sup 10}Li (in fragmentation of {sup 11}Li) and from the momentum distribution of {sup 13}Be (in fragmentation of {sup 14}Be). The shell structure of these nuclei is of great interest in understanding the neutron-halo properties. (orig.)

Mass measurement of halo nuclides and beam cooling with the mass spectrometer Mistral; Mesure de masse de noyaux a halo et refroidissement de faisceaux avec l'experience MISTRAL

Energy Technology Data Exchange (ETDEWEB)

Bachelet, C

2004-12-01

Halo nuclides are a spectacular drip-line phenomenon and their description pushes nuclear theories to their limits. The most critical input parameter is the nuclear binding energy; a quantity that requires excellent measurement precision, since the two-neutron separation energy is small at the drip-line by definition. Moreover halo nuclides are typically very short-lived. Thus, a high accuracy instrument using a quick method of measurement is necessary. MISTRAL is such an instrument; it is a radiofrequency transmission mass spectrometer located at ISOLDE/CERN. In July 2003 we measured the mass of the Li{sup 11}, a two-neutron halo nuclide. Our measurement improves the precision by a factor 6, with an error of 5 keV. Moreover the measurement gives a two-neutron separation energy 20% higher than the previous value. This measurement has an impact on the radius of the nucleus, and on the state of the two valence neutrons. At the same time, a measurement of the Be{sup 11} was performed with an uncertainty of 4 keV, in excellent agreement with previous measurements. In order to measure the mass of the two-neutron halo nuclide Be{sup 14}, an ion beam cooling system is presently under development which will increase the sensitivity of the spectrometer. The second part of this work presents the development of this beam cooler using a gas-filled Paul trap. (author)

Projected shell model study of yrast states of neutron-deficient odd-mass Pr nuclei

International Nuclear Information System (INIS)

Ibanez-Sandoval, A.; Ortiz, M. E.; Velazquez, V.; Galindo-Uribarri, A.; Hess, P. O.; Sun, Y.

2011-01-01

A wide variety of modern instruments allow us to study neutron-deficient nuclei in the A=130 mass region. Highly deformed nuclei have been found in this region, providing opportunities to study the deformed rotational bands. The description of the 125,127,129,131,133 Pr isotopes with the projected shell model is presented in this paper. Good agreement between theory and experiment is obtained and some characteristics are discussed, including the dynamic moment of inertia J (2) , kinetic moment of inertia J (1) , the crossing of rotational bands, and backbending effects.

Beam halo in high-intensity beams

International Nuclear Information System (INIS)

Wangler, T.P.

1993-01-01

In space-charge dominated beams the nonlinear space-charge forces produce a filamentation pattern, which in projection to the 2-D phase spaces results in a 2-component beam consisting of an inner core and a diffuse outer halo. The beam-halo is of concern for a next generation of cw, high-power proton linacs that could be applied to intense neutron generators for nuclear materials processing. The author describes what has been learned about beam halo and the evolution of space-charge dominated beams using numerical simulations of initial laminar beams in uniform linear focusing channels. Initial results are presented from a study of beam entropy for an intense space-charge dominated beam

Evolution of the low-lying dipole strength in deformed nuclei with extreme neutron excess with the Relativistic QRPA

International Nuclear Information System (INIS)

Pena Arteaga, D.; Khan, E.; Ring, P.

2009-01-01

Covariant density functional theory, in the framework of self-consistent Relativistic Hartree Bogoliubov (HFB) and Relativistic Quasiparticle Random Phase approximation (RQRPA), is for the first time applied to axially deformed nuclei [1]. The fully self-consistent RHB+RQRPA equations are posed for the case of axial symmetry and different energy functionals, and solved with the help of a new parallel code. As a sample application, the El strength is systematically analyzed in very neutron-rich Sn nuclei, beyond 1 32S n until 1 66S n [2]. The great neutron excess favors the appearance of a deformed ground state for 1 42-162S n. The evolution of the low-lying strength in deformed nuclei is discussed, and in particular its dependence on the interplay of two major and competing factors, isospin asymmetry and deformation.(author)

Array detector for neutron pre-emission investigations

International Nuclear Information System (INIS)

Petrascu, M.; Cruceru, I.; Bordeanu, C.

1999-01-01

It was predicted that in a fusion experiment induced by 11 Li halo nuclei on light targets, due to the very large dimension of 11 Li, one may expect that the valence neutrons will not be absorbed together with the 9 Li core, but will be emitted in the early stage of the fusion process. The experiment aiming at checking this expectation was performed at the RIKEN-RIPS facility. It was found from neutron energy spectra measurements, that an important number of fusions, more than 30%, are preceded by the pre-emission of one or two neutrons. In the position spectra measurements a very narrow neutron component has been found. This component is much narrower than that calculated by using the Cluster Shell Model Approximation (COSMA). The recent results of time- position coincidence measurements show that within the narrow component the neutrons are pre-emitted predominantly as neutron pairs. The Program Advisory Committee of RIKEN has approved a new measurement at RIKEN Ring Cyclotron aiming at investigation of neutron-neutron coincidences by using a new neutron array detector. This detector has been recently accomplished within the collaboration existing between IFIN-HH, Romania and RIKEN, Japan. The array system consists of 81 4 x 4 x 12 cm 3 BC400 plastic scintillators each coupled to XP2972 Phototubes. The mounting and the testing of the new neutron array detector will be done at RIKEN. The components of one of the 81 elements of the array detector are shown in a photo. The Monte Carlo calculated neutron detection efficiencies as a function of energy are shown. This detector will be used for the investigation of neutron-neutron coincidences in the case of Si( 11 Li, fusion) reaction. The cross- talk between adjacent and non adjacent detectors will be determined by using a 9 Li beam. As it is known in the case of Si( 9 Li, fusion) the neutrons are of evaporation origin, and since these neutrons are emitted in 4 π the chance for detecting 2 coincident neutrons in the

Effects of tensor forces in nuclei

International Nuclear Information System (INIS)

Tanihata, Isao

2013-01-01

Recent studies of nuclei far from the stability line have revealed drastic changes in nuclear orbitals and reported the appearance of new magic numbers and the disappearance of magic numbers observed at the stability line. One of the important reasons for such changes is considered to be because of the effect of tensor forces on nuclear structure. Although the role of tensor forces in binding very light nuclei such as deuterons and 4 He has been known, direct experimental evidence for the effect on nuclear structure is scarce. In this paper, I review known effects of tensor forces in nuclei and then discuss the recently raised question of s–p wave mixing in a halo nucleus of 11 Li. Following these reviews, the development of a new experiment to see the high-momentum components due to the tensor forces is discussed and some of the new data are presented. (paper)

Study of reactions induced by the halo nucleus 11Li with the active target MAYA

International Nuclear Information System (INIS)

Roger, Th.

2009-09-01

Active targets are perfect tools for the study of nuclear reactions induced by very low intensity radioactive ion beams. They also enable the simultaneous study of direct and compound nuclear reactions. The active target MAYA, built at GANIL, has been used to study the reactions induced by a 4.3*A MeV 11 Li beam at the ISAC2 accelerator TRIUMF (Canada). The angular distributions for the elastic scattering and the one and two neutron transfer reaction have been reconstructed. The elastic scattering angular distribution indicates a strong enhancement of the flux absorption with respect to the neighbouring nuclei. From a coupled channel analysis of the two neutron transfer reaction for different three body models, the information on the structure of the halo of the Borromean nucleus 11 Li have been extracted. Meanwhile, the energy dependence of the elastic scattering reaction has been studied, using the active target MAYA as a thick target. The resulting spectrum shows a resonance around 3 MeV centre of mass. This resonance could be an isobaric analog state of 12 Li, observed in 12 Be. R matrix calculations have been performed in order to extract the parameters (spin and parity) of this state. (author)

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

Science.gov (United States)

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

2010-04-01

The structure of neutron-rich nuclei in the vicinity of 78Ni have been investigated via the β-decay of 71,73,75Cu isotopes (ISOLDE, CERN). Experimental results have been compared with shell-model calculations performed with the ANTOINE code using a large (2p3/21f5/22p1/21g9/2) valence space and a 56/28Ni28 core.

Spectroscopy on neutron-rich nuclei at RIKEN. Present and future

International Nuclear Information System (INIS)

Sakurai, H.

2003-01-01

Recent studies on nuclear structure by using radioactive isotope beams available at the RIKEN projectile-fragment separator (RIPS) are introduced. Special emphasis is given to experiments selected from the recent programs that highlight studies at N=20-28; on the large deformation of 30 Ne and 34 Mg via the in-beam gamma spectroscopy, and on the particle stability of very neutron-rich nuclei, 34 Ne, 37 Na and 43 Si. The RI Beam Factory (RIBF) project is illustrated through review of such present research activities at RIPS. (author)

Measurement method of activation cross-sections of reactions producing short-lived nuclei with 14 MeV neutrons

CERN Document Server

Kawade, K; Kasugai, Y; Shibata, M; Iida, T; Takahashi, A; Fukahori, T

2003-01-01

We describe a method for obtaining reliable activation cross-sections in the neutron energy range between 13.4 and 14.9 MeV for the reactions producing short-lived nuclei with half-lives between 0.5 and 30 min. We noted neutron irradiation fields and measured induced activities, including (1) the contribution of scattered low-energy neutrons, (2) the fluctuation of the neutron fluence rate during the irradiation, (3) the true coincidence sum effect, (4) the random coincidence sum effect, (5) the deviation in the measuring position due to finite sample thickness, (6) the self-absorption of the gamma-ray in the sample material and (7) the interference reactions producing the same radionuclides or the ones emitting the gamma-ray with the same energy of interest. The cross-sections can be obtained within a total error of 3.6%, when good counting statistics are achieved, including an error of 3.0% for the standard cross-section of sup 2 sup 7 Al (n, alpha) sup 2 sup 4 Na. We propose here simple methods for measuri...

Descriptions of carbon isotopes within the energy density functional theory

International Nuclear Information System (INIS)

Ismail, Atef; Cheong, Lee Yen; Yahya, Noorhana; Tammam, M.

2014-01-01

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 15 C, 17 C and 19 C, and the two-neutron halo structures in 16 C and 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

Level structures in Yb nuclei far from stable nuclei

International Nuclear Information System (INIS)

Hashizume, Akira

1982-01-01

Applying n-γ, γ-γ coincidence techniques, the excited levels in 158 Yb and in 157 Yb nuclei were studied. Stress is placed ona neutron detection technique to assign (HI,xn) reactions which produce the nuclei far from β stability line. (author)

Production of neutron-rich nuclei in fission induced by neutrons generated by the p+ sup 1 sup 3 C reaction at 55 MeV

CERN Document Server

Stroe, L; Andrighetto, A; Tecchio, L B; Dendooven, P; Huikari, J; Pentillä, H; Peraejaervi, K; Wang, Y

2003-01-01

Cross-sections for the production of neutron-rich nuclei obtained by neutron-induced fission of natural uranium have been measured. The neutrons were generated by bombarding a sup 1 sup 3 C target with 55 MeV protons. The results, position of the maximum in the (Z, A)-plane, width and magnitude, are very comparable with those where the neutrons are generated by bombardment of natural sup 1 sup 2 C graphite with 50 MeV deuterons. Depending on the geometry of the converter/target assembly the isotope yields, however, are a factor of 2-3 lower due to less efficient production of neutrons per primary projectile, especially at small forward angles. (orig.)

Mass measurement of halo nuclides and beam cooling with the mass spectrometer Mistral

International Nuclear Information System (INIS)

Bachelet, C.

2004-12-01

Halo nuclides are a spectacular drip-line phenomenon and their description pushes nuclear theories to their limits. The most critical input parameter is the nuclear binding energy; a quantity that requires excellent measurement precision, since the two-neutron separation energy is small at the drip-line by definition. Moreover halo nuclides are typically very short-lived. Thus, a high accuracy instrument using a quick method of measurement is necessary. MISTRAL is such an instrument; it is a radiofrequency transmission mass spectrometer located at ISOLDE/CERN. In July 2003 we measured the mass of the Li 11 , a two-neutron halo nuclide. Our measurement improves the precision by a factor 6, with an error of 5 keV. Moreover the measurement gives a two-neutron separation energy 20% higher than the previous value. This measurement has an impact on the radius of the nucleus, and on the state of the two valence neutrons. At the same time, a measurement of the Be 11 was performed with an uncertainty of 4 keV, in excellent agreement with previous measurements. In order to measure the mass of the two-neutron halo nuclide Be 14 , an ion beam cooling system is presently under development which will increase the sensitivity of the spectrometer. The second part of this work presents the development of this beam cooler using a gas-filled Paul trap. (author)

Continuous energy Neutron Transport Monte Carlo Simulator Project: Decomposition of the neutron energy spectrum by target nuclei tagging

Energy Technology Data Exchange (ETDEWEB)

Barcellos, Luiz Felipe F.C.; Bodmann, Bardo E.J.; Vilhena, Marco T.M.B., E-mail: luizfelipe.fcb@gmail.com, E-mail: bardo.bodmann@ufrgs.br, E-mail: mtmbvilhena@gmail.com [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Grupo de Estudos Nucleares; Leite, Sergio Q. Bogado, E-mail: sbogado@ibest.com.br [Comissao Nacional de Energia Nuclear (CNEN), Rio de Janeiro, RJ (Brazil)

2017-07-01

In this work a Monte Carlo simulator with continuous energy is used. This simulator distinguishes itself by using the sum of three probability distributions to represent the neutron spectrum. Two distributions have known shape, but have varying population of neutrons in time, and these are the fission neutron spectrum (for high energy neutrons) and the Maxwell-Boltzmann distribution (for thermal neutrons). The third distribution has an a priori unknown and possibly variable shape with time and is determined from parametrizations of Monte Carlo simulation. It is common practice in neutron transport calculations, e.g. multi-group transport, to consider that the neutrons only lose energy with each scattering reaction and then to use a thermal group with a Maxwellian distribution. Such an approximation is valid due to the fact that for fast neutrons up-scattering occurrence is irrelevant, being only appreciable at low energies, i.e. in the thermal energy region, in which it can be regarded as a Maxwell-Boltzmann distribution for thermal equilibrium. In this work the possible neutron-matter interactions are simulated with exception of the up-scattering of neutrons. In order to preserve the thermal spectrum, neutrons are selected stochastically as being part of the thermal population and have an energy attributed to them taken from a Maxwellian distribution. It is then shown how this procedure can emulate the up-scattering effect by the increase in the neutron population kinetic energy. Since the simulator uses tags to identify the reactions it is possible not only to plot the distributions by neutron energy, but also by the type of interaction with matter and with the identification of the target nuclei involved in the process. This work contains some preliminary results obtained from a Monte Carlo simulator for neutron transport that is being developed at Federal University of Rio Grande do Sul. (author)

Inelastic scattering of 1-2.5 MeV neutrons by 235U and 238U nuclei

International Nuclear Information System (INIS)

Kornilov, N.V.; Kagalenko, A.B.; Baryba, V.Ya.; Balitskij, A.V.; Androsenko, A.A.; Androsenko, P.A.

1993-07-01

The inelastic scattering cross-sections of 1-2.5 MeV neutrons for 235 U and 238 0 nuclei were measured. A detailed description is given of the data processing procedures used, and the methods for determining the neutron flux in the sample. The Monte Carlo method was used to calculate the corrections for multiple neutron scattering and neutron flux attenuation in the sample. Pursuant to an analysis of the fission neutron spectra, we concluded that the systematic error level of the results is ± 3.27%. The results of these cross-section and spectrum measurements for inelastically scattered neutrons are compared with results from other sources and existing evaluations, the possible causes of the divergences for neutrons with an energy level of less than 1 MeV are analysed, and suggestions are put forward for future research work. (author)

Experimental study on p-wave neutron strength functions for light nuclei

International Nuclear Information System (INIS)

Koester, L.; Waschkowski, W.; Meier, J.; Rau, G.; Salehi, M.

1988-01-01

Broad energy distributions in fast neutron beams have been achieved by appropriate filtering of the 236 U fission radiation provided from the RENT converter facility at the FRM research reactor. Transmission measurements in such beams result in average cross sections to which resonance reactions and shape elastic scattering contribute. We used a silicon (124.5 cm) filtered beam with a median energy of 143 keV (width 20 keV) and beams with 1.3 MeV (0.55 to 3 MeV) and 2.1 MeV (1 to 5.5 MeV) obtained through different filter combinations of lead and polyethylene. The relative high energies and the broad spectra made it possible to determine experimentally the contributions of s- and p-wave resonance reactions to the average cross section even for light nuclei. Using the three different beams we determined the average cross sections for the elements in the mass region A = 9 to 65. Analysing the measured cross sections by means of the R matrix formalism provided a complete set of p-wave strength functions and distant level parameters. Moreover, single particle shell effects in the cross sections were observed. In conclusion we obtained information on the 2P and the 3S size resonances and about the validity of the optical model for neutron reactions with light nuclei. (orig.)

Cosmology and unstable nuclei

International Nuclear Information System (INIS)

Schramm, D.N.

1995-01-01

Primordial nucleosynthesis has established itself as one of the three pillars of Big Bang cosmology. Many of the Big Bang Nucleosynthesis reactions involve unstable nuclei. Hence there is a tight relationship hetween the subject of this conference and cosmology. The prime role of unstable nuclei in cosmology is related to lithium synthesis and the lack of cosmological synthesis of Be and B. These nuclei will thus be focused upon. Nucleosynthesis involves comparing calculated abundances with observed abundances. In general, abundance determinations are dominated by systematic rather than statistical errors, and work on bounding systematics is crucial. The quark-hadron inspired inhomogeneous calculations now unanimously agree that only relatively small variations in Ω b are possible vis-a-vis the homogeneous model; hence the robustness of Ω b ∼0.05 is now apparent. (These calculations depend critically on unstable nuclei.) The above argues that the bulk of the baryons in the universe are not producing visible light. A comparison with the ROSAT cluster data is also shown to be consistent with the standard BBN model. Ω b ∼1 seems to be definitely excluded, so if Ω TOTAL =1, as some recent observations may hint, then non-baryonic dark matter is required. The implications of the recently reported halo microlensing events are discussed. In summary, it is argued that the physics of unstable nuclei affects the fundamental dark matter argument. ((orig.))

Beam halo formation from space-charge dominated beams in uniform focusing channels

International Nuclear Information System (INIS)

O'Connell, J.S.; Wangler, T.P.; Mills, R.S.; Crandall, K.R.

1993-01-01

In space-charge dominated beams the nonlinear space-charge forces produce a filamentation pattern, which results in a 2-component beam consisting of an inner core and an outer halo. The halo is very prominent in mismatched beams, and the potential for accelerator activation is of concern for a next generation of cw, high-power proton linacs that could be applied for intense neutron generators to process nuclear materials. We present new results about beam halo and the evolution of space-charge dominated beams from multiparticle simulation of initial laminar beams in a uniform linear focusing channel, and from a model consisting of single particle interactions with a uniform-density beam core. We study the energy gain from particle interactions with the space-charge field of the core, and we identify the resonant characteristic of this interaction as the basic cause of the separation of the beam into the two components. We identify three different particle-trajectory types, and we suggest that one of these types may lead to continuous halo growth, even after the halo is removed by collimators

Halo and space charge issues in the SNS Ring

International Nuclear Information System (INIS)

Fedotov, A.V.; Abell, D.T.; Beebe-Wang, J.; Lee, Y.Y.; Malitsky, N.; Wei, J.; Gluckstern, R.L.

2000-01-01

The latest designs for high-intensity proton rings require minimizing beam-induced radioactivation of the vacuum chamber. Although the tune depression in the ring is much smaller than in high-intensity linacs, space-charge contributions to halo formation and, hence, beam loss may be significant. This paper reviews our current understanding of halo formation issues for the Spallation Neutron Source (SNS) accumulator ring

Halo and space charge issues in the SNS Ring

Energy Technology Data Exchange (ETDEWEB)

Fedotov, A.V.; Abell, D.T.; Beebe-Wang, J.; Lee, Y.Y.; Malitsky, N.; Wei, J.; Gluckstern, R.L.

2000-06-30

The latest designs for high-intensity proton rings require minimizing beam-induced radioactivation of the vacuum chamber. Although the tune depression in the ring is much smaller than in high-intensity linacs, space-charge contributions to halo formation and, hence, beam loss may be significant. This paper reviews our current understanding of halo formation issues for the Spallation Neutron Source (SNS) accumulator ring.

New Horizon in Nuclear Physics and Astrophysics Using Radioactive Nuclear Beams

Science.gov (United States)

Tanihata, Isao

Beams of β- radioactive nuclei, having a lifetime as short as 1 ms have been used for studies of the nuclear structure and reaction relevant to nucleosynthesis in the universe. In nuclear-structure studies, decoupling of the proton and neutron distributions in nuclei has been discovered. The decoupling appeared as neutron halos and neutron skins on the surface of neutron-rich unstable nuclei. In astrophysics, reaction cross sections have been determined for many key reactions of nucleosynthesis involving short-lived nuclei in the initial and final states. One such important reaction, 13N+p → 14O +γ, has been studied using beams of unstable 13N nuclei. Such studies became possible after the invention of beams of radioactive nuclei in the mid-80's. Before that, the available ion beams were restricted to ions of stable nuclei for obvious reasons. In the next section the production method of radioactive beams is presented, then a few selected studies using radioactive beams are discussed in the following sections. In the last section, some useful properties of radioactive nuclei for other applications is shown.

One particle-hole excitations in p- and fp-shell nuclei

International Nuclear Information System (INIS)

Hees, A.G.M. van.

1982-01-01

Results are presented of shell model calculations of medium and light atomic nuclei. The influence of the allowance of one particle-hole excitations is investigated. This enables improved descriptions of intermediate mass nuclei in the fp-shell. For light p-shell nuclei one particle-hole excitations create exclusively situations with abnormal parity. The description of situations with normal parity is not changed by enlarging the model space. In the first chapter shell-model calculations are performed on the light Ni-isotopes (A = 57-59). One nucleon is allowed to be excited from the fsub(7/2) orbit to one of the other fp-shell orbits. The general observation in the enlarged model space is that one can use operators that require a much weaker 'renormalization' and the calculation requires only a selected set of matrix elements of the Hamiltonian. An additional advantage of the inclusion of one particle-hole excitations is that it allows a description of several intruder states, i.e. states that cannot be produced with the assumption of a closed 56 Ni core. In the second chapter the nuclei with mass number A = 52-55, i.e. a small number of holes in the 56 Ni core, are investigated similarly. In the third chapter much lighter nuclei (A = 4-16) are discussed. For a theoretical description of nonnormal-parity states one has to admit the excitation of at least one nucleon to a higher harmonic-oscillator major-shell. (Auth.)

The method to set up file-6 in neutron data library of light nuclei below 20 MeV

International Nuclear Information System (INIS)

Zhang Jingshang; Han Yinlu

2001-01-01

So far there is no file-6 (double differential cross section data, DDX) of the light nuclei in the main evaluated neutron nuclear data libraries in the world. Therefore, locating a proper description on the double differential cross section of all kinds of outgoing particles from neutron induced light nucleus reaction below 20 MeV is necessary. The motivation for this work is to introduce a way to set up file-6 in the neutron data library

Laserspectroscopic studies of collective properties of neutron deficient Ba nuclei

International Nuclear Information System (INIS)

Bekk, K.; Andl, A.; Goering, S.; Hanser, A.; Nowicki, G.; Rebel, H.; Schatz, G.

1979-01-01

Isotope shifts and hyperfine structure of the BaI resonance-line (lambda=553.6 nm) have been measured by dye laser induced resonance fluorescence on an atomic beam for sup(135m,129g,129m,126) Ba thus extending previous high resolution measurements of neutron deficient Ba nuclides (N - isomers sup(135m) Ba and sup(135m) Ba show a decreased staggering. Conspicuously the isomer shift of the g 7/2 + isomer sup(129m) Ba proves to be negative. The nuclear structure information is discussed in the context of gamma-spectroscopic studies of transitional nuclei with 50 [de

One-neutron knockout from {sup 51-55}Sc

Energy Technology Data Exchange (ETDEWEB)

Schwertel, S.; Maierbeck, P.; Gernhaeuser, R.; Bildstein, V.; Boehmer, M.; Eppinger, K.; Faestermann, T.; Friese, J.; Fabbietti, L.; Maier, L.; Winkler, S. [Technische Universitaet Muenchen, Physik Department E12, Garching (Germany); Kruecken, R. [Technische Universitaet Muenchen, Physik Department E12, Garching (Germany); TRIUMF, Vancouver (Canada); University of British Columbia, Department of Physics and Astronomy, Vancouver (Canada); Kroell, T. [Technische Universitaet Muenchen, Physik Department E12, Garching (Germany); Technische Universitaet Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany); Alvarez-Pol, H.; Benjamim, E.A.; Benlliure, J.; Caamano, M.; Cortina-Gil, D.; Gascon, M.; Kurtukian, T.; Perez, D.; Rodriguez-Tajes, C. [Universidade de Santiago de Compostela, Departamento de Fisica de Particulas, Santiago de Compostela (Spain); Aksouh, F.; Aumann, T.; Behr, K.; Boretzky, K.; Bruenle, A.; Chatillon, A.; Chulkov, L.V.; Geissel, H.; Gerl, J.; Gorska, M.; Kojouharov, I.; Klimkiewicz, A.; Kurz, N.; Nociforo, C.; Schaffner, H.; Simon, H.; Stanoiu, M.; Suemmerer, K.; Weick, H. [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Borge, M.J.G.; Pascual-Izarra, C.; Perea, A.; Tengblad, O. [CSIC, Instituto de Estructura de la Materia, Madrid (Spain); Buerger, A. [University of Oslo, SAFE/OCL, Oslo (Norway); CEA, Gif-sur-Yvette (France); Casarejos, E.; Brown, B.A. [University of Vigo, Vigo (Spain); Enders, J.; Schrieder, G. [Technische Universitaet Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany); Hansen, P.G. [Michigan State University, NSCL, East Lansing, Michigan (United States); Jonson, B.; Nyman, G. [Chalmers Tekniska Hoegskola och Goeteborgs Universitet, Experimentell Fysik, Goeteborg (Sweden); Kanungo, R. [TRIUMF, Vancouver (Canada); GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Saint Mary' s University, Halifax (Canada); Kiselev, O. [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Johannes Gutenberg Universitaet, Mainz (Germany); Paul Scherrer Institut, Villigen (Switzerland); Larsson, K. [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Chalmers Tekniska Hoegskola och Goeteborgs Universitet, Experimentell Fysik, Goeteborg (Sweden); Le Bleis, T. [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); IN2P3-CNRS/Universite Louis Pasteur, Institut Pluridisciplinaire Hubert Curien, Strasbourg Cedex 2 (France); Mahata, K. [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Paul Scherrer Institut, Villigen (Switzerland); Nilsson, T. [Technische Universitaet Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany); Chalmers Tekniska Hoegskola och Goeteborgs Universitet, Experimentell Fysik, Goeteborg (Sweden); Prochazka, A. [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Comenius University, Faculty of Mathematics and Physics, Bratislava (Slovakia); Rossi, D. [Johannes Gutenberg Universitaet, Mainz (Germany); Sitar, B. [Comenius University, Faculty of Mathematics and Physics, Bratislava (Slovakia); Otsuka, T. [University of Tokyo, Hongo, Bunkyo-ku, Department of Physics, Tokyo (Japan); Tostevin, J.A. [University of Surrey, Department of Physics, Faculty of Engineering and Physical Sciences, Guildford (United Kingdom); Rae, W.D.M. [Garsington, Oxfordshire (United Kingdom)

2012-12-15

Results are presented from a one-neutron knockout experiment at relativistic energies of {approx} 420 A MeV on {sup 51-55}Sc using the GSI Fragment Separator as a two-stage magnetic spectrometer and the MINIBALL array for gamma-ray detection. Inclusive longitudinal momentum distributions and cross-sections were measured enabling the determination of the contributions corresponding to knockout from the {nu}p{sub 1/2}, {nu}p{sub 3/2}, (L = 1) and {nu}f{sub 7/2}, {nu}f{sub 5/2} (L = 3) neutron orbitals. The observed L = 1 and L = 3 contributions are compared with theoretical cross-sections using eikonal knockout theory and spectroscopic factors from shell model calculations using the GXPF1A interaction. The measured inclusive knockout cross-sections generally follow the trends expected theoretically and given by the spectroscopic strength predicted from the shell model calculations. However, the deduced L = 1 cross-sections are generally 30-40% higher while the L = 3 contributions are about a factor of two smaller than predicted. This points to a promotion of neutrons from the {nu}f{sub 7/2} to the {nu}p{sub 3/2} orbital indicating a weakening of the N = 28 shell gap in these nuclei. While this is not predicted for the phenomenological GXPF1A interaction such a weakening is predicted by recent calculations using realistic low-momentum interactions V{sub low} {sub k} obtained by evolving a chiral N3LO nucleon-nucleon potential. (orig.)

Descriptions of carbon isotopes within the energy density functional theory

Energy Technology Data Exchange (ETDEWEB)

Ismail, Atef [Fundamental and Applied Sciences Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak, Malaysia and Department of Physics, Al-Azhar University, 71524 Assiut (Egypt); Cheong, Lee Yen; Yahya, Noorhana [Fundamental and Applied Sciences Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Tammam, M. [Department of Physics, Al-Azhar University, 71524 Assiut (Egypt)

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.

Study of the odd-${A}$, high-spin isomers in neutron-deficient trans-lead nuclei with ISOLTRAP

CERN Multimedia

Herfurth, F; Blaum, K; Beck, D; Kowalska, M; Schwarz, S; Stanja, J; Huyse, M L; Wienholtz, F

We propose to measure the excitation energy of the $\\frac{13^{+}}{2}$ isomers in the neutron-deficient isotopes $^{193,195,197}$Po with the ISOLTRAP mass spectrometer. The assignment of the low- and high-spin isomers will be made by measuring the energy of the $\\alpha$- particles emitted in the decay of purified beams implanted in a windmill system. Using $\\alpha$-decay information, it is then also possible to determine the excitation energy of the similar isomers in the $\\alpha$-daughter nuclei $^{189,191,193}$Pb, $\\alpha$-parent nuclei $^{197,199,201}$Rn, and $\\alpha$-grand-parent nuclei $^{201,203,205}$Ra. The polonium beams are produced with a UC$_{\\textrm{x}}$ target and using the RILIS.

Statistical and non statistical models for delayed neutron emission: applications to nuclei near A = 90

International Nuclear Information System (INIS)

De Oliveira, Z.M.

1980-01-01

A detailed analysis of the simple statistical model description for delayed neutron emission of 87 Br, 137 I, 85 As and 135 Sb has been performed. In agreement with experimental findings, structure in the #betta#-strength function is required to reproduce the envelope of the neutron spectrum from 87 Br. For 85 As and 135 Sb the model is found incapable of simultaneously reproducing envelopes of delayed neutron spectra and neutron branching ratios to excited states in the final nuclei for any choice of #betta#-strength function. The results indicate that partial widths for neutron emission are not compatible with optical-model transmission coefficients. The simple shell model with pairing is shown to qualitatively describe the main features of the #betta#-strength functions for decay of 87 Br and 91 93 95 97 Rb. It is found that the location of apparent resonances in the experimental data are in rough agreement with the location of centroids of strength calculated with this model. An extension of the shell model picture which includes the Gamow-Teller residual interaction is used to investigate decay properties of 84 86 As, 86 92 Br and 88 102 Rb. For a realistic choice of interaction strength, the half lives of these isotopes are fairly well reproduced and semiquantitative agreement with experimental #betta#-strength functions is found. Delayed neutron emission probabilities are reproduced for precursors nearer stability with systematic deviations being observed for the heavier nuclei. Contrary to the assumption of a structureless Gamow-Teller giant resonance as embodied gross theory of #betta#-decay, we find that structures in the tail of the Gamow-Teller giant resonances are expected which strongly influence the decay properties of nuclides in this region

Quasifree (p ,p N ) scattering of light neutron-rich nuclei near N =14

Science.gov (United States)

Díaz Fernández, P.; Alvarez-Pol, H.; Crespo, R.; Cravo, E.; Atar, L.; Deltuva, A.; Aumann, T.; Avdeichikov, V.; Beceiro-Novo, S.; Bemmerer, D.; Benlliure, J.; Bertulani, C. A.; Boillos, J. M.; Boretzky, K.; Borge, M. J. G.; Caamaño, M.; Cabanelas, P.; Caesar, C.; Casarejos, E.; Catford, W.; Cederkäll, J.; Chartier, M.; Chulkov, L. V.; Cortina-Gil, D.; Datta Pramanik, U.; Dillmann, I.; Elekes, Z.; Enders, J.; Ershova, O.; Estradé, A.; Farinon, F.; Fernández-Domínguez, B.; Fraile, L. M.; Freer, M.; Galaviz, D.; Geissel, H.; Gernhäuser, R.; Golubev, P.; Göbel, K.; Hagdahl, J.; Heftrich, T.; Heil, M.; Heine, M.; Heinz, A.; Henriques, A.; Holl, M.; Hufnagel, A.; Ignatov, A.; Johansson, H. T.; Jonson, B.; Jurčiukonis, D.; Kalantar-Nayestanaki, N.; Kanungo, R.; Kelic-Heil, A.; Knyazev, A.; Kröll, T.; Kurz, N.; Labiche, M.; Langer, C.; Le Bleis, T.; Lemmon, R.; Lindberg, S.; Machado, J.; Marganiec, J.; Moro, A. M.; Movsesyan, A.; Nacher, E.; Najafi, A.; Nikolskii, E.; Nilsson, T.; Nociforo, C.; Panin, V.; Paschalis, S.; Perea, A.; Petri, M.; Pietras, B.; Pietri, S.; Plag, R.; Reifarth, R.; Ribeiro, G.; Rigollet, C.; Rossi, D.; Röder, M.; Savran, D.; Scheit, H.; Simon, H.; Sorlin, O.; Syndikus, I.; Taylor, J. T.; Tengblad, O.; Thies, R.; Togano, Y.; Vandebrouck, M.; Velho, P.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Wheldon, C.; Wilson, G.; Winfield, J. S.; Woods, P.; Yakorev, D.; Zhukov, M.; Zilges, A.; Zuber, K.; R3B Collaboration

2018-02-01

Background: For many years, quasifree scattering reactions in direct kinematics have been extensively used to study the structure of stable nuclei, demonstrating the potential of this approach. The R 3B collaboration has performed a pilot experiment to study quasifree scattering reactions in inverse kinematics for a stable 12C beam. The results from that experiment constitute the first quasifree scattering results in inverse and complete kinematics. This technique has lately been extended to exotic beams to investigate the evolution of shell structure, which has attracted much interest due to changes in shell structure if the number of protons or neutrons is varied. Purpose: In this work we investigate for the first time the quasifree scattering reactions (p ,p n ) and (p ,2 p ) simultaneously for the same projectile in inverse and complete kinematics for radioactive beams with the aim to study the evolution of single-particle properties from N =14 to N =15 . Method: The structure of the projectiles 23O, 22O, and 21N has been studied simultaneously via (p ,p n ) and (p ,2 p ) quasifree knockout reactions in complete inverse kinematics, allowing the investigation of proton and neutron structure at the same time. The experimental data were collected at the R3B -LAND setup at GSI at beam energies of around 400 MeV/u. Two key observables have been studied to shed light on the structure of those nuclei: the inclusive cross sections and the corresponding momentum distributions. Conclusions: The knockout reactions (p ,p n ) and (p ,2 p ) with radioactive beams in inverse kinematics have provided important and complementary information for the study of shell evolution and structure. For the (p ,p n ) channels, indications of a change in the structure of these nuclei moving from N =14 to N =15 have been observed, i.e., from the 0 d5 /2 shell to the 1 s1 /2 . This supports previous observations of a subshell closure at N =14 for neutron-rich oxygen isotopes and its weakening

Fission barriers of two odd-neutron heavy nuclei

International Nuclear Information System (INIS)

Koh, Meng-Hock; Bonneau, L.; Nhan Hao, T. V.; Duc, Dao Duy; Quentin, P.

2015-01-01

The fission barriers of two odd-neutron heavy odd nuclei,namely the 235 U and 239 Pu isotopes have been calculated within a self-consistent Hartree-Fock-plus-BCS approach with blocking. A Skyrme nucleon-nucleon effective interaction has been used together with a seniority force to describe pairing correlations. A full account of the genuine time-reversal symmetry breaking due to the presence of an unpaired nucleon has been incorporated at the mean field level. The SIII and SkM* parametrizations of the Skyrme interaction have been retained as well as for a part a newer parametrization, SLy5*. The seniority force parameters have been fitted to reproduce experimental odd-even mass differences in the actinide region. To assess the relevance of our calculated fission barrier distribution (as a function of the quantum numbers), we have studied the quality of our results with respect to the spectroscopy of band heads (for configurations deemed to be a pure single particle character) in the ground and fission isomeric states. Fission barriers of the considered odd nuclei have been compared with what is obtained for their even-even neighbouring isotopes (namely 234 U and 236 U, 238 Pu and 240 Pu respectively) to determine the so-called specialization energies. Various corrections and associated uncertainties have been discussed in order to compare our results with available data

On radii of neutron distributions in nuclei

International Nuclear Information System (INIS)

Varma, G.K.; Zamick, L.

1978-01-01

The analyses of the differences between rms radii (Δ=rsub(n) - rsub(p) of neutron and proton distributions are considered in a wide variety of nuclei. It is noted that apart from its own intrinsic interest, the quantity Δ is of importance for isotope shifts, core polarization contributions to the Coulomb energy difference of mirror pairs (Nolen-Schiffer anomaly) and the renormalization of the effective interaction. For example, if Δ were very small in 48 Ca then the Nolen-Schiffer anomaly could be explained by a core polarization mechanism. The various methods of determining Δ are considered critically and it is concluded that at present probably the most reliable method is high energy (approximately 1 GeV) proton-nucleon scattering. The different theoretical analyses based upon, e.g. the multiple diffraction theory (where Glauber amplitude is the leading term) or the optical potential (KMT) formalisms appear to be converging to essentially the same answer when analyzing the same data. High energy α-particles and medium energy pions can also become useful sources of information if higher order optical potentials are treated with care. It is found that Δ is rather large in 48 Ca, i.e. there is a neutron skin, so that the Nolen-Schiffer anomaly cannot be explained by a core polarization mechanism. The results of high energy proton-nucleus scattering are in excellent agreement with current density dependent Hartree-Fock calculation. (Auth.)

Decay spectroscopy of neutron-rich nuclei around {sup 37,38}Al

Energy Technology Data Exchange (ETDEWEB)

Steiger, Konrad [Physik-Department E12, Technische Universitaet Muenchen (Germany); Collaboration: CAITEN-Collaboration

2013-07-01

An experiment at RIBF (Radioactive Isotope Beam Factory at RIKEN, Japan) investigated N=20 nuclei above {sup 29}F and the midshell region around {sup 37}Al. These nuclei were produced by relativistic projectile fragmentation of a 345 AMeV {sup 48}Ca primary beam from the superconducting ring cyclotron SRC with an average intensity of 70 pnA. The secondary cocktail beam was separated and identified with the BigRIPS fragment separator and the ZeroDegree spectrometer. The identified fragments were implanted in the CAITEN detector (Cylindrical Active Implantation Target for Efficient Nuclear-decay study). The main part of this detector is a highly segmented plastic scintillator with the shape of a hollow cylinder. To reduce background decay events the scintillator was moved axially and vertically similar to a tape-transport system. Implantations and decays were correlated in time and space. For the first time β-delayed γ-rays were measured in the neutron-rich isotopes {sup 37,38}Si (with three germanium clover detectors). From β-γ-γ coincidences partial level schemes could be constructed. The results were compared to shell model calculations and a tentative assignment for spins and parities of the experimental level schemes was possible. Significantly more precise half-lives for the implanted nuclei were measured.

Beyond assembly bias: exploring secondary halo biases for cluster-size haloes

Science.gov (United States)

Mao, Yao-Yuan; Zentner, Andrew R.; Wechsler, Risa H.

2018-03-01

Secondary halo bias, commonly known as `assembly bias', is the dependence of halo clustering on a halo property other than mass. This prediction of the Λ Cold Dark Matter cosmology is essential to modelling the galaxy distribution to high precision and interpreting clustering measurements. As the name suggests, different manifestations of secondary halo bias have been thought to originate from halo assembly histories. We show conclusively that this is incorrect for cluster-size haloes. We present an up-to-date summary of secondary halo biases of high-mass haloes due to various halo properties including concentration, spin, several proxies of assembly history, and subhalo properties. While concentration, spin, and the abundance and radial distribution of subhaloes exhibit significant secondary biases, properties that directly quantify halo assembly history do not. In fact, the entire assembly histories of haloes in pairs are nearly identical to those of isolated haloes. In general, a global correlation between two halo properties does not predict whether or not these two properties exhibit similar secondary biases. For example, assembly history and concentration (or subhalo abundance) are correlated for both paired and isolated haloes, but follow slightly different conditional distributions in these two cases. This results in a secondary halo bias due to concentration (or subhalo abundance), despite the lack of assembly bias in the strict sense for cluster-size haloes. Due to this complexity, caution must be exercised in using any one halo property as a proxy to study the secondary bias due to another property.

Low energy E0 transitions in odd-mass nuclei of the neutron deficient 180 < A < 200 region

International Nuclear Information System (INIS)

Zganjar, E.F.; Kortelahti, M.O.; Wood, J.L.; Papanicolopulos, C.D.

1987-01-01

The region of neutron-deficient nuclei near Z = 82 and N = 104 provides the most extensive example of low-energy shape coexistence anywhere on the mass surface. It is shown that E0 and E0 admixed transitions may be used as a fingerprint to identify shape coexistence in odd-mass nuclei. It is also shown that all the known cases of low energy E0 and E0 admixed transitions in odd-mass nuclei occur where equally low-lying O + states occur in neighboring even-even nuclei. A discussion of these and other relevant data as well as suggestions for new studies which may help to clarify and, more importantly, quantify the connection between E0 transitions and shape coexistence are presented. 60 refs., 7 figs., 4 tabs

Beta decay and magnetic moments as tools to probe nuclear structure. Study of neutron-rich nuclei around N=40; Decroissance beta et moments magnetiques comme outils pour sonder la structure nucleaire. Etude des noyaux riches en neutrons autour de N=40

Energy Technology Data Exchange (ETDEWEB)

Matea, I

2003-12-01

The evolution of nuclear structure in nuclei far from the {beta} stability line is one of the 'hot topics' in modern experimental and theoretical nuclear physics. The present thesis is devoted to the study of structure of neutron-rich nuclei around N=40. The evolution of the neutron g9/2 orbital with increasing number of neutrons is one of the key points defining the structure of these nuclei at low excitation energy. We used for this investigation as experimental tools the magnetic dipole moments measurements and the {beta} decay spectroscopy. For the measurement of the gyromagnetic factor of the 9/2{sup +} isomeric state in Fe{sup 61} we have applied the TDPAD method. This method (like most of measurements of nuclear moments) requires an oriented ensemble of nuclei. The orientation of Fe{sup 61m} was achieved via the fragmentation of Ni{sup 64} at 55 MeV/u and the selection of the fragment momentum with the LISE spectrometer at GANIL. The experimental device was specially conceived to preserve the alignment up to the implantation point. The measured value of the g factor was compared with large-scale shell model and Hartree-Fock-Bogoliubov model predictions. The nuclei studied via {beta} decay were produced by the fragmentation of Kr{sup 86} at 58 MeV/u. For the selection of reaction products we used for the first time the LISE2000 spectrometer and for the detection of {gamma} rays four EXOGAM clover detectors. We measured 5 new lifetimes and 4 lifetimes with a higher precision. From the prompt {beta}{gamma} coincidences we identified new states in the daughter nuclei, as it is the case of the first 2{sup +} excited states in Fe{sup 68} and Ni{sup 72}. The results were compared with the predictions of the large-scale shell model. Other transitions were observed for the first time in {beta}{gamma} decay of Ti{sup 60}, Fe{sup 70} and Co{sup 71,73}. (author)

One dark matter mystery: halos in the cosmic web

International Nuclear Information System (INIS)

Gaite, Jose

2015-01-01

The current cold dark matter cosmological model explains the large scale cosmic web structure but is challenged by the observation of a relatively smooth distribution of matter in galactic clusters. We consider various aspects of modeling the dark matter around galaxies as distributed in smooth halos and, especially, the smoothness of the dark matter halos seen in N-body cosmological simulations. We conclude that the problems of the cold dark matter cosmology on small scales are more serious than normally admitted

One dark matter mystery: halos in the cosmic web

Science.gov (United States)

Gaite, Jose

2015-01-01

The current cold dark matter cosmological model explains the large scale cosmic web structure but is challenged by the observation of a relatively smooth distribution of matter in galactic clusters. We consider various aspects of modeling the dark matter around galaxies as distributed in smooth halos and, especially, the smoothness of the dark matter halos seen in N-body cosmological simulations. We conclude that the problems of the cold dark matter cosmology on small scales are more serious than normally admitted.

Half-lives of cluster decay of neutron rich nuclei in trans-tin region

International Nuclear Information System (INIS)

Swamy, G.S.; Umesh, T.K.

2011-01-01

In this work, the logarithmic half-life [log 10 (T 1/2 )] values have been reported for the exotic decay of some neutron rich even–even parent nuclei (56≤Z≤64) accompanied by the emission of alpha-like and non-alpha-like clusters in the trans-tin region. These values were calculated by using the single line of universal curve (UNIV) for alpha and cluster radioactive decay as well as the universal decay law (UDL). The half-life values were also separately calculated by considering the interacting nuclear potential barrier as the sum of Coulomb and proximity potentials. The half-life values based on the three calculations mentioned above, were found to agree with one another within a few orders of magnitude. Possible conclusions are drawn based on the present study. (author)

International symposium on exotic nuclear structures. Book of abstracst

International Nuclear Information System (INIS)

2000-01-01

The following topics were discussed at the meeting: Physics of weakly bound nuclei, neutron skin and halo; Evolution of shell structures for neutron-rich nuclei; Collective excitations in nuclei with exotic nuclear shapes; Cluster structures; Super- and hyperdeformed nuclei, exotic structures in the actinides; Superheavy elements; Towards understanding the structure of nucleons; New experimental techniques, facilities for radioactive beams. All abstracts (75 items) were submitted as full text to the INIS database. (R.P.)

Influence of isovector pairing and particle-number projection effects on spectroscopic factors for one-pair like-particle transfer reactions in proton-rich even-even nuclei

Science.gov (United States)

Benbouzid, Y.; Allal, N. H.; Fellah, M.; Oudih, M. R.

2018-04-01

Isovector neutron-proton (np) pairing and particle-number fluctuation effects on the spectroscopic factors (SF) corresponding to one-pair like-particle transfer reactions in proton-rich even-even nuclei are studied. With this aim, expressions of the SF corresponding to two-neutron stripping and two-proton pick-up reactions, which take into account the isovector np pairing effect, are established within the generalized BCS approach, using a schematic definition proposed by Chasman. Expressions of the same SF which strictly conserve the particle number are also established within the Sharp-BCS (SBCS) discrete projection method. In both cases, it is shown that these expressions generalize those obtained when only the pairing between like particles is considered. First, the formalism is tested within the Richardson schematic model. Second, it is applied to study even-even proton-rich nuclei using the single-particle energies of a Woods-Saxon mean-field. In both cases, it is shown that the np pairing effect and the particle-number projection effect on the SF values are important, particularly in N = Z nuclei, and must then be taken into account.

New approach to the nuclear in beam γ spectroscopy of neutron rich nuclei at N=20 using projectile fragmentation

International Nuclear Information System (INIS)

Lopez-Jimenez, M.J.; Saint-Laurent, M.G.; Achouri, L.; Daugas, J.M.; Belleguic, M.; Azaiez, F.; Bourgeois, C.; Angelique, J.C.

1999-01-01

The structure of nuclei far from stability around 32 Mg have been recently investigated by means of a novel method. In-beam γ-decay spectroscopy of a large number of exotic neutron-rich nuclei produced by projectile fragmentation of a 36 S projectile has been performed, using coincidences between the recoil fragments collected at the focal plane of SPEG spectrometer and γ-rays emitted at the target location. Preliminary results on both the population mechanism and the decay of excited states in nuclei around 32 Mg are presented. (author)

Critical and shape-unstable nuclei

CERN Document Server

Cailliau, M; Husson, J P; Letessier, J; Mang, H J

1973-01-01

The authors' experimental work on the decay of neutron deficient mercury osmium nuclei, some other studies at ISOLDE (CERN) and their first theoretical analysis show that the nuclei around /sup 186/Pt (Z=78, N=108) are at the limit of spherical, oblate, prolate nuclei, have (the even one) their first 0/sup +/ excited states at very low energy; quasi- rotational bands are associated to these states. The energy of this O/sup +/ state in /sup 186-/Pt deviate from the Kumar value: angular shape instability is not enough to explain this result. The authors look at radial shape and pairing fluctuations. The position of the 4p-4n state must also be known. (0 refs).

The structure of neutron-rich nuclei explored via in-beam gamma-ray spectroscopy of fast beams

International Nuclear Information System (INIS)

Glasmacher, T.; Campbell, C.M.; Church, J.A.; Dinca, D.C.; Hansen, P.G.; Olliver, H.; Perry, B.C.; Sherrill, B.M.; Terry, J.R.; Bazin, D.; Enders, J.; Gade, A.; Hu, Z.; Mueller, W.F.

2003-01-01

In-beam gamma-ray spectroscopy with fast exotic beams provides an efficient tool to study bound states in exotic neutron-rich nuclei. Specialized experimental techniques have been developed and explore different aspects of nuclear structure. Inelastic scattering experiments with γ-ray detection can measure the response of exotic nuclei to electromagnetic (Coulomb excitation with a heavy target) or hadronic probes (proton scattering with hydrogen target). In-beam fragmentation populates higher-lying bound states to establish levels. Single- and two-nucleon knockout reactions allow for detailed wavefunction spectroscopy of individual levels and for the measurement of spectroscopic factors. Experimental programs employing these techniques are now underway at all projectile-fragmentation facilities around the world. Here we report on several successful in-beam gamma-ray spectroscopy experiments that have been performed at the Coupled Cyclotron Facility at Michigan State University with an emphasis on elucidating the evolution of nuclear structure around neutron numbers N=16, N=20, and N=28 in the π(sd) shell. (orig.)

$\\beta$-delayed neutrons from oriented $^{137,139}$I and $^{87,89}$Br nuclei

CERN Multimedia

We propose a world-first measurement of the angular distribution of $\\beta$‐delayed n and $\\gamma$-radiation from oriented $^{137, 139}$I and $^{87,89}$Br nuclei, polarised at low temperature at the NICOLE facility. $\\beta$­-delayed neutron emission is an increasingly important decay mechanism as the drip line is approached and its detailed understanding is essential to phenomena as fundamental as the r‐process and practical as the safe operation of nuclear power reactors. The experiments offer sensitive tests of theoretical input concerning the allowed and first­‐forbidden $\\beta$‐decay strength, the spin-density of neutron emitting states and the partial wave barrier penetration as a function of nuclear deformation. In $^{137}$I and $^{87}$Br the decay feeds predominantly the ground state of the daughters $^{136}$Xe and $^{86}$Kr whereas in $^{139}$I and $^{89}$Br we will explore the use of n-$\\gamma$- coincidence to study neutron transitions to the first and second excited states in the daughters...

Neutron-proton pairing effect on the proton-rich nuclei moment of inertia

International Nuclear Information System (INIS)

Mokhtari, D.; Ami, I.; Fellah, M.; Allal, N.H.; Fellah, M.; Allal, N.H.

2008-01-01

The neutron-proton (n-p) pairing effect on the nuclear moment of inertia is studied within the BCS approximation in the isovector case. An analytical expression of the moment of inertia is established by means of the cranking model. This expression generalizes the usual BCS one (i.e. when only the pairing between like-particles is considered). The moment of inertia of N = Z even-even nuclei, for which experimental values are known, i.e., such as 32 ≤ A ≤ 80, has been numerically evaluated, with and without inclusion of the n-p pairing effect. The used single-particle and Eigen-states are those of a deformed Woods-Saxon mean field. It turns out that the inclusion of the n-p pairing improves the obtained values when compared to the usual BCS approximation, since the average discrepancies with the experimental data are respectively 7% and 37%. (authors)

Neutron-proton pairing effect on the proton-rich nuclei moment of inertia

Energy Technology Data Exchange (ETDEWEB)

Mokhtari, D.; Ami, I.; Fellah, M.; Allal, N.H. [Laboratoire de Physique Theorique, Faculte de Physique, USTHB, Algiers (Algeria); Fellah, M.; Allal, N.H. [Centre de Recherche Nucleaire d' Alger, COMENA, Algiers (Algeria)

2008-07-01

The neutron-proton (n-p) pairing effect on the nuclear moment of inertia is studied within the BCS approximation in the isovector case. An analytical expression of the moment of inertia is established by means of the cranking model. This expression generalizes the usual BCS one (i.e. when only the pairing between like-particles is considered). The moment of inertia of N = Z even-even nuclei, for which experimental values are known, i.e., such as 32 {<=} A {<=} 80, has been numerically evaluated, with and without inclusion of the n-p pairing effect. The used single-particle and Eigen-states are those of a deformed Woods-Saxon mean field. It turns out that the inclusion of the n-p pairing improves the obtained values when compared to the usual BCS approximation, since the average discrepancies with the experimental data are respectively 7% and 37%. (authors)

Microscopic theory of light exotic nuclei. Shell Models Embedded in the Continuum

International Nuclear Information System (INIS)

Bennaceur, K.

1999-01-01

The recent advances in experimental nuclear physics make it possible to study nuclear systems far from the beta stability line. The discovery of new phenomena, like halos or neutron skins, requires the development of new theoretical models which enable to study these systems. The first part of this work is devoted to the development and the applications of the Shell Model Embedded in the Continuum (SMEC). This new formalism allows to take into account the correlations between the bound and scattering states of loosely bound nuclei. SMEC is applied here to the study of the spectroscopy of the Mirror nuclei 8 B- 8 Li and 17 F- 17 O. It can also be used to calculate the cross sections of the elastic scattering, the Coulomb breakup processes and the radiative n,p capture processes. The results concerning the reactions of astrophysical interest: 18 O(p, γ) 17 F and 7 Be(p, γ) 8 B, are discussed in details. This last reaction is very important because the disintegration of 8 B is the main source of High energy neutrinos in the sun. The second part of this work is related to the analysis of pairing interaction for weakly bound nuclei. We have developed a new approach, based on the Hartree-Fock-Bogolyubov (HFB) theory, that allows to study the pairing correlations between bound and scattering states, both resonant and not resonant ones. The 'particle-hole' potential is replaced by a model potential for which the solutions are analytically known. This method allows to analyse the effect of pairing on bound and resonant states, independently of their energy position. We have clearly demonstrated that the non-resonant continuum plays a crucial role in the loosely bound nuclei and that solving the HFB equations in the coordinate space is the only method that permits to treat this problem correctly. (author)

One-pot sequential synthesis of O-(halo-substituted benzyl hydroxylammonium salts

Directory of Open Access Journals (Sweden)

Saeed Emami

2017-02-01

Full Text Available In this study, we described a simple one-pot preparation of O-(halo-substituted benzyl hydroxylamine derivatives by O-benzylation of N-hydroxyurethane, followed by basic N-deprotection. The advantages of the method were the chemo- and regio-selectivity in obtaining the desired O-benzyl hydroxylammonium salts in a high yield as well as the simplicity of the purification process.

Structure of Warm Nuclei

International Nuclear Information System (INIS)

Aaberg, S.; Uhrenholt, H.

2009-01-01

We study the structure of nuclei in the energy region between the ground state and the neutron separation energy, here called warm nuclei. The onset of chaos in the nucleus as excitation energy is increased is briefly reviewed. Chaos implies fluctuations of energies and wave functions qualitatively the same for all chaotic nuclei. On the other hand, large structure effects are seen, e.g. in the level-density function at same excitation energies. A microscopic model for the level density is reviewed and we discuss effects on structure of the total level-density function, parity enhancement, and the spin distribution function. Comparisons to data are performed at the neutron separation energy for all observed nuclei, and structure of the level-density function for a few measured cases. The role of structure effects in the level-density function for fission dynamics is exemplified.

Halo-independent direct detection of momentum-dependent dark matter

Energy Technology Data Exchange (ETDEWEB)

Cherry, John F. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Frandsen, Mads T.; Shoemaker, Ian M., E-mail: jcherry@lanl.gov, E-mail: frandsen@cp3-origins.net, E-mail: shoemaker@cp3-origins.net [CP3-Origins and the Danish Institute for Advanced Study, University of Southern Denmark, Campusvej 55, DK-5230 Odense M (Denmark)

2014-10-01

We show that the momentum dependence of dark matter interactions with nuclei can be probed in direct detection experiments without knowledge of the dark matter velocity distribution. This is one of the few properties of DM microphysics that can be determined with direct detection alone, given a signal of dark matter in multiple direct detection experiments with different targets. Long-range interactions arising from the exchange of a light mediator are one example of momentum-dependent DM. For data produced from the exchange of a massless mediator we find for example that the mediator mass can be constrained to be ∼< 10 MeV for DM in the 20-1000 GeV range in a halo-independent manner.

Halo-independent direct detection of momentum-dependent dark matter

International Nuclear Information System (INIS)

Cherry, John F.; Frandsen, Mads T.; Shoemaker, Ian M.

2014-01-01

We show that the momentum dependence of dark matter interactions with nuclei can be probed in direct detection experiments without knowledge of the dark matter velocity distribution. This is one of the few properties of DM microphysics that can be determined with direct detection alone, given a signal of dark matter in multiple direct detection experiments with different targets. Long-range interactions arising from the exchange of a light mediator are one example of momentum-dependent DM. For data produced from the exchange of a massless mediator we find for example that the mediator mass can be constrained to be ∼< 10 MeV for DM in the 20-1000 GeV range in a halo-independent manner

Primordial nuclei

International Nuclear Information System (INIS)

Anon.

1995-01-01

The recent detection of intergalactic helium by NASA's Astro-2 mission backs up two earlier measurements by ESA and the University of California, San Diego, using instruments aboard the Hubble Space Telescope. Taken together, these results give strong evidence that this helium is primordial, confirming a key prediction of the Big Bang theory. The amount of helium the results imply could also account for some of the Universe's invisible dark matter - material which affects galactic motion but is otherwise undetectable. According to theory, helium nuclei formed at around 100 seconds after the Big Bang, but the amount of helium depended on even earlier events. Initially, protons turned into neutrons with the same probability that neutrons turned into protons. But after about one second, the Universe had cooled down enough for the weak interaction to freeze out. Neutrons continued to decay into the slightly lighter protons, whilst the opposite reaction became much more scarce. At around 100 seconds, thermonuclear fusion reactions could begin, and all the neutrons that were left became absorbed into helium nuclei, leaving the remaining protons locked up in hydrogen. The ratio of helium to hydrogen was therefore determined by events occurring when the Universe was just one second old. Standard models of primordial nucleosynthesis fix this ratio at slightly less than 2 5% by mass. All heavier elements were cooked up much later in the stars, and amount to less than 1 % of the Universe's mass. These predictions have been borne out remarkably well by observation, although proof of the primordial origins of hydrogen and helium has remained elusive until now. Big Bang nucleosynthesis goes on to estimate that primordial baryonic matter in the form of light nuclei could account for around 10% of the Universe's dark matter. All three recent measurements used the same technique of looking at distant quasars, some of the most luminous objects in the Universe, to

Possibilities at LAMPF for studying nuclei of astrophysical interest

International Nuclear Information System (INIS)

Talbert, W.L. Jr.; Bunker, M.E.

1985-01-01

Nuclear data needs in astrophysics range from neutron capture cross sections of a number of stable or near-stable nuclei to decay and neutron binding-energy data for highly neutron-rich nuclei. LAMPF has the potential to contribute significantly to these needs. The new Los Alamos Neutron Scattering Center (LANSCE, aka WNR/PSR) offers world-class capabilities for neutron capture studies up to an MeV or so. The study of nuclei far from stability could be extended into some regions of astrophysical interest using a proposed He-jet coupled mass separator system with a target/production chamber in the LAMPF beam stop area. Specific examples of possible studies at each facility are presented

Study of nuclear level densities for exotic nuclei

International Nuclear Information System (INIS)

Nasrabadi, M. N.; Sepiani, M.

2012-01-01

Nuclear level density is one of the properties of nuclei with widespread applications in astrophysics and nuclear medicine. Since there has been little experimental and theoretical research on the study of nuclei which are far from stability line, studying nuclear level density for these nuclei is of crucial importance. Also, as nuclear level density is an important input for nuclear research codes, hence studying the methods for calculation of this parameter is essential. Besides introducing various methods and models for calculating nuclear level density for practical applications, we used exact spectra distribution (SPDM) for determining nuclear level density of two neutron and proton enriched exotic nuclei with the same mass number.

Evidence for two-dimensional ising structure in atomic nuclei

International Nuclear Information System (INIS)

MacGregor, M.H.

1976-01-01

Although the unpaired nucleons in an atomic nucleus exhibit pronounced shell-model-like behavior, the situation with respect to the paired-off ''core region'' nucleons is considerably more obscure. Several recent ''multi-alpha knockout'' and ''quasi-fission'' experiments indicate that nucleon clustering is prevalent throughout the core region of the nucleus; this same conclusion is suggested by nuclear-binding-energy systematics, by the evidence for a ''neutron halo'' in heavy nuclei and by the magnetic-moment systematics of low-mass odd-A nuclei. A number of arguments suggests, in turn, that this nucleon clustering is not spherical or spheroidal in shape, as has generally been assumed, but instead is in the form of two-dimensional Ising-like layers, with the layers arrayed perpendicular to the symmetry axis of the nucleus. The effects of this two-dimensional layering are observed most clearly in low-energy-induced fission, where nuclei with an even (odd) number of Ising layers fission symmetrically (asymmetrically). This picture of the nucleus gives an immediate quantitative explanation for the observed asymmetry in the fission of uranium, and also for the transition from symmetric to asymmetric and back to symmetric fission as the atomic number of the fissioning nuclues increase from A = 197 up to A = 258. These results suggest that, in the shell model formulation of the atomic nucleus, the basis states for the paired-off nucleon core region should be modified so as to contain laminar nucleon cluster correlations

Statistical analysis of P-wave neutron reduced widths

International Nuclear Information System (INIS)

Joshi, G.C.; Agrawal, H.M.

2000-01-01

The fluctuations of the p-wave neutron reduced widths for fifty one nuclei have been analyzed with emphasis on recent measurements by a statistical procedure which is based on the method of maximum likelihood. It is shown that the p-wave neutron reduced widths of even-even nuclei fallow single channel Porter Thomas distribution (χ 2 -distribution with degree of freedom ν=1) for most of the cases where there are no intermediate structure. It is emphasized that the distribution in nuclei other than even-even may differ from a χ 2 -distribution with one degree of freedom. Possible explanation and significance of this deviation from ν=1 is given. (author)

Clusters in nuclei. Vol. 1

International Nuclear Information System (INIS)

Beck, Christian

2010-01-01

Following the pioneering discovery of alpha clustering and of molecular resonances, the field of nuclear clustering is presently one of the domains of heavy-ion nuclear physics facing both the greatest challenges and opportunities. After many summer schools and workshops, in particular over the last decade, the community of nuclear molecular physics decided to team up in producing a comprehensive collection of lectures and tutorial reviews covering the field. This first volume, gathering seven extensive lectures, covers the follow topics: - Cluster Radioactivity - Cluster States and Mean Field Theories - Alpha Clustering and Alpha Condensates - Clustering in Neutron-rich Nuclei - Di-neutron Clustering - Collective Clusterization in Nuclei - Giant Nuclear Molecules By promoting new ideas and developments while retaining a pedagogical nature of presentation throughout, these lectures will both serve as a reference and as advanced teaching material for future courses and schools in the fields of nuclear physics and nuclear astrophysics. (orig.)

Neutrino-induced charged-current reaction rates for r-process nuclei

CERN Document Server

Langanke, K

2001-01-01

Neutrino-induced reactions play an important role during and after the r-process if it occurs in an environment with extreme neutrino fluxes, as in the neutrino-driven wind model or neutron star mergers. The neutrino reactions can excite the daughter nucleus above the neutron threshold, which is quite low for r-process nuclei. Thus the daughter nucleus will decay by emission of one or several neutrons. We have calculated the relevant total (nu sub e , e sup -) cross sections as well as the partial neutron spallation cross sections for r-process nuclei with neutron numbers N=41-135 and proton numbers Z=21-82. The supernova neutrino spectrum is described by a Fermi-Dirac distribution with various temperature parameters between T=2.8 MeV and T=10 MeV and with the degeneracy parameters alpha=0 and alpha=3. Our calculations of the nuclear response are based on the random phase approximation and consider allowed as well as forbidden transitions.

Efimov effect in 2-neutron halo nuclei

Indian Academy of Sciences (India)

. B33, 563 (1970). [3] V Efimov, Comm. Nucl. Part. Phys. 19, 271 (1990). [4] Th Cornelius and W Glöckle, J. Chem. Phys. 85, 3906 (1986). B D Esry, C D Lin and C H Greene, Phys. Rev. A54, 394 (1996). J P D'Incao, H Suno and B D Esry, Phys.

Sc and neutron-capture abundances in Galactic low- and high-alpha field halo stars

DEFF Research Database (Denmark)

Fishlock, Cherie K.; Yong, D.; Karakas, Amanda I.

2017-01-01

We determine relative abundance ratios for the neutron-capture elements Zr, La, Ce, Nd and Eu for a sample of 27 Galactic dwarf stars with -1.5 stars separate into three populations (low-and high-a halo and thick-disc stars) based......-alpha stars have a lower abundance compared to the high-alpha stars. The low-alpha stars display the same abundance patterns of high [Ba/Y] and low [Y/Eu] as observed in present-day dwarf spheroidal galaxies, although with smaller abundance differences, when compared to the high-alpha stars. These distinct...... chemical patterns have been attributed to differences in the star formation rate between the two populations and the contribution of low-metallicity, low-mass asymptotic giant branch (AGB) stars to the low-alpha population. By comparing the low-alpha population with AGB stellar models, we place constraints...

Study of neutron-rich nuclei structure around the N=28 shell closure using the in-beam gamma spectroscopy technique

International Nuclear Information System (INIS)

Bastin, B.

2007-10-01

For a few years now, a loss of magicity in neutron-rich nuclei near the neutron drip-line at N=28 has been suggested and observed. Deformation in these nuclei has been observed. The deformation was explained in S isotopes as being due to a moderate reduction of the N=28 shell closure together with a proton induced collectivity originating from the near degeneracy of the proton d3/2 and s1/2 orbitals. As a consequence, the observed deformation seems to result from a subtle interplay between neutron and proton excitations. Since the proton configuration in the Si isotopes is expected to be more stable due to the Z=14 sub-shell gap, 42 Si was considered as a key nucleus in order to distinguish the different effects responsible for the structural changes observed at N=28. Even if it is at the limits of our technical possibilities, an in-beam gamma-spectroscopy experiment using two-step fragmentation and one or several nucleons knockout reaction mechanisms was performed at GANIL. The measurement of the energy of the first excited state in 42 Si, combined with the observation of 38,40 Si and the spectroscopy of 41,43 P, has given evidence for the loss of magicity at N=28 far from stability. Modifications of the effective interaction used in modern shell model calculations have been completed following this investigation, increasing its predictive character. This study confirms the role of the tensor force and the density dependence of the spin-orbit interaction in the collapse of the N=28 shell closure. (author)

Mean-Field and RPA Approaches to Stable and Unstable Nuclei with Semi-Realistic Interactions

International Nuclear Information System (INIS)

Nakada, H.

2009-01-01

We have developed semi-realistic NN interactions [1, 2] by modifying the M3Y interaction [3] that was derived from the G-matrix. The modification has been made so that the saturation and the spin-orbit splittings could be reproduced. The new interactions contain finite-range LS and tensor channels, as well as Yukawa-form central channels having reasonable spin and spin-isospin properties. In order to handle such interactions in practical calculations, we have also developed new numerical methods [4-6], in which the Gaussian expansion method [7] is applied. It is noted that these methods have the following advantages: (i) we can efficiently describe the energy-dependent asymptotics of single-particle wave functions at large r, as is typified in arguments on the deformed neutron halo in 4 0M g [6], (ii) we can handle various effective interactions, including those having non-locality, and (iii) a single-set of bases is applicable to wide mass range of nuclei and therefore is suitable to systematic calculations. Thereby we can implement Hartree-Fock, Hartree-Fock-Bogolyubov and RPA calculations for stable and unstable nuclei with the semi-realistic interactions. It will be shown first that the new interactions have desired characters for the nuclear matter and for the single- and double-closed nuclei. We shall particularly focus on roles of specific channels of the effective interaction, by studying (a) 'shell evolution' and role of the spin-isospin and the tensor channels [8] in stable and unstable nuclei, and (b) the magnetic response in a fully self-consistent RPA calculation with the tensor force [9]. All these properties seem to be simultaneously and naturally reproduced by the semi-realistic interactions. Thus the semi-realistic interactions are promising in describing various aspects of nuclear structure from stable to drip-line nuclei, in a self-consistent and unified manner. Since they have microscopic origin with minimal modification, we can expect high

Coulomb excitation of neutron-rich$^{28,29,30}$Na nuclei with MINIBALL at REX-ISOLDE: Mapping the borders of the island of inversion

CERN Multimedia

Butler, P; Cederkall, J A; Reiter, P; Wiens, A; Blazhev, A A; Kruecken, R; Voulot, D; Kalkuehler, M; Wadsworth, R; Gernhaeuser, R A; Hess, H E; Holler, A; Finke, F; Leske, J; Huyse, M L; Seidlitz, M

We propose to study the properties of neutron-rich nuclei $^{28,29,30}$Na via Coulomb excitation experiments using the REX-ISOLDE facility coupled with the highly efficient MINIBALL array. Reliable B(E2,0$^{+}$ $\\rightarrow$ 2$^{+}$) values for $^{30,32}$Mg were obtained at ISOLDE. Together with recent new results on $^{31}$Mg, collective and single particle properties are probed for Z=12 at the N=20 neutron closed shell, the 'island of inversion'. We would like to extend this knowledge to the neighbouring $^{28,29,30}$Na isotopes where a different transition from the usual filling of the neutron levels into the region with low lying 2p-2h cross shell configurations is predicted by theory. Detailed theoretical predictions on the transition strength in all three Na nuclei are awaiting experimental verification and are the subject of this proposal. At REX beam energies of 3.0 MeV /nucleon the cross-sections for Coulomb excitation are sufficient. Moreover the results from the close-by $^{30,31,32}$Mg nuclei de...

Magnetic moment measurement of 140Ba nuclei using transient field technique

International Nuclear Information System (INIS)

Saxena, Mansi; Mandal, S.; Siwal, Davinder; Rainovski, G.; Danchev, M.; Damyanova, A.; Gladnishki, K.; Leske, J.; Bauer, C.; Bloch, T.; John, P.; Pietralla, N.; Wollersheim, H.J.; Kojouharov, I.; Pietri, S.; Schaffner, H.

2011-01-01

Mixed symmetry states have been identified in the neutron proton version of the Interacting Boson Model. The motivation of this experiment is to identify uniquely one phonon mixed symmetry states in 140 Ba nuclei by g factor measurement of the states. Magnetic moments measurements provide substantial information on the microscopic structure of the nuclei as the magnetic moment of a nuclei is described by the wave function of one state only. In this present paper we report the preliminary results of the g factor measurement of the first 2 + state of 140 Ba

Near and sub-barrier fusion studies with radioactive nuclei: an overview

International Nuclear Information System (INIS)

Majumdar, Harashit

2004-01-01

Full text: Understanding of the reaction mechanism with radioactive nuclei, e.g., halo nuclei, at near barrier energies appears to be a challenging problem at present. Recent experimental and theoretical investigations of fusion of exotic nuclei with stable targets have yielded new insights into the structure of these nuclei and its effects on the fusion reaction dynamics. One interesting and intriguing result of this type of study is the controversy over fusion enhancement in the presence of strong break-up channels. Other novel information include an increase of break-up cross-sections and weakening or absence of threshold anomaly, related to energy dependence of optical model potentials, in the neighbourhood of the barrier. It is believed that the coupling of the entrance channel to different non-elastic channels (including break-up) is responsible for the above phenomena and these aspects are more prominent in the near barrier region. An overview of the experimental studies of fusion excitation function with RIB will be presented

Near and sub-barrier fusion studies with radioactive nuclei: an overview

International Nuclear Information System (INIS)

Majumdar, Harashit

2004-01-01

Full Text: Understanding of the reaction mechanism with radioactive nuclei, e.g., halo nuclei, at near barrier energies appears to be a challenging problem at present. Recent experimental and theoretical investigations of fusion of exotic nuclei with stable targets have yielded new insights into the structure of these nuclei and its effects on the fusion reaction dynamics. One interesting and intriguing result of this type of study is the controversy over fusion enhancement in the presence of strong break-up channels. Other novel information include an increase of break-up cross-sections and weakening or absence of threshold anomaly, related to energy dependence of optical model potentials, in the neighbourhood of the barrier. It is believed that the coupling of the entrance channel to different non-elastic channels (including break-up) is responsible for the above phenomena and these aspects are more prominent in the near barrier region. An overview of the experimental studies of fusion excitation function with RIB will be presented

$\\beta$-delayed neutrons from oriented $^{137,139}$I and $^{87,89}$Br nuclei

CERN Document Server

Grzywacz, Robert; Stone, Nicholas; Köster, Ulli; Singh, Barlaj; Bingham, Carrol; Gaulard, S; Kolos, Karolina; Madurga, Miguel; Nikolov, J; Otsubo, T; Roccia, S; Veskovic, Miroslav; Walker, Phil; Walters, William

2013-01-01

We propose a world-­‐first measurement of the angular distribution of $\\beta$-­‐delayed n and $\\gamma$- radiation from oriented $^{137, 139}$I and $^{87,89}$Br nuclei, polarised at low temperature at the NICOLE facility. $\\beta$-­‐delayed neutron emission is an increasingly important decay mechanism as the drip line is approached and its detailed understanding is essential to phenomena as fundamental as the r‐process and practical as the safe operation of nuclear power reactors. The experiments offer sensitive tests of theoretical input concerning the allowed and first-­‐forbidden $\\beta$‐decay strength, the spin-­‐density of neutron emitting states and the partial wave barrier penetration as a function of nuclear deformation. In $^{137}$I and $^{87}$Br the decay feeds predominantly the ground state of the daughters $^{136}$Xe and $^{86}$Kr whereas in $^{139}$I and $^{89}$Br we will explore the use of n-$\\gamma$- coincidence to study neutron transitions to the first and second excited state...

Study of beta-delayed neutron with proton-neutron QRPA plus statistical model

International Nuclear Information System (INIS)

Minato, Futoshi; Iwamoto, Osamu

2015-01-01

β-delayed neutron is known to be important for safety operation of nuclear reactor and prediction of elemental abundance after freeze-out of r-process. A lot of researches on it have been performed. However, the experimental data are far from complete since the lifetime of most of the relevant nuclei is so short that one cannot measure in a high efficiency. In order to estimate half-lives and delayed neutron emission probabilities of unexplored nuclei, we developed a new theoretical method which combines a proton-neutron quasi-particle random-phase-approximation and the Hauser-Feshbach statistical model. The present method reproduces experimentally known β-decay half-lives within a factor of 10 and about 40% of within a factor of 2. However it fails to reproduce delayed neutron emission probabilities. We discuss the problems and remedy for them to be made in future. (author)

Strangeness in nuclei and neutron stars

Science.gov (United States)

Lonardoni, Diego

2017-01-01

The presence of exotic particles in the core of neutron stars (NS) has been questioned for a long time. At present, it is still an unsolved problem that drives intense research efforts, both theoretical and experimental. The appearance of strange baryons in the inner regions of a NS, where the density can exceed several times the nuclear saturation density, is likely to happen due to energetic considerations. The onset of strange degrees of freedom is considered as an effective mechanism to soften the equation of state (EoS). This softening affects the entire structure of the star, reducing the pressure and therefore the maximum mass that the star can stably support. The observation of two very massive NS with masses of the order of 2M⊙ seems instead to rule out soft EoS, apparently excluding the possibility of hyperon formation in the core of the star. This inconsistency, usually referred to as the hyperon puzzle, is based on what we currently know about the interaction between strange particles and normal nucleons. The combination of a poor knowledge of the hypernuclear interactions and the difficulty of obtaining clear astrophysical evidence of the presence of hyperons in NS makes the understanding of the behavior of strange degrees of freedom in NS an intriguing theoretical challenge. We give our contribution to the discussion by studying the general problem of the hyperon-nucleon interaction. We attack this issue by employing a quantum Monte Carlo (QMC) technique, that has proven to be successful in the description of strongly correlated Fermion systems, to the study of finite size nuclear systems including strange degrees of freedom, i.e. hypernuclei. We show that many-body hypernuclear forces are fundamental to properly reproduce the ground state physics of Λ hypernuclei from light- to medium-heavy. However, the poor abundance of experimental data on strange nuclei leaves room for a good deal of indetermination in the construction of hypernuclear

Proceedings of the specialists' meeting on 'nuclear spectroscopy and condensed matter physics using short-lived nuclei'

International Nuclear Information System (INIS)

Kobayashi, Yoshio; Shibata, Michihiro; Ohkubo, Yoshitaka

2016-02-01

The research reactor at Research Reactor Institute, Kyoto University is a very useful neutron generator, providing us neutron-rich unstable nuclei by bombarding nuclei with those neutrons. The produced unstable nuclei exhibit aspects distinct from those of stable ones. Nuclear structure studies on a variety of excited states reflecting dynamic nuclear properties are one of fascinating research subjects of physics. On the other hand, some radioactive nuclei can be used as useful probes for understanding interesting properties of condensed matters through studies of hyperfine interactions of static nuclear electromagnetic moments with extranuclear fields. Concerning these two research fields and related areas, the 2nd symposium under the title of 'Nuclear Spectroscopy and Condensed Matter Physics Using Short-lived Nuclei' was held at the Institute for two days on November 4 and 5 in 2015. We are pleased that many hot discussions were made. The talks were given on the followings: 1) Nuclear spectroscopic experiments, 2) TDPAC (time-differential perturbed angular correlation), 3) β-NMR (nuclear magnetic resonance), 4) Moessbauer spectroscopy, 5) muon, etc. This issue is the collection of 17 papers presented at the entitled meeting. The 6 of the presented papers are indexed individually. (J.P.N.)

Theory of dressed bosons and nuclear matter distributions

International Nuclear Information System (INIS)

Tomaselli, M.; Liu, L.C.; Tanihata, I.

2002-09-01

The structure of nuclei with large neutron or proton-neutron excess, i.e., with large isospin components, is investigated in the Boson Dynamic Correlation Model where the valence particle pairs are dressed by their interactions with the microscopic clusters of the core. The mixed-mode states of the model are the eigenstates of a set of nonlinear equations. We solve these equations in terms of the cluster factorizations that are introduced to compute the n-boson matrix elements. Our calculation of the energy levels of 18 O reveals a strong mixing between the valence and core clusters which leads to a large reduction of the spectroscopic factors as calculated in Shell-Model approximations. The coupling of valence- to core-clusters gives a new insight into the halo formation in neutron-rich nuclei, namely, the halo is also a consequence of the excitation of the core protons. The calculated matter distributions of 6 He and 6 Li exhibit strong similarities, which indicate that halo formation in nuclei with proton-neutron excess must be postulated. The matter distributions of these two isotopes reproduce well the differential cross sections obtained in the proton elastic scattering experiments performed at GSI in inverse kinematics at an energy of 0.7 GeV/u. (orig.)

Fusion and reactions of exotic nuclei

Directory of Open Access Journals (Sweden)

Sánchez-Benítez A.M.

2011-10-01

Full Text Available Close to the drip lines, the scattering cross sections of halo nuclei show a different behaviour as compared to the tightly bound projectiles of the stability line. Several experiments carried out in the last decade have been dedicated to investigate the competition between transfer, breakup and fusion channels at energies around and below the Coulomb barrier. The rather complex scenario gives rise to conflicting conclusions concerning the effect of breakup and transfer on reaction dynamics and the sub-barrier fusion process. In this work we discuss recent experimental findings in fusion and reactions of 6He halo nucleus at energies around the Coulomb barrier.

Simulation of neutron rich nuclei production through 239U fission at intermediates energies

International Nuclear Information System (INIS)

Mirea, M.; Clapier, F.; Pauwels, N.; Proust, J.

1997-01-01

The theoretical part and some results obtained from a model realised for fission processes in wide range of mass-asymmetries are presented. The fission barriers are computed in a tridimensional configuration space using the Yukawa - plus - exponential macroscopic energies corrected within the Strutinsky procedure. It is assumed that channel probabilities are proportional with Gamow penetrabilities. The model is applied for the disintegration of the 239 U in order to determine the relative yields for the production of neutron rich nuclei at diverse intermediate energies. (author)

Superheavy nuclei in the relativistic mean-field theory

International Nuclear Information System (INIS)

Lalazissis, G.A.; Ring, P.; Gambhir, Y.K.

1996-01-01

We have carried out a study of superheavy nuclei in the framework of the relativistic mean-field theory. Relativistic Hartree-Bogoliubov (RHB) calculations have been performed for nuclei with large proton and neutron numbers. A finite-range pairing force of Gogny type has been used in the RHB calculations. The ground-state properties of very heavy nuclei with atomic numbers Z=100-114 and neutron numbers N=154-190 have been obtained. The results show that in addition to N=184 the neutron numbers N=160 and N=166 exhibit an extra stability as compared to their neighbors. For the case of protons the atomic number Z=106 is shown to demonstrate a closed-shell behavior in the region of well deformed nuclei about N=160. The proton number Z=114 also indicates a shell closure. Indications for a doubly magic character at Z=106 and N=160 are observed. Implications of shell closures on a possible synthesis of superheavy nuclei are discussed. (orig.)

The Halo Occupation Distribution of obscured quasars: revisiting the unification model

Science.gov (United States)

Mitra, Kaustav; Chatterjee, Suchetana; DiPompeo, Michael A.; Myers, Adam D.; Zheng, Zheng

2018-06-01

We model the projected angular two-point correlation function (2PCF) of obscured and unobscured quasars selected using the Wide-field Infrared Survey Explorer (WISE), at a median redshift of z ˜ 1 using a five parameter Halo Occupation Distribution (HOD) parametrization, derived from a cosmological hydrodynamic simulation by Chatterjee et al. The HOD parametrization was previously used to model the 2PCF of optically selected quasars and X-ray bright active galactic nuclei (AGNs) at z ˜ 1. The current work shows that a single HOD parametrization can be used to model the population of different kinds of AGN in dark matter haloes suggesting the universality of the relationship between AGN and their host dark matter haloes. Our results show that the median halo mass of central quasar hosts increases from optically selected (4.1^{+0.3}_{-0.4} × 10^{12} h^{-1} M_{⊙}) and infra-red (IR) bright unobscured populations (6.3^{+6.2}_{-2.3} × 10^{12} h^{-1} M_{⊙}) to obscured quasars (10.0^{+2.6}_{-3.7} × 10^{12} h^{-1} M_{⊙}), signifying an increase in the degree of clustering. The projected satellite fractions also increase from optically bright to obscured quasars and tend to disfavour a simple `orientation only' theory of active galactic nuclei unification. Our results also show that future measurements of the small-scale clustering of obscured quasars can constrain current theories of galaxy evolution where quasars evolve from an IR-bright obscured phase to the optically bright unobscured phase.

Spectroscopy of heavy fissionable nuclei

Indian Academy of Sciences (India)

2015-08-05

Aug 5, 2015 ... Nuclei in the actinide chain and beyond are prone to fission owing to ... mass nuclei are typically more difficult, because the intensity is .... j15/2 neutron alignments in a region where shell stablization effects are crucial.

Tune-Based Halo Diagnostics

International Nuclear Information System (INIS)

Cameron, Peter

2003-01-01

Tune-based halo diagnostics can be divided into two categories -- diagnostics for halo prevention, and diagnostics for halo measurement. Diagnostics for halo prevention are standard fare in accumulators, synchrotrons, and storage rings, and again can be divided into two categories -- diagnostics to measure the tune distribution (primarily to avoid resonances), and diagnostics to identify instabilities (which will not be discussed here). These diagnostic systems include kicked (coherent) tune measurement, phase-locked loop (PLL) tune measurement, Schottky tune measurement, beam transfer function (BTF) measurements, and measurement of transverse quadrupole mode envelope oscillations. We refer briefly to tune diagnostics used at RHIC and intended for the SNS, and then present experimental results. Tune-based diagnostics for halo measurement (as opposed to prevention) are considerably more difficult. We present one brief example of tune-based halo measurement

Spectroscopy of light neutron deficient nuclei: 31Ar and 27S decays

International Nuclear Information System (INIS)

Borrel, V.

1991-01-01

Light neutron-deficient nuclei exhibit several interesting decay modes. In some cases, beta-delayed alpha emission becomes possible, and beta-delayed three-proton emission can be allowed. The energy spectra of the emitted protons should give informations on the position of the isobaric analog state and on its deexcitation modes. Experimental results obtained at GANIL with the LISE spectrometer on the decay of the isotopes 31 Ar and 27 S are presented. These data are discussed and compared with the predicted isobaric analog state excitation energies and with shell-model calculations. (G.P.) 13 refs.; 7 figs.; 1 tab

Stability of bubble nuclei through Shell-Effects

OpenAIRE

Dietrich, Klaus; Pomorski, Krzysztof

1997-01-01

We investigate the shell structure of bubble nuclei in simple phenomenological shell models and study their binding energy as a function of the radii and of the number of neutron and protons using Strutinsky's method. Shell effects come about, on the one hand, by the high degeneracy of levels with large angular momentum and, on the other, by the big energy gaps between states with a different number of radial nodes. Shell energies down to -40 MeV are shown to occur for certain magic nuclei. E...

Bubble nuclei in relativistic mean field theory

International Nuclear Information System (INIS)

Shukla, A.; Aberg, S.; Patra, S.K.

2011-01-01

Bubble nuclei are characterized by a depletion of their central density, i.e. the formation of the proton or neutron void and subsequently forming proton or neutron bubble nuclei. Possibility of the formation of bubble nuclei has been explored through different nuclear models and in different mass regions. Advancements in experimental nuclear physics has led our experimental access to many new shapes and structures, which were inaccessible hitherto. In the present paper, the possibility of observing nuclear bubble in oxygen isotopes, particularly for 22 O has been studied

The astrophysical r-process and its dependence on properties of nuclei far from stability beta strength functions and neutron capture rates

CERN Document Server

Klapdor-Kleingrothaus, H V; Metzinger, J; Oda, T; Thielemann, F K

1981-01-01

It is shown that the astrophysical r-process and the question of its site are very sensitive to 'standard' nuclear physics parameters like the beta decay properties and neutron capture rates. Since for these quantities in almost all r-process calculations up to now, and also in all estimates of the production rates of chronometric pairs, only very rough assumptions have been made, it is attempted to present procedures which put the calculation of these quantities for nuclei far from stability on a reliable physical basis. This is done by a microscopic description of the beta strength function and by using a statistical model based on a 'next to first principles' optical potential including effects of deformation for the neutron capture rates. The beta -decay rates for approximately 6000 nuclei between the beta -stability line and the neutron drip line are calculated. The heavy element synthesis by explosive He burning then is calculated using these beta -rates and using realistic star models treating the supe...

Density slope of the nuclear symmetry energy from the neutron skin thickness of heavy nuclei

International Nuclear Information System (INIS)

Chen Liewen; Ko Che Ming; Xu Jun; Li Baoan

2010-01-01

Expressing explicitly the parameters of the standard Skyrme interaction in terms of the macroscopic properties of asymmetric nuclear matter, we show in the Skyrme-Hartree-Fock approach that unambiguous correlations exist between observables of finite nuclei and nuclear matter properties. We find that existing data on neutron skin thickness Δr np of Sn isotopes give an important constraint on the symmetry energy E sym (ρ 0 ) and its density slope L at saturation density ρ 0 . Combining these constraints with those from recent analyses of isospin diffusion and the double neutron/proton ratio in heavy-ion collisions at intermediate energies leads to a more stringent limit on L approximately independent of E sym (ρ 0 ). The implication of these new constraints on the Δr np of 208 Pb as well as the core-crust transition density and pressure in neutron stars is discussed.

Study of proton and 2 protons emission from light neutron deficient nuclei around A=20

International Nuclear Information System (INIS)

Zerguerras, T.

2001-09-01

Proton and two proton emission from light neutron deficient nuclei around A=20 have been studied. A radioactive beam of 18 Ne, 17 F and 20 Mg, produced at the Grand Accelerateur National d'Ions Lourds by fragmentation of a 24 Mg primary beam at 95 MeV/A, bombarded a 9 Be target to form unbound states. Proton(s) and nuclei from the decay were detected respectively in the MUST array and the SPEG spectrometer. From energy and angle measurements, the invariant mass of the decaying nucleus could be reconstructed. Double coincidence events between a proton and 17 F, 16 O, 15 O, 14 O and 18 Ne were registered to obtain excitation energy spectra of 18 Ne, 17 F, 16 F, 15 F et 19 Na. Generally, the masses measures are in agreement with previous experiments. In the case of 18 Ne, excitation energy and angular distributions agree well with the predictions of a break up model calculation. From 17 Ne proton coincidences, a first experimental measurement of the ground state mass excess of 18 Na has been obtained and yields 24,19(0,15)MeV. Two proton emission from 17 Ne and 18 Ne excited states and the 19 Mg ground state was studied through triple coincidences between two proton and 15 O, 16 O and 17 Ne respectively. In the first case, the proton-proton relative angle distribution in the center of mass has been compared with model calculation. Sequential emission from excited states of 17 Ne, above the proton emission threshold, through 16 F is dominant but a 2 He decay channel could not be excluded. No 2 He emission from the 1.288 MeV 17 Ne state, or from the 6.15 MeV 18 Ne state has been observed. Only one coincidence event between 17 Ne and two proton was registered, the value of the one neutron stripping reaction cross section of 20 Mg being much lower than predicted. (author)

Spectroscopic Studies of Exotic Nuclei at ISOLDE

CERN Multimedia

2002-01-01

Experiment IS50 is designed to: a) Investigate the full range of the @b strength function of heavy (A~$>$~48)~K nuclei b)~Study the decay of isomeric states in n-deficient bromine nuclei (A~=~72 and 70). The heavy K isotopes appeared to have complex decay schemes, including feeding by the @b-decay of levels having open neutron channels (Beta decay energy Q(@b) exceeds neutron binding energy S^n); in addition, a large fraction of the delayed transitions populate excited levels in the daughter nuclei. The allowed @b-decay selects states in the daughter nucleus with wave functions having a large overlap with the initial state. Hence, the @b strength functions, deduced from these deca reveal simple structures correlated to the particle-hole excitation energies in the Ca nuclei. These results are valuable for the application of the shell-model calculations far from stability. The delayed neutron spectra are measured with a large area curved scintillator in coincidence either with high resolution Ge(Li) detectors, ...

Excitations of one-valence-proton, one-valence-neutron nucleus {sup 210}Bi from cold-neutron capture

Energy Technology Data Exchange (ETDEWEB)

Cieplicka-Oryńczak, N. [INFN sezione di Milano, Via Celoria 16, 20133 Milano (Italy); Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Kraków (Poland); Fornal, B.; Szpak, B. [Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Kraków (Poland); Leoni, S.; Bottoni, S. [INFN sezione di Milano, Via Celoria 16, 20133 Milano (Italy); Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy); Bazzacco, D. [Dipartimento di Fisica e Astronomia dell’Università, I-35131 Padova (Italy); INFN Sezione di Padova, I-35131 Padova (Italy); Blanc, A.; Jentschel, M.; Köster, U.; Mutti, P.; Soldner, T. [Institute Laue-Langevin, 6, rue Jules Horowitz, 38042 Grenoble Cedex 9 (France); Bocchi, G. [Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy); France, G. de [GANIL, Bd. Becquerel, BP 55027, 14076 CAEN Cedex 05 (France); Simpson, G. [LPSC, Université Joseph Fourier Grenoble 1, CNRS/IN2P3, Institut National Polytechnique de Grenoble, F-38026 Grenoble Cedex (France); Ur, C. [INFN Sezione di Padova, Via F. Marzolo 8, I-35131 Padova (Italy); Urban, W. [Faculty of Physics, University of Warsaw, ul. Hoża 69, 02-681, Warszawa (Poland)

2015-10-15

The low-spin structure of one-proton, one-neutron {sup 210}Bi nucleus was investigated in cold-neutron capture reaction on {sup 209}Bi. The γ-coincidence measurements were performed with use of EXILL array consisted of 16 HPGe detectors. The experimental results were compared to shell-model calculations involving valence particles excitations. The {sup 210}Bi nucleus offers the potential to test the effective proton-neutron interactions because most of the states should arise from the proton-neutron excitations. Additionally, it was discovered that a few states should come from the couplings of valence particles to the 3{sup −} octupole vibration in {sup 208}Pb which provides also the possibility of testing the calculations involving the core excitations.

Effects of Brown-Rho scalings in nuclear matter, neutron stars and finite nuclei

Science.gov (United States)

Kuo, T. T. S.; Dong, Huan

2011-01-01

We have carried out calculations for nuclear matter, neutron stars and finite nuclei using NN potentials with and without the medium-dependent modifications based on the Brown-Rho (BR) scalings. Using the Vlow-k low-momentum interactions derived from such potentials, the equations of state (EOS) for symmetric and asymmetric nuclear matter, for densities up to ~ 5ρ0, are calculated using a RPA method where the particle-particle hole-hole ring diagrams are summed to all orders. The medium effects from both a linear BR scaling (BR1) and a non-linear one (BR2) are considered, and they both are essential for our EOSs to reproduce the nuclear matter saturation properties. For densities ρ below ρ0, results from BR1 and BR2 are close to each other. For higher densities, the EOS given by BR2 is more desirable and is well reproduced by that given by the interaction (Vlow-k+TBF) where Vlow-k is the unsealed low-momentum interaction and TBF is an empirical Skyrme three-body force. The moment of inertia of neutron stars is ~ 60 and ~ 25Modotkm2 respectively with and without the inclusion of the above BR2 medium effects. Effects from the BR scaling are important for the long half-life, ~ 5000yrs, of the 14C - 14N β-decay.

The creation of new nuclei

International Nuclear Information System (INIS)

Armbruster, P.; Hessberger, F.P.

1998-01-01

In the last 60 years physicists have created 20 artificial elements beyond uranium. In 1934 Enrico Fermi predicted the creation of new elements by bombarding atoms with neutrons. This method led to the discovery of neptunium (Z=93), plutonium, americium, curium, berkelium, californium, einsteinium and fermium (Z=100). In fact the capture of a neutron is followed by a beta-decay which increases the atomic number (Z) by one unit. Beyond Z=100 beta-decay no more occurs so a new approach was necessary. Between the American Lawrence Berkeley Laboratory and the Russian Dubna Institute a fierce competition broke out to produce new elements by bombarding transuranium nuclei with light elements such as helium, carbon, nitrogen. This new method required heavy equipment: ion accelerator and detectors but led to the creation of all the elements from Z=101 to Z=106. A new idea was to provoke the fusion of heavy nuclei such as lead and bismuth with colliding argon, nickel or zinc ion beams. This method called 'cold fusion' opened the way to reach the nuclei beyond Z=107. In 1996 the element Z=112 was the last discovered. The next step could be the element Z=114 for which a particular stability is expected. (A.C.)

Pairing correlations in N ∝Z pf-shell nuclei

International Nuclear Information System (INIS)

Langanke, K.; Dean, D.J.; Koonin, S.E.; Radha, P.B.

1997-01-01

We perform shell model Monte Carlo calculations to study pair correlations in the ground states of N=Z nuclei with masses A=48-60. We find that T=1, J π =0 + proton-neutron correlations play an important, and even dominant role, in the ground states of odd-odd N=Z nuclei, in agreement with experiment. By studying pairing in the ground states of 52-58 Fe, we observe that the isovector proton-neutron correlations decrease rapidly with increasing neutron excess. In contrast, both the proton, and trivially the neutron correlations increase as neutrons are added. We also study the thermal properties and the temperature dependence of pair correlations for 50 Mn and 52 Fe as exemplars of odd-odd and even-even N=Z nuclei. While for 52 Fe results are similar to those obtained for other even-even nuclei in this mass range, the properties of 50 Mn at low temperatures are strongly influenced by isovector neutron-proton pairing. In coexistence with these isovector pair correlations, our calculations also indicate an excess of isoscalar proton-neutron pairing over the mean-field values. The isovector neutron-proton correlations rapidly decrease with temperatures and vanish for temperatures above T=700 keV, while the isovector correlations among like-nucleons persist to higher temperatures. Related to the quenching of the isovector proton-neutron correlations, the average isospin decreases from 1, appropriate for the ground state, to 0 as the temperature increases. (orig.)

Spectroscopy of few-particle nuclei around magic 132Sn from fission product γ-ray studies

International Nuclear Information System (INIS)

Zhang, C. T.

1998-01-01

We are studying the yrast structure of very neutron-rich nuclei around doubly magic 132 Sn by analyzing fission product γ-ray data from a 248 Cm source at Eurogam II. Yrast cascades in several few-valence-particle nuclei have been identified through γγ cross coincidences with their complementary fission partners. Results for two-valence-particle nuclei 132 Sb, 134 Te, 134 Sb and 134 Sn provide empirical nucleon-nucleon interactions which, combined with single-particle energies already known in the one-particle nuclei, are essential for shell-model analysis in this region. Findings for the N = 82 nuclei 134 Te and 135 I have now been extended to the four-proton nucleus 136 Xe. Results for the two-neutron nucleus 134 Sn and the N = 83 isotones 134 Sb, 135 Te and 135 I open up the spectroscopy of nuclei in the northeast quadrant above 132 Sn

Coulomb excitation of neutron-rich nuclei between the N=40 and N=50 shell gaps using REX-ISOLDE and the Ge MINIBALL array

CERN Multimedia

2002-01-01

We propose to perform Coulomb excitation experiments of neutron-rich nuclei in the vicinity of $^{68}$Ni towards $^{78}$Ni using the REX-ISOLDE facility coupled with the highly efficient MINIBALL array. Major changes in the structure of the atomic nucleus are expected around the N = 40 subshell closure. Recent B(E2) measurements suggested that $^{68}$Ni behaves like a doubly magic nucleus while neutron-rich Zn isotopes with N>38 exhibit a sudden increase of B(E2) values which may be the signature of deformation. We would like to check and test these predictions for neutron-rich nuclei in the vicinity of N = 40 and N = 50 shell closures like $^{72}$Zn, $^{74}$Zn, $^{76}$Zn, $^{68}$Ni, $^{70}$Ni. Our calculations show that an energy upgrade from 2.2 to 3 MeV/nucleon will be of crucial importance for a part of our study while some nuclei can still be very efficiently studied at an energy of 2.2 MeV/nucleon. Therefore, to perform our experiment in an efficient way, we request 21 shifts of beam time before the ene...

DETERMINATION OF THE POINT-SPREAD FUNCTION FOR THE FERMI LARGE AREA TELESCOPE FROM ON-ORBIT DATA AND LIMITS ON PAIR HALOS OF ACTIVE GALACTIC NUCLEI

Energy Technology Data Exchange (ETDEWEB)

Ackermann, M. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Ajello, M.; Allafort, A.; Bechtol, K.; Bloom, E. D.; Borgland, A. W.; Bottacini, E.; Buehler, R. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Asano, K. [Interactive Research Center of Science, Tokyo Institute of Technology, Meguro City, Tokyo 152-8551 (Japan); Atwood, W. B. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Baldini, L.; Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d' Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Brandt, T. J. [CNRS, IRAP, F-31028 Toulouse cedex 4 (France); Brigida, M. [Dipartimento di Fisica ' M. Merlin' dell' Universita e del Politecnico di Bari, I-70126 Bari (Italy); Bruel, P., E-mail: mdwood@slac.stanford.edu, E-mail: mar0@uw.edu [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, F-91128 Palaiseau (France); and others

2013-03-01

The Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to detect photons with energies from Almost-Equal-To 20 MeV to >300 GeV. The pre-launch response functions of the LAT were determined through extensive Monte Carlo simulations and beam tests. The point-spread function (PSF) characterizing the angular distribution of reconstructed photons as a function of energy and geometry in the detector is determined here from two years of on-orbit data by examining the distributions of {gamma} rays from pulsars and active galactic nuclei (AGNs). Above 3 GeV, the PSF is found to be broader than the pre-launch PSF. We checked for dependence of the PSF on the class of {gamma}-ray source and observation epoch and found none. We also investigated several possible spatial models for pair-halo emission around BL Lac AGNs. We found no evidence for a component with spatial extension larger than the PSF and set upper limits on the amplitude of halo emission in stacked images of low- and high-redshift BL Lac AGNs and the TeV blazars 1ES0229+200 and 1ES0347-121.

Study of {sup 19}C by breakup reactions; Etude du {sup 19}C par reactions de cassure

Energy Technology Data Exchange (ETDEWEB)

Liegard, Emmanuel [Lab. de Physique Corpusculaire, Caen Univ., 14 Caen (France)

1998-01-07

To date studies of halo nuclei have been principally focussed on the A 11 systems {sup 11}Li and {sup 11}Be. The evolution of the properties of the halo with the mass of the system and the binding energy and angular momentum of the halo nucleons is a question of fundamental importance. It was in this spirit that the present study of {sup 19}C (S{sub n} = 240 {+-} 100 keV) was undertaken. The experiment was performed at GANIL using a secondary {sup 19}C beam ({approx_equal} 15 pps at 36 MeV/nucleon) produced via fragmentation. The experimental setup which included the neutron array DEMON, provided for identification of the core-breakup and dissociation reaction channels. In the first case, a very narrow single neutron angular distribution (FWHM = 64 {+-} 17 MeV/c) was observed for {sup 19}C, in contrast to that found for three `reference` nuclei {sup 21}N, {sup 22}O and {sup 24}F (FWHM {approx_equal} 165 MeV/c). This result could be interpreted within the framework of the core-breakup reaction model of a one-neutron halo nucleus. The results obtained for dissociation, while supporting the existence of the halo, indicated that it is not well developed. In addition, a comparison between the present results, the parallel momentum distributions for the core ({sup 18}C) and theoretical predictions have allowed conclusions to be drawn regarding the configuration of the valence neutron. In particular, a purely 2s{sub 1/2} of 1d{sub 5/2} configuration is excluded and mixing, possible with core excited states, must be considered. A probable ground state spin-parity assignment of 3{sup +}/2 or 5{sup +}/2 is suggested. (author) 150 refs., 278 figs., 28 tabs.

Neutron emission spectra of excited 126–140Sn nuclei

International Nuclear Information System (INIS)

Aggarwal, Mamta; Rajasekaran, M.

2004-01-01

We investigate one-neutron and two-neutron emission from 132 Sn and its neighboring isotopes due to thermal excitation. The rotational states of 132 Sn at different temperatures are investigated. The effects of separation energy and thermal excitation energy on neutron emission probability are studied. (author)

Measurements of electric quadrupole moments of neutron-deficient Au, Pt, and Ir nuclei with NMR-ON in hcp-Co

CERN Multimedia

Smolic, E; Hagn, E; Zech, E; Seewald, G

2002-01-01

The aim of the experiments is the measurement of $\\,$i) nuclear magnetic moments and electric quadrupole moments of neutron-deficient isotopes in the region Os-Ir-Pt-Au with the methods of quadrupole-interaction-resolved NMR on oriented nuclei " QI-NMR-ON " and modulated adiabatic passage on oriented nuclei " MAPON " and $\\,$ii) the magnetic hyperfine field, electric field gradient (EFG), and spin-lattice relaxation of 5d elements in ferromagnetic Fe, Ni, fcc-Co and hcp-Co.\\\\ The measurements on Au isotopes have been finished successfully. The quadrupole moments of $^{186}$Au, $^{193m}$Au, $^{195}$Au, $^{195m}$Au, $^{197m}$Au, $^{198}$Au and $^{199}$Au were determined with high precision.\\\\ For neutron-deficient Ir isotopes QI-NMR-ON measurements were performed after implantation of Hg precursors. The EFG of Ir in hcp-Co has been calibrated. Thus precise values for the spectroscopic quadrupole mo...

Neutron emission probability at high excitation and isospin

International Nuclear Information System (INIS)

Aggarwal, Mamta

2005-01-01

One-neutron and two-neutron emission probability at different excitations and varying isospin have been studied. Several degrees of freedom like deformation, rotations, temperature, isospin fluctuations and shell structure are incorporated via statistical theory of hot rotating nuclei

Chemical Cartography. I. A Carbonicity Map of the Galactic Halo

Energy Technology Data Exchange (ETDEWEB)

Lee, Young Sun; Kim, Young Kwang [Department of Astronomy and Space Science, Chungnam National University, Daejeon 34134 (Korea, Republic of); Beers, Timothy C.; Placco, Vinicius; Yoon, Jinmi [Department of Physics and JINA Center for the Evolution of the Elements, University of Notre Dame, Notre Dame, IN 46556 (United States); Carollo, Daniela [Research School of Astronomy and Astrophysics, The Australian National University, Canberra, ACT 2611 (Australia); Masseron, Thomas [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Jung, Jaehun, E-mail: youngsun@cnu.ac.kr [Department of Astronomy, Space Science, and Geology, Chungnam National University, Daejeon 34134 (Korea, Republic of)

2017-02-10

We present the first map of carbonicity, [C/Fe], for the halo system of the Milky Way, based on a sample of over 100,000 main-sequence turnoff stars with available spectroscopy from the Sloan Digital Sky Survey. This map, which explores distances up to 15 kpc from the Sun, reveals clear evidence for the dual nature of the Galactic halo, based on the spatial distribution of stellar carbonicity. The metallicity distribution functions of stars in the inner- and outer-halo regions of the carbonicity map reproduce those previously argued to arise from contributions of the inner- and outer-halo populations, with peaks at [Fe/H] = −1.5 and −2.2, respectively. From consideration of the absolute carbon abundances for our sample, A (C), we also confirm that the carbon-enhanced metal-poor (CEMP) stars in the outer-halo region exhibit a higher frequency of CEMP-no stars (those with no overabundances of heavy neutron-capture elements) than of CEMP- s stars (those with strong overabundances of elements associated with the s -process), whereas the stars in the inner-halo region exhibit a higher frequency of CEMP- s stars. We argue that the contrast in the behavior of the CEMP-no and CEMP- s fractions in these regions arises from differences in the mass distributions of the mini-halos from which the stars of the inner- and outer-halo populations formed, which gives rise in turn to the observed dichotomy of the Galactic halo.

MAGIC NUCLEI: Tin-100 turns up

International Nuclear Information System (INIS)

Anon.

1994-01-01

In the same way as the Periodic Table of chemical elements reflects the successive filling of orbital electron shells, in nuclear physics the socalled 'magic' numbers correspond to closed shells of 2, 8, 20, 28, 50, 82, 126,... neutrons and/or protons. More tightly bound than other nuclei, these are the nuclear analogues of the inert gases. 'Doubly magic' nuclei have closed shells of both neutrons and protons. Examples in nature are helium-4 (2 protons and 2 neutrons), oxygen-16 (8 and 8), calcium-40 (20 and 20) and calcium-48 (20 and 28). Radioactive tin-132 (50+82) has been widely studied

Neutron radiative capture reactions on nuclei of relevance to 0νββ, dark matter and neutrino/antineutrino searches

OpenAIRE

Tornow W.; Bhike Megha

2015-01-01

A program is underway at the Triangle Universities Nuclear Laboratory (TUNL) to measure the neutron capture cross section in the 0.5 to 15 MeV energy range on nuclei whose radioactive daughters could potentially create backgrounds in searches for rare events. Here, we refer to neutrino-less double-beta decay and dark-matter searches, and to detectors built for neutrino and/or antineutrino studies. Neutron capture cross-section data obtained by using the activation method are reported for 40Ar...

Low energy resonance in the neutron rich nucleus of 48Ca. New detectors for the study of unstable nuclei: MUST and CATS

International Nuclear Information System (INIS)

Ottini, St.

1998-01-01

Two new detectors have been developed to study reactions resulting from exotic beams. The first one, MUST, a set of Si strip detectors is devoted to light recoil particles detection between 500 eV and 120 MeV. The 40 Ar elastic and inelastic scattering analysis at 77 MeV per nucleon showed a non ambiguous identification of the particles in the detector, thanks the time and energy resolutions. The second one, CATs, is a set of beam detectors. These low pressure wire chambers allow each particle measurement of the exotic beams with an accuracy of 0,4 mm. A special interest is given to the halo nuclei low excitation energy spectra. A dipolar low energy resonance should be observed. The inelastic scattering at 60 MeV per nucleon on two targets ( 40 Ca and 48 Ca) has been studied with SPEG at Ganil (France), to search a low energy resonance. It is not possible to conclude on this low energy resonance existence. (A.L.B.)

The TENDL neutron data library and the TEND1038 38-group neutron constant system

International Nuclear Information System (INIS)

Abramovich, S.N.; Gorelov, V.P.; Gorshikhin, A.A.; Grebennikov, A.N.; Il'in, V.N.; Krut'ko, N.A.; Farafontov, G.G.

2002-01-01

The library contains neutron data for 103 nuclei - i.e. for 38 actinide nuclei (from 232 Th to 249 Cm), 26 fission fragment nuclei and 39 nuclei in structural and technological materials. The 38-group constants were obtained from TENDL. The high-energy group boundary is 20 MeV. The energy range below 1.2 eV contains 11 groups. Temperature and resonance effects were taken into account. The delayed neutron parameters for 6 groups and the yields of 40 fission fragments were obtained (light and heavy, stable and non-stable). The fast neutron features of spherical critical assemblies were calculated using constants from TEND1038. (author)

High energy neutron cross-sections and kerma values of biomedical interest calculated with a nuclear model applicable to light nuclei

International Nuclear Information System (INIS)

Brenner, D.J.

1984-01-01

A model has been developed for calculating fast neutron cross sections (E > 14 MeV) for light nuclei of biomedical interest. The model explicitly includes experimental nuclear structure information. Some calculations for 12 C, 14 N, and 16 O are presented

Nuclei in neutrino-degenerate dense matter, 1

International Nuclear Information System (INIS)

Ogasawara, Ryusuke; Sato, Katsuhiko

1982-01-01

The properties of nuclei in cold dense matter with strongly degenerate neutrinos are investigated with the aid of an extended Thomas-Fermi model of nuclei. The following results are obtained. 1) The proton number of nucleus increases with the increasing density of the matter and it becomes very huge compared with that of the cold catalyzed matter due to the decrease of the Coulomb energy caused by the effect of the lattice-Coulomb energy. 2) The matter densities at the neutron-drip points, where the chemical potentials of neutrons equal zero are obtained as a function of the number of leptons per nucleon Y sub(L), and it is found that nuclei coalesce before neutron drip when Y sub(L) is greater than about 0.4 for the case b.c.c. lattice. 3) Along the neutron-drip points, an infinite network of linked nuclei may be formed at the matter density rho sub(P) asymptotically equals 9 x 10 13 g cm - 3 , and the bubble-phase appears at the matter density rho sub(B) asymptotically equals 1.1 x 10 14 g cm - 3 . When the matter density becomes higher than rho sub(H) asymptotically equals 1.7 x 10 14 g cm - 3 , the bubbles melt into a homogeneous matter. (author)

One-nucleon absorption of slow pions by atomic nuclei and π condensation

International Nuclear Information System (INIS)

Troitskij, M.A.; Koldaev, M.V.; Chekunaev, N.I.

1977-01-01

Solved is a problem of one-nucleon absorption of slow pions by real nuclei. Without ion condensate one-nucleon absorption forbiddenness decreases due to nucleus finiteness, as nucleus finiteness results in nucleon momentum nonconservation. As a result one-nucleon absorption probability differs from a zero and equals the order of 10 -3 . Calculated is one-nucleon absorption probability in nuclear matter as well as in atomic nuclei due to π condensate existence. The condensate part is shown to be considerable in a finite system as well. For heavy nuclei the condensate presence results in this probability increase about 100 times. Experiments on one-nucleon absorption of slow pions may be critical to elucidate a question of π condensate presence in nuclear systems. In conclusion experimental data available on pion absorption are discussed and it is paid attention to the necessity of carrying out further experiments

Heavy ions as probes of nuclei far from stability

International Nuclear Information System (INIS)

Moltz, D.M.; Nitschke, J.M.; Wilmarth, P.A.; Toth, K.S.

1989-01-01

Nuclei located far from stability provide us with an opportunity for studying nuclear matter existing under unusual conditions. In these regions of instability, radioactive decay becomes the predominant technique by which one can obtain structure information. We have been involved in the investigation of nuclear properties of nuclei close to the proton drip line. In our explorations we have utilized heavy-ion fusion, followed by particle evaporation, to produce the extremely neutron-deficient nuclei of interest. In our studies, single-particle states near the 82-neutron shell, populated in the β decay of short-lived nuclides, have been examined and their excitation energies determined. Numerous new isotopes, isomers, and β-delayed-proton and α-particle emitters have been discovered. This contribution will discuss our particle-decay investigations. These decay modes provide us with a convenient means of discovering new isotopes whose identification opens the way for further, more extensive explorations. Also, particle-decay energies in many instances can be used to determine mass differences between parent and daughter ground states. Such measurements are therefore used to test mass formulae and to obtain estimates of masses for proton rich nuclei. 19 refs., 13 figs

Stability and production of superheavy nuclei

International Nuclear Information System (INIS)

Moeller, P.; Los Alamos National Lab., NM; Nix, J.R.

1997-01-01

Beyond uranium heavy elements rapidly become increasingly unstable with respect to spontaneous fission as the proton number Z increases, because of the disruptive effect of the long-range Coulomb force. However, in the region just beyond Z = 100 magic proton and neutron numbers and the associated shell structure enhances nuclear stability sufficient to allow observation of additional nuclei. Some thirty years ago it was speculated that an island of spherical, relatively stable superheavy nuclei would exist near the next doubly magic proton-neutron combination beyond 208 Pb, that is, at proton number Z 114 and neutron number N = 184. Theory and experiment now show that there also exists a rock of stability in the vicinity of Z = 110 and N = 162 between the actinide region, which previously was the end of the peninsula of known elements, and the predicted island of spherical superheavy nuclei slightly southwest of the magic numbers Z = 114 and N = 184. The authors review here the stability properties of the heavy region of nuclei. Just as the decay properties of nuclei in the heavy region depend strongly on shell structure, this structure also dramatically affects the fusion entrance channel. The six most recently discovered new elements were all formed in cold-fusion reactions. They discuss here the effect of the doubly magic structure of the target in cold-fusion reactions on the fusion barrier and on dissipation

Structure and clusters of light unstable nuclei

International Nuclear Information System (INIS)

En'yo, Yoshiko

2010-01-01

As it is known, cluster structures are often observed in light nuclei. In the recent evolution of unstable nuclear research (on nuclei having unbalanced number of neutron and proton) further new types of clusters are coming to be revealed. In this report, structures of light unstable nuclei and some of the theoretical models to describe them are reviewed. The following topics are picked up. 1. Cluster structure and theoretical models, 2. Cluster structure of unstable nuclei (low excited state). 3. Cluster structure of neutron excess beryllium isotopes. 4. Cluster gas like state in C isotope. 5. Dineutron structure of He isotopes. Numbers of strange nuclear structures of light nuclei are illustrated. Antisymmetrized molecular dynamics (AMD) is the recently developed theoretical framework which has been successfully used in heavy ion reactions and nuclear structure studies. Successful application of AMD to the isotopes of Be, B and C are illustrated. (S. Funahashi)

Weighing halo nuclides

International Nuclear Information System (INIS)

Lunney, D.

2009-01-01

Weak binding energy is one of the fundamental criteria characterizing the unique properties of nuclear halos. As such, it must be known with great accuracy and is best obtained through direct mass measurements. The global mass market is now a competitive one. Of the many investment vehicles, the Penning trap has emerged as providing the best rate of return and reliability. We examine mass-market trends, highlighting the recent cases of interest. We also hazard a prediction for the halo futures market. (author)

Rotation-aligned coupling and axial asymmetry in the neutron deficient lanthanum nuclei. Progress report, May 15, 1975--May 14, 1976

International Nuclear Information System (INIS)

Zganjar, E.F.

1976-01-01

The work on the neutron deficient nuclei in the Au region was brought nearer to completion, and systems necessary to extend the investigation to the La nuclei were developed. Twelve reports, including five journals articles, were generated during the reporting period, and the principal investigator received invitations to two international conferences. The LSU nuclear spectroscopy group was given a good deal of support and added strength (by the Department of Physics and Astronomy) through the addition of a nuclear structure theorist and a departmentally sponsored postdoctoral position

Long-lived high-spin isomers in the neutron-deficient 1g sub(9/2)-shell nuclei

International Nuclear Information System (INIS)

Ogawa, K.

1981-09-01

The neutron-deficient 1g sub(9/2)-shell nuclei are studied in the framework of the shell model with active nucleons occuping the 1g sub(9/2) and 2p sub(1/2) shells. The calculated result for 95 Pd shows good agreement with the recent experiment by Nolte and Hick. Many ''spin-gap'' Isomers are predicted in the region of A = 76 -- 84 and A = 95 -- 100. (author)

Neutron Skins and Neutron Stars

OpenAIRE

Piekarewicz, J.

2013-01-01

The neutron-skin thickness of heavy nuclei provides a fundamental link to the equation of state of neutron-rich matter, and hence to the properties of neutron stars. The Lead Radius Experiment ("PREX") at Jefferson Laboratory has recently provided the first model-independence evidence on the existence of a neutron-rich skin in 208Pb. In this contribution we examine how the increased accuracy in the determination of neutron skins expected from the commissioning of intense polarized electron be...

Pramana – Journal of Physics | Indian Academy of Sciences

Indian Academy of Sciences (India)

Hyperspherical harmonics expansion method is applied to a three-body model of two neutron halo nuclei. Convergence of the expansion has been ensured. A repulsive part is introduced in the interaction between the core and the extra-core neutron, to simulate Pauli principle. Two neutron separation energy, r.m.s. radii, ...

Structure of exotic nuclei and superheavy elements in meson field theory

Energy Technology Data Exchange (ETDEWEB)

Linn, Khin Nyan

2008-07-15

In this work the nuclear structure of exotic nuclei and superheavy nuclei is studied in a relativistic framework. In the relativistic mean-field (RMF) approximation, the nucleons interact with each other through the exchange of various effective mesons (scalar, vector, isovector-vector). Ground state properties of exotic nuclei and superheavy nuclei are studied in the RMF theory with the three different parameter sets (ChiM,NL3,NL-Z2). Axial deformation of nuclei within two drip lines are performed with the parameter set (ChiM). The position of drip lines are investigated with three different parameter sets (ChiM,NL3,NL-Z2) and compared with the experimental drip line nuclei. In addition, the structure of hypernuclei are studied and for a certain isotope, hyperon halo nucleus is predicted. (orig.)

Structure of exotic nuclei and superheavy elements in meson field theory

International Nuclear Information System (INIS)

Linn, Khin Nyan

2008-07-01

In this work the nuclear structure of exotic nuclei and superheavy nuclei is studied in a relativistic framework. In the relativistic mean-field (RMF) approximation, the nucleons interact with each other through the exchange of various effective mesons (scalar, vector, isovector-vector). Ground state properties of exotic nuclei and superheavy nuclei are studied in the RMF theory with the three different parameter sets (ChiM,NL3,NL-Z2). Axial deformation of nuclei within two drip lines are performed with the parameter set (ChiM). The position of drip lines are investigated with three different parameter sets (ChiM,NL3,NL-Z2) and compared with the experimental drip line nuclei. In addition, the structure of hypernuclei are studied and for a certain isotope, hyperon halo nucleus is predicted. (orig.)

Attempt to detection of laser radiation effect on the neutron interaction with 139La nuclei

International Nuclear Information System (INIS)

Vertebnyj, V.P.; Razbudej, V.F.; Sidorov, S.V.; Muravitskij, A.V.; Vorona, P.N.

1982-01-01

Phenomenon predicted theoretically was attempted to discover at the WWR-M nuclear reactor. Transmission of a 139 La sample in the radiation field of a CO 2 laser was measured with a neutron spectrometer by means of the time-of-flight method. No satellite resonances near the 0.734 eV resonance, expected according to the Zaretsky-Lomonosov theory, were detected. Causes of disagreement between experiment and theory are not clear yet. The following possible causes can be suggested: 1) neutron resonance at 0.734 eV energy is not p resonance in fact; 2) atom electron shells screen nuclei and considerably weaken external electric field; 3) R=1.2xAsup(1/3)=6.216 and R'=4.9 fermi used values are not exact. Really the value (R-R') can be much less

Effects of momentum-dependent symmetry potential on heavy-ion collisions induced by neutron-rich nuclei

International Nuclear Information System (INIS)

Li Baoan; Das, Champak B.; Das Gupta, Subal; Gale, Charles

2004-01-01

Using an isospin- and momentum-dependent transport model we study effects of the momentum-dependent symmetry potential on heavy-ion collisions induced by neutron-rich nuclei. It is found that symmetry potentials with and without the momentum-dependence but corresponding to the same density-dependent symmetry energy E sym (ρ) lead to significantly different predictions on several E sym (ρ)-sensitive experimental observables especially for energetic nucleons. The momentum- and density-dependence of the symmetry potential have to be determined simultaneously in order to extract the E sym (ρ) accurately. The isospin asymmetry of midrapidity nucleons at high transverse momenta is particularly sensitive to the momentum-dependence of the symmetry potential. It is thus very useful for investigating accurately the equation of state of dense neutron-rich matter

Transitional nuclei near shell closures

Energy Technology Data Exchange (ETDEWEB)

Mukherjee, G. [Variable Energy Cyclotron Centre, 1/AF Bidhan Nagar, Kolkata 700064 (India); Pai, H. [Variable Energy Cyclotron Centre, 1/AF Bidhan Nagar, Kolkata 700064, India and Present Address: Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstrasse 9, 64289 Darmstadt (Germany)

2014-08-14

High spin states in Bismuth and Thallium nuclei near the Z = 82 shell closure and Cesium nuclei near the N = 82 shell closure in A = 190 and A = 130 regions, respectively, have been experimentally investigated using heavy-ion fusion evaporation reaction and by detecting the gamma rays using the Indian National Gamma Array (INGA). Interesting shape properties in these transitional nuclei have been observed. The results were compared with the neighboring nuclei in these two regions. The total Routhian surface (TRS) calculations have been performed for a better understanding of the observed properties. In mass region A = 190, a change in shape from spherical to deformed has been observd around neutron number N = 112 for the Bi (Z = 83) isotopes with proton number above the magic gap Z = 82, whereas, the shape of Tl (Z = 81) isotopes with proton number below the magic gap Z = 82 remains stable as a function of neutron number. An important transition from aplanar to planar configuration of angular momentum vectors leading to the occurance of nuclar chirality and magnetic rotation, respectively, has been proposed for the unique parity πh{sub 11/2}⊗νh{sub 11/2} configuration in Cs isotopes in the mass region A ∼ 130 around neutron number N = 79. These results are in commensurate with the TRS calculations.

Study of single particle properties of nuclei in the region of the "island of inversion" by means of neutron-transfer reactions

CERN Multimedia

Kruecken, R; Voulot, D

2007-01-01

We are aiming at the investigation of single particle properties of neutron-rich nuclei in the region of the "island of inversion" where intruder states from the $\\{fp}$-shell favour deformed ground states instead of the normal spherical $\\textit{sd}$-shell states. As first experiment, we propose to study single particle states in the neutron-rich isotope $^{31}$Mg. The nucleus will be populated by a one-neutron transfer reaction with a $^{30}$Mg beam at 3 MeV/u obtained from REX-ISOLDE impinging on a CD$_{2}$ target. The $\\gamma$-rays will be detected by the MINIBALL array and the particles by a newly built set-up of segmented Si detectors with a angular coverage of nearly 4$\\pi$. Relative spectroscopic factors extracted from the cross sections will enable us to pin down the configurations of the populated states. These will be compared to recent shell model calculations involving new residual interactions. This will shed new light on the evolution of single particle structure leading to the breaking of the ...

Effects of pairing correlation on low-lying quasi-particle resonance in neutron drip-line nuclei

OpenAIRE

Kobayashi, Yoshihiko; Matsuo, Masayuki

2015-01-01

We discuss effects of pairing correlation on quasi-particle resonance. We analyze in detail how the width of low-lying quasi-particle resonance is governed by the pairing correlation in the neutron drip-line nuclei. We consider the 46Si + n system to discuss low-lying p wave quasi-particle resonance. Solving the Hartree-Fock-Bogoliubov equation in the coordinate space with scattering boundary condition, we calculate the phase shift, the elastic cross section, the resonance width and the reson...

Dipole resonances in light neutron-rich nuclei studied with time-dependent calculations of antisymmetrized molecular dynamics

International Nuclear Information System (INIS)

Kanada-En'yo, Y.; Kimura, M.

2005-01-01

To study isovector dipole responses of neutron-rich nuclei, we applied a time-dependent method of antisymmetrized molecular dynamics. The dipole resonances in Be, B, and C isotopes were investigated. In 10 Be, 15 B, and 16 C, collective modes of the vibration between a core and valence neutrons cause soft resonances at the excitation energy E x =10-15 MeV below the giant dipole resonance (GDR). In 16 C, we found that a remarkable peak at E x =14 MeV corresponds to the coherent motion of four valence neutrons against a 12 C core, whereas the GDR arises in the E x >20 MeV region because of vibration within the core. In 17 B and 18 C, the dipole strengths in the low-energy region decline compared with those in 15 B and 16 C. We also discuss the energy-weighted sum rule for the E1 transitions

Influence of the halo upon angular distributions for elastic scattering and breakup

International Nuclear Information System (INIS)

Capel, P.; Hussein, M.S.; Baye, D.

2010-01-01

The angular distributions for elastic scattering and breakup of halo nuclei are analysed using a near-side/far-side decomposition within the framework of the dynamical eikonal approximation. This analysis is performed for 11 Be impinging on Pb at 69 MeV/nucleon. These distributions exhibit very similar features. In particular they are both near-side dominated, as expected from Coulomb-dominated reactions. The general shape of these distributions is sensitive mostly to the projectile-target interactions, but is also affected by the extension of the halo. This suggests the elastic scattering not to be affected by a loss of flux towards the breakup channel.

Gamma-ray measurements in the one-neutron knockout of {sup 17}C, {sup 19}N, {sup 21}O and {sup 25}F

Energy Technology Data Exchange (ETDEWEB)

Rodriguez-Tajes, C.; Cortina-Gil, D.; Alvarez-Pol, H.; Benjamim, E.; Benlliure, J.; Caamano, M.; Casarejos, E.; Gascon, M.; Kurtukian, T.; Perez-Loureiro, D. [Universidade de Santiago de Compostela, Departmento de Fisica de Particulas, Santiago de Compostela (Spain); Aumann, T.; Chatillon, A.; Geissel, H.; Nociforo, C.; Prochazka, A.; Simon, H.; Suemmerer, K.; Weick, H.; Winkler, M. [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Borge, M.J.G.; Pascual-Izarra, C.; Perea, A.; Tengblad, O. [CSIC, Instituto de Estructura de la Materia, Madrid (Spain); Chulkov, L.V. [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Kurchatov Institute, Moscow (Russian Federation); Eppinger, K.; Faestermann, T.; Gernhaeuser, R.; Kruecken, R.; Maierbeck, P.; Schwertel, S. [Technische Universitaet Muenchen, Physik Department E12, Garching (Germany); Jonson, B. [Chalmers Tekniska Hoegskola, Fundamental Fysik, Goeteborg (Sweden); CERN, PH Department, Geneve (Switzerland); Kanungo, R. [Saint Mary' s University, Astronomy and Physics Department, Halifax, NS (Canada); Nilsson, T.; Zhukov, M.V. [Chalmers Tekniska Hoegskola, Fundamental Fysik, Goeteborg (Sweden)

2012-07-15

One-neutron knockout reactions in a {sup 9}Be target have been investigated at relativistic energies, near 700 MeV/u, for a set of sd-shell, neutron-rich nuclei. The experiment was performed in the FRS spectrometer, at GSI. {gamma}-ray measurements were carried out by means of the MINIBALL {gamma}-ray spectrometer and allowed the determination of partial cross-sections and branching ratios corresponding to the final states of the emerging knockout fragments. Experimental results are presented for {sup 17}C, {sup 19}N, {sup 21}O and {sup 25}F projectiles. The role of excited states of the N - 1 fragments in the composition of the ground state of these neutron-rich projectiles is outlined in this work. (orig.)

Nuclear polarization and neutrons

International Nuclear Information System (INIS)

Glaettli, H.

1985-01-01

Different possibilities for the use of polarized nuclei in thermal neutron scattering on condensed matter are reviewed. Highly polarized nuclei are the starting point for studying dipolar magnetic order. Systematic measurement of spin-dependent scattering lengths is possible on samples with polarized nuclei. Highly polarized hydrogen should help to unravel complicated structures in chemistry and biology. The use of polarized proton targets as an energy-independent neutron polarizer in the thermal and epithermal region should be considered afresh. (author)

Vibrational-rotational model of odd-odd nuclei

International Nuclear Information System (INIS)

Afanas'ev, A.V.; Guseva, T.V.; Tamberg, Yu.Ya.

1988-01-01

The rotational vibrational (RV) model of odd nuclei is generalized to odd-odd nuclei. The hamiltonian, wave functions and matrix elements of the RV-model of odd-odd nuclei are obtained. The expressions obtained for matrix elements of the RV-model of odd-odd nuclei can be used to study the role of vibrational additions in low-lying two-particle states of odd-odd deformed nuclei. Such calculations permit to study more correctly the residual neutron-proton interaction of valent nucleons with respect to collectivization effects

Direct mass and lifetime measurements of neutron-rich nuclei up to A∼100 using the TOFI spectrometer at LAMPF

International Nuclear Information System (INIS)

Lind, V.G.

1993-01-01

This project was directed toward the study of neutron-rich nuclei using the experimental facilities at LAMPF, which is a part of LANL. The principal results of the investigation include the discovery of many new isotopes along with a measurement of their masses and in particular those nuclides in the Z = 7--19 and 14 --26 regions of the chart of the nuclides.Thirty-four new nuclides were detected and studied with their masses being measured with relatively high accuracy, and an additional twenty-six that were previously known and measured were remeasured to an improved accuracy. Besides providing new information about the mass surface in new and extended redons of the chart of the nuclides, this investigation enabled properties and previously unknown structure of some of the nuclei to be determined such as nuclear deformation among some of the nuclides. Also a study of the neutron pairing gaps and the proton pairing gaps among these nuclides was made. Other developments also achieved included instrument (TOFI) improvements and upgrades and theoretical investigations into the masses of the hadrons

Synthesis and study of neutron-rich nuclides

International Nuclear Information System (INIS)

Luo Yixiao

1995-01-01

During the past few years our understanding of the decay properties and nuclear structure has been extended in a systematic fashion for the neutron-rich nuclei. This review will first sketch the production and identification of the neutron-rich nuclei throughout the whole mass region, and will then discuss the impressive progress in the studies of the exotic decay properties and nuclear structure of neutron-rich nuclei. Their astrophysical implications will also be outlined

Investigation of the neutron emission spectra of some deformed nuclei for (n, xn) reactions up to 26 MeV energy

International Nuclear Information System (INIS)

Kaplan, A.; Bueyuekuslu, H.; Tel, E.; Aydin, A.; Boeluekdemir, M.H.

2011-01-01

In this study, neutron-emission spectra produced by (n, xn) reactions up to 26 MeV for some deformed target nuclei as 165 Ho, 181 Ta, 184 W, 232 Th and 238 U have been investigated. Also, the mean free path parameter's effect for 9n, xn) neutron-emission spectra has been examined. In the calculations, pre-equilibrium neutron-emission spectra have been calculated by using new evaluated hybrid model and geometry dependent hybrid model, full exciton model and cascade exciton model. The reaction equilibrium component has been calculated by Weisskopf-Ewing model. The obtained results have been discussed and compared with the available experimental data and found agreement with each other. (author)

High Accuracy mass Measurement of the very Short-Lived Halo Nuclide $^{11}$Li

CERN Multimedia

Le scornet, G

2002-01-01

The archetypal halo nuclide $^{11}$Li has now attracted a wealth of experimental and theoretical attention. The most outstanding property of this nuclide, its extended radius that makes it as big as $^{48}$Ca, is highly dependent on the binding energy of the two neutrons forming the halo. New generation experiments using radioactive beams with elastic proton scattering, knock-out and transfer reactions, together with $\\textit{ab initio}$ calculations require the tightening of the constraint on the binding energy. Good metrology also requires confirmation of the sole existing precision result to guard against a possible systematic deviation (or mistake). We propose a high accuracy mass determintation of $^{11}$Li, a particularly challenging task due to its very short half-life of 8.6 ms, but one perfectly suiting the MISTRAL spectrometer, now commissioned at ISOLDE. We request 15 shifts of beam time.

Electron-capture Rates for pf-shell Nuclei in Stellar Environments and Nucleosynthesis

Science.gov (United States)

Suzuki, Toshio; Honma, Michio; Mori, Kanji; Famiano, Michael A.; Kajino, Toshitaka; Hidakai, Jun; Otsuka, Takaharu

Gamow-Teller strengths in pf-shell nuclei obtained by a new shell-model Hamltonian, GXPF1J, are used to evaluate electron-capture rates in pf-shell nuclei at stellar environments. The nuclear weak rates with GXPF1J, which are generally smaller than previous evaluations for proton-rich nuclei, are applied to nucleosynthesis in type Ia supernova explosions. The updated rates are found to lead to less production of neutron-rich nuclei such as 58Ni and 54Cr, thus toward a solution of the problem of over-production of neutron-rich isotopes of iron-group nuclei compared to the solar abundance.

On peculiarities of the cascade γ decay of heavy nuclei

International Nuclear Information System (INIS)

Boneva, S.T.; Khitrov, V.A.; Popov, Yu.P.; Sukhovoj, A.M.; Vasil'eva, E.V.; Yazvitskij, Yu.S.

1987-01-01

Comparison of measured and calculated by statistical theory sums of two-quanta cascade intensities in compound-nuclei 163 ≤ A ≤ 183 points to the dependence of cascade intensity on the structure of initial and intermediate levels. The dependence of two-quanta cascade intensity sum on reduced neutron widths of compound states of even-even nuclei-targets of rare earth regions is detected. In 175 Yb and 179 Hf nuclei a considerable increase in the intensity of two-quanta cascades at the energy of their intermediate level in the range of the calculated position of one-quasiparticle states of the Saxon-Woods deformed potential is observed

Neutron radiative capture reactions on nuclei of relevance to 0νββ, dark matter and neutrino/antineutrino searches

Science.gov (United States)

Tornow, W.; Bhike, Megha

2015-05-01

A program is underway at the Triangle Universities Nuclear Laboratory (TUNL) to measure the neutron capture cross section in the 0.5 to 15 MeV energy range on nuclei whose radioactive daughters could potentially create backgrounds in searches for rare events. Here, we refer to neutrino-less double-beta decay and dark-matter searches, and to detectors built for neutrino and/or antineutrino studies. Neutron capture cross-section data obtained by using the activation method are reported for 40Ar, 74,76Ge, 128,130Te and 136Xe and compared to model calculations and evaluations.

Neutron radiative capture reactions on nuclei of relevance to 0νββ, dark matter and neutrino/antineutrino searches

Directory of Open Access Journals (Sweden)

Tornow W.

2015-01-01

Full Text Available A program is underway at the Triangle Universities Nuclear Laboratory (TUNL to measure the neutron capture cross section in the 0.5 to 15 MeV energy range on nuclei whose radioactive daughters could potentially create backgrounds in searches for rare events. Here, we refer to neutrino-less double-beta decay and dark-matter searches, and to detectors built for neutrino and/or antineutrino studies. Neutron capture cross-section data obtained by using the activation method are reported for 40Ar, 74,76Ge, 128,130Te and 136Xe and compared to model calculations and evaluations.

Revealing the Cosmic Web-dependent Halo Bias

Science.gov (United States)

Yang, Xiaohu; Zhang, Youcai; Lu, Tianhuan; Wang, Huiyuan; Shi, Feng; Tweed, Dylan; Li, Shijie; Luo, Wentao; Lu, Yi; Yang, Lei

2017-10-01

Halo bias is the one of the key ingredients of the halo models. It was shown at a given redshift to be only dependent, to the first order, on the halo mass. In this study, four types of cosmic web environments—clusters, filaments, sheets, and voids—are defined within a state-of-the-art high-resolution N-body simulation. Within these environments, we use both halo-dark matter cross correlation and halo-halo autocorrelation functions to probe the clustering properties of halos. The nature of the halo bias differs strongly between the four different cosmic web environments described here. With respect to the overall population, halos in clusters have significantly lower biases in the {10}11.0˜ {10}13.5 {h}-1 {M}⊙ mass range. In other environments, however, halos show extremely enhanced biases up to a factor 10 in voids for halos of mass ˜ {10}12.0 {h}-1 {M}⊙ . Such a strong cosmic web environment dependence in the halo bias may play an important role in future cosmological and galaxy formation studies. Within this cosmic web framework, the age dependency of halo bias is found to be only significant in clusters and filaments for relatively small halos ≲ {10}12.5 {h}-1 {M}⊙ .

Investigation of the core-halo structure of the neutron-rich nuclei {sup 6}He and {sup 8}He by intermediate-energy elastic proton scattering at high momentum transfer; Etude de la structure coeur-halo des noyaux riches en neutron {sup 6}He et {sup 8}He par la diffusion elastique de protons aux energies intermediaires etendue a la region du premier minimum de diffraction

Energy Technology Data Exchange (ETDEWEB)

Aksouh, F

2002-12-01

The elastic proton scattering from the halo nuclei {sup 6}He and {sup 8}He was investigated in inverse kinematics at energies around 700 MeV/u with the aim to deduce the differential cross sections for the region of high momentum transfer, covering the first diffraction minimum. For this purpose, a liquid-hydrogen target was specially developed and used for the first time allowing to obtain low-background data as compared to commonly used targets made from C-H compounds. Previous data taken in the region of small momentum transfer were sensitive to the size and the peripheral shape of the total nuclear matter density distribution but not to the inner part. The present data allow for a more detailed insight in the structure of the alike core in {sup 6,8}He through a better determination of the matter density distributions. Several density distributions calculated from different microscopic models were used to derive elastic scattering cross sections which are compared with the obtained data. (author)

Nuclei at the limits of particle stability

International Nuclear Information System (INIS)

Mueller, A.C.

1993-01-01

The properties and synthesis of nuclei at the limits of particle stability are reviewed. Nuclear reactions were induced and studied by means of the 'exotic' nuclear beams, i.e. beams of radioactive drip-line nuclei. The beams are mostly generated in heavy-ion projectile fragmentation. The cases of both neutron-rich and proton-rich nuclei are discussed. (K.A.) 270 refs.; 13 figs.; 1 tab

Effects of the residual proton-neutron interaction in the development of collectivity in nuclei

International Nuclear Information System (INIS)

Casten, R.F.

1990-01-01

The widespread effects of the residual T=0 proton-neutron (p-n) interaction in the evolution of nuclear structure are discussed. Although these effects in inducing single nucleon configuration mixing, and hence in the development of non-spherical nuclear shapes, collectivity, and the associated shape and phase transitions have been known for four decades, it is only in recent years that their deep ramifications have become more fully appreciated. This had led to a unified phenomenological understanding of the role of the p-n interaction in nuclear collectivity and to, for example, the proposal of the N p N n scheme and the associated concept of the P factor, which is a normalized value of N p N n reflecting the average number of p-n interactions per valence nucleon. Simultaneously, experimentally-determined p-n matrix elements for many nuclei have been extracted: they disclose striking anomalies for N=Z nuclei, and intriguing microstructure. These developments and empirical results will be discussed along with microscopic calculations that can be used to interpret them. 18 refs., 13 figs

The r-process nucleosynthesis during the decompression of neutron star crust material

Energy Technology Data Exchange (ETDEWEB)

Goriely, S. [Institut d' Astronomie et d' Astrophysique, CP-226, Université Libre de Bruxelles, 1050 Brussels (Belgium); Bauswein, A. [Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece and Max-Planck-Institut für Astrophysik, Postfach 1317, 85741 Garching (Germany); Janka, H.-T. [Max-Planck-Institut für Astrophysik, Postfach 1317, 85741 Garching (Germany); Sida, J.-L.; Lemaître, J.-F.; Panebianco, S. [C.E.A. Saclay, Irfu/Service de Physique Nucléaire, 91191 Gif-sur-Yvette (France); Dubray, N.; Hilaire, S. [CEA, DAM, DIF, F-91297 Arpajon (France)

2014-05-02

About half of the nuclei heavier than iron observed in nature are produced by the so-called rapid neutron capture process, or r-process, of nucleosynthesis. The identification of the astrophysics site and the specific conditions in which the r-process takes place remains, however, one of the still-unsolved mysteries of modern astrophysics. Another underlying difficulty associated with our understanding of the r-process concerns the uncertainties in the predictions of nuclear properties for the few thousands exotic neutron-rich nuclei involved, for which essentially no experimental data exist. The present paper emphasizes some important future challenges faced by nuclear physics in this problem, particularly in the determination of the nuclear structure properties of exotic neutron-rich nuclei as well as their radiative neutron capture rates and their fission probabilities. These quantities are particularly relevant to determine the composition of the matter resulting from the r-process. Both the astrophysics and the nuclear physics difficulties are critically reviewed with special attention paid to the r-process taking place during the decompression of neutron star matter following the merging of two neutron stars.

Fusion enhancement/suppression and irreversibility in reactions induced by weakly bound nuclei

International Nuclear Information System (INIS)

Gomes, P.R.S.; Lubian, J.; Canto, L.F.; Chamon, L.C.; Crema, E.; Hussein, M.S.

2011-01-01

We show that halo effects enhance fusion cross sections of weakly bound systems, comparing with the situation when there is no-halo. We introduce dimensionless fusion functions and energy variable quantity to investigate systematical trends in the fusion cross sections of weakly bound nuclei at near-barrier energies. We observe very clearly complete fusion suppression at energies above the barrier due to dynamic effects of the breakup on fusion. We explain this suppression in terms of the repulsive polarization potential produced by the breakup. (author)

Microscopic Cluster Theory for Exotic Nuclei

International Nuclear Information System (INIS)

Tomaselli, M; Kuehl, T; Ursescu, D; Fritzsche, S

2006-01-01

For a better understanding of the dynamics of complex exotic nuclei it is of crucial importance to develop a practical microscopic theory easy to be applied to a wide range of masses. In this paper we propose to calculate the structure of neutron-rich nuclei within a dynamic model based on the EoM theory

Mean-field models and exotic nuclei

Energy Technology Data Exchange (ETDEWEB)

Bender, M; Buervenich, T; Maruhn, J A; Greiner, W [Inst. fuer Theoretische Physik, Univ. Frankfurt (Germany); Rutz, K [Inst. fuer Theoretische Physik, Univ. Frankfurt (Germany); [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany); Reinhard, P G [Inst. fuer Theoretische Physik, Univ. Erlangen (Germany)

1998-06-01

We discuss two widely used nuclear mean-field models, the relativistic mean-field model and the (nonrelativistic) Skyrme-Hartree-Fock model, and their capability to describe exotic nuclei. Test cases are superheavy nuclei and neutron-rich Sn isotopes. New information in this regime helps to fix hitherto loosely determined aspects of the models. (orig.)

Mean-field models and exotic nuclei

International Nuclear Information System (INIS)

Bender, M.; Buervenich, T.; Maruhn, J.A.; Greiner, W.; Rutz, K.; Reinhard, P.G.

1998-01-01

We discuss two widely used nuclear mean-field models, the relativistic mean-field model and the (nonrelativistic) Skyrme-Hartree-Fock model, and their capability to describe exotic nuclei. Test cases are superheavy nuclei and neutron-rich Sn isotopes. New information in this regime helps to fix hitherto loosely determined aspects of the models. (orig.)

Role of external neutrons of weakly bound nuclei in reactions with their participation

Science.gov (United States)

Naumenko, M. A.; Penionzhkevich, Yu E.; Samarin, V. V.; Sobolev, Yu G.

2018-05-01

The paper presents the results of measurement of the total cross sections for reactions 4,6He+Si and 6,7,9Li+Si in the beam energy range 5–50 A MeV. The enhancements of the total cross sections for reaction 6He+Si compared with reaction 4He+Si and 9Li+Si compared with reactions 6,7Li+Si have been observed. The performed microscopic analysis of total cross sections for reactions 6He+Si and 9Li+Si based on numerical solution of the time-dependent Schrödinger equation for external neutrons of projectile nuclei 6He and 9Li yielded good agreement with experimental data.

Halo Mitigation Using Nonlinear Lattices

CERN Document Server

Sonnad, Kiran G

2005-01-01

This work shows that halos in beams with space charge effects can be controlled by combining nonlinear focusing and collimation. The study relies on Particle-in-Cell (PIC) simulations for a one dimensional, continuous focusing model. The PIC simulation results show that nonlinear focusing leads to damping of the beam oscillations thereby reducing the mismatch. It is well established that reduced mismatch leads to reduced halo formation. However, the nonlinear damping is accompanied by emittance growth causing the beam to spread in phase space. As a result, inducing nonlinear damping alone cannot help mitigate the halo. To compensate for this expansion in phase space, the beam is collimated in the simulation and further evolution of the beam shows that the halo is not regenerated. The focusing model used in the PIC is analysed using the Lie Transform perturbation theory showing that by averaging over a lattice period, one can reuduce the focusing force to a form that is identical to that used in the PIC simula...

What we have learned so far on reactions and scattering with weakly bound nuclei at near barrier energies

International Nuclear Information System (INIS)

Gomes, P.R.S.

2011-01-01

Reactions involving weakly bound nuclei, especially halo nuclei, at near barrier energies, are an important subject not yet fully understood. Due to the low threshold energy for breakup, this process is particularly important and may affect significantly the fusion process and elastic scattering. In this talk I will show the systematic of results so far available in this field, concerning static and dynamical effects of halo and breakup on fusion and total reaction cross sections, the energy dependence of the optical potential on the elastic scattering and coupling effects on quasi-elastic scattering barrier distributions involving weakly bound nuclei, both stable and radioactive. The data to be discussed are new data from our group and from the literature, together with some older data. I will also present some experimental challenges for the development of this field. (author)

Possible existence of backbending in actinide nuclei

International Nuclear Information System (INIS)

Dudek, J.; Nazarewicz, W.; Szymanski, Z.

1982-01-01

The possibilities for the backbending effect to occur in actinide nuclei are studied using the pairing-self-consistent independent quasiparticle method. The Hamiltonian used is that of the deformed Woods-Saxon potential plus monopole pairing term. The results of the calculations explain why there is no backbending in most actinide nuclei and simultaneously suggest that in some light neutron deficient nuclei around Th and 22 Ra a backbending effect may occur

Thermal neutron actinide data

International Nuclear Information System (INIS)

Tellier, H.

1992-01-01

During the 70's, the physicists involved in the cross section measurements for the low energy neutrons were almost exclusively interested in the resonance energy range. The thermal range was considered as sufficiently known. In the beginning of the 80's, reactor physicists had again to deal with the delicate problem of the power reactor temperature coefficient, essentially for the light water reactors. The measured value of the reactivity temperature coefficient does not agree with the computed one. The later is too negative. For obvious safety reasons, it is an important problem which must be solved. Several causes were suggested to explain this discrepancy. Among all these causes, the spectral shift in the thermal energy range seems to be very important. Sensibility calculations shown that this spectral shift is very sensitive to the shape of the neutron cross sections of the actinides for energies below one electron-volt. Consequently, reactor physicists require new and accurate measurements in the thermal and subthermal energy ranges. A part of these new measurement results were recently released and reviewed. The purpose of this study is to complete the preceding review with the new informations which are now available. In reactor physics the major actinides are the fertile nuclei, uranium 238, thorium 232 and plutonium 240 and the fissile nuclei, uranium 233, uranium 235 and plutonium 239. For the fertile nuclei the main datum is the capture cross section, for the fissile nuclei the data of interest are nu-bar, the fission and capture cross sections or a combination of these data such as η or α. In the following sections, we will review the neutron data of the major actinides for the energy below 1 eV

Laser-assisted decay and optical spectroscopy studies of neutron-deficient thallium isotopes

CERN Document Server

Van Beveren, Céline; Huyse, Mark

The neutron-deficient thallium isotopes with one proton less than the Z = 82 shell closure, are situated in an interesting region of the nuclear chart, notorious for intruder states and shape coexistence. Shape coexistence is the remarkable phenomenon in which two or more distinct types of deformation occur at low energy in the same atomic nucleus. Shape coexistence has been studied intensively, experimentally as well as theoretically in different nuclei in the light-lead region and the isomerism in the thallium isotopes was among the first indications of this phenomenon. Different shapes, whose structure has been linked to specific proton orbitals above and below the Z = 82 shell closure, are present at low energy in the neutron-deficient odd-mass thallium nuclei. In the odd-odd nuclei, the coupling of an unpaired proton and unpaired neutron gives rise to multiplets of low-lying states from which some can be isomeric. Since thallium has one proton missing in the major proton shell, and when approaching neutr...

Study of shell closures N=40 and N=50 in neutron-rich nuclei; Etude des fermetures de couches N=40 et N=50 dans les noyaux riches en neutrons

Energy Technology Data Exchange (ETDEWEB)

Perru, O

2004-12-01

For this thesis I have studied 2 neutron shell closures: N=40 and N=50. On N=50, an experiment was done in February 2001 on the ISOL line PARRNe, the issue was to measure the first excited states of {sup 83}Ge (Z=32, N=51) by studying the beta decay of {sup 83}Ga produced by fission of {sup 238}U.The extreme precision of the experimental device, with the operation of hot plasma ion sources made it possible to reach spectroscopic information of the Ge isotopes beyond the magic gap N=50. Two transitions have been attributed to {sup 83}Ge: at 867 keV and at 1238 keV. The level scheme of {sup 83}Ge could be interpreted in terms of weak coupling: the excited states of this nucleus are due to the couplings between the single neutron beyond N=50 and the remaining nucleons.On N=40, we wanted to determine the transition probability between ground state and first excited state, called B(E2), in {sup 70}Ni (N=42) and {sup 74}Zn (N=44) from Coulomb excitation. These exotic nuclei are produced by fragmentation of a primary beam of {sup 76}Ge on a target of {sup 58}Ni, selected by the spectrometer LISE, then interact with a secondary {sup 208}Pb target to induce the Coulomb excitation. At the end of this analysis, the following values have been obtained: B(E2,{sup 70}Ni)=860(170) e{sup 2}fm{sup 4}, B(E2,{sup 74}Zn)=1960(140) e{sup 2}fm{sup 4}. These values have been compared on the one hand to variational calculations which I have realised, on the other hand to published shell model calculations.These calculations point out the complex aspect of the Ni nuclei, which do not seem to have a typical behaviour of semi magic nuclei although they are located on a closed shell in protons (Z=28). (author)

Study on neutron interactions with protons and carbon nuclei at p=4.2 GeV/c

International Nuclear Information System (INIS)

Bekmirzaev, R.N.; Muminov, M.M.; Sultanov, M.U.; Grishina, O.V.; Dolejsi, J.; Tas, P.; Trka, Z.

1988-01-01

The production of neutrons with p=4.2 GeV/c in d(C 3 H 8 ) collisions and their interaction with proton and carbon nuclei are studied. The experimental material has been obtained using the 2m propane bubble chamber irradiated by deuterons with p=4.2 GeV/c per nucleon at the Dubna synchrophasotron, JINR. The data on multiplicity and momentum characteristics of secondary particles in np and nC interactions compared with the calculations on the LUND model are obtained

Coulomb displacement energies in nuclei: a new approach

International Nuclear Information System (INIS)

Auerbach, N.; Tel Aviv Univ.; Bernard, V.; Nguyen, V.G.

1978-04-01

The neutron core polarization gives rise to an important correction to the direct Coulomb contribution when one calculates the Coulomb displacement energies. In the Hartree-Fock model it is shown that this correction is about 2% to 4.5% in medium and heavy nuclei. The core polarization as well as other higher order effects can be included by using a selfconsistent description of the analog state in a complete proton particle-neutron hole space. The Coulomb displacement energies in 48 Ca, 88 Sr and 208 Pb have been calculated using Skyrme interactions SIII and SIV. A good agreement with experiment is obtained

Collective excitations in neutron-rich nuclei within the model of a Fermi liquid drop

International Nuclear Information System (INIS)

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

2000-01-01

We discuss a new mechanism of splitting of giant multipole resonances (GMR) in spherical neutron-rich nuclei. This mechanism is associated with the basic properties of an asymmetric drop of nuclear Fermi liquid. In addition to well-known isospin shell-model predictions, our approach can be used to describe the GMR splitting phenomenon in the wide nuclear-mass region A ∼ 40-240. For the dipole isovector modes, the splitting energy, the relative strength of resonance peaks, and the contribution to the energy-weighted sum rules are in agreement with experimental data for the integrated cross sections for photonuclear (γ, n) and (γ, p) reactions

Quarks in Few Body Nuclei

Directory of Open Access Journals (Sweden)

Holt Roy J.

2016-01-01

Full Text Available Electron scattering at very high Bjorken x from hadrons provides an excellent test of models, has an important role in high energy physics, and from nuclei, provides a window into short range correlations. Light nuclei have a key role because of the relatively well-known nuclear structure. The development of a novel tritium target for Jefferson Lab has led to renewed interest in the mass three system. For example, deep inelastic scattering experiments in the light nuclei provide a powerful means to determine the neutron structure function. The isospin dependence of electron scattering from mass-3 nuclei provide information on short range correlations in nuclei. The program using the new tritium target will be presented along with a summary of other experiments aimed at revealing the large-x structure of the nucleon.

Structure of light proton-rich nuclei on the drip-line

International Nuclear Information System (INIS)

Guimaraes, V.; Toyokawa, H.; Yun, C.C.; Niizeki, T.; Ito, K.; Kishida, T.; Kubo, T.; Pu, Y.; Ohura, M.; Orihara, H.; Terakawa, T.; Hamada, S.; Hirai, M.; Miyatake, H.

1995-01-01

Among proton-rich unstable nuclei on the light proton drip-line, nuclear structure of 21 Mg, 17 Ne, 13 O, 11 N and 9 C have been investigated by the three-neutron pick-up reaction ( 3 He, 6 He). The angular distributions measured for this reaction have shown a characteristic feature of a transferred angular-momentum (L) dependence, which provides spin-parity assignments for the new levels in these nuclei. Here, the results on the nuclear structure of 17 Ne and 11 N are reported. The nucleus 17 Ne we almost unknown before, except that the mass excess had been determined and a few states had been suggested. Many T = 3/2 states were known in the other three members ( 17 N, 17 O and 17 F). Thus, the inclusion of the data on 17 Ne levels has enabled an extensive analysis in terms of the Isobaric Multiplet Mass Equation (IMME) for several excited state quartets. This is the first report on such an extensive analysis in the same mass ststem for a wide range in excitation energy. The 11 N nucleus was investigated to learn about the structure of A 11 system. This mass has been intensively studied, specially because of the halo structure observed in 11 Li and the spin parity-inversion of the 11 Be ground-state. The 11 N nucleus was totally unknown before except for the possible ground state

Electron scattering and reactions from exotic nuclei

International Nuclear Information System (INIS)

Karataglidis, S.

2017-01-01

The SCRIT and FAIR/ELISe experiments are the first to attempt to measure directly electron scattering form factors from nuclei far from stability. This will give direct information for the (one-body) charge densities of those systems, about which there is little information available. The SCRIT experiment will be taking data for medium-mass exotic nuclei, while the electron-ion collider at ELISe, when constructed, will be able to measure form factors for a wide range of exotic nuclei, as available from the radioactive ion beams produced by the FAIR experiment. Other facilities are now being proposed, which will also consider electron scattering from exotic nuclei at higher energies, to study short-range correlations in exclusive reactions. This review will consider all available information concerning the current status (largely theoretical) of electron scattering from exotic nuclei and, where possible, complement such information with equivalent information concerning the neutron densities of those exotic systems, as obtained from intermediate energy proton scattering. The issue of long- and short-range correlations will be discussed, and whether extending such studies to the exotic sector will elicit new information. (orig.)

Electron scattering and reactions from exotic nuclei

Energy Technology Data Exchange (ETDEWEB)

Karataglidis, S. [University of Johannesburg, Department of Physics, Auckland Park (South Africa); University of Melbourne, School of Physics, Victoria (Australia)

2017-04-15

The SCRIT and FAIR/ELISe experiments are the first to attempt to measure directly electron scattering form factors from nuclei far from stability. This will give direct information for the (one-body) charge densities of those systems, about which there is little information available. The SCRIT experiment will be taking data for medium-mass exotic nuclei, while the electron-ion collider at ELISe, when constructed, will be able to measure form factors for a wide range of exotic nuclei, as available from the radioactive ion beams produced by the FAIR experiment. Other facilities are now being proposed, which will also consider electron scattering from exotic nuclei at higher energies, to study short-range correlations in exclusive reactions. This review will consider all available information concerning the current status (largely theoretical) of electron scattering from exotic nuclei and, where possible, complement such information with equivalent information concerning the neutron densities of those exotic systems, as obtained from intermediate energy proton scattering. The issue of long- and short-range correlations will be discussed, and whether extending such studies to the exotic sector will elicit new information. (orig.)

The neutron long counter NERO for studies of β-delayed neutron emission in the r-process

International Nuclear Information System (INIS)

Pereira, J.; Hosmer, P.; Lorusso, G.; Santi, P.; Couture, A.; Daly, J.; Del Santo, M.; Elliot, T.

2010-01-01

The neutron long counter NERO was built at the National Superconducting Cyclotron Laboratory (NSCL), Michigan State University, for measuring β-delayed neutron-emission probabilities. The detector was designed to work in conjunction with a β-delay implantation station, so that β decays and β-delayed neutrons emitted from implanted nuclei can be measured simultaneously. The high efficiency of about 40%, for the range of energies of interest, along with the small background, are crucial for measuring β-delayed neutron emission branchings for neutron-rich r-process nuclei produced as low intensity fragmentation beams in in-flight separator facilities.

One-neutron knockout from Ne24-28 isotopes

CERN Document Server

Rodriguez-Tajes, C; Caamano, M; Faestermann, T; Cortina-Gil, D; Zhukov, M; Simon, H; Nilsson, T; Borge, M J G; Alvarez-Pol, H; Winkler, M; Prochazka, A; Nociforo, C; Weick, H; Kanungo, R; Perez-Loureiro, D; Kurtukian, T; Suemmerer, K; Eppinger, K; Perea, A; Chatillon, A; Maierbeck, P; Benlliure, J; Pascual-Izarra, C; Gernhaeuser, R; Geissel, H; Aumann, T; Kruecken, R; Larsson, K; Tengblad, O; Benjamim, E; Jonson, B; Casarejos, E

2010-01-01

One-neutron knockout reactions of Ne24-28 in a beryllium target have been studied in the Fragment Separator (FRS), at GSI. The results include inclusive one-neutron knockout cross-sections as well as longitudinal-momentum distributions of the knockout fragments. The ground-state structure of the neutron-rich neon isotopes was obtained from an analysis of the measured momentum distributions. The results indicate that the two heaviest isotopes, Ne-27 and Ne-28, are dominated by a configuration in which a s(1/2) neutron is coupled to an excited state of the Ne-26 and Ne-27 core, respectively. (C) 2010 Elsevier B.V. All rights reserved.

Identification of new neutron-rich rare-earth nuclei produced in /sup 252/Cf spontaneous fission

CERN Document Server

Greenwood, R C; Gehrke, R J; Meikrantz, D H

1981-01-01

A program of systematic study of the decay properties of neutron-rich rare-earth nuclei with 30 sneutron-rich rare-earth isotopes including /sup 155/Pm (t/sub 1/2/=48+or-4 s) and /sup 163/Gd (t/sub 1 /2/=68+or-3 s), in addition to 5.51 min /sup 158/Sm which was identified in an earlier series of experiments. (11 refs).

Collective modes and hydrodynamics in the inner crust of neutron stars

International Nuclear Information System (INIS)

Martin, Noel

2016-01-01

Neutron stars have been extensively studied since Baade and Zwicky have proposed their existence in 1934. Their description is at the interface of numerous domains of physics, e.g., X-ray astrophysics, pulsar signal observation, general relativity and nowadays gravitational waves, solid state physics, and also nuclear physics. In this thesis we will concentrate on the nuclear physics description, especially of the inner crust. These stars are characterized by their large mass from one to two solar masses, in a radius of 10 km. Their inner structure can be divided in three major layers: the outer crust, the inner crust and the core. The outer crust consists of nuclei coexisting with an electron gas to ensure charge neutrality. If one goes deeper into the crust, the ratio of neutrons with respect to the total nucleon number increases. Eventually, the excess of neutrons in the nuclei gets so high that they drip out from the nuclei and create a dilute neutron gas. From now on, we will speak of nuclear clusters instead of nuclei. This phenomenon defines the limit between the outer crust and the inner crust. This complicated structure and composition is at the origin of many characteristic properties of neutron stars. Hence, we will construct our work in three major parts. First, we start to account for the neutron gas surrounding the clusters, which we treat as uniform. Here, the neutron gas is assumed to be superfluid, and one can expect a Goldstone mode. This description will be done in the framework of QRPA. Second, we will focus on the study of properties of the clusters contained in the inner crust. Under these conditions we expect to see crystal of spheres, rods and plates of bound nucleons, that we will describe with the help of the ETF approximation. Third, we will finish by treating the interaction between the clusters and the gas with hydrodynamics. The results will be applied to astrophysics and in particular to glitches. (author)