Evidence for a spin-aligned neutron-proton paired phase from the level structure of (92)Pd

4 páginas, 4 figuras.-- El Pdf es la versión pre-print.-- et al.

Proton-hole states in theN=30neutron-rich isotopeK49

Excited states in the N=30 neutron-rich isotope {sup 49}K have been studied using multinucleon transfer reactions with thin targets and the PRISMA-CLARA spectrometer combined with thick-target {gamma}-coincidence data from Gammasphere. The d{sub 3/2} proton-hole state is located 92 keV above the s{sub 1/2} ground state, and the proton-particle f{sub 7/2} state is suggested at 2104 keV. Three other levels are established as involving the coupling to 2{sup +} of two neutrons above the N=28 shell. The measured or estimated lifetimes served to reinforce the interpretation of the observed level structure, which is found to be in satisfactory agreement with shell-model calculations.

High-Statistics Sub-Barrier Coulomb Excitation of $^{106,108,110}$Sn

International audience; A Coulomb excitation campaign on $^{106,108,110}$Sn at 4.4–4.5 MeV/u was launched at the HIE-ISOLDE facility at CERN. Larger excitation cross sections and γ-ray statistics were achieved compared to previous experiments at ∼2.8 MeV/u. More precise $(B(E2;0_{1}^{ + } \to 2_{1}^{ + }))$ values, lifetimes of states via the Doppler shift attenuation method, and new $(B(E2;0_{1}^{ + } \to 2_{x}^{ + })), (B(E2;2_{1}^{ + } \to 4_{1}^{ + }))$ and $(Q(2_{1}^{ + }))$ values from the new Miniball data will be obtained and applied to test modern nuclear structure theories.

New neutron-deficient isotopes from $^{78}$Kr fragmentation

In an experiment with the BigRIPS separator at the RIKEN Nishina Center, the fragmentation of a $^{78}$Kr beam allowed the observation of new neutron-deficient isotopes at the proton drip-line. Clean identification spectra could be produced and $^{63}$Se, $^{67}$Kr, and $^{68}$Kr were identified for the first time. In addition, $^{59}$Ge was also observed. Three of these isotopes, $^{59}$Ge, $^{63}$Se, and $^{67}$Kr, are potential candidates for ground-state two-proton radioactivity. In addition, the isotopes $^{58}$Ge, $^{62}$Se, and $^{66}$Kr were also sought but without success. The present experiment also allowed the determination of production cross sections for some of the most exotic…

Lifetimes of core-excited states in semi-magic $^{95}$Rh

Lifetimes of negative-parity states have been determined in the neutron deficient semi-magic (N = 50) nucleus 95Rh. The fusion-evaporation reaction 58Ni(40Ca,3p) was used to populate high-spin states in 95Rh at the Grand Accélérateur National d’Ions Lourds (GANIL) accelerator facility. The results were obtained using the Doppler Shift Attenuation Method (DSAM) based on the Doppler broadened line shapes produced during the slowing down process of the residual nuclei in a thick 6mg/cm2 metallic target. B(M1) and B(E2) reduced transition strengths are compared with predictions from large-scale shell-model calculations. peerReviewed

Transition probabilities in 31P and 31S : A test for isospin symmetry

International audience; Excited states in the mirror nuclei 31P and 31S were populated in the 1p and 1n exit channels of the reaction 20Ne + 12C, at a beam energy of 33 MeV. The 20Ne beam was delivered for the first time by the Piave-Alpi accelerator of the Laboratori Nazionali di Legnaro. Angular correlations of coincident γ-rays and Doppler-shift attenuation lifetime measurements were performed using the multi-detector array GASP in conjunction with the EUCLIDES charged particle detector. In the observed B(E1) strengths, the isoscalar component, amounting to 24% of the isovector one, provides strong evidence for breaking of the isospin symmetry in the A=31 mass region. Self-consistent bey…

Structure of the As, Ge, Ga nuclei

Abstract The level structures of the N = 50 83As, 82Ge, and 81Ga isotones have been investigated by means of multi-nucleon transfer reactions. A first experiment was performed with the CLARA–PRISMA setup to identify these nuclei. A second experiment was carried out with the GASP array in order to deduce the γ-ray coincidence information. The results obtained on the high-spin states of such nuclei are used to test the stability of the N = 50 shell closure in the region of 78Ni ( Z = 28 ). The comparison of the experimental level schemes with the shell-model calculations yields an N = 50 energy gap value of 4.7(3) MeV at Z = 28 . This value, in a good agreement with the prediction of the fini…

γ-ray linear polarization measurements and(g9/2)−3neutron alignment in91Ru

The authors would like to thank the operators of the GANIL cyclotrons for providing the 36Ar beam. We would also like to thank the EXOGAM Collaboration for use of the clover Ge detector array, the DIAMANT Collaboration for use of the charged particle detector system, and the European gamma-ray Spectroscopy Pool for use of the neutron detector system. We acknowledge funding support from the French-Polish LEA COPIGAL and the IN2P3-Polish laboratories COPIN Agreement No. 06-122, from the UK STFC, from the Swedish Research Council (Contracts No. 2007-4067 and No. 2008-5793), from the Goran Gustafsson Foundation, from the OTKA under Contract No. K100835, and from the Bolyai Janos Foundation. AG …

Maximum spin aligned states in 98 47Ag51

New excited states have been observed in the neutron deficient isotope Ag-98 following the Ni-58+Cr-50-->Te-108* heavy-ion reaction. One of these states may be interpreted as a maximum spin aligned state of the pi g(9/2)(-3) nu vg(7/2) configuration. Other possible interpretations within the nuclear shell model are discussed as well.

β decay of Ni75 and the systematics of the low-lying level structure of neutron-rich odd- A Cu isotopes

Background: Detailed spectroscopy of neutron-rich odd-A Cu isotopes is of great importance for studying the shell evolution in the region of Ni78. While there is experimental information on excited states in Cu69−73,77,79 isotopes, the information concerning Cu75 is very limited. Purpose: Experimentally observed single-particle, core-coupling, and proton-hole intruder states in Cu75, will complete the systematics of these states in the chain of isotopes. Method: Excited states in Cu75 were populated in the β decay of Ni75 isotopes. The Ni nuclei were produced by the in-flight fission of U238 projectiles, and were separated, identified, and implanted in a highly segmented Si detector array f…

High intensity neutrino oscillation facilities in Europe

The EUROnu project has studied three possible options for future, high intensity neutrino oscillation facilities in Europe. The first is a Super Beam, in which the neutrinos come from the decay of pions created by bombarding targets with a 4 MW proton beam from the CERN High Power Superconducting Proton Linac. The far detector for this facility is the 500 kt MEMPHYS water Cherenkov, located in the Frejus tunnel. The second facility is the Neutrino Factory, in which the neutrinos come from the decay of mu(+) and mu(-) beams in a storage ring. The far detector in this case is a 100 kt magnetized iron neutrino detector at a baseline of 2000 km. The third option is a Beta Beam, in which the neu…

Isospin Character of Low-Lying Pygmy Dipole States inPb208via Inelastic Scattering ofO17Ions

The properties of pygmy dipole states in Pb-208 were investigated using the Pb-208(O-17, O-17'gamma) reaction at 340 MeV and measuring the gamma decay with high resolution with the AGATA demonstrator array. Cross sections and angular distributions of the emitted gamma rays and of the scattered particles were measured. The results are compared with (gamma, gamma') and (p, p') data. The data analysis with the distorted wave Born approximation approach gives a good description of the elastic scattering and of the inelastic excitation of the 2(+) and 3(-) states. For the dipole transitions a form factor obtained by folding a microscopically calculated transition density was used for the first t…

Shape coexistence in neutron-deficient Hg188 investigated via lifetime measurements

Background: Shape coexistence in the Z≈82 region has been established in mercury, lead, and polonium isotopes. For even-even mercury isotopes with 100≤N≤106 multiple fingerprints of this phenomenon are observed, which seems to be no longer present for N≥110. According to a number of theoretical calculations, shape coexistence is predicted in the Hg188 isotope. Purpose: The aim of this work was to measure lifetimes of excited states in Hg188 to infer their collective properties, such as the deformation. Extending the investigation to higher-spin states, which are expected to be less affected by band-mixing effects, can provide additional information on the coexisting structures. Methods: The…

Decay studies in the A∼225 Po-Fr region from the DESPEC campaign at GSI in 2021

The HISPEC-DESPEC collaboration aims at investigating the struc-ture of exotic nuclei formed in fragmentation reactions with decay spectroscopymeasurements, as part of the FAIR Phase-0 campaign at GSI. This paper reportson first results of an experiment performed in spring 2021, with a focus on beta-decaystudies in the Po-Fr nuclei in the 220 < A <230 island of octupole deformationexploiting the DESPEC setup. Ion-beta correlations and fast-timing techniques arebeing employed, giving an insight into this difficult-to-reach region. peerReviewed

Studying the Exotic Decay $^{70}Kr$ $\rightarrow$ $^{70}Br$

Acta physica Polonica / B 51(3), 587 (2020). doi:10.5506/APhysPolB.51.587

The GALILEO γ-ray array at the Legnaro National Laboratories

Abstract GALILEO, a new 4 π high-resolution γ -detection array, based on HPGe detectors, has been developed and installed at the Legnaro National Laboratories. The GALILEO array greatly benefits from a fully-digital read-out chain, customized DAQ, and a variety of complementary detectors to improve the resolving power by the detection of particles, ions or high-energy γ -ray transitions. In this work, a full description of the array, including electronics and DAQ, is presented together with its complementary instrumentation.

Neutron detection and γ-ray suppression using artificial neural networks with the liquid scintillators BC-501A and BC-537

Abstract In this work we present a comparison between the two liquid scintillators BC-501A and BC-537 in terms of their performance regarding the pulse-shape discrimination between neutrons and γ rays. Special emphasis is put on the application of artificial neural networks . The results show a systematically higher γ -ray rejection ratio for BC-501A compared to BC-537 applying the commonly used charge comparison method. Using the artificial neural network approach the discrimination quality was improved to more than 95% rejection efficiency of γ rays over the energy range 150 to 1000 keV for both BC-501A and BC-537. However, due to the larger light output of BC-501A compared to BC-537, neu…

Is Seniority a Partial Dynamic Symmetry in the First $\nu g_{9/2}$ Shell?

The low-lying structures of the midshell νg9/2 Ni isotopes 72Ni and 74Ni have been investigated at the RIBF facility in RIKEN within the EURICA collaboration. Previously unobserved low-lying states were accessed for the first time following β decay of the mother nuclei 72Co and 74Co. As a result, we provide a complete picture in terms of the seniority scheme up to the first (8+) levels for both nuclei. The experimental results are compared to shell-model calculations in order to define to what extent the seniority quantum number is preserved in the first neutron g9/2 shell. We find that the disappearance of the seniority isomerism in the (81+) states can be explained by a lowering of the se…

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

5 pags., 6 figs.

Monte Carlo simulation of a single detector unit for the neutron detector array NEDA

WOS: 000301813500009

Kr-96(36)60-Low-Z Boundary of the Island of Deformation at N=60

Prompt.-ray spectroscopy of the neutron-rich Kr-96, produced in transfer-and fusion-induced fission reactions, has been performed using the combination of the Advanced Gamma Tracking Array and the VAMOS + +spectrometer. A second excited state, assigned to J pi = 4(+), is observed for the first time, and a previously reported level energy of the first 2+ excited state is confirmed. The measured energy ratio R-4/2 = E(4(+))/E(2(+)) = 2.12(1) indicates that this nucleus does not show a well-developed collectivity contrary to that seen in heavier N = 60 isotones. This new measurement highlights an abrupt transition of the degree of collectivity as a function of the proton number at Z = 36, of s…

Isomers and high-spin structures in the N=81 isotones Xe135 and Ba137

The high-spin structures of the N = 81 isotones 135Xe and 137Ba are investigated after multinucleontransfer (MNT) and fusion-evaporation reactions. Both nuclei are populated in (i) 136Xe+238U and (ii) 136Xe+208Pb MNT reactions employing the high-resolution Advanced Gamma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA, (iii), in the 136Xe+198Pt MNT reaction employing the -ray array GAMMASPHERE in combination with the gas detector array Chico, and (iv) via a 11B+130Te fusion-evaporation reaction. The high-spin level schemes of 135Xe and 137Ba are considerably extended to higher energies. The 2058-keV (19=2 ) state in 135Xe is identified as an isomer, completing the systema…

In-beam γ-ray spectroscopy of 102Cd

Neutron deficient nuclei close to 100Sn have been studied using the NORDBALL Ge-detector array together with ancillary particle detectors. Evaporation residues from the compound nucleus 108Te were identified with charged particle and neutron detectors. In this paper a considerable extension of the level scheme of the nucleus 102Cd is presented. The strongest cascade of the new level scheme reveals an irregular sequence of dipole transitions above Iπ = 10+ extending up to spin 17. A strongly populated rather regular side band consisting of four quadrupole transitions ranging from spin 9 to spin 17 was also discovered. This band was tentatively assigned negative parity. Shell model calculatio…

Maximally aligned states in the proton drip line nucleus 106Sb

High-spin states in Sb-106 have been investigated in the Fe-54(Ni-58, 1α 1p1n) reaction by in-beam γ-spectroscopic methods using the EUROBALL detector array equipped with charged particle and neutr ...

Role of the Δ Resonance in the Population of a Four-Nucleon State in the Fe56→Fe54 Reaction at Relativistic Energies

The 54Fe nucleus was populated from a 56Fe beam impinging on a Be target with an energy of E=A ¼ 500 MeV. The internal decay via γ-ray emission of the 10þ metastable state was observed. As the structure of this isomeric state has to involve at least four unpaired nucleons, it cannot be populated in a simple two-neutron removal reaction from the 56Fe ground state. The isomeric state was produced in the low-momentum (-energy) tail of the parallel momentum (energy) distribution of 54Fe, suggesting that it was populated via the decay of the Δ0 resonance into a proton. This process allows the population of fournucleon states, such as the observed isomer. Therefore, it is concluded that the obser…

β decay of the nuclei 60Ga (Tz=−1), 62Ga, and 70Br (Tz=0)

Lifetime measurements in neutron-rich63,65Co isotopes using the AGATA demonstrator

Lifetimes of the low-lying (11/2-) states in 63,65Co have been measured employing the recoil distance doppler shift method (RDDS) with the AGATA γ-ray array and the PRISMA mass spectrometer. These nuclei were populated via a multinucleon transfer reaction by bombarding a 238U target with a beam of 64Ni. The experimental B(E2) reduced transition probabilities for 63,65Co are well reproduced by large-scale shell-model calculations that predict a constant trend of the B(E2) values up to the N=40 67Co isotope

High-spin studies of the neutron deficient nuclei 103In, 105In, 107In, and 109In

High-spin states of the isotopes In-103,In-105,In-107,In-109 have been investigated using in-beam gamma-ray spectroscopic methods. Results from three different experiments are presented. Targets of Fe-54, Cr-50, and Mo-92 were bombarded by a 270 and 261 MeV Ni-58 beam and by a 95 MeV F-19 beam, respectively. Reaction channel separation was achieved with a charged-particle detector array and in the first two experiments also with a 1 pi neutron detector system. As a result of these experiments the level schemes of In-103,In-105,In-107,In-109 were significantly extended. Excited states of these odd-A indium isotopes are discussed within the framework of the nuclear shell model and the hole-co…

Symmetries in mirror nuclei $^{31}$S and $^{31}$P

Excited states in mirror nuclei 31S and 31P were populated in the 1n and 1p exit channels, respectively, of the reaction 20Ne + 12C. The beam of 20Ne, with an energy of 33 MeV, was delivered for the first time by the Piave-Alpi accelerator of the Laboratori Nazionali di Legnaro. Angular correlations of coincident pairs and Doppler-shift attenuation lifetime measurements in 31S and 31P were performed using the multidetector array GASP in conjunction with the EUCLIDES charged particle detector. A comparison of the determined B(E1) strengths of the analog mirror 7/2- → 5/2+ transitions indicates the presence of a violation of isospin symmetry.

Lifetime measurements of excited states in neutron-rich nuclei around 48 Ca

The lifetimes of the first excited states of the N = 30 isotones 50Ca and 51Sc and the Z = 18 isotopes 44−46Ar isotopes have been determined using a novel technique that combines the Recoil Distance Doppler Shift method with the CLARA-PRISMA spectrometers in multinucleon transfer reactions. The results allow determinination of the effective charges above 48Ca and test the strength of the N = 28 magic number when moving away from the stability line. Gadea Raga, Andrés, Gadea.Andres@ific.uv.es ; Algora, Alejandro, Alejandro.Algora@ific.uv.es ; Rubio Barroso, Berta, Berta.Rubio@ific.uv.es

Kr369660 –Low- Z Boundary of the Island of Deformation at N=60

Prompt γ-ray spectroscopy of the neutron-rich $^{96}$Kr, produced in transfer- and fusion-induced fission reactions, has been performed using the combination of the Advanced Gamma Tracking Array and the VAMOS++ spectrometer. A second excited state, assigned to $J^π$ = $4^+$, is observed for the first time, and a previously reported level energy of the first 2+ excited state is confirmed. The measured energy ratio R4/2 = E($4^+$)/E($2^+$) = 2.12(1) indicates that this nucleus does not show a well-developed collectivity contrary to that seen in heavier N = 60 isotones. This new measurement highlights an abrupt transition of the degree of collectivity as a function of the proton number at Z = …

In-beam γ-ray spectroscopy of 103Cd

Excited states of Cd-103 were studied in the reaction Ni-58(Cr-50,4pn)Cd-103. The NORDBALL array with neutron and charged particle detectors was employed for the detection of gamma rays and light evaporated particles. The level scheme of Cd-103 was significantly extended. A strong cascade of E2 transitions connecting negative parity states was found, Shell model calculations were performed and positive parity excited states were interpreted in terms of neutron-particle and proton-hole excitations with respect to the doubly magic N = Z = 50 core. The negative parity band was well reproduced by the total routhian surface calculations. (C) 1997 Elsevier Science B.V.

Conceptual design and infrastructure for the installation of the first AGATA sub-array at LNL

WOS: 000295765100014

Collective and broken pair states of65,67Ga

Excited states of 65Ga and 67Ga nuclei were populated through the 12C(58Ni,αp) and 12C(58Ni,3p) reactions, respectively, and investigated by in-beam γ-ray spectroscopic methods. The NORDBALL array equipped with a charged particle ball and 11 neutron detectors was used to detect the evaporated particles and γ rays. The level schemes of 65,67Ga were constructed on the basis of γγ-coincidence relations up to 8.6 and 10 MeV excitation energy, and Iπ=27/2 and 33/2+ spin and parity, respectively. The structure of 65,67Ga nuclei was described in the interacting boson-fermion plus broken pair model, including quasiproton, quasiproton-two-quasineutron, and three-quasiproton fermion configurations in…

Selective properties of neutron transfer reactions in the 90Zr + 208Pb system for the population of excited states in zirconium isotopes

Abstract Nuclei produced via multineutron transfer channels have been studied in 90 Zr + 208 Pb close to the Coulomb barrier energy in a fragment- γ coincident measurement employing the PRISMA magnetic spectrometer coupled to the CLARA γ -array. The selective properties of the reaction mechanism have been discussed in terms of states and their strength excited in the neutron transfer channels leading to 89–94 Zr isotopes. A strong population of yrast states, with energies up to ∼7.5 MeV has been observed.

Pronounced shape change induced by quasiparticle alignment

Mean lifetimes of high-spin states of Kr-74 have been determined using the Doppler-shift attenuation method. The high-spin states were studied using the Ca-40(Ca-40, alpha 2p) reaction at a beam energy of 160 MeV with the GASP gamma-ray spectrometer. The ground-state band and negative parity side band show the presence of three different configurations in terms of transitional quadrupole deformations. A dramatic shape change was found along the ground-state band after the S-band crossing. The deduced quadrupole deformation changes are well reproduced by cranked Woods-Saxon Strutinsky calculations.

Neutron Excitations Across the N=50 Shell Gap in 102In

The structure of In-102 has been investigated by in-beam gamma-spectroscopic methods. Knowledge on the excited states of this nucleus has significantly been extended. Three cascades of transitions were observed to exceed the spin-energy domain spanned by the pig(9/2)(-1)v(d(5/2),g(7/2))(3) configurations. The new high spin states at similar to 4 MeV excitation energy could be assigned to the pig(9/2)(-1)v(d(5/2), g(7/2))(2)h (11/2) configuration, while at least those at 4.733, 5.192 and 5.853 MeV most likely arise from the vg(9/2) --> vd(5/2), g(7/2) one-particle-one-hole excitation across the N = 50 shell closure.

Structure of high-spin states in Pd

High-spin states of the neutron deficient (100)pd nucleus have been investigated via the Cr-50(Ni-58, 4p alpha) and Zn-70(S-36,6n) heavy-ion induced reactions. For the detection of evaporated particles and gamma rays the NORDBALL array equipped with ancillary detectors and the EUROGAM II detector system were utilized. By the use of in-beam spectroscopic methods 89 transitions belonging to (100)pd have been observed, 49 of which were identified for the first time. The level scheme has been extended up to E-X approximate to 16 MeV excitation energy and I approximate to 25h. The experimental results were compared with the predictions of cranked shell model calculations. Maximal spin alignments…

'beta'-decay studies of neutron-rich 'TL', 'PB', and 'BI' isotopes

The fragmentation of relativistic uranium projectiles has been exploited at the Gesellschaft fur Schwerionenforschung laboratory to investigate the β decay of neutron-rich nuclei just beyond 208Pb. This paper reports on β-delayed γ decays of 211-213Tl, 215Pb, and 215-219Bi de-exciting states in the daughters 211-213Pb, 215Bi, and 215-219Po. The resulting partial level schemes, proposed with the help of systematics and shell-model calculations, are presented. The role of allowed Gamow-Teller and first-forbidden β transitions in this mass region is discussed. © 2014 American Physical Society.

Lifetime measurement of neutron-rich even-even molybdenum isotopes

D. Ralet et al. -- 11 pags., 10 figs., 3 tabs.

Spectroscopy of Kr70 and isospin symmetry in the T=1 fpg shell nuclei

The recoil-β tagging technique has been used in conjunction with the 40 Ca(32 S ,2n) reaction at a beam energy of 88 MeV to identify transitions associated with the decay of the 2 + and, tentatively, 4 + states in the nucleus 70 Kr. These data are used, along with previously published data, to examine the triplet energy differences (TED) for the mass 70 isobars. The experimental TED values are compared with shell model calculations, performed with the JUN45 interaction in the fpg model space, that include a J = 0 isospin nonconserving (INC) interaction with an isotensor strength of 100 keV. The agreement is found to be very good up to spin 4 and supports the expectation for analog states th…

Digital Front-End Electronics for the Neutron Detector NEDA

19th Real Time Conference (RT) -- MAY 26-30, 2014 -- Nara, JAPAN

Pygmy dipole resonance in 124Sn populated by inelastic scattering of 17O

L. Pellegri et al. ; 5 pags. ; 6 figs. ; open access article under the CC BY license. Funded by SCOAP3

Coulomb excitation of Rn-222

The nature of quadrupole and octupole collectivity in 222Rn was investigated by determining the electric-quadrupole (E2) and octupole (E3) matrix elements using subbarrier, multistep Coulomb excitation. The radioactive 222Rn beam, accelerated to 4.23 MeV/u, was provided by the HIE-ISOLDE facility at CERN. Data were collected in the Miniball γ-ray spectrometer following the bombardment of two targets, 120Sn and 60Ni. Transition E2 matrix elements within the ground-state and octupole bands were measured up to 10ℏ and the results were consistent with a constant intrinsic electric-quadrupole moment, 518(11)efm2. The values of the intrinsic electric-octupole moment for the 0+→3− and 2+→5− transi…

Study of medium-spin states of neutron-rich 87, 89, 91Rb isotopes

International audience; Excited states of the rubidium isotopes$_{37}^{87, 89, 91}$Rb have been studied at the INFN Legnaro National Laboratory. Measurements of the $\gamma$ -ray decay of fragments produced in binary grazing reactions resulting from the interaction of a beam of 530 MeV$^{96}$Zr ions with a$^{124}$Sn target have been complemented by studies of the $\gamma$ -ray decay of fission fragments produced in the interaction of a beam of 230 MeV$^{36}$S ions with a thick$^{176}$Yb target. The structure of the yrast states of$_{37}^{87, 89, 91}$Rb has been discussed within the context of spherical shell-model and cranked Nilsson-Strutinsky calculations.

Plunger Lifetime Measurements in 102Pd

Recently, an intense experimental effort has been devoted to the search of empirical proofs of critical‐point symmetries in nuclear structure. These symmetries describe shape‐phase transitions and provide parameter‐free predictions (up to over‐all scale factors) for excitation spectra and B(E2) values. This contribution reports on recent plunger‐lifetime measurements ON 102Pd carried out at LNL, Legnaro, with the Cologne plunger apparatus coupled to the GASP spectrometer and using the 92Zr(13C,3n)102Pd reaction at 48 MeV. According to the results of our measurements, 102Pd is so far the best known paradigm of the E(5) critical‐point symmetry.

Low-lying excitations in Ni 72

A. I. Morales et al.; 14 págs.; 9 figs.; 3 tabs.

High-spin structures in Xe132 and Xe133 and evidence for isomers along the N=79 isotones

Author(s): Vogt, A; Siciliano, M; Birkenbach, B; Reiter, P; Hadynska-Klȩk, K; Wheldon, C; Valiente-Dobon, JJ; Teruya, E; Yoshinaga, N; Arnswald, K; Bazzacco, D; Blazhev, A; Bracco, A; Bruyneel, B; Chakrawarthy, RS; Chapman, R; Cline, D; Corradi, L; Crespi, FCL; Cromaz, M; De Angelis, G; Eberth, J; Fallon, P; Farnea, E; Fioretto, E; Fransen, C; Freeman, SJ; Fu, B; Gadea, A; Gelletly, W; Giaz, A; Gorgen, A; Gottardo, A; Hayes, AB; Hess, H; Hetzenegger, R; Hirsch, R; Hua, H; John, PR; Jolie, J; Jungclaus, A; Karayonchev, V; Kaya, L; Korten, W; Lee, IY; Leoni, S; Liang, X; Lunardi, S; MacChiavelli, AO; Menegazzo, R; Mengoni, D; Michelagnoli, C; Mijatovic, T; Montagnoli, G; Montanari, D; Muller-…

Shell model and octupole states in148Gd from in-beam experiments

Through (α, 4n) and (τ, 3n) reactions the high-spin states in the two-neutron nucleus148Gd were populated up toI π=21− at 7.2 MeV, including numerous states above the yrast line. The148Gd energy spectrum is interpreted in terms of the spherical shell model. Identification of the (νf 7/2 i 1 3/2)10− state gives the νi 13/2 single particle energy free of octupole admixtures as 2.1(1) MeV. Eight high-spin states between 1.2 and 3.7 MeV were identified as the couplings of the two valence-particles to the146Gd octupole phonon, and three above-lying levels are assigned as double-octupole excitations including a 12+ state which decays by anE3-E3 stretched cascade. All these octupole levels can be …

A New Front-End High-Resolution Sampling Board for the New-Generation Electronics of EXOGAM2 and NEDA Detectors

19th Real Time Conference (RT) -- MAY 26-30, 2014 -- Nara, JAPAN WOS: 000356458000028 This paper presents the final design and results of the FADC Mezzanine for the EXOGAM (EXOtic GAMma array spectrometer) and NEDA (Neutron Detector Array) detectors. The measurements performed include those of studying the effective number of bits, the energy resolution using HP-Ge detectors, as well as timing histograms and discrimination performance. Finally, the conclusion shows how a common digitizing device has been integrated in the experimental environment of two very different detectors which combine both low-noise acquisition and fast sampling rates. Not only the integration fulfilled the expected …

Structure of 68As studied via the 12C(58Ni,pn) reaction

Excited states of As-68 nucleus were populated through the C-12(Ni-58,pn) reaction and investigated by in-beam gamma-spectroscopic methods. The NORDBALL detector array equipped with charged particle and neutron detectors was used to detect the evaporated particles and gamma-rays. The level scheme of As-68 was constructed on the basis of gamma gamma-coincidence relations up to 6 MeV excitation energy and J(pi) = (15(+)). The structure of the nucleus is discussed in the framework of the interacting boson-fermion-fermion model. The states below 2.3 MeV are described as members of proton-neutron-phonon multiplets. (C) 1998 Elsevier Science B.V.

Two-Proton Radioactivity ofKr67

In an experiment with the BigRIPS separator at the RIKEN Nishina Center, we observed two-proton (2p) emission from 67Kr. At the same time, no evidence for 2p emission of 59Ge and 63Se, two other potential candidates for this exotic radioactivity, could be observed. This observation is in line with Q value predictions which pointed to 67Kr as being the best new candidate among the three for two-proton radioactivity. 67Kr is only the fourth 2p ground-state emitter to be observed with a half-life of the order of a few milliseconds. The decay energy was determined to be 1690(17) keV, the 2p emission branching ratio is 37(14)%, and the half-life of 67Kr is 7.4(30) ms.

Single-neutron orbits near 78 Ni: Spectroscopy of theN=49isotope 79 Zn

Single-neutron states in the Z=30, N=49isotope 79Zn have been populated using the 78Zn(d,p)79Zn transfer reaction at REX-ISOLDE, CERN. The experimental setup allowed the combined detection of protons ejected in the reaction, and of γrays emitted by 79Zn. The analysis reveals that the lowest excited states populated in the reaction lie at approximately 1MeV of excitation, and involve neutron orbits above the N=50shell gap. From the analysis of γ-ray data and of proton angular distributions, characteristic of the amount of angular momentum transferred, a5/2+configuration was assigned to a state at 983keV. Comparison with large-scale-shell-model calculations supports a robust neutron N=50shell…

Conceptual design of the AGATA 1$\pi$ array at GANIL

The Advanced GAmma Tracking Array (AGATA) has been installed at the GANIL facility, Caen-France. This setup exploits the stable and radioactive heavy-ions beams delivered by the cyclotron accelerator complex of GANIL. Additionally, it benefits from a large palette of ancillary detectors and spectrometers to address in-beam γ-ray spectroscopy of exotic nuclei. The set-up has been designed to couple AGATA with a magnetic spectrometer, charged-particle and neutron detectors, scintillators for the detection of high-energy γ rays and other devices such as a plunger to measure nuclear lifetimes. In this paper, the design and the mechanical characteristics of the set-up are described. Based on sim…

Digital pulse-timing technique for the neutron detector array NEDA

WOS: 000348040900011

An innovative Superconducting Recoil Separator for HIE-ISOLDE

International audience; The ISOLDE Scientific Infrastructure at CERN offers a unique range of post-accelerated radioactive beams. The scientific program can be improved with the “Isolde Superconducting Recoil Separator” (ISRS), an innovative spectrometer able to deliver unprecedented (A, Z) resolution. In this paper we present an overview of the physics and ongoing technical developments.

Isospin mixing in the N = Z nucleus Ge-64

The N=Z nucleus 64Ge has been investigated in two experiments using the EUROBALL III and EUROBALL IV spectrometers coupled to ancillary devices. Multipole mixing ratios, linear polarization and picosecond lifetimes for various transitions have been measured. The linear polarization results determine unambiguously the multipole character of the 5--->4+ 1665 keV transition, allowing to extract the electric dipole strength and to investigate for the first time the amount of isospin mixing implied by the presence of a forbidden E1 transition.

β decay of the very neutron-deficient Ge60 and Ge62 nuclei

We report here the results of a study of the $\beta$ decay of the proton-rich Ge isotopes, $^{60}$Ge and $^{62}$Ge, produced in an experiment at the RIKEN Nishina Center. We have improved our knowledge of the half-lives of $^{62}$Ge (73.5(1) ms), $^{60}$Ge (25.0(3) ms) and its daughter nucleus, $^{60}$Ga (69.4(2) ms). We measured individual $\beta$-delayed proton and $\gamma$ emissions and their related branching ratios. Decay schemes and absolute Fermi and Gamow-Teller transition strengths have been determined. The mass excesses of the nuclei under study have been deduced. A total $\beta$-delayed proton-emission branching ratio of 67(3)% has been obtained for $^{60}$Ge. New information has…

Coulomb Excitation of (142) Xe

5 pags., 2 figs. -- Open Access funded by Creative Commons Atribution Licence 4.0. -- Presented at the XXXV Mazurian Lakes Conference on Physics, Piaski, Poland, September 3–9, 2017.

Evolution of collectivity in the78Ni region: Coulomb excitation of74Ni at intermediate energies.

The study of the collective properties of nuclear excitations far from stability provides information about the shell structure at extreme conditions. Spectroscopic ob- servables such as the energy or the transition probabilities of the lowest states, in nuclei with large neutron excess, allow to probe the density and isospin dependence of the ef- fective interaction. Indeed, it was recently shown that tensor and three-body forces play an important role in breaking and creating magic numbers. Emblematic is the case of the evolution of the Ni isotopic chain where several features showed up moving from the most neutron rich stable isotope ( 64 Ni) towards the 78 Ni nucleus where the large neu…

Pulse pile-up identification and reconstruction for liquid scintillator based neutron detectors

WOS: 000433206800010 The issue of pulse pile-up is frequently encountered in nuclear experiments involving high counting rates, which will distort the pulse shapes and the energy spectra. A digital method of off-line processing of pile-up pulses is presented. The pile-up pulses were firstly identified by detecting the downward-going zero-crossings in the first-order derivative of the original signal, and then the constituent pulses were reconstructed based on comparing the pile-up pulse with four models that are generated by combining pairs of neutron and.. standard pulses together with a controllable time interval. The accuracy of this method in resolving the pile-up events was investigate…

Study of the γ decay of high-lying states in 208Pb via inelastic scattering of 17O ions

A measurement of the high-lying states in 208Pb has been made using 17O beams at 20 MeV/u. The gamma decay following inelastic excitation was measured with the detector system AGATA Demonstrator based on segmented HPGe detectors, coupled to an array of large volume LaBr3:Ce scintillators and to an array of Si detectors. Preliminary results in comparison with (γ,γ’) data, for states in the 5-8 MeV energy interval, are presented.

Gamma-ray linear polarization measurements and (g(9/2))(-3) neutron alignment in Ru-91

Linear polarization measurements have been performed for gamma rays in Ru-91 produced with the Ni-58(Ar-36,2p1n gamma)Ru-91 reaction at a beam energy of 111 MeV. The EXOGAM Ge clover array has been used to measure the gamma-gamma coincidences, gamma-ray linear polarization, and gamma-ray angular distributions. The polarization sensitivity of the EXOGAM clover detectors acting as Compton polarimeters has been determined in the energy range 0.3-1.3 MeV. Several transitions have been observed for the first time. Measurements of linear polarization and angular distribution have led to the firm assignments of spin differences and parity of high-spin states in Ru-91. More specifically, calculatio…

Simultaneous investigation of the T=1(Jπ=0+) and T=0(Jπ=9+) β decays in Br70

The $\beta$ decay of the odd-odd nucleus $^{70}$Br has been investigated with the BigRIPS and EURICA setups at the Radioactive Ion Beam Factory (RIBF) of the RIKEN Nishina Center. The $T=0$ ($J^{\pi}=9^+$) and $T=1$ ($J^{\pi}=0^+$) isomers have both been produced in in-flight fragmentation of $^{78}$Kr with ratios of 41.6(8)\% and 58.4(8)\%, respectively. A half-life of $t_{1/2}=2157^{+53}_{-49}$ ms has been measured for the $J^{\pi}=9^+$ isomer from $\gamma$-ray time decay analysis. Based on this result, we provide a new value of the half-life for the $J^{\pi}=0^+$ ground state of $^{70}$Br, $t_{1/2}=78.42\pm0.51$ ms, which is slightly more precise, and in excellent agreement, with the bes…

Maximally aligned states in $^{99}$Ag

Excited states of Ag-99 were populated via the Cr-50 + Ni-58 (261 MeV) reaction using the NORDBALL detector array equipped with charged-particle and neutron. detector systems for reaction channel separation. On the basis of the measured gammagamma-coincidence relations and angular distribution ratios a significantly extended level scheme has been constructed up to E-x similar to 7.8 MeV and I = 35/2. The experimental results were described within the framework of the shell model. Candidates for states fully aligned in the pig(9/2)(-3)nu(d(5/2),g(7/2))(2) valence configuration space were found at 4109 and 6265 keV.

Performance of the Advanced GAmma Tracking Array at GANIL

The performance of the Advanced GAmma Tracking Array (AGATA) at GANIL is discussed, on the basis of the analysis of source and in-beam data taken with up to 30 segmented crystals. Data processing is described in detail. The performance of individual detectors are shown. The efficiency of the individual detectors as well as the efficiency after $\gamma$-ray tracking are discussed. Recent developments of $\gamma$-ray tracking are also presented. The experimentally achieved peak-to-total is compared with simulations showing the impact of back-scattered $\gamma$ rays on the peak-to-total in a $\gamma$-ray tracking array. An estimate of the achieved position resolution using the Doppler broadeni…

Hindered Gamow-Teller Decay to the Odd-OddN=ZGa62: Absence of Proton-NeutronT=0Condensate inA=62

Search for a new kind of superfluidity built on collective proton-neutron pairs with aligned spin is performed studying the Gamow-Teller decay of the T=1, Jπ=0+ ground state of Ge62 into excited states of the odd-odd N=Z nucleus Ga62. The experiment is performed at GSI Helmholtzzentrum fur Schwerionenforschung with the Ge62 ions selected by the fragment separator and implanted in a stack of Si-strip detectors, surrounded by the RISING Ge array. A half-life of T1/2=82.9(14) ms is measured for the Ge62 ground state. Six excited states of Ga62, populated below 2.5 MeV through Gamow-Teller transitions, are identified. Individual Gamow-Teller transition strengths agree well with theoretical pred…

High-spin structure of ^{95}Pd

The level scheme of the neutron-deficient nucleus ${}^{95}$Pd has been studied with the ${}^{58}$Ni + ${}^{40}$Ca fusion-evaporation reaction at 135 MeV with the GASP $\ensuremath{\gamma}$-ray array, the ISIS silicon ball, and the N-ring neutron detector. Excited levels with spins at least up to $\frac{45}{2}\ensuremath{\hbar}$ are reported for both parities. The observed experimental data are compared to large-scale shell-model calculations.

Gamma-ray linear polarization measurement and $(g9/2)-3$ neutron alignment in 91Ru

Linear polarization measurements have been performed for γ rays in 91Ru produced with the 58Ni(36Ar, 2p1nγ ) 91Ru reaction at a beam energy of 111 MeV. The EXOGAM Ge clover array has been used to measure the γ -γ coincidences, γ -ray linear polarization, and γ -ray angular distributions. The polarization sensitivity of the EXOGAM clover detectors acting as Compton polarimeters has been determined in the energy range 0.3–1.3 MeV. Several transitions have been observed for the first time. Measurements of linear polarization and angular distribution have led to the firm assignments of spin differences and parity of high-spin states in 91Ru. More specifically, calculations using a semiempirical…

Probing the nature of particle–core couplings in 49Ca with γ spectroscopy and heavy-ion transfer reactions

Neutron rich nuclei around 48Ca have been measured with the CLARA–PRISMA setup, making use of 48Ca on 64Ni binary reactions, at 5.9 MeV/A. Angular distributions of γ rays give evidence, in several transfer channels, for a large spin alignment (≈70%) perpendicular to the reaction plane, making it possible to firmly establish spin and parities of the excited states. In the case of 49Ca, states arising from different types of particle–core couplings are, for the first time, unambiguously identified on basis of angular distribution, polarization and lifetime measurements. Shell model and particle–vibration coupling calculations are used to pin down the nature of the states. Evidence is found fo…

Oblate Collectivity in the Yrast Structure of 194Pt

A deep inelastic reaction using a 460 MeV 82Se beam incident upon a thick 192Os target was performed at the Legnaro National Laboratory, Italy. The resulting γ-decays were measured using the GASP array. Results for 194Pt extend the known level scheme of the yrast structure from spin I = (12 ħ) to (20 ħ). The irregularities in the sequence of the new transition energies and total Routhian surface calculations show a breakdown in collectivity with an yrast oblate shape remaining to high spin. Rubio Barroso, Berta, Berta.Rubio@ific.uv.es

First Exploration of Neutron Shell Structure Below Lead and Beyond $\boldsymbol{N=126}$

The nuclei below lead but with more than 126 neutrons are crucial to an understanding of the astrophysical $r$-process in producing nuclei heavier than $A\sim190$. Despite their importance, the structure and properties of these nuclei remain experimentally untested as they are difficult to produce in nuclear reactions with stable beams. In a first exploration of the shell structure of this region, neutron excitations in $^{207}$Hg have been probed using the neutron-adding ($d$,$p$) reaction in inverse kinematics. The radioactive beam of $^{206}$Hg was delivered to the new ISOLDE Solenoidal Spectrometer at an energy above the Coulomb barrier. The spectroscopy of $^{207}$Hg marks a first step…

Band-terminating states in 101Ag

Excited states of the neutron deficient Ag-101 nucleus have been investigated via the Cr-50(Ni-58, 3rho1alpha) heavy-ion induced reaction at 261 meV by use of in-beam spectroscopic methods. On the basis of the measured gammagamma-cincidence relations and angular distribution ratios high-spin bands have been extended up to I-pi = 35/2(+), 45/2((-)) and (49/2(-)). The negative parity states at the highest energy have been interpreted as terminating non-collective oblate states in the framework of the Nilsson-Strutinsky cranking formalism.

Lifetime Measurements with the Doppler Shift Attenuation Method Using a Thick Homogeneous Production Target — Verification of the Method

International audience; Doppler Shift Attenuation Method (DSAM) analysis of excited-state lifetimes normally employs thin production targets mounted on a thick stopper foil (“backing”) serving to slow down and stop the recoiling nuclei of interest in a well-defined manner. Use of a thick, homogeneous production target leads to a more complex analysis as it results in a substantial decrease in the energy of the incident projectile which traverses the target with an associated change in the production cross section of the residues as a function of penetration depth. Here, a DSAM lifetime analysis using a thick homogeneous target has been verified using the Doppler broadened lineshapes of γ ra…

Spectroscopy of Kr 70 and isospin symmetry in the T=1 fpg shell nuclei SPECTROSCOPY of Kr 70 and ISOSPIN SYMMETRY ... D. M. DEBENHAM et al.

The recoil-β tagging technique has been used in conjunction with the Ca40(S32,2n) reaction at a beam energy of 88 MeV to identify transitions associated with the decay of the 2+ and, tentatively, 4+ states in the nucleus Kr70. These data are used, along with previously published data, to examine the triplet energy differences (TED) for the mass 70 isobars. The experimental TED values are compared with shell model calculations, performed with the JUN45 interaction in the fpg model space, that include a J=0 isospin nonconserving (INC) interaction with an isotensor strength of 100 keV. The agreement is found to be very good up to spin 4 and supports the expectation for analog states that all t…

Very high rotational frequencies and band termination in73Br

Rotational bands in ${}^{73}\mathrm{Br}$ have been investigated up to spins of $I=65/2$ using the EUROBALL III spectrometer. One of the negative-parity bands displays the highest rotational frequency $\ensuremath{\Elzxh}\ensuremath{\omega}=1.85\mathrm{MeV}$ reported to date in nuclei with $Ag~25.$ At high frequencies, the experimental ${\mathcal{J}}^{(2)}$ dynamic moment of inertia for all bands decreases to very low values, ${\mathcal{J}}^{(2)}l~10{\ensuremath{\Elzxh}}^{2}{\mathrm{MeV}}^{\ensuremath{-}1}.$ The bands are described in the configuration-dependent cranked Nilsson--Strutinsky model. The calculations indicate that one of the negative-parity bands is observed up to its terminatin…

Isomeric decay spectroscopy of theBi217isotope

The structure of the neutron-rich bismuth isotope 217Bi has been studied for the first time. The fragmentation of a primary 238U beam at the FRS-RISING setup at GSI was exploited to perform γ-decay spectroscopy, since μs isomeric states were expected in this nucleus. Gamma rays following the decay of a t1/2=3 μs isomer were observed, allowing one to establish the low-lying structure of 217Bi. The level energies and the reduced electric quadrupole transition probability B(E2) from the isomeric state are compared to large-scale shell-model calculations.

Spectroscopy of neutron-rich (168,170)Dy: Yrast band evolution close to the N(p)N(n) valence maximum

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

Population of lead isotopes in binary reactions using a Rb 94 radioactive beam

8 pags., 9 figs.

Multinucleon transfer reactions in closed-shell nuclei

Multinucleon transfer reactions in 40Ca+96Zr and 90Zr+208Pb have been measured at energies close to the Coulomb barrier in a high resolution gamma-particle coincidence experiment. The large solid angle magnetic spectrometer PRISMA coupled to the CLARA gamma-array has been employed. Trajectory reconstruction has been applied for the complete identification of transfer products. Mass and charge yields, total kinetic energy losses, gamma transitions of the binary reaction partners, and comparison of data with semiclassical calculations are reported. Specific transitions in 95Zr populated in one particle transfer channels are discussed in terms of particle-phonon couplings. The gamma decays fro…

Lifetime Measurements of the Neutron-RichN=30IsotonesCa50andSc51: Orbital Dependence of Effective Charges in thefpShell

The lifetimes of the first excited states of the N=30 isotones Ca-50 and Sc-51 have been determined using the Recoil Distance Doppler Shift method in combination with the CLARA-PRISMA spectrometers. This is the first time such a method is applied to measure lifetimes of neutron-rich nuclei populated via a multinucleon transfer reaction. This extends the lifetime knowledge beyond the f(7/2) shell closure and allows us to derive the effective proton and neutron charges in the fp shell near the doubly magic nucleus Ca-48, using large-scale, shell-model calculations. These results indicate an orbital dependence of the core polarization along the fp shell.

New μs Isomers in the Neutron-rich 210Hg Nucleus

Neutron-rich nuclei in the lead region, beyond N = 126, have been studied at the FRS-RISING setup at GSI, exploiting the fragmentation of a primary uranium beam. Two isomeric states have been identified in Hg-210: the 8(+) isomer expected from the seniority scheme in the vg(9/2) shell and a second one at low spin and low excitation energy. The decay strength of the 8(+) isomer confirms the need of effective three-body forces in the case of neutron-rich lead isotopes. The other unexpected low-lying isomer has been tentatively assigned as a 3(-) state, although this is in contrast with theoretical expectations. (C) 2013 Elsevier B.V. All rights reserved.

Access to Gamma-ray Spectroscopy of Neutron-Rich sdfp Shell Nuclei

γ-rays in neutron-rich sdfp shell nuclei, produced in deep-inelastic processes during collisions of 37Cl and 40Ar ions on 208Pb and of 48Ca ions on 48Ca, have been studied using large Ge multidetector arrays. Candidates for new yrast states in heavy argon and sulfur isotopes have been identified.

Reaction dynamics and nuclear structure studies via deep inelastic collisions with heavy-ions: spin and parity assignment in49Ca

The population and gamma decay of neutron rich nuclei around 48Ca has been measured at Legnaro National Laboratory with the PRISMA-CLARA setup, using deep-inelastic collisions (DIC) on 64Ni, at an energy approximately twice the Coulomb barrier. The reaction properties of the main products are investigated, focusing on total cross sections and angular distributions both integrated in energy and associated to the population of specific excited states. Gamma spectroscopy studies are also performed, giving evidence, for the first time in transfer reactions with heavy ions, of a large spin alignment (~70%), perpendicular to the reaction plane. This makes possible the use of angular distributions…

High-spin structure of Xe134

A. Vogt et al. ; 12 págs.; 9 figs.; 1 tab.

Evolution of Octupole Deformation in Radium Nuclei from Coulomb Excitation of Radioactive Ra222 and Ra228 Beams

There is sparse direct experimental evidence that atomic nuclei can exhibit stable "pear" shapes arising from strong octupole correlations. In order to investigate the nature of octupole collectivity in radium isotopes, electric octupole (E3) matrix elements have been determined for transitions in ^{222,228}Ra nuclei using the method of sub-barrier, multistep Coulomb excitation. Beams of the radioactive radium isotopes were provided by the HIE-ISOLDE facility at CERN. The observed pattern of E3 matrix elements for different nuclear transitions is explained by describing ^{222}Ra as pear shaped with stable octupole deformation, while ^{228}Ra behaves like an octupole vibrator.

In-beam γ -ray spectroscopy of the neutron-rich platinum isotope Pt200 toward the N=126 shell gap

The neutron-rich nucleus \nucleus{200}{Pt} is investigated via in-beam \gamma-ray spectroscopy in order to study the shape evolution in the neutron-rich platinum isotopes towards the N = 126 shell closure. The two-neutron transfer reaction \nucleus{198}{Pt}(\nucleus{82}{Se}, \nucleus{80}{Se})\nucleus{200}{Pt} is used to populate excited states of \nucleus{200}{Pt}. The Advanced Gamma Ray Tracking Array (AGATA) demonstrator coupled with the PRISMA spectrometer detects \gamma rays coincident with the \nucleus{80}{Se} recoils, the binary partner of \nucleus{200}{Pt}. The binary partner method is applied to extract the \gamma-ray transitions and build the level scheme of \nucleus{200}{Pt}. The …

Test of digital neutron-gamma discrimination with four different photomultiplier tubes for the NEutron Detector Array (NEDA)

WOS: 000344994600012

Production of very neutron-deficient isotopes near Sn via reactions involving light-particle and cluster emission

Abstract The production of very neutron-deficient isotopes near 100Sn has been investigated by using on-line mass separation of evaporation residues produced by heavy-ion induced complete-fusion reactions. We measured the cross sections for 99Cd, 100In, 101Sn and 102In via 58Ni+58Ni fusion reactions followed by cluster emission, and via 58Ni+50Cr fusion reactions accompanied by evaporation of protons, neutrons or α particles. Both types of reactions yield similar cross sections for the production of exotic nuclei near 100Sn. The data are discussed in comparison with results obtained from statistical-model calculations.

Spin distribution measurement for 64Ni + 100Mo at near and above barrier energies

Spin distribution measurements were performed for the reaction 64 Ni + 100 Mo at three beam energies ranging from 230 to 260 MeV. Compound nucleus (CN) spin distributions were obtained channel selective for each evaporation residue populated by the de-excitation cascade. A comparison of the spin distribution at different beam energies indicates that its slope becomes steeper and steeper with increasing beam energy. This change in slope of the spin distribution is mainly due to the onset of fission competition with particle evaporation at higher beam energies.

Lifetime measurements in mirror nuclei31S and31P: A test for isospin mixing

Using the 20Ne + 12C fusion-evaporation reaction at E20Ne = 33 MeV and the multidetector array GASP in conjuction with the EUCLIDES charged particle detector, angular correlations of coincident pairs of γ transitions and lifetimes in mirror nuclei 31S and 31P have been measured at the Piave-Alpi accelerator of the Laboratori Nazionali di Legnaro. A comparison of the determined B(E1) strengths of the analog mirror 7/2− → 5/2+ transitions indicates the presence of a violation of isospin symmetry.

First Exploration of Neutron Shell Structure below Lead and beyond N=126

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

Coulomb excitation of 222Rn

International audience; The nature of quadrupole and octupole collectivity in $^{222}$Rn was investigated by determining the electric-quadrupole (E2) and octupole (E3) matrix elements using subbarrier, multistep Coulomb excitation. The radioactive $^{222}$Rn beam, accelerated to 4.23 MeV/u, was provided by the HIE-ISOLDE facility at CERN. Data were collected in the Miniball $\gamma$ -ray spectrometer following the bombardment of two targets, $^{120}$Sn and $^{60}$Ni. Transition E2 matrix elements within the ground-state and octupole bands were measured up to 10 ¯h and the results were consistent with a constant intrinsic electric-quadrupole moment, 518(11) $e$ fm$^2$ . The values of the int…

Shape isomerism and shape coexistence effects on the Coulomb energy differences in theN=Znucleus66As and neighboringT=1multiplets

Excited states of the $N=Z=33$ nucleus ${}^{66}$As have been populated in a fusion-evaporation reaction and studied using $\ensuremath{\gamma}$-ray spectroscopic techniques. Special emphasis was put into the search for candidates for the $T=1$ states. A new 3${}^{+}$ isomer has been observed with a lifetime of 1.1(3) ns. This is believed to be the predicted oblate shape isomer. The excited levels are discussed in terms of the shell model and of the complex excited Vampir approaches. Coulomb energy differences are determined from the comparison of the $T=1$ states with their analog partners. The unusual behavior of the Coulomb energy differences in the $A=70$ mass region is explained through…

High-spin states in the neutron-rich A∼100 region

Two experimental setups have been used to study excited states of neutron‐rich nuclei in the A∼100 region. Extended level schemes and lifetime measurements were obtained using deep‐inelastic and fusion‐fission reactions with the CLARA‐PRISMA spectrometer and the Ge‐array GASP respectively. Experimental information from GASP has been used to complement the CLARA‐PRISMA experiment. Time spectra have been used to measure the lifetimes of isomeric states. Preliminary results are presented for 89Rb.

The observation of vibrating pear-shapes in radon nuclei

6 pags., 4 fig.s, 1 tab. -- Open Access funded by Creative Commons Atribution Licence 4.0

Sn108studied with intermediate-energy Coulomb excitation

The unstable neutron-deficient Sn-108 isotope has been studied in inverse kinematics by intermediate-energy Coulomb excitation using the RISING/FRS experimental setup at GSI. This is the highest Z nucleus studied so far with this method. Its reduced transition probability B (E2;0(g.s.)(+)-> 2(1)(+)) has been measured for the first time. The extracted B(E2) value of 0.230(57)e(2) b(2) has been determined relative to the known value in the stable Sn-112 isotope. The result is discussed in the framework of recent large-scale shell model calculations performed with realistic effective interactions. The roles of particle-hole excitations of the Sn-100 core and of the Z=50 shell gap for the E2 po…

Stability ofS50100n50Deduced from Excited States inC4899d51

Excited states of neutron deficient nuclei close to Sn-100 were investigated in an in-beam spectroscopic experiment using the NORDBALL detector array. Excited states in Cd-99 were identified for the first time. The measured half-life of an isomeric state in Cd-99 indicates that the stability with respect to quadrupole shape changes is as large in Sn-100 as for other heavy doubly magic nuclei.

Spectroscopic studies with the PRISMA-CLARA set-up

The large solid angle magnetic spectrometer for heavy ions PRISMA, installed at Laboratori Nazionali di Legnaro (LNL), was operated up to the end of March 2008 in conjunction with the highly efficient CLARA set-up. It allowed to carry out nuclear structure and reaction mechanism studies in several mass regions of the nuclide chart. Results obtained in the vicinity of the island of inversion and for the heavy iron and chromium isotopes are presented in this contribution. The status of the new focal plane detectors specifically designed for light ions and slow moving heavy ions is also reported.

Very high rotational frequencies and band termination in 73Br

Rotational bands in 73Br have been investigated up to spins of 65/2 using the EUROBALL III spectrometer. One of the negative-parity bands displays the highest rotational frequency 1.85 MeV reported to date in nuclei with mass number greater than 25. At high frequencies, the experimental dynamic moment of inertia for all bands decrease to very low values, indicating a loss of collectivity. The bands are described in the configuration-dependent cranked Nilsson-Strutinsky model. The calculations indicate that one of the negative-parity bands is observed up to its terminating single-particle state at spin 63/2. This result establishes the first band termination case in the A = 70 mass region.

Pseudospin Symmetry and Microscopic Origin of Shape Coexistence in the Ni78 Region: A Hint from Lifetime Measurements

Lifetime measurements of excited states of the light N = 52 isotones 88 Kr , 86 Se , and 84 Ge have been performed, using the recoil distance Doppler shift method and VAMOS and AGATA spectrometers for particle identification and gamma spectroscopy, respectively. The reduced electric quadrupole transition probabilities B ( E 2 ; 2 + → 0 + ) and B ( E 2 ; 4 + → 2 + ) were obtained for the first time for the hard-to-reach 84 Ge . While the B ( E 2 ; 2 + → 0 + ) values of 88 Kr , 86 Se saturate the maximum quadrupole collectivity offered by the natural valence ( 3 s , 2 d , 1 g 7 / 2 , 1 h 11 / 2 ) space of an inert 78 Ni core, the value obtained for 84 Ge largely exceeds it, suggesting that sh…

High-spin structure in the transitional nucleus Xe131 : Competitive neutron and proton alignment in the vicinity of the N=82 shell closure

The transitional nucleus 131Xe is investigated after multinucleon transfer (MNT) in the 136Xe+208Pb and 136Xe+238U reactions employing the high-resolution Advanced GAmma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy and as an elusive reaction product in the fusion-evaporation reaction 124Sn(11B,p3n) 131Xe employing the HORUS γ-ray array coupled to a double-sided silicon strip detector (DSSSD) at the University of Cologne, Germany. The level scheme of 131Xe is extended to 5 MeV. A pronounced backbending is observed at ~ω ≈ 0.4 MeV along the negative-parity one-quasiparticle νh11/2(α = −1/2) band. The results are compared to t…

AGATA-Advanced GAmma Tracking Array

WOS: 000300864200005

Isospin Properties of Nuclear Pair Correlations from the Level Structure of the Self-Conjugate Nucleus Ru88

The low-lying energy spectrum of the extremely neutron-deficient self-conjugate (N = Z) nuclide 88 44Ru44 has been measured using the combination of the Advanced Gamma Tracking Array (AGATA) spectrometer, the NEDA and Neutron Wall neutron detector arrays, and the DIAMANT charged particle detector array. Excited states in 88Ru were populated via the 54Fe(36Ar; 2n )88Ru fusion-evaporation reaction at the Grand Acc�el�erateur National d'Ions Lourds (GANIL) accelerator complex. The observed -ray cascade is assigned to 88Ru using clean prompt - -2-neutron coincidences in anti-coincidence with the detection of charged particles, con�rming and extending the previously assigned sequence of low-lyin…