-
L Chen,
P M Walker,
H Geissel,
Yu. A Litvinov,
K Beckert,
P Beller,
F Bosch,
D Boutin,
L Caceres,
J J Carroll, [......],
C Scheidenberger,
E C Simpson,
M Shindo,
M Steck,
B Sun,
S J Williams,
H Weick,
M Winkler,
H -J Wollersheim,
T Yamaguchi
[show abstract]
[hide abstract]
ABSTRACT: Long-lived isomers in 212Bi have been studied following 238U projectile fragmentation at 670 MeV per nucleon. The fragmentation products were injected as highly charged ions into a storage ring, giving access to masses and half-lives. While the excitation energy of the first isomer of 212Bi was confirmed, the second isomer was observed at 1478(30) keV, in contrast to the previously accepted value of >1910 keV. It was also found to have an extended Lorentz-corrected in-ring half-life >30 min, compared to 7.0(3) min for the neutral atom. Both the energy and half-life differences can be understood as being due a substantial, though previously unrecognized, internal decay branch for neutral atoms. Earlier shell-model calculations are now found to give good agreement with the isomer excitation energy. Furthermore, these and new calculations predict the existence of states at slightly higher energy that could facilitate isomer deexcitation studies.
Physical Review Letters 03/2013; 110(12):122502. · 7.37 Impact Factor
-
A Gottardo,
J J Valiente-Dobón,
G Benzoni,
R Nicolini,
A Gadea,
S Lunardi,
P Boutachkov,
A M Bruce, M Górska,
J Grebosz, [......],
P Strmen,
T P D Swan,
I Szarka,
C A Ur,
P M Walker,
O Wieland,
H-J Wollersheim,
F Nowacki,
E Maglione,
A P Zuker
[show abstract]
[hide abstract]
ABSTRACT: The neutron-rich lead isotopes, up to ^{216}Pb, have been studied for the first time, exploiting the fragmentation of a primary uranium beam at the FRS-RISING setup at GSI. The observed isomeric states exhibit electromagnetic transition strengths which deviate from state-of-the-art shell-model calculations. It is shown that their complete description demands the introduction of effective three-body interactions and two-body transition operators in the conventional neutron valence space beyond ^{208}Pb.
Physical Review Letters 10/2012; 109(16):162502. · 7.37 Impact Factor
-
G. Benzoni,
A.I. Morales,
J.J. Valiente-Dobón,
A. Gottardo,
A. Bracco,
F. Camera,
F.C.L. Crespi,
A.M. Corsi,
S. Leoni,
B. Million, [......],
A. Sharma,
B. Sitar,
D. Siwal,
K. Steiger,
P. Strmen,
T.P.D. Swan,
I. Szarka,
C.A. Ur,
P.M. Walker,
H.-J. Wollersheim
[show abstract]
[hide abstract]
ABSTRACT: Neutron-rich isotopes around lead, beyond N = 126 , have been studied exploiting the fragmentation of an uranium primary beam at the FRS-RISING setup at GSI. For the first time β-decay half-lives of Bi 219 and Tl 211 , 212 , 213 isotopes have been derived. The half-lives have been extracted using a numerical simulation developed for experiments in high-background conditions. Comparison with state of the art models used in r-process calculations is given, showing a systematic underestimation of the experimental values, at variance from close-lying nuclei.
Physics Letters B 09/2012; 715(4–5):293-297. · 3.95 Impact Factor
-
C B Hinke,
M Böhmer,
P Boutachkov,
T Faestermann,
H Geissel,
J Gerl,
R Gernhäuser, M Górska,
A Gottardo,
H Grawe, [......],
A Procházka,
P H Regan,
C Rigollet,
H Schaffner,
C Scheidenberger,
S Schwertel,
P-A Söderström,
S J Steer,
A Stolz,
P Strmeň
[show abstract]
[hide abstract]
ABSTRACT: The shell structure of atomic nuclei is associated with 'magic numbers' and originates in the nearly independent motion of neutrons and protons in a mean potential generated by all nucleons. During β(+)-decay, a proton transforms into a neutron in a previously not fully occupied orbital, emitting a positron-neutrino pair with either parallel or antiparallel spins, in a Gamow-Teller or Fermi transition, respectively. The transition probability, or strength, of a Gamow-Teller transition depends sensitively on the underlying shell structure and is usually distributed among many states in the neighbouring nucleus. Here we report measurements of the half-life and decay energy for the decay of (100)Sn, the heaviest doubly magic nucleus with equal numbers of protons and neutrons. In the β-decay of (100)Sn, a large fraction of the strength is observable because of the large decay energy. We determine the largest Gamow-Teller strength so far measured in allowed nuclear β-decay, establishing the 'superallowed' nature of this Gamow-Teller transition. The large strength and the low-energy states in the daughter nucleus, (100)In, are well reproduced by modern, large-scale shell model calculations.
Nature 06/2012; 486(7403):341-5. · 36.28 Impact Factor
-
N. Al-Dahan,
P. H. Regan,
Zs. Podolyák,
P. M. Walker,
N. Alkhomashi,
G. D. Dracoulis,
G. Farrelly,
J. Benlliure,
S. B. Pietri,
R. F. Casten, [......],
Z. Liu,
P. J. Mason,
C. Mihai,
F. Molina,
D. Mücher,
B. Rubio,
A. Tamii,
S. Tashenov,
J. J. Valiente-Dobón,
P. J. Woods
[show abstract]
[hide abstract]
ABSTRACT: β decays from heavy, neutron-rich nuclei with A∼190 have been investigated following their production via the relativistic projectile fragmentation of an E/A=1 GeV 208Pb primary beam on a ∼2.5 g/cm2 9Be target. The reaction products were separated and identified using the GSI FRagment Separator (FRS) and stopped in the RISING active stopper. γ decays were observed and correlated with these secondary ions on an event-by-event basis such that γ-ray transitions following from both internal (isomeric) and β decays were recorded. A number of discrete, β-delayed γ-ray transitions associated with β decays from 194Re to excited states in 194Os have been observed, including previously reported decays from the yrast Iπ=(6+) state. Three previously unreported γ-ray transitions with energies 194, 349, and 554 keV are also identified; these transitions are associated with decays from higher spin states in 194Os. The results of these investigations are compared with theoretical predictions from Nilsson multi-quasiparticle (MQP) calculations. Based on lifetime measurements and the observed feeding pattern to states in 194Os, it is concluded that there are three β−-decaying states in 194Re.
Physical Review C 05/2012; 85(3):034301. · 3.31 Impact Factor
-
L. Batist, M. Górska,
H. Grawe,
Z. Janas,
M. Kavatsyuk,
M. Karny,
R. Kirchner,
M. La Commara,
I. Mukha,
A. Plochocki,
E. Roeckl
[show abstract]
[hide abstract]
ABSTRACT: The energy centroids and integrated strengths of Gamow-Teller transitions in the b+ \beta^{+}_{} and electron-capture decay are analyzed for nuclei whose proton number Z and neutron number N are restricted to 44 £ \leq
Z
£ \leq 50 and 50 £ \leq
N
£ \leq 58 . The analysis is based on data measured both with high-resolution g \gamma -ray spectrometry and total g \gamma -ray absorption techniques. The dependence of the considered quantities on the relative neutron excess are established after
taking into account the effects due to the Coulomb interaction and mean-field level occupancies. An extrapolation of this
dependence to the lightest known tin isotopes is used to estimate the decay characteristics of 100Sn and 101Sn . The values extrapolated for the half-lives of 100Sn and 101Sn agree with experimental data. Using the extrapolated values together with shell model predictions, the Q values for the electron-capture decay of 100Sn is evaluated. The quenching factor for b+ \beta^{+}_{} and the electron-capture decay of the nuclei under consideration here is established to be 0.56(2) with a possible weak dependence
on N - Z .
European Physical Journal A 04/2012; 46(1):45-53. · 2.19 Impact Factor
-
M. Rejmund,
K. H. Maier,
R. Broda,
B. Fornal,
M. Lach,
J. Wrzesiński,
J. Blomqvist,
A. Gadea,
J. Gerl, M. Górska,
H. Grawe,
M. Kaspar,
H. Schaffner,
Ch. Schlegel,
R. Schubart,
H. J. Wollersheim
[show abstract]
[hide abstract]
ABSTRACT: High-spin states in nuclei around 208Pb were populated in deep inelastic collisions of 136Xe and 208Pb projectiles with 208Pb targets at beam energies about 12% above the Coulomb barrier. New states in nuclei in the vicinity of 208Pb have been found that result from the coupling of one and two quasi particles to the lowest 3− excitation of the 208Pb core. They show the influence of particle octupole-vibration coupling in a pronounced and clear way and verify the validity
of this concept.
European Physical Journal A 04/2012; 8(2):161-164. · 2.19 Impact Factor
-
A. Ekström,
J. Cederkäll,
C. Fahlander,
M. Hjorth-Jensen,
T. Engeland,
A. Blazhev,
P. A. Butler,
T. Davinson,
J. Eberth,
F. Finke, [......],
S. Siem,
G. Sletten,
I. Stefanescu,
G. M. Tveten,
J. Van de Walle,
D. Voulot,
N. Warr,
D. Weisshaar,
F. Wenander,
M. Zielińska
[show abstract]
[hide abstract]
ABSTRACT: The low-lying states in the odd-odd and unstable isotopes 106, 108In have been Coulomb excited from the ground state and the first excited isomeric state at the REX-ISOLDE facility at CERN.
With the additional data provided here the p \pi
g
9/2
-1 ⊗ n \nu
d
5/2 and p \pi
g
9/2
-1 ⊗ n \nu
g
7/2 multiplets have been re-analyzed and are modified compared to previous results. The observed g \gamma -ray de-excitation patterns were interpreted within a shell model calculation based on a realistic effective interaction.
The agreement between theory and experiment is satisfactory and the calculations reproduce the observed differences in the
excitation pattern of the two isotopes. The calculations exclude a 6+ ground state in 106In . This is in agreement with the conclusions drawn using other techniques. Furthermore, based on the experimental results,
it is also concluded that the ordering of the isomeric and ground state in 108In is inverted compared to the shell model prediction. Limits on B(E2) values have been extracted where possible. A previously unknown low-lying state at 367keV in 106In is also reported.
European Physical Journal A 04/2012; 44(3):355-361. · 2.19 Impact Factor
-
Zs. Podolyák,
S. J. Steer,
S. Pietri, M. Górska,
P. H. Regan,
D. Rudolph,
A. B. Garnsworthy,
R. Hoischen,
J. Gerl,
H. J. Wollersheim, [......],
R. Krücken,
S. Lalkovski,
Z. Liu,
A. Maj,
S. Myalski,
S. Schwertel,
T. Shizuma,
P. M. Walker,
E. Werner-Malento,
O. Wieland
[show abstract]
[hide abstract]
ABSTRACT: Heavy neutron-rich nuclei have been populated through the relativistic fragmentation of a 20882Pb\ensuremath ^{208}_{\ 82}{\rm Pb} beam at E/A = 1\ensuremath E/A = 1 GeV on a 2.5 g/cm2\ensuremath 2.5 {\rm g/cm^2} thick Be target. The synthesised nuclei were selected and identified in-flight using the fragment separator at GSI. Approximately
300 ns after production, the selected nuclei were implanted in an ~ 8\ensuremath \sim 8 mm thick perspex stopper, positioned at the centre of the RISING g\ensuremath \gamma -ray detector spectrometer array. A previously unreported isomer with a half-life T1/2 = 163(5)\ensuremath T_{1/2} = 163(5) ns has been observed in the N = 126 closed-shell nucleus 20579Au\ensuremath ^{205}_{\ 79}{\rm Au} . Through g \gamma -ray singles and g \gamma -g \gamma coincidence analysis a level scheme was established. The comparison with a shell model calculation tentatively identifies
the spin-parity of the excited states, including the isomer itself, which is found to be Ip = (19/2+)\ensuremath I^{\pi} = (19/2^+) .
European Physical Journal A 04/2012; 42(3):489-493. · 2.19 Impact Factor
-
D. Rudolph,
R. Hoischen,
M. Hellström,
S. Pietri,
Zs. Podolyák,
P. H. Regan,
A. B. Garnsworthy,
S. J. Steer,
F. Becker,
P. Bednarczyk, [......],
L. -L. Andersson,
L. Atanasova,
D. L. Balabanski,
M. A. Bentley,
A. Blazhev,
C. Brandau,
J. R. Brown,
C. Fahlander,
E. K. Johansson,
A. Jungclaus
[show abstract]
[hide abstract]
ABSTRACT: The fragmentation of a 550MeV/u primary beam of 58Ni on a 9Be target has been used to measure time- and energy-correlated γ decays following the implantation of event-by-event discriminated
secondary fragments into a 9Be stopper plate. A new isomeric γ decay with T
1/2 = 14(
6 4 \begin{smallmatrix}6 4\end{smallmatrix}
) ns and E
γ = 646.2(2) keV is observed and attributed to the decay of the yrast 3/2- state in 53
27Co26 . This short-lived isomeric state has been populated by means of nuclear reactions during the stopping process of the secondary
fragments. The experimental findings are discussed in the framework of large-scale spherical shell model calculations in conjunction
with isospin symmetry-breaking residual interactions for the A = 53 , T
z = ±1/2 mirror nuclei 53Co and 53Fe .
European Physical Journal A 04/2012; 36(2):131-138. · 2.19 Impact Factor
-
K. Schmidt,
C. Mazzocchi,
R. Borcea,
J. Döring,
S. Galanopoulos, M. Górska,
H. Grawe,
S. Harissopulos,
M. Hellström,
Z. Janas,
R. Kirchner,
G. Kriembardis,
M. La Commara,
A. N. Ostrowski,
G. Rainovski,
E. Roeckl
[show abstract]
[hide abstract]
ABSTRACT: The very neutron-deficient isotope 93Pd was produced in fusion-evaporation reactions of a 40Ca beam on a 58Ni target. The reaction products were separated at the GSI Online Mass Separator, using ion sources of the FEBIAD type. The
β-decay properties of 93Pd were studied by detecting β-delayed protons and β-delayed γ-rays. The feeding of excited levels in the daughter nucleus 93Rh and the β-decay half-life of 93Pd were determined. The experimental results are discussed in comparison to shell model predictions.
European Physical Journal A 04/2012; 8(3):303-306. · 2.19 Impact Factor
-
M. Kmiecik,
A. Maj,
J. Gerl,
G. Neyens,
L. Atanasova,
D. L. Balabanski,
F. Becker,
P. Bednarczyk,
G. Benzoni,
N. Blasi, [......],
N. Saito,
T. R. Saito,
A. Saltarelli,
G. S. Simpson,
J. Styczeń,
N. Vermeulen,
E. Werner-Malento,
O. Wieland,
H. J. Wollersheim,
M. Ziȩbliński
[show abstract]
[hide abstract]
ABSTRACT: The feasibility of measuring g -factors using the TDPAD method applied to high-energy, heavy fragmentation products is explored. The 2623keV Ip=12+\ensuremath I^{\pi}=12^+ isomer in 192Pb with t \tau = 1.57 μs has been produced using the fragmentation of a 1A GeV 238U beam. The results presented demonstrate for the first time that such heavy nuclei produced in a fragmentation reaction with
a relativistic beam are sufficiently well spin-aligned. Moreover, the rather large value of the alignment, 28(10)% of the
maximum possible, is preserved during the separation process allowing the determination of magnetic moments. The measured
values of the lifetime, t \tau = 1.54(9) μs, and the g -factor, g = - 0.175(20) , agree with the results of previous investigations using fusion-evaporation reactions.
European Physical Journal A 04/2012; 45(2):153-158. · 2.19 Impact Factor
-
L. Chen,
W. R. Plaß,
H. Geissel,
R. Knöbel,
Kozhuharov,
Yu. A. Litvinov,
Z. Patyk,
C. Scheidenberger,
K. Siegień-Iwaniuk,
B. Sun, [......],
S. Rigby,
N. Saito,
T. Saito,
M. Shindo,
M. Steck,
P. M. Walker,
S. Williams,
M. Winkler,
H.-J. Wollersheim,
T. Yamaguchi
Nuclear Physics A 01/2012; 71:882. · 1.54 Impact Factor
-
A. M. Bruce,
A. M. Denis Bacelar,
G. Benzoni,
A. Gadea, M. Górska,
A. Gottardo,
S. Pietri,
Podolyák Zs,
J. J. Valiente-Dobón,
J. A. Alcántara-Núñez, [......],
H. Schaffner,
A. Sharma,
B. Sitar,
Siwal Davinder,
K. Steiger,
P. Strmen,
I. Szarka,
P. M. Walker,
H. Weick,
H. J. Wollersheim
[show abstract]
[hide abstract]
ABSTRACT: The population of 102 Zr following the β decay of 102 Y produced in the projectile fission of 238 U at the GSI facility in Darmstadt, Germany has been studied. 102 Y is known to ß decay into 102 Zr via two states, one of high spin and the other low spin. These states preferentially populate different levels in the 102 Zr daughter. In this paper the intensities of transitions in 102 Zr observed are compared with those from the decay of the low-spin level studied at the TRISTAN facility at Brookhaven National Laboratory and of the high-spin level studied at the JOSEF separator at the Kernforschungsanlage Jülich.
Journal of Physics Conference Series 01/2012; 381(1):012053.
-
B S Nara Singh,
Z Liu,
R Wadsworth,
H Grawe,
T S Brock,
P Boutachkov,
N Braun,
A Blazhev, M Górska,
S Pietri, [......],
S Rinta-Antila,
C Scholl,
H Schaffner,
P-A Söderström,
N Warr,
H Weick,
H-J Wollersheim,
P J Woods,
F Nowacki,
K Sieja
[show abstract]
[hide abstract]
ABSTRACT: A β-decaying high-spin isomer in (96)Cd, with a half-life T(1/2)=0.29(-0.10)(+0.11) s, has been established in a stopped beam rare isotope spectroscopic investigations at GSI (RISING) experiment. The nuclei were produced using the fragmentation of a primary beam of (124)Xe on a (9)Be target. From the half-life and the observed γ decays in the daughter nucleus, (96)Ag, we conclude that the β-decaying state is the long predicted 16(+) "spin-gap" isomer. Shell-model calculations, using the Gross-Frenkel interaction and the πν(p(1/2),g(9/2)) model space, show that the isoscalar component of the neutron-proton interaction is essential to explain the origin of the isomer. Core excitations across the N=Z=50 gaps and the Gamow-Teller strength, B(GT) distributions have been studied via large-scale shell-model calculations using the πν(g,d,s) model space to compare with the experimental B(GT) value obtained from the half-life of the isomer.
Physical Review Letters 10/2011; 107(17):172502. · 7.37 Impact Factor
-
P. Boutachkov, M. Górska,
H. Grawe,
A. Blazhev,
N. Braun,
T. S. Brock,
Z. Liu,
B. S. Nara Singh,
R. Wadsworth,
S. Pietri, [......],
M. Pfützner,
P. H. Regan,
P. Reiter,
S. Rinta-Antila,
C. Scholl,
P.-A. Söderström,
N. Warr,
P. J. Woods,
F. Nowacki,
K. Sieja
[show abstract]
[hide abstract]
ABSTRACT: Excited states in 96Ag were populated in fragmentation of an 850-MeV/u 124Xe beam on a 4-g/cm2 Be target. Three new high-spin isomers were identified and the structure of the populated states was investigated. The level scheme of 96Ag was established, and a spin parity of (13−), (15+), and (19+) was assigned to the new isomeric states. Shell-model calculations were performed in various model spaces, including πν(p1/2,g9/2,f5/2,p3/2) and the large-scale shell-model space πν(gds), to account for the observed parity changing M2 and E3 transitions from the (13−) isomer and the E2 and E4 transitions from the (19+) core-excited isomer, respectively. The calculated level schemes and reduced transition strengths are found to be in very good agreement with the experiment.
Phys. Rev. C. 10/2011; 84(4).
-
P Boutachkov,
N Braun,
T Brock,
B S Nara Singh,
A Blazhev,
Z Liu,
R Wadsworth, M Górska,
H Grawe,
S Pietri, [......],
A Gottardo,
C Hinke,
R Krücken,
M Pfützner,
P Regan,
S Rinta-Antila,
D Rudolph,
P Woods,
A Ataç,
E Merchán
[show abstract]
[hide abstract]
ABSTRACT: The RISING setup at the GSI-FRS facility was used to investigate the isomer and beta decays in N~Z~50 Cd, Ag and Pd isotopes. A preliminary analysis of the data has revealed new results on the Tz=1, 94Pd, 96Ag and 98Cd isotopes. In 94Pd a new high-spin isomer was observed, whilst in 96Ag 3 new isomeric states were identified, including core-excited states. In 98Cd a new high-energy isomeric γ-ray transition is observed, thus enabling us to confirm the previous spin assignment for the core-excited 12+ isomer.
Journal of Physics Conference Series 09/2011; 312(9):092019.
-
A Jungclaus,
J Walker,
J Leske,
K-H Speidel,
A E Stuchbery,
M East,
P Boutachkov,
J Cederkäll,
P Doornenbal,
J L Egido, [......],
I Kojouharov,
P Maier-Komor,
V Modamio,
F Naqvi,
N Pietralla,
S Pietri,
W Prokopowicz,
H Schaffner,
R Schwengner,
H-J Wollersheim
[show abstract]
[hide abstract]
ABSTRACT: Precise measurements of lifetimes in the picosecond range of excited states in the stable even-A Sn isotopes 112,114,116,122Sn have been performed using the Doppler shift attenuation technique. For the first excited 2+ states in 112Sn, 114Sn and 116Sn the E2 transition strengths deduced from the measured lifetimes are in disagreement with the previously adopted values. They indicate a shallow minimum at N = 66 in contrast to the maximum at mid-shell predicted by modern shell model calculations.
Journal of Physics Conference Series 09/2011; 312(9):092033.
-
A Gottardo,
J J Valiente-Dobón,
G Benzoni,
R Nicolini,
J Alcántara Núñez,
A Algora,
N Al-Dahan,
G de Angelis,
Y Ayyad,
N Alkhomashi, [......],
B Sitar,
D Siwal,
K Steger,
P Strmen,
T P D Swan,
I Szarka,
P M Walker,
O Wieland,
H Weick,
H-J Wollersheim
[show abstract]
[hide abstract]
ABSTRACT: Neutron-rich nuclei beyond N = 126 in the lead region were populated by fragmenting a 238U beam at 1 GeV A on a Be target and then separated by the Fragment Separator (FRS) at GSI. Their isomeric decays were observed, enabling study of the shell structure of neutron-rich nuclei around the Z=82 shell closure. Some preliminary results are reported in this paper.
Journal of Physics Conference Series 09/2011; 312(9):092026.
-
J. Walker,
A. Jungclaus,
J. Leske,
K.-H. Speidel,
A. Ekström,
P. Boutachkov,
J. Cederkäll,
P. Doornenbal,
J. Gerl,
R. Gernhäuser, [......],
I. Kojouharov,
P. Maier-Komor,
V. Modamio,
F. Naqvi,
N. Pietralla,
S. Pietri,
W. Prokopowicz,
H. Schaffner,
R. Schwengner,
H.-J. Wollersheim
[show abstract]
[hide abstract]
ABSTRACT: The g factors of the first excited 2+ states in the 112,114,116,122,124Sn isotopes have been measured with high accuracy using the transient field technique in combination with Coulomb excitation in inverse kinematics. The experimental results are discussed in a qualitative way on the basis of empirical single-particle g factors of the relevant proton and neutron orbitals and are compared to a number of different theoretical calculations. The results are found to be best described by shell-model calculations in an extended configuration space. Clear evidence for the contribution of neutron pair excitations from the 1d3/2 to the 0h11/2 orbital to the wave function of the 21+ state in 122,124Sn has been obtained.
Phys. Rev. C. 07/2011; 84(1).
