-
A.Korgul,
K.P. Rykaczewski,
J.A. Winger,
S.V. Ilyushkin,
C.J. Gross,
J.C. Batchelder,
C. Bingham,
I.N. Borzov,
C. Goodin R. Grzywacz,
J.H. Hamilton, [......], S.N. Liddick,
F. Nowacki,
C. Mazzocchi,
C. Nelson,
S. Padgett,
A. Piechaczek,
M.M. Rajabali,
D. Shapira,
K. Sieja,
E.F. Zganjar
[show abstract]
[hide abstract]
ABSTRACT: Theβ-decay properties of neutron-rich Cu isotopes produced in proton-induced fission of 238U were studied at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The data were collected using high-resolution online mass separation, reacceleration, and digital β-γ spectroscopy methods. An improved decay scheme of N=49 78Cu and the first observation of N=50 79Cu β-delayed neutron decay followed by a gamma transition are reported. Spin and parity (5−) are deduced for 78gsCu. The β-delayed neutron branching ratios (Pβn) for the 77Cu and 79Cu precursors are analyzed with the help of nuclear structure models.
Physical Review C 08/2012; 86:024304. · 3.31 Impact Factor
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A. Korgul,
K. P. Rykaczewski,
J. A. Winger,
S. V. Ilyushkin,
C. J. Gross,
J. C. Batchelder,
C. R. Bingham,
I. N. Borzov,
C. Goodin,
R. Grzywacz, [......], S. N. Liddick,
C. Mazzocchi,
C. Nelson,
F. Nowacki,
S. Padgett,
A. Piechaczek,
M. M. Rajabali,
D. Shapira,
K. Sieja,
E. F. Zganjar
[show abstract]
[hide abstract]
ABSTRACT: Theβ-decay properties of neutron-rich Cu isotopes produced in proton-induced fission of 238U were studied at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The data were collected using high-resolution online mass separation, reacceleration, and digital β-γ spectroscopy methods. An improved decay scheme of N=49 78Cu and the first observation of N=50 79Cu β-delayed neutron decay followed by a gamma transition are reported. Spin and parity (5−) are deduced for 78gsCu. The β-delayed neutron branching ratios (Pβn) for the 77Cu and 79Cu precursors are analyzed with the help of nuclear structure models.
Phys. Rev. C. 08/2012; 86(2).
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I. Stefanescu,
W. B. Walters,
P. F. Mantica,
B. A. Brown,
A. D. Davies,
A. Estrade,
P. T. Hosmer,
N. Hoteling, S. N. Liddick,
W. D. M. Rae, [......],
W. F. Mueller,
M. Ouellette,
E. Pellegrini,
P. Santi,
D. Seweryniak,
H. Schatz,
J. Shergur,
A. Stolz,
J. R. Stone,
B. E. Tomlin
[show abstract]
[hide abstract]
ABSTRACT: Excited states in the neutron-rich 121, 123, 125Ag were studied via the fragmentation of a 136Xe beam at 120MeV/nucleon in a thick 9Be target. The levels in 121Ag were populated in the b \beta decay of 121Pd while those assigned to 123, 125Ag were identified via isomer spectroscopy. The transitions identified in 121Ag are consistent with the g \gamma -rays reported in 117, 119Ag . The newly observed transitions were placed in the level schemes of 123, 125Ag based on the analysis of g \gamma -g \gamma coincidences and the systematics. We attribute the onset of isomerism in the 123, 125Ag isotopes to the drop in energy of the negative-parity levels similar to the 5- state in the even-even Cd cores. The proposed level scheme for 125Ag is well described by the NuShellX shell model calculations.
European Physical Journal A 04/2012; 42(3):407-413. · 2.19 Impact Factor
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K. Miernik,
W. Dominik,
Z. Janas,
M. Pfützner,
L. Grigorenko,
C. Bingham,
H. Czyrkowski,
M. Ćwiok,
I. G. Darby,
R. Da̧browski,
T. Ginter,
R. Grzywacz,
M. Karny,
A. Korgul,
W. Kuśmierz, S. N. Liddick,
M. Rajabali,
K. Rykaczewski,
A. Stolz
[show abstract]
[hide abstract]
ABSTRACT: The decay of the extremely neutron-deficient isotope 45Fe has been studied by using a new type of gaseous detector in which a technique of optical imaging is used to record tracks
of charged particles. The two-proton radioactivity and the b \beta -decay channels were clearly identified. For the first time, the angular and energy correlations between two protons emitted
from the 45Fe ground state were measured. The obtained results were confronted with predictions of a three-body model.
European Physical Journal A 04/2012; 42(3):431-439. · 2.19 Impact Factor
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M. M. Rajabali,
R. Grzywacz, S. N. Liddick,
C. Mazzocchi,
J. C. Batchelder,
T. Baumann,
C. R. Bingham,
I. G. Darby,
T. N. Ginter,
S. V. Ilyushkin,
M. Karny,
W. Królas,
P. F. Mantica,
K. Miernik,
M. Pfützner,
K. P. Rykaczewski,
D. Weisshaar,
J. A. Winger
[show abstract]
[hide abstract]
ABSTRACT: Low-energy excited states in 71,73Ni populated via the {\beta} decay of
71,73Co were investigated in an experiment performed at the National
Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU).
Detailed analysis led to the construction of level schemes of 71,73Ni, which
are interpreted using systematics and analyzed using shell model calculations.
The 5/2- states attributed to the the f5/2 orbital and positive parity 5/2+ and
7/2+ states from the g9/2 orbital have been identified in both 71,73Ni. In 71Ni
the location of a 1/2- {\beta}-decaying isomer is proposed and limits are
suggested as to the location of the isomer in 73Ni. The location of positive
parity cluster states are also identified in 71,73Ni. Beta-delayed neutron
branching ratios obtained from this data are given for both 71,73Co.
03/2012;
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S. N. Liddick,
B. Abromeit,
A. Ayres,
A. Bey,
C. R. Bingham,
M. Bolla,
L. Cartegni,
H. L. Crawford,
I. G. Darby,
R. Grzywacz,
S. Ilyushkin,
N. Larson,
M. Madurga,
D. Miller,
S. Padgett,
S. Paulauskas,
M. M. Rajabali,
K. Rykaczewski,
S. Suchyta
[show abstract]
[hide abstract]
ABSTRACT: The low-energy level structures for the neutron-rich Co isotopes at N = 39 and N = 41 are constructed following the beta decay of the respective even-even Fe isotopes. Spin and parity assignments of the lowest energy populated state in 66Co and 68Co are consistent with a 1+ spin and parity assignment and attributed to the coupling of the deformed proton configurations identified in 67Co and deformed neutron configurations inferred from neighboring Fe isotones. Comparisons along the N = 39 and N = 41 isotonic chains reveal a similarity in the structures of the Co and Mn isotopes.
Phys. Rev. C. 01/2012; 85(1).
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M. Pomorski,
Marek Pfutzner,
W. Dominik,
Robert Kazimierz Grzywacz,
T. Baumann,
H. Czyrkowski,
Ryszard Dabrowski,
T. N. Ginter,
J. Johnson,
A. Kaminski, S. N. Liddick,
Karl Maier,
C. Mazzocchi,
S. Mianowski,
K. Miernik,
J. Pereira,
Krzysztof Piotr Rykaczewski,
A. Stolz,
S. Suchyta
[show abstract]
[hide abstract]
ABSTRACT: The decay of the extremely neutron deficient {sup 48}Ni was studied by means of an imaging time projection chamber which allowed recording tracks of charged particles. Four decays with two-proton tracks clearly corresponding to two-proton radioactivity were registered, providing the first direct evidence for this decay mode in {sup 48}Ni. The half-life of {sup 48}Ni is determined to be T{sub 1/2} = 2.1{sub -0.4}{sup +1.4} ms. The measured decay energy is 1.28(6) MeV.
Acta Physica Polonica B. 12/2011; 43(2).
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S.N. Liddick,
S. Suchyta,
B. Abromeit,
A. Ayres,
A. Bey,
C.R. Bingham,
M. Bolla,
M.P. Carpenter,
L. Cartegni,
C.J. Chiara, [......],
E. A. McCutchan,
D. Miller,
S. Padgett,
S.V. Paulauskas,
J. Pereira,
M. M. Rajabali,
K. Rykaczewski,
S. Vinnikova,
W. B. Walters,
and S. Zhu
[show abstract]
[hide abstract]
ABSTRACT: The low-energy level structures of 2564Mn39 and 2566Mn41 were investigated through both the decay of Mn metastable states and the population of levels following the β decay of 64Cr and 66Cr. The deduced level schemes and tentatively assigned spins and parities suggest the coexistence of spherical and deformed configurations above and below N=40 for the odd-odd Mn isotopes. The low-energy deformed configurations are attributed to the coupling between a proton in a K=1/2− level with neutrons in either the K=1/2− or the K=3/2+ levels originating from the πp3/2, νp1/2, and νg9/2 single-particle states, respectively.
Physical Review C 12/2011; 84:061305. · 3.31 Impact Factor
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M. Pomorski,
M. Pfützner,
W. Dominik,
R. Grzywacz,
T. Baumann,
J. S. Berryman,
H. Czyrkowski,
R. Dąbrowski,
T. Ginter,
J. Johnson, [......],
M. Madurga,
C. Mazzocchi,
S. Mianowski,
K. Miernik,
D. Miller,
S. Paulauskas,
J. Pereira,
K. P. Rykaczewski,
A. Stolz,
and S. Suchyta
[show abstract]
[hide abstract]
ABSTRACT: The decay of the extremely neutron-deficient 48Ni was studied by means of an imaging time-projection chamber, which allowed the recording of tracks of charged particles. The decays of six atoms were observed. Four of them clearly correspond to two-proton radioactivity, providing the first direct evidence for this decay mode in 48Ni. Two decays represent β-delayed proton emission. The half-life of 48Ni is determined to be T1/2=2.1-0.4+1.4 ms.
Physical Review C 06/2011; 83:061303. · 3.31 Impact Factor
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S. V. Ilyushkin,
J. A. Winger,
K. P. Rykaczewski,
C. J. Gross,
J. C. Batchelder,
L. Cartegni,
I. G. Darby,
R. Grzywacz,
J. H. Hamilton,
A. Korgul,
W. Królas, S. N. Liddick,
C. Mazzocchi,
T. Mendez,
S. Padgett,
M. M. Rajabali,
D. Shapira,
D. W. Stracener,
E. F. Zganjar
[show abstract]
[hide abstract]
ABSTRACT: The β decay of 75Cu [t1/2=1.222(8)s] to levels in 75Zn was studied at the Holifield Radioactive Ion Beam Facility of Oak Ridge National Laboratory. The γγ and βγ data were collected at the Low-energy Radioactive Ion Beam Spectroscopy Station using the high-resolution isobar separator to obtain a purified 75Cu beam with a rate of over 2000 ions per second. The excited states in 75Zn have been identified for the first time. A total of 120 γ-ray transitions were placed in a level scheme containing 59 levels including two states above the neutron separation energy and a previously unknown 1/2- isomeric state at 127 keV. Spins and parities of several states were deduced and interpreted based on the observed β feeding and γ-decay pattern.
Phys. Rev. C. 01/2011; 83(1).
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M. Pomorski,
K. Miernik,
W. Dominik,
Z. Janas,
M. Pfützner,
C. R. Bingham,
H. Czyrkowski,
M. Ćwiok,
I. G. Darby,
R. Dąbrowski,
T. Ginter,
R. Grzywacz,
M. Karny,
A. Korgul,
W. Kuśmierz, S. N. Liddick,
M. Rajabali,
K. Rykaczewski,
A. Stolz
[show abstract]
[hide abstract]
ABSTRACT: The β+ decay of very neutron-deficient 43Cr was studied by means of an imaging time projection chamber that allowed recording tracks of charged particles. Events of β-delayed emission of one, two, and three protons were clearly identified. The absolute branching ratios for these channels were determined to be (81±4)%, (7.1±0.4)%, and (0.08±0.03)%, respectively. 43Cr is thus established as the second case in which the β-3p decay occurs. Although the feeding to the proton-bound states in 43V is expected to be negligible, the large branching ratio of (12±4)% for decays without proton emission is found.
Phys. Rev. C. 01/2011; 83(1).
-
S. Padgett,
M. Madurga,
R. Grzywacz,
I. G. Darby, S. N. Liddick,
S. V. Paulauskas,
L. Cartegni,
C. R. Bingham,
C. J. Gross,
K. Rykaczewski, [......],
J. A. Winger,
S. V. Ilyushkin,
A. Korgul,
W. Królas,
E. Zganjar,
C. Mazzocchi,
S. Liu,
J. H. Hamilton,
J. C. Batchelder,
M. M. Rajabali
[show abstract]
[hide abstract]
ABSTRACT: The β decay of the N=51 nucleus 81Zn was studied by means of β-γ spectroscopy and from isotopically pure beams produced at the Holifield Radioactive Ion Beam Facility (HRIBF). We observe several competing β transitions populating 81Ga that are interpreted as allowed Gamow-Teller decays to positive parity, core excited states, and first-forbidden decays to negative parity states. The measured β-decay pattern suggests an assignment of Iπ=5/2+ for the 81Zn ground state. The systematics of core excited states in N=50 isotones indicate a strengthening of the N=40 subshell gap near 78Ni.
Phys. Rev. C. 12/2010; 82(6).
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M. Pomorski,
K. Miernik,
W Dominik,
Z. Janas,
M. Pfützner,
C R Bingham,
H. Czyrkowski,
M Cwiok,
I G Darby,
R. D{\ka}browski,
T. Ginter,
R Grzywacz,
M. Karny,
A. Korgul,
W. Kuśmierz, S N Liddick,
M. Rajabali,
K Rykaczewski,
A. Stolz
[show abstract]
[hide abstract]
ABSTRACT: The beta+ decay of very neutron deficient 43Cr has been studied by means of
an imaging time projection chamber which allowed recording tracks of charged
particles. Events of beta-delayed emission of one-, two-, and three protons
were clearly identified. The absolute branching ratios for these channels were
determined to be 81(4)%, 7.1(4)%, and 0.08(3)%, respectively. The 43Cr is thus
established as the second case in which the beta-3p decay occurs. Although the
feeding to the proton-bound states in 43V is expected to be negligible, the
large branching ratio of 12(4)% for decays without proton emission is found.
12/2010;
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P. Hosmer,
H. Schatz,
A. Aprahamian,
O. Arndt,
R. R. C. Clement,
A. Estrade,
K. Farouqi,
K. -L. Kratz, S N Liddick,
A. F. Lisetskiy, [......],
E. Pellegrini,
J. Pereira,
B. Pfeiffer,
P. Reeder,
P. Santi,
M. Steiner,
A. Stolz,
B. E. Tomlin,
W. B. Walters,
A Wöhr
[show abstract]
[hide abstract]
ABSTRACT: The {\beta} decays of very neutron-rich nuclides in the Co-Zn region were studied experimentally at the National Superconducting Cyclotron Laboratory using the NSCL {\beta}-counting station in conjunction with the neutron detector NERO. We measured the branchings for {\beta}-delayed neutron emission (Pn values) for 74Co (18 +/- 15%) and 75-77Ni (10 +/- 2.8%, 14 +/- 3.6%, and 30 +/- 24%, respectively) for the first time, and remeasured the Pn values of 77-79Cu, 79,81Zn, and 82Ga. For 77-79Cu and for 81Zn we obtain significantly larger Pn values compared to previous work. While the new half-lives for the Ni isotopes from this experiment had been reported before, we present here in addition the first half-life measurements of 75Co (30 +/- 11 ms) and 80Cu (170+110 -50 ms). Our results are compared with theoretical predictions, and their impact on various types of models for the astrophysical rapid neutron-capture process (r-process) is explored. We find that with our new data, the classical r-process model is better able to reproduce the A = 78-80 abundance pattern inferred from the solar abundances. The new data also influence r-process models based on the neutrino-driven high-entropy winds in core collapse supernovae. Comment: 13 pages, 13 figures
11/2010;
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I G Darby,
R K Grzywacz,
J C Batchelder,
C R Bingham,
L Cartegni,
C J Gross,
M Hjorth-Jensen,
D T Joss, S N Liddick,
W Nazarewicz,
S Padgett,
R D Page,
T Papenbrock,
M M Rajabali,
J Rotureau,
K P Rykaczewski
[show abstract]
[hide abstract]
ABSTRACT: By studying the (109)Xe→(105)Te→(101)Sn superallowed α-decay chain, we observe low-lying states in (101)Sn, the one-neutron system outside doubly magic (100)Sn. We find that the spins of the ground state (J=7/2) and first excited state (J=5/2) in (101)Sn are reversed with respect to the traditional level ordering postulated for (103)Sn and the heavier tin isotopes. Through simple arguments and state-of-the-art shell-model calculations we explain this unexpected switch in terms of a transition from the single-particle regime to the collective mode in which orbital-dependent pairing correlations dominate.
Physical Review Letters 10/2010; 105(16):162502. · 7.37 Impact Factor
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P. Hosmer,
H. Schatz,
A. Aprahamian,
O. Arndt,
R. R. C. Clement,
A. Estrade,
K. Farouqi,
K.-L. Kratz, S. N. Liddick,
A. F. Lisetskiy, [......],
E. Pellegrini,
J. Pereira,
B. Pfeiffer,
P. Reeder,
P. Santi,
M. Steiner,
A. Stolz,
B. E. Tomlin,
W. B. Walters,
A. Wöhr
[show abstract]
[hide abstract]
ABSTRACT: The β decays of very neutron-rich nuclides in the Co–Zn region were studied experimentally at the National Superconducting Cyclotron Laboratory using the NSCL β-counting station in conjunction with the neutron detector NERO. We measured the branchings for β-delayed neutron emission (Pn values) for 74Co (18±15%) and 75-77Ni (10±2.8%, 14±3.6%, and 30±24%, respectively) for the first time, and remeasured the Pn values of 77-79Cu, 79,81Zn, and 82Ga. For 77-79Cu and for 81Zn we obtain significantly larger Pn values compared to previous work. While the new half-lives for the Ni isotopes from this experiment had been reported before, we present here in addition the first half-life measurements of 75Co (30±11 ms) and 80Cu (170-50+110 ms). Our results are compared with theoretical predictions, and their impact on various types of models for the astrophysical rapid neutron-capture process (r-process) is explored. We find that with our new data, the classical r-process model is better able to reproduce the A=78–80 abundance pattern inferred from the solar abundances. The new data also influence r-process models based on the neutrino-driven high-entropy winds in core collapse supernovae.
Phys. Rev. C. 08/2010; 82(2).
-
J. A. Winger,
K. P. Rykaczewski,
C. J. Gross,
R. Grzywacz,
J. C. Batchelder,
C. Goodin,
J. H. Hamilton,
S. V. Ilyushkin,
A. Korgul,
W. Królas, S. N. Liddick,
C. Mazzocchi,
S. Padgett,
A. Piechaczek,
M. M. Rajabali,
D. Shapira,
E. F. Zganjar,
J. Dobaczewski
[show abstract]
[hide abstract]
ABSTRACT: The structure of neutron-rich nuclei beyond 78Ni was studied using postaccelerated radioactive beams of 83,84,85Ga utilizing β γ and β-n γ spectroscopy. Our data, when combined with energy level systematics, suggests a possible new spherical subshell closure at N=58 is created by the nearly degenerated ν3s1/2 and ν2d5/2 orbitals being well separated from other orbitals above N=50. The near degeneracy of these states could be evidenced by isomerism in this region. The energies of the 21+ and proposed 41+ states observed in N=52 84Ge are interpreted as an indication of a possible weakening of the doubly magic 78Ni core for nuclei beyond N=50. The experimental evidence is supported by spherical HFB calculations using the SkOT functional involving the tensor term in the nucleon-nucleon interaction.
Phys. Rev. C. 04/2010; 81(4).
-
S. V. Ilyushkin,
J. A. Winger,
C. J. Gross,
K. P. Rykaczewski,
J. C. Batchelder,
L. Cartegni,
I. G. Darby,
C. Goodin,
R. Grzywacz,
J. H. Hamilton,
A. Korgul,
W. Królas, S. N. Liddick,
C. Mazzocchi,
S. Padgett,
A. Piechaczek,
M. M. Rajabali,
D. Shapira,
E. F. Zganjar
[show abstract]
[hide abstract]
ABSTRACT: Isobarically purified beams of 77Cu with energies of 225 and 0.2 MeV were used at the Holifield Radioactive Ion Beam Facility of Oak Ridge National Laboratory to study β decay into states in 77Zn. Data taken at 225 MeV allowed the determination of absolute branching ratios relative to the decay of 77Cu for this β decay as well as its daughters. From these we obtained a refined β-delayed neutron emission probability of 30.3(22)% and a probability that the decay proceeds through 77Zng of 49.1(26)%. A total of 64 γ rays were placed in a level scheme for 77Zn containing 35 excited states including one state above the neutron separation energy, whereas two γ rays were observed for the βn branch to states in 76Zn. The growth and decay curves of some prominent γ rays indicate a single β-decaying state with a half-life of 480(9) ms. The decay pattern for 77Cu, with observed feeding of 8(3)% to 7/2+ 77Zng and 6(3)% to 1/2- 77Znm, in contrast to the large feeding observed for decay of πp3/2 73Cug to 1/2- 73Zng, strongly suggests a πf5/2 ground state for the studied 77Cu activity.
Phys. Rev. C. 11/2009; 80(5).
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J A Winger,
S V Ilyushkin,
K P Rykaczewski,
C J Gross,
J C Batchelder,
C Goodin,
R Grzywacz,
J H Hamilton,
A Korgul,
W Królas, S N Liddick,
C Mazzocchi,
S Padgett,
A Piechaczek,
M M Rajabali,
D Shapira,
E F Zganjar,
I N Borzov
[show abstract]
[hide abstract]
ABSTRACT: The beta-delayed neutron branching ratios (P{betan}) for nuclei near doubly magic 78Ni have been directly measured using a new method combining high-resolution mass separation, reacceleration, and digital beta-gamma spectroscopy of 238U fission products. The P{betan} values for the very neutron-rich isotopes ;{76-78}Cu and 83Ga were found to be much higher than previously reported and predicted. Revised calculations of the betan process, accounting for new mass measurements and an inversion of the pi2p{3/2} and pi1f{5/2} orbitals, are in better agreement with these new experimental results.
Physical Review Letters 05/2009; 102(14):142502. · 7.37 Impact Factor
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J. A. Winger,
S. V. Ilyushkin,
K. P. Rykaczewski,
C. J. Gross,
J. C. Batchelder,
C. Goodin,
R. Grzywacz,
J. H. Hamilton,
A. Korgul,
W. Królas, S. N. Liddick,
C. Mazzocchi,
S. Padgett,
A. Piechaczek,
M. M. Rajabali,
D. Shapira,
E. F. Zganjar,
I. N. Borzov
[show abstract]
[hide abstract]
ABSTRACT: The β-delayed neutron branching ratios (Pβn) for nuclei near doubly magic 78Ni have been directly measured using a new method combining high-resolution mass separation, reacceleration, and digital β-γ spectroscopy of 238U fission products. The Pβn values for the very neutron-rich isotopes 76–78Cu and 83Ga were found to be much higher than previously reported and predicted. Revised calculations of the βn process, accounting for new mass measurements and an inversion of the π2p3/2 and π1f5/2 orbitals, are in better agreement with these new experimental results.
Physical Review Letters 04/2009; 102(14):142502. · 7.37 Impact Factor
