-
[show abstract]
[hide abstract]
ABSTRACT: High-spin states of 172Os have been investigated by γ-γ coincidence studies. These states were populated by the 144Nd(32S,4n) reaction using 162-MeV 32S ions. Gamma-gamma coincidence measurements were made with a Compton-suppression spectrometer system. The yrast band was observed up through the 30+ state, and four sidebands were deduced from γ-γ coincidence relationships. A band identified as belonging to 173Os was also observed. Results were interpreted using average nuclear field calculations which incorporated the deformed Woods-Saxon potential with its ‘‘universal’’ parametrization, a cranking approximation, and the Hartree-Fock-Bogoliubov method. The calculations indicate the presence of strongly interacting quasiparticle band crossings for 0.2<ħω<0.3, in semiquantitative agreement with experiment. Both the quasiparticle band structures and decline of neutron pairing are discussed.
Phys. Rev. C. 05/2013; 40(2).
-
J. H. Hamilton,
J. K. Hwang,
J. Komicki,
Yu. Ts. Oganessian,
M. Sakhaee,
A. V. Ramayya,
M. A. Stoyer,
X. Q. Zhang,
B. R. S. Babu,
G. M. Ter-Akopian, [......],
K. E. Gregorich,
M. W. Drigert,
Pau San-li,
M. F. Mohar,
Zhu Sheng-jiang,
Yang Li-ming, J. O. Rasmussen,
S. G. Prussin,
A. V. Daniel,
I. Y. Lee
-
B. L. Goldblum,
M. Wiedeking,
T. Reed,
K. Alfonso,
J. M. Allmond,
L. A. Bernstein,
D. L. Bleuel,
F. S. Dietrich,
R. Hatarik,
P. T. Lake, I.-Y. Lee,
S. R. Lesher,
S. Paschalis,
M. Petri,
L. Phair,
N. D. Scielzo,
R. Vial,
J. Vujic
[show abstract]
[hide abstract]
ABSTRACT: The 92Mo(n,γ) cross section was obtained using both the absolute surrogate approach and surrogate ratio method (SRM), relative to the 94Mo(n,γ) cross section, in an equivalent neutron energy range of 80 to 890 keV. Excited 93Mo and 95Mo nuclei were populated using the 92Mo(d,p) and 94Mo(d,p) reactions, respectively. Both discrete and statistical tagging approaches were employed to identify the γ-decay channel and were examined in terms of their sensitivity to the initial angular momentum population distribution. The absolute surrogate 92Mo(n,γ) cross sections disagree with evaluated neutron capture cross section data by as much as a factor of 4, whereas the results obtained using the SRM trend more favorably with the evaluated result. Experimental results suggest that discrete and statistical tagging approaches may sample different contributions of the γ cascade for near-spherical nuclei. This work uses the surrogate method in the determination of neutron capture cross sections on spherical and quasispherical nuclei in the mass-90 region and provides a possible pathway to extend the SRM to a broader mass range.
Physical Review C 05/2012; 85(5). · 3.31 Impact Factor
-
E. Y. Yeoh,
S. J. Zhu,
J. H. Hamilton,
A. V. Ramayya,
Y. C. Yang,
Y. Sun,
J. K. Hwang,
S. H. Liu,
J. G. Wang,
Y. X. Luo,
J. O. Rasmussen, I. Y. Lee,
H. B. Ding,
K. Li,
L. Gu,
Q. Xu,
Z. G. Xiao,
W. C. Ma
[show abstract]
[hide abstract]
ABSTRACT: High-spin states of the neutron-rich 152Nd nucleus have been reinvestigated by measuring the prompt g \gamma -rays in the spontaneous fission of 252Cf . The ground-state band and a side negative-parity band have been updated. A new band based on the 2243.7keV isomeric state
has been identified. The half-life for the isomeric state has been measured to be 63(7)ns. The projected shell model is employed
to study the band structure of this nucleus. The results show that the calculated levels of the bands are in good agreement
with the experimental ones, and the isomeric state and the negative-parity band are based on the proton p \pi5/2-[532] ⊗ p \pi9/2+[404] and neutron n \nu3/2-[521] ⊗ n \nu5/2+[642] two-quasiparticles configurations, respectively.
European Physical Journal A 04/2012; 45(2):147-151. · 2.19 Impact Factor
-
M Wiedeking,
L A Bernstein,
M Krtička,
D L Bleuel,
J M Allmond,
M S Basunia,
J T Burke,
P Fallon,
R B Firestone,
B L Goldblum,
R Hatarik,
P T Lake, I-Y Lee,
S R Lesher,
S Paschalis,
M Petri,
L Phair,
N D Scielzo
[show abstract]
[hide abstract]
ABSTRACT: A new experimental technique is presented using proton-γ-γ correlations from (94)Mo(d,p)(95)Mo reactions which allows for the model-independent extraction of the photon strength function at various excitation energies using primary γ-ray decay from the quasicontinuum to individual low-lying levels. Detected particle energies provide the entrance excitation energies into the residual nucleus while γ-ray transitions from low-lying levels specify the discrete states being fed. Results strongly support the existence of the previously reported low-energy enhancement in the photon strength function.
Physical Review Letters 04/2012; 108(16):162503. · 7.37 Impact Factor
-
Y X Luo,
J O Rasmussen,
C S Nelson,
J H Hamilton,
A V Ramayya,
J K Hwang,
S H Liu,
C Goodin,
N J Stone,
S J Zhu,
N T Brewer,
Ke Li, I Y Lee,
G M Ter-Akopian,
A V Daniel,
M A Stoyer,
R Donangelo,
W C Ma,
J D Cole
Nuclear Physics A 01/2012; 874:32-61. · 1.54 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The high-spin structure above the previously known 10(+) isomers of the Sn-118,Sn-120,Sn-122,Sn-124 isotopes was studied via prompt gamma-ray spectroscopy. All isotopes were populated as fragments following the fission of much heavier compound nuclei formed in three fusion-fission reactions. The Sn-118,Sn-120,Sn-122 isotopes were also independently populated and studied as evaporation residues in the Sn-124(n, xn gamma) reactions, with x = 3, 5, 7. Transitions above the previously known 10(+) isomers were observed for the first time and the corresponding level schemes above these isomers were established up to 6646-, 5673-, 5386-, and 5952-keV excitation energy for Sn-118,Sn-120,Sn-122,Sn-124, respectively. The experimental results are compared with predictions from shell-model calculations.
Physical Review C 11/2011; 84(5):054310. · 3.31 Impact Factor
-
E. S. Paul,
C. Fox,
A. J. Boston,
H. J. Chantler,
C. J. Chiara,
R. M. Clark,
M. Cromaz,
M. Descovich,
P. Fallon,
D. B. Fossan,
A. A. Hecht,
T. Koike, I. Y. Lee,
A. O. Macchiavelli,
P. J. Nolan,
K. Starosta,
R. Wadsworth,
I. Ragnarsson
[show abstract]
[hide abstract]
ABSTRACT: High-spin states have been studied in 59135Pr, populated through the 116Cd(23Na,4n) reaction at 115 MeV, using the Gammasphere γ-ray spectrometer. The negative-parity yrast band has been significantly extended to spin ∼45ℏ and excitation energy 21.5 MeV, showing evidence for several rotational alignments. The positive-parity yrast band of 58134Ce, populated through the p4n channel of this reaction, was also populated to spin ∼38ℏ and excitation energy 18 MeV. Cranking calculations indicate that these nuclei are soft with respect to the triaxiality parameter γ and that several competing nuclear shapes occur at high spin.
Phys. Rev. C. 10/2011; 84(4).
-
J. Timár,
K. Starosta,
I. Kuti,
D. Sohler,
D. B. Fossan,
T. Koike,
E. S. Paul,
A. J. Boston,
H. J. Chantler,
M. Descovich,
R. M. Clark,
M. Cromaz,
P. Fallon, I. Y. Lee,
A. O. Macchiavelli,
C. J. Chiara,
R. Wadsworth,
A. A. Hecht,
D. Almehed,
S. Frauendorf
[show abstract]
[hide abstract]
ABSTRACT: Medium- and high-spin states of 134Pr were populated using the 116Cd(23Na,5n) reaction and studied with the GAMMASPHERE spectrometer. Several new bands have been found in this nucleus, one of them being linked to the previously observed chiral-candidate twin-band structure. The ground state of 134Pr could be determined through establishing a level structure that connects the two previously known long-lived isomeric states. Unambiguous spin-parity assignments for the excited states could be performed based on the known 2− spin-parity of the ground state combined with the present experimental data. Intrinsic single-particle configurations have been assigned to the newly observed bands on the basis of the measured B(M1)/B(E2) ratios, alignments, band-crossing frequencies, bandhead spins, the observed single-particle configurations in the neighboring nuclei, and taking into account the predictions of total Routhian surface and tilted-axis cranking calculations.
Phys. Rev. C. 10/2011; 84(4).
-
S Paschalis,
P Fallon,
A O Macchiavelli,
M Petri,
P C Bender,
M P Carpenter,
X Chen,
C J Chiara,
R M Clark,
M Cromaz, [......],
C J Lister,
E A McCutchan,
L Phair,
W Reviol,
D G Sarantites,
D Seweryniak,
S L Tabor,
Y Toh,
M Wiedeking,
S Zhu
[show abstract]
[hide abstract]
ABSTRACT: The energy of the lowest deformed 2-particle 2-hole (2p2h) 0+ state in even-even N = 20 nuclei is a key observable directly related to the size of the neutron N = 20 shell closure. 34Si, with 14 protons and 20 neutrons, lies at the boundary of the "island of inversion", where the deformed 2p2h 0+ state is the ground state in even-A nuclei. In 34Si, the 2p2h 0+ state is expected to be particularly low lying - in some theories it is even predicted to lie below the first 2+ state. While there have been a number of attempts, using various techniques, no experiment to date has been able to firmly locate the 34Si 2p2h 0+ state although a number of candidates have been suggested. Here we present, for the first time, data obtained from a fusion-evaporation reaction 18O(18O, 2p) to produce 34Si. Gammasphere and Microball were used to detect γ-γ coincidences and charged particles (two protons), respectively. The increased sensitivity of this experiment using γ-γ coincidences and a high charged-particle detection efficiency helped to exclude previously reported candidates and provided a stringent limit on the anticipated γ decay from the first 2+ state to the 2p2h 0+ state.
Journal of Physics Conference Series 09/2011; 312(9):092050.
-
J S Berryman,
R M Clark,
K E Gregorich,
J M Allmond,
D L Bleuel,
R J Cooper,
M Cromaz,
M A Deleplanque,
I Dragojević,
J Dvorak, [......],
H Nitsche,
S Paschalis,
M Petri,
J Qian,
L Stavsetra,
F S Stephens,
M A Stoyer,
T J Ross,
H Watanabe,
M Wiedeking
[show abstract]
[hide abstract]
ABSTRACT: Recently it has become possible to perform detailed spectroscopy on nuclei beyond Z = 100 with the aim of understanding the underlying single-particle structure of superheavy elements. A number of such experiments have been performed at the 88-Inch Cyclotron of the Lawrence Berkeley National Laboratory using the Berkeley Gas-filled Separator (BGS), coupled with delayed γ-ray and electron-decay spectroscopy. Experiments have been performed on 254No (Z = 102), 257Rf (Z = 104), and 261Sg (Z = 106). The results provide new information on the properties of transactinide nuclei, which is important for testing models of the heaviest elements.
Journal of Physics Conference Series 09/2011; 312(9):092017.
-
M Petri,
P Fallon,
A O Macchiavelli,
S Paschalis,
K Starosta,
T Baugher,
D Bazin,
L Cartegni,
R M Clark,
H L Crawford, [......],
S McDaniel,
D Miller,
M M Rajabali,
A Ratkiewicz,
W Rother,
P Voss,
K A Walsh,
D Weisshaar,
M Wiedeking,
B A Brown
[show abstract]
[hide abstract]
ABSTRACT: Establishing how and when large N/Z values require modified or new theoretical tools is a major quest in nuclear physics. Here we report the first measurement of the lifetime of the 2(1)+ state in the near-dripline nucleus 20C. The deduced value of τ(2(1)+)=9.8±2.8(stat)(-1.1)(+0.5)(syst) ps gives a reduced transition probability of B(E2; 2(1)+→0(g.s.)+)=7.5(-1.7)(+3.0)(stat)(-0.4)(+1.0)(syst) e2 fm4 in good agreement with a shell model calculation using isospin-dependent effective charges.
Physical Review Letters 09/2011; 107(10):102501. · 7.37 Impact Factor
-
K Li,
J H Hamilton,
A V Ramayya,
S H Liu,
X Q Zhang,
N T Brewer,
J K Hwang,
C Goodin,
S J Zhu,
Y X Luo, [......], I Y Lee,
S C Wu,
R Donangelo,
A V Daniel,
G M Ter-Akopian,
Yu. Ts. Oganessian,
A Unzhakova,
J D Cole,
W C Ma,
M A Stoyer
International Journal of Modern Physics E 08/2011; 20(8):1825-1832. · 0.60 Impact Factor
-
J Gibelin,
M Wiedeking,
L Phair,
P Fallon,
S Basunia,
L A Bernstein,
J T Burke,
D L Bleuel,
R M Clark,
M Cromaz, [......],
H B Jeppesen,
P T Lake, I.-Y Lee,
S R Lesher,
A O Macchiavelli,
M A Mcmahan,
J Pavan,
E Rodriguez-Vieitez,
N D Scielzo,
L G Moretto
[show abstract]
[hide abstract]
ABSTRACT: a b s t r a c t Experimental results for the minor decay channels of fusion-evaporation in light projectile plus light target systems are presented. These new data were obtained during test campaigns to measure the opening of different decay channels. Experiments were designed to provide relative cross-section information on weakly populated channels for gamma-ray spectroscopy experiments in coincidence with charged-particles. The results are compared to publicly available fusion-evaporation codes. The data follow a simple estimate which is useful in predicting experimental conditions to make the fusion-evaporation reaction a viable nuclear structure tool to study weakly populated light neutron-rich nuclei. & 2011 Elsevier B.V. All rights reserved.
Nucl. Instrum. Methods Phys. Res. A. 07/2011; 648:109.
-
E. Y. Yeoh (杨韵颐,
S. J. Zhu (朱胜江,
J. H. Hamilton,
K. Li,
A. V. Ramayya,
Y. X. Liu (刘艳鑫,
J. K. Hwang,
S. H. Liu,
J. G. Wang (王建国,
Y. Sun (孙扬,
J. A. Sheikh,
G. H. Bhat,
Y. X. Luo,
J. O. Rasmussen, I. Y. Lee,
H. B. Ding (丁怀博,
L. Gu (顾龙,
Q. Xu (徐强,
Z. G. Xiao (肖志刚,
W. C. Ma
[show abstract]
[hide abstract]
ABSTRACT: High-spin levels of the neutron-rich 114Ru have been investigated by measuring the prompt γ rays in the spontaneous fission of 252Cf. The ground-state band and one-phonon γ-vibrational band have been extended up to 14+ and 9+, respectively. Two levels are proposed as the members of a two-phonon γ-vibrational band. A back bending (band crossing) has been observed in the ground-state band at ℏω≈ 0.40 MeV. Using the triaxial deformation parameters, the cranked shell model calculations indicate that this back bending in 114Ru should originate from the alignment of a pair of h11/2 neutrons. Triaxial projected shell model calculations for the γ-vibrational band structures of 114Ru are in good agreement with the experimental data. However, when using the oblate deformation parameters, both of the above-calculated results are not in agreement with the experimental data.
Phys. Rev. C. 05/2011; 83(5).
-
J S Berryman,
R M Clark,
K E Gregorich,
J M Allmond,
D L Bleuel,
R J Cooper,
M Cromaz,
M A Deleplanque,
I Dragojevic,
J Dvorak, [......],
H Nitsche,
S Paschalis,
M Petri,
J Qian,
L Stavsetra,
F S Stephens,
M A Stoyer,
T J Ross,
H Watanabe,
M Wiedeking
INTERNATIONAL NUCLEAR PHYSICS CONFERENCE 2010 (INPC): NUCLEAR STRUCTURE; 01/2011
-
P A Ellison,
K E Gregorich,
J S Berryman,
D L Bleuel,
R M Clark,
I Dragojevi,
J Dvorak,
P Fallon,
C Fineman-Sotomayor,
J M Gates,
O R Gothe, I Y Lee,
W D Loveland,
J P Mclaughlin,
S Paschalis,
M Petri,
J Qian,
L Stavsetra,
M Wiedeking,
H Nitsche
[show abstract]
[hide abstract]
ABSTRACT: The new, neutron-deficient, superheavy element isotope 285 114 was produced in 48 Ca irradiations of 242 Pu targets at a center-of-target beam energy of 256 MeV (E Ã ¼ 50 MeV). The decay of 285 114 was followed by the sequential decay of four daughter nuclides, 281 Cn, 277 Ds, 273 Hs, and 269 Sg. 265 Rf was observed to decay by spontaneous fission. The measured -decay Q values were compared with those from a macroscopic-microscopic nuclear mass model to give insight into superheavy element shell effects.
Physical Review Letters 10/2010; 90. · 7.37 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A low power and highly linear CMOS active tracking bandpass filter is presented to overcome a local oscillator harmonic mixing problem for Digital TV tuner ICs. A transconductor linearization technique based on a method of dynamic source degenerated differential pair is adopted to improve the linearity performance. The newly proposed low power high quality factor (Q) biquad and the linearized transconductor with negative resistance load (NRL) enables a low power and high Q RF tracking filter design. The total chip area is 0.25 mm X 0.9 mm. The fabricated tracking filter based on the 0.13 um CMOS process shows 48~300 MHz tracking range with 10~50 MHz bandwidth, more than 38 dB 3rd order harmonic rejection, 6 dB unwanted signal rejection@N+6 channel offset, and a maximum IIP3 of 6 dBm at 5 dB gain while drawing 6.4 mA from a 1.2 V supply.
Custom Integrated Circuits Conference (CICC), 2010 IEEE; 10/2010
-
P A Ellison,
K E Gregorich,
J S Berryman,
D L Bleuel,
R M Clark,
I Dragojević,
J Dvorak,
P Fallon,
C Fineman-Sotomayor,
J M Gates,
O R Gothe, I Y Lee,
W D Loveland,
J P McLaughlin,
S Paschalis,
M Petri,
J Qian,
L Stavsetra,
M Wiedeking,
H Nitsche
[show abstract]
[hide abstract]
ABSTRACT: The new, neutron-deficient, superheavy element isotope ²⁸⁵114 was produced in ⁴⁸Ca irradiations of ²⁴²Pu targets at a center-of-target beam energy of 256 MeV (E*=50 MeV). The α decay of ²⁸⁵114was followed by the sequential α decay of four daughter nuclides, 281Cn, 277Ds, 273Hs, and 269Sg. 265Rf was observed to decay by spontaneous fission. The measured α-decay Q values were compared with those from a macroscopic-microscopic nuclear mass model to give insight into superheavy element shell effects. The²⁴²Pu (⁴⁸Ca,5n²)²⁸⁵114 cross section was 0.6(-0.5)+0.9 pb.
Physical Review Letters 10/2010; 105(18):182701. · 7.37 Impact Factor
-
Gu Long,
Zhu Sheng-Jiang,
J. H. Hamilton,
A. V. Ramayya,
J. K. Hwang,
S. H. Liu,
Wang Jian-Guo,
Y. X. Luo,
J. O. Rasmussen, I. Y. Lee,
Xu Qiang,
E. Y. Yeoh,
W. C. Ma
[show abstract]
[hide abstract]
ABSTRACT: The high spin states of the neutron-rich 109Tc nucleus are reinvestigated by observing prompt γ-rays from the spontaneous fission of 252Cf. The previously known yrast band based on the 7/2+ state is updated. A side band built on the 11/2+ state is expanded and a new band based on the 15/2+ state is identified. Band crossing in the yrast band occurs around ħω ≈ 0.36MeV. This band crossing is associated with the alignment of two h11/2 neutrons according to the cranked shell model calculations. The band based on the 11/2+ state is proposed as a candidate for the one-phonon γ-vibrational band, and the band built on the 15/2+ state is proposed as a candidate for the two-phonon γ-vibrational band. Other characteristics for the observed bands are discussed.
Chinese Physics Letters 06/2010; 27(6):062501. · 0.73 Impact Factor
