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A Chakraborty,
E E Peters,
B P Crider,
C Andreoiu,
P C Bender, D S Cross,
G A Demand,
A B Garnsworthy,
P E Garrett,
G Hackman, [......],
K G Leach,
M T McEllistrem,
J Pore,
F M Prados-Estévez,
E T Rand,
B Singh,
E R Tardiff,
Z-M Wang,
J L Wood,
S W Yates
[show abstract]
[hide abstract]
ABSTRACT: Based on results from a measurement of weak decay branches observed following the β^{-} decay of ^{94}Y and on lifetime data from a study of ^{94}Zr by inelastic neutron scattering, collective structure is deduced in the closed-subshell nucleus ^{94}Zr. These results establish shape coexistence in ^{94}Zr. The role of subshells for nuclear collectivity is suggested to be important.
Physical Review Letters 01/2013; 110(2):022504. · 7.37 Impact Factor
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P. E. Garrett,
J. Bangay,
A. Diaz Varela,
G. C. Ball, D. S. Cross,
G. A. Demand,
P. Finlay,
A. B. Garnsworthy,
K. L. Green,
G. Hackman, [......],
A. J. Radich,
E. T. Rand,
M. A. Schumaker,
C. E. Svensson,
C. Sumithrarachchi,
S. Triambak,
N. Warr,
J. Wong,
J. L. Wood,
S. W. Yates
[show abstract]
[hide abstract]
ABSTRACT: A study of the β+-electron capture decay of 110In into levels of 110Cd is combined with a reanalysis of data from a previous study of 110Cd with the (n,n′γ) reaction with monoenergetic neutrons. The γγ coincidences from the 110In decay leads to many new assignments of γ rays observed in the (n,n′γ) reaction, permitting the observation of weak low-energy transitions, and setting stringent upper limits on unobserved decay branches. The uncertainties on many of the lifetimes from the (n,n′γ) reaction are significantly reduced, and limits are established for the lifetimes of levels too long for a direct measurement. The absence of enhanced transitions between the previously assigned phonon states and the deformed intruder states strongly suggests that mixing between the configurations is generally weak, refuting the strong-mixing scenario as an explanation of the decay pattern of the excited 0+ states in 110Cd. The decay pattern of the nonintruder states is suggestive of a γ-soft rotor, or O(6) nucleus, rather than a vibrational, or U(5), pattern. The existence of a four-particle–six-hole proton excitation in 110Cd is also suggested.
Phys. Rev. C. 09/2012; 86(4).
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S. Triambak,
P. Finlay,
C. S. Sumithrarachchi,
G. Hackman,
G. C. Ball,
P. E. Garrett,
C. E. Svensson, D. S. Cross,
A. B. Garnsworthy,
R. Kshetri, [......],
R. A. E. Austin,
R. Churchman,
M. K. Djongolov,
R. D'Entremont,
C. Kierans,
L. Milovanovic,
S. O'Hagan,
S. Reeve,
S. K. L. Sjue,
S. J. Williams
[show abstract]
[hide abstract]
ABSTRACT: We report a precise determination of the 19Ne half-life to be $T_{1/2} =
17.262 \pm 0.007$ s. This result disagrees with the most recent precision
measurements and is important for placing bounds on predicted right-handed
interactions that are absent in the current Standard Model. We are able to
identify and disentangle two competing systematic effects that influence the
accuracy of such measurements. Our findings prompt a reassessment of results
from previous high-precision lifetime measurements that used similar equipment
and methods.
06/2012;
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M. A. Schumaker,
D. Cline,
G. Hackman,
C. Pearson,
C. E. Svensson,
C. Y. Wu,
A. Andreyev,
R. A. E. Austin,
G. C. Ball,
D. Bandyopadhyay, [......],
J. J. Ressler,
R. Roy,
C. Ruiz,
F. Sarazin,
D. P. Scraggs,
J. C. Waddington,
J. M. Wan,
A. Whitbeck,
S. J. Williams,
J. Wong
[show abstract]
[hide abstract]
ABSTRACT: The low-energy structures of the radioactive nuclei 20, 21Na have been examined using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. Beams of ∼ 5×106 ions/s were accelerated to 1.7MeV/A and Coulomb excited in a 0.5mg/cm^2 natTi target. Two TIGRESS HPGe clover detectors perpendicular to the beam axis were used for g \gamma -ray detection, while scattered nuclei were observed by the Si detector BAMBINO. For 21Na , Coulomb excitation from the 3/2+ ground state to the first excited 5/2+ state was observed, while for 20Na , Coulomb excitation was observed from the 2+ ground state to the first excited 3+ and 4+ states. For both beams, B ( l \lambda
L) values were determined using the 2+
® \rightarrow 0+ de-excitation in 48Ti as a reference. The resulting B(E2) ↓ value for 21Na is 137±9 e^2fm^4, while the resulting B(l \lambda
L) ↓ values for 20Na are 55±6 e^2fm^4 for the 3+
® \rightarrow 2+ , 35.7±5.7 e^2 fm^4 for the 4+
® \rightarrow 2+ , and 0.154±0.030 μ_N^2 for the 4+
® \rightarrow 3+ transitions. This analysis significantly improves the measurement of the 21Na B(E2) value, and provides the first experimental determination of B(l \lambda
L) values for the proton dripline nucleus 20Na .-1
European Physical Journal A 04/2012; 42(3):477-484. · 2.19 Impact Factor
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P. Finlay,
G.C. Ball,
J.R. Leslie,
C.E. Svensson,
C. Andreoiu,
R.A.E. Austin,
D. Bandyopadhyay, D.S. Cross,
G. Demand,
M. Djongolov, [......],
K.L. Green,
G.F. Grinyer,
G. Hackman,
K.G. Leach,
C.J. Pearson,
A.A. Phillips,
E.T. Rand,
C.S. Sumithrarachchi,
S. Triambak,
S.J. Williams
Physical Review C 01/2012; 85:055501. · 3.31 Impact Factor
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J N Orce,
T E Drake,
M K Djongolov,
P Navratil,
S Triambak,
G C Ball,
H Al Falou,
R Churchman, D S Cross,
P Finlay, [......],
F Sarazin,
S K L Sjue,
M A Stoyer,
C S Sumithrarachchi,
C E Svensson,
E R Tardiff,
A Teigelhoefer,
S J Williams,
J Wong,
C Y Wu
Physical Review C 01/2012; 86(4). · 3.31 Impact Factor
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D S Cross,
G C Ball,
P E Garrett,
S Triambak,
S J Williams,
C Andreoiu,
R Churchman,
A B Garnsworthy,
G Hackman,
J R Leslie,
J N Orce,
C S Sumithrarachchi,
C E Svensson
[show abstract]
[hide abstract]
ABSTRACT: The Di-pentagonal Array for Nuclear Timing Experiments (DANTE) is an array of ten BaF2 detectors used in conjunction with the 8π gamma-ray spectrometer at the TRIUMF-ISAC radioactive-ion beam facility. DANTE is used to conduct direct lifetime measurements of nuclear excited states in the picosecond - nanosecond range. This, in turn, will aid in probing the collective structures of deformed nuclei. The capability of DANTE to measure nanosecond-scale lifetimes is demonstrated by using a 152Eu source. The half-life of the Iπ = 21+ state of 152Sm is measured to be 1.426 ± 0.018 ns.
Journal of Instrumentation 08/2011; 6(08):P08008. · 1.87 Impact Factor
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P Finlay,
S Ettenauer,
G C Ball,
J R Leslie,
C E Svensson,
C Andreoiu,
R A E Austin,
D Bandyopadhyay, D S Cross,
G Demand, [......],
P E Garrett,
K L Green,
G F Grinyer,
G Hackman,
K G Leach,
C J Pearson,
A A Phillips,
C S Sumithrarachchi,
S Triambak,
S J Williams
[show abstract]
[hide abstract]
ABSTRACT: A high-precision half-life measurement for the superallowed β+ emitter 26Al(m) was performed at the TRIUMF-ISAC radioactive ion beam facility yielding T 1/2 6346.54 ± 0.46(stat) ± 0.60 (syst) ms, consistent with, but 2.5 times more precise than, the previous world average. The 26Al(m) half-life and ft value, 3037.53(61) s, are now the most precisely determined for any superallowed β decay. Combined with recent theoretical corrections for isospin-symmetry-breaking and radiative effects, the corrected Ft value for (26)Al(m), 3073.0(12) s, sets a new benchmark for the high-precision superallowed Fermi β-decay studies used to test the conserved vector current hypothesis and determine the V(ud) element of the Cabibbo-Kobayashi-Maskawa quark mixing matrix.
Physical Review Letters 01/2011; 106(3):032501. · 7.37 Impact Factor
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R Kanungo,
A T Gallant,
M Uchida,
C Andreoiu,
R A E Austin,
D Bandyopadhyay,
G C Ball,
J A Becker,
A J Boston,
H C Boston, [......],
A C Shotter,
C S Sumitharachchi,
C E Svensson,
I Tanihata,
S Triambak,
C Unsworth,
S J Williams,
P Walden,
J Wong,
C Y Wu
Physics Letters B. 01/2010; 682(4-5):391-395.
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R Kanungo,
A T Gallant,
M Uchida,
C Andreoiu,
R A E Austin,
D Bandyopadhyay,
G C Ball,
J A Becker,
A J Boston,
H C Boston, [......],
A C Shotter,
C S Sumitharachchi,
C E Svensson,
I Tanihata,
S Triambak,
C Unsworth,
S J Williams,
P Walden,
J Wong,
C Y Wu
Physics Letters B 01/2010; 682(4-5):391-395. · 3.95 Impact Factor
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M. A. Schumaker,
A. M. Hurst,
C. E. Svensson,
C. Y. Wu,
J. A. Becker,
D. Cline,
G. Hackman,
C. J. Pearson,
M. A. Stoyer,
A. Andreyev, [......],
D. P. Scraggs,
C. S. Sumithrarachchi,
S. Triambak,
J. C. Waddington,
P. M. Walker,
J. Wan,
A. Whitbeck,
S. J. Williams,
J. Wong,
J. L. Wood
[show abstract]
[hide abstract]
ABSTRACT: The TRIUMF‐ISAC Gamma‐Ray Escape Suppressed Spectrometer (TIGRESS) is a state‐of‐the‐art γ‐ray spectrometer being constructed at the ISAC‐II radioactive ion beam facility at TRIUMF. TIGRESS will be comprised of twelve 32‐fold segmented high‐purity germanium (HPGe) clover‐type γ‐ray detectors, with BGO∕CsI(Tl) Compton‐suppression shields, and is currently operational at ISAC‐II in an early‐implementation configuration of six detectors. Results have been obtained for the first experiments performed using TIGRESS, which examined the A = 20, 21, and 29 isotopes of Na by Coulomb excitation.
AIP Conference Proceedings. 03/2009; 1099(1):754-759.
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M A Schumaker,
A M Hurst,
C E Svensson,
C Y Wu,
J A Becker,
D Cline,
G Hackman,
C J Pearson,
M A Stoyer,
A Andreyev, [......],
D P Scraggs,
C S Sumithrarachchi,
S Triambak,
J C Waddington,
P M Walker,
J Wan,
A Whitbeck,
S J Williams,
J Wong,
J L Wood
APPLICATION OF ACCELERATORS IN RESEARCH AND INDUSTRY; 01/2009
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M. A. Schumaker,
D. Cline,
G. Hackman,
A. C. Morton,
C. J. Pearson,
C. E. Svensson,
C. Y. Wu,
A. Andreyev,
R. A. E. Austin,
G. C. Ball, [......],
J. J. Ressler,
R. Roy,
C. Ruiz,
F. Sarazin,
D. P. Scraggs,
J. C. Waddington,
J. M. Wan,
A. Whitbeck,
S. J. Williams,
J. Wong
[show abstract]
[hide abstract]
ABSTRACT: The low-energy structures of the mirror nuclei 21Ne and radioactive 21Na have been examined by using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. Beams of ~5×106 ions/s were accelerated to 1.7 MeV/A and Coulomb excited in a 0.5 mg/cm2 natTi target. Scattered beam and target particles were detected by the segmented Si detector BAMBINO, while γ rays were observed by using two TIGRESS HPGe clover detectors perpendicular to the beam axis. For each isobar, Coulomb excitation from the 3/2+ ground state to the first excited 5/2+ state was observed and B(E2) values were determined by using the 2+→0+ de-excitation in 48Ti as a reference. The ϕ segmentation of BAMBINO was used to deduce tentative assignments for the signs of the mixing ratios between the E2 and M1 components of the transitions. The resulting B(E2)↑ values are 131±9 e2 fm4 (25.4±1.7 W.u.) for 21Ne and 205±14 e2 fm4 (39.7±2.7 W.u.) for 21Na. The fit to the present data and the known lifetimes determined E2/M1 mixing ratios and B(M1)↓ values of δ=(-)0.0767±0.0027 and 0.1274±0.0025 μN2 and δ=(+)0.0832±0.0028 and 0.1513±0.0017 μN2 for 21Ne and 21Na, respectively (with Krane and Steffen sign convention). By using the effective charges ep=1.5e and en=0.5e, the B(E2) values produced by the p-sd shell model are 30.7 and 36.4 W.u. for 21Ne and 21Na, respectively. This analysis resolves a significant discrepancy between a previous experimental result for 21Na and shell-model calculations.
Phys. Rev. C. 10/2008; 78(4).
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[show abstract]
[hide abstract]
ABSTRACT: Excitations in 94Ru were populated through the β+/ε decay of 94Rh following the fusion evaporation reaction 58Ni(40Ca,3pn)94Rh. Recoiling nuclei were implanted on the Yale moving tape collector at the Wright Nuclear Structure Laboratory, and delayed γ-rays were observed via an array of four Compton suppressed HPGe clover detectors. Nine new γ-transitions and five new levels were added to the level scheme of (π1g9/2)Jπ=6+4 level, in close agreement with prediction.
Phys. Rev. C. 04/2007; 75(4).
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R. S. Chakrawarthy,
P. M. Walker,
J. J. Ressler,
E. F. Zganjar,
G. C. Ball,
M. B. Smith,
A. N. Andreyev,
S. F. Ashley,
R. A. E. Austin,
D. Bandyopadhyay, [......],
R. Kanungo,
W. D. Kulp,
Y. Litvinov,
A. C. Morton,
W. J. Mills,
C. J. Pearson,
R. Propri,
C. E. Svensson,
R. Wheeler,
S. J. Williams
[show abstract]
[hide abstract]
ABSTRACT: Gamma-ray and conversion-electron spectroscopy have established the existence of a 2.29(1) s, Kπ=0+, isomeric state in neutron-rich 174Tm. The isomer deexcites via 100- and 152-keV electromagnetic transitions. First results from a newly commissioned Si(Li) detector array have established their M1 and E3 multipolarities, respectively. The single-particle configurations of the excited states suggest that the E3 transition originates from a πh11/2-1→πd3/2 configuration change, whereas the M1 transition occurs between members of a Gallaghar-Moszkowski doublet. From the measured half-life, the deduced B(E3) value of 0.024(2) W.u. is highly hindered. The reported measurements resolve ambiguities in the previously proposed β decay scheme of 174Er to 174Tm.
Phys. Rev. C. 02/2006; 73(2).
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A.M. Hurst,
C.Y. Wu,
J.A. Becker,
M.A. Stoyer,
C.J. Pearson,
G. Hackman,
M.A. Schumaker,
C.E. Svensson,
R.A.E. Austin,
G.C. Ball, [......],
A.A. Phillips,
M. Porter-Peden,
S.V. Rigby,
F. Sarazin,
C.S. Sumithrarachchi,
S. Triambak,
P.M. Walker,
S.J. Williams,
J. Wong,
J.L. Wood
[show abstract]
[hide abstract]
ABSTRACT: The wave-function composition for the low-lying states in 29Na was explored by measuring their electromagnetic properties using the Coulomb-excitation technique. A beam of 29Na ions, postaccelerated to 70 MeV, bombarded a 110Pd target with a rate of up to 600 particles per second at the recently commissioned ISAC-II facility at TRIUMF. Six segmented HPGe clover detectors of the TIGRESS γ-ray spectrometer were used to detect deexcitation γ rays in coincidence with scattered or recoiling charged particles in the segmented silicon detector, BAMBINO. The reduced transition matrix element in 29Na was derived to be 0.237(21) e b from the measured γ-ray yields for both projectile and target. This first-time measured value is consistent with the most recent Monte Carlo shell-model calculation, indicating a significant admixture of both sd and pf components in the wave function, and also providing evidence for the narrowing of the neutron sd–pf shell gap from ∼6 MeV for stable nuclei to ∼3 MeV for 29Na.
Physics Letters B. 674(3):168-171.
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R. S. Chakrawarthy,
P. M. Walker,
J. J. Ressler,
E F Zganjar,
G. C. Ball,
M. B. Smith,
A. N. Andreyev,
S. F. Ashley,
R. A. E. Austin,
D. Bandyopadhyay, [......],
R. Kanungo,
W. D. Kulp,
Y. Litvinov,
A. C. Morton,
W J Mills,
C. J. Pearson,
R. Propri,
C E Svensson,
R. Wheeler,
S. J. Williams
Nuclear Physics Group.
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R. S. Chakrawarthy,
P. M. Walker,
J. J. Ressler,
E F Zganjar,
G. C. Ball,
M. B. Smith,
A. N. Andreyev,
S. F. Ashley,
R A Austin,
D. Bandyopadhyay, [......],
R. Kanungo,
W. D. Kulp,
Y. Litvinov,
A. C. Morton,
W J Mills,
C. J. Pearson,
R. Propri,
C E Svensson,
R. Wheeler,
S. J. Williams
[show abstract]
[hide abstract]
ABSTRACT: Gamma-ray and conversion-electron spectroscopy have established the existence of a 2.29(1) s, K-pi=0(+), isomeric state in neutron-rich Tm-174. The isomer deexcites via 100- and 152-keV electromagnetic transitions. First results from a newly commissioned Si(Li) detector array have established their M1 and E3 multipolarities, respectively. The single-particle configurations of the excited states suggest that the E3 transition originates from a pi h(11/2)(-1)->pi d(3/2) configuration change, whereas the M1 transition occurs between members of a Gallaghar-Moszkowski doublet. From the measured half-life, the deduced B(E3) value of 0.024(2) W.u. is highly hindered. The reported measurements resolve ambiguities in the previously proposed beta decay scheme of Er-174 to Tm-174.
Nuclear Physics Group.
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M. A. Schumaker,
D. Cline,
G. Hackman,
C. J. Pearson,
C. E. Svensson,
C. Y. Wu,
A. Andreyev,
R. A. E. Austin,
G. C. Ball,
D. Bandyopadhyay, [......],
J. J. Ressler,
R. Roy,
C. Ruiz,
F. Sarazin,
D. P. Scraggs,
J. C. Waddington,
J. M. Wan,
A. Whitbeck,
S. J. Williams,
J. Wong
[show abstract]
[hide abstract]
ABSTRACT: The low-energy structure of the proton dripline nucleus 20Na has been studied using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. A 1.7-MeV/nucleon 20Na beam of ~5×106 ions/s was Coulomb excited by a 0.5-mg/cm2 natTi target. Scattered beam and target particles were detected by the BAMBINO segmented Si detector while γ rays were detected by two TIGRESS HPGe clover detectors set perpendicular to the beam axis. Coulomb excitation from the 2+ ground state to the first excited 3+ and 4+ states was observed, and B(λL) values were determined using the 2+→0+ de-excitation in 48Ti as a reference. The resulting B(λL)↓ values are B(E2;3+→2+)=55±6 e2 fm4 (17.0±1.9 W.u.), B(E2;4+→2+)=35.7±5.7 e2 fm4 (11.1±1.8 W.u.), and B(M1;4+→3+)=0.154±0.030 μN2 (0.086±0.017 W.u.). These measurements provide the first experimental determination of B(λL) values for this proton dripline nucleus of astrophysical interest.
Phys. Rev. C. 80(4).
