R. A. E. Austin

Publications (56)64.1 Total impact

• Article: High-Precision Measurement of the 19Ne Half-Life and Implications for Right-Handed Weak Currents

  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
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  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;
• Article: Coulomb excitation of radioactive 20, 21Na

  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
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  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
• Article: High-precision branching-ratio measurement for the superallowed beta+ emitter 26Alm

  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
• Source

  Available from: Paul E. Garrett

  Article: Evidence for Shape Co-existence at medium spin in 76Rb

  R Wadsworth, I Ragnarsson, B. G. Carlsson, Hai-Liang Ma, P. J. Davies, C. Andreoiu, R. A. E. Austin, M P Carpenter, D. Dashdorj, S J Freeman, [......], F. Johnston-Theasby, P. Joshi, A O Macchiavelli, F. Moore, G. Mukherjee, W Reviol, D G Sarantites, D Seweryniak, C E Svensson, J. J. Valiente-Dobón
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  ABSTRACT: Four previously known rotational bands in 76Rb have been extended to moderate spins using the Gammasphere and Microball gamma ray and charged particle detector arrays and the 40Ca(40Ca,3pn) reaction at a beam energy of 165 MeV. The properties of two of the negative-parity bands can only readily be interpreted in terms of the highly successful Cranked Nilsson-Strutinsky model calculations if they have the same configuration in terms of the number of g9/2 particles, but they result from different nuclear shapes (one near-oblate and the other near-prolate). These data appear to constitute a unique example of shape co-existing structures at medium spins.
  06/2011;
• Article: SHARC: Silicon Highly-segmented Array for Reactions and Coulex used in conjunction with the TIGRESS γ-ray spectrometer

  C Aa Diget, S P Fox, A Smith, S Williams, M Porter-Peden, L Achouri, P Adsley, H Al-Falou, R A E Austin, G C Ball, [......], N A Orr, C J Pearson, C Ruiz, F Sarazin, S Sjue, D Smalley, C E Svensson, M Taggart, E Tardiff, G L Wilson
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  ABSTRACT: The combination of γ-ray spectroscopy and charged-particle spectroscopy is a powerful tool for the study of nuclear reactions with beams of nuclei far from stability. This paper presents a new silicon detector array, SHARC, the Silicon Highly-segmented Array for Reactions and Coulex. The array is used at the radioactive-ion-beam facility at TRIUMF (Canada), in conjunction with the TIGRESS γ-ray spectrometer, and is built from custom Si-strip detectors utilising a fully digital readout. SHARC has more than 50% efficiency, approximately 1000-strip segmentation, angular resolutions of Δθ ≈ 1.3 deg and Δ ≈ 3.5 deg, 25–30 keV energy resolution, and thresholds of 200 keV for up to 25 MeV particles. SHARC is now complete, and the experimental program in nuclear astrophysics and nuclear structure has commenced.
  Journal of Instrumentation 02/2011; 6(02):P02005. · 1.87 Impact Factor
• Article: High-precision half-life measurement for the superallowed β+ emitter ²⁶Al(m).

  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
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  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
• Article: Structure of states in 12Be via the 11Be(d,p) reaction

  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.
• Article: Structure of states in $^12$Be via the $^11$Be($d$,$p$) reaction

  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
• Article: Line-shape analysis of Doppler-broadened γ lines following the β decay of^{11} Li

  C. M. Mattoon, F. Sarazin, C. Andreoiu, A. N. Andreyev, R. A. E. Austin, G. C. Ball, R. S. Chakrawarthy, D. Cross, E. S. Cunningham, J. Daoud, P. E. Garrett, G. F. Grinyer, G. Hackman, D. Melconian, C. Morton, C. Pearson, J. J. Ressler, J. Schwarzenberg, M. B. Smith, C. E. Svensson
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  ABSTRACT: The β decay of 11Li is studied at the TRIUMF Isotope Separation and Acceleration (ISAC) facility using the 8π γ-ray spectrometer coupled with an inner array of 20 plastic scintillators for β detection. Doppler-broadened line shapes resulting from the decay of the excited states in 10Be populated by β-delayed one-neutron emission are analyzed using Monte Carlo simulations. New β-delayed neutron decay branches are shown to contribute to the complex decay of 11Li. The half-lives of all but one bound excited state in 10Be are also deduced from this work. Among them, the half-life of the 2- state in 10Be is shown to be much shorter than previously thought, yielding a new experimental B(E1) now well within the range of theoretical predictions and providing further evidence that the 2- state in 10Be is an excited halo state. The nature of the 8.82-MeV state in 11Be and its decay paths to excited states in 10Be are found to be consistent with the β decay of the core proceeding through this particular state.
  Phys. Rev. C. 09/2009; 80(3).
• Article: First Results with TIGRESS and Accelerated Radioactive Ion Beams from ISAC: Coulomb Excitation of 20,21,29Na

  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
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  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.
• Conference Proceeding: First Results with TIGRESS and Accelerated Radioactive Ion Beams from ISAC: Coulomb Excitation of (20,21,29)Na

  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
• Article: Coulomb excitation of radioactive 21Na and its stable mirror 21Ne

  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
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  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).
• Article: Deformation of rotational structures in^{73} Kr and^{74} Rb: Probing the additivity principle at triaxial shapes

  F. Johnston-Theasby, A. V. Afanasjev, C. Andreoiu, R. A. E. Austin, M. P. Carpenter, D. Dashdorj, S. J. Freeman, P. E. Garrett, J. Greene, A. Görgen, [......], F. Moore, G. Mukherjee, W. Reviol, D. Sarantites, D. Seweryniak, M. B. Smith, C. E. Svensson, J. J. Valiente-Dobón, R. Wadsworth, D. Ward
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  ABSTRACT: Lifetimes have been deduced in the intermediate/high-spin range for the three known rotational bands in 73Kr and the T=0 band in 74Rb using the residual Doppler shift method. This has enabled relative transition quadrupole moments to be studied for the first time in triaxial nuclei as a function of spin. The data suggest that the additivity principle for transition quadrupole moments is violated, a result that is in disagreement with predictions from cranked Nilsson-Strutinsky and cranked relativistic mean-field theory calculations. The reasons for the discrepancy are not understood but may indicate that important correlations are missing from the models.
  Phys. Rev. C. 09/2008; 78(3).
• Article: High-precision branching ratio measurement for the superallowed β^{+} emitter^{62} Ga

  P. Finlay, G. C. Ball, J. R. Leslie, C. E. Svensson, I. S. Towner, R. A. E. Austin, D. Bandyopadhyay, A. Chaffey, R. S. Chakrawarthy, P. E. Garrett, [......], K. G. Leach, C. M. Mattoon, A. C. Morton, C. J. Pearson, A. A. Phillips, J. J. Ressler, F. Sarazin, H. Savajols, M. A. Schumaker, J. Wong
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  ABSTRACT: A high-precision branching ratio measurement for the superallowed β+ decay of 62Ga was performed at the Isotope Separator and Accelerator (ISAC) radioactive ion beam facility. The 8π spectrometer, an array of 20 high-purity germanium detectors, was employed to detect the γ rays emitted following Gamow-Teller and nonanalog Fermi β+ decays of 62Ga, and the SCEPTAR plastic scintillator array was used to detect the emitted β particles. Thirty γ rays were identified following 62Ga decay, establishing the superallowed branching ratio to be 99.858(8)%. Combined with the world-average half-life and a recent high-precision Q-value measurement for 62Ga, this branching ratio yields an ft value of 3074.3±1.1 s, making 62Ga among the most precisely determined superallowed ft values. Comparison between the superallowed ft value determined in this work and the world-average corrected Ft̅ value allows the large nuclear-structure-dependent correction for 62Ga decay to be experimentally determined from the CVC hypothesis to better than 7% of its own value, the most precise experimental determination for any superallowed emitter. These results provide a benchmark for the refinement of the theoretical description of isospin-symmetry breaking in A⩾62 superallowed decays.
  Phys. Rev. C. 08/2008; 78(2).
• Article: Internal gamma decay and the superallowed branching ratio for the beta(+) emitter (38)K(m).

  K G Leach, C E Svensson, G C Ball, J R Leslie, R A E Austin, D Bandyopadhyay, C Barton, E Bassiachvilli, S Ettenauer, P Finlay, [......], D Melconian, A C Morton, S Mythili, O Newman, C J Pearson, M R Pearson, A A Phillips, H Savajols, M A Schumaker, J Wong
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  ABSTRACT: The branching ratio for the superallowed beta(+) decay of (38)K(m) was measured at TRIUMF's ISAC radioactive ion beam facility. The M3 internal transition between the isomer and the ground state of (38)K(m) was observed with a branching ratio of 330(43) ppm. A search for the nonanalogue beta-decay branch to the first excited 0(+) state in (38)Ar was also performed and yielded an upper limit of < or =12 ppm at 90% C.L. These measurements lead to a revised superallowed branching ratio for (38)K(m) of 99.967(4)%, and increase the (38)K(m) ft value by its entire quoted uncertainty to ft=3052.1(10) s. Implications for tests of the nuclear-structure dependent corrections in superallowed beta decays and the extraction of the Cabibbo-Kobayashi-Maskawa matrix element V(ud) are discussed.
  Physical Review Letters 05/2008; 100(19):192504. · 7.37 Impact Factor
• Article: Low-spin lifetime measurements in 74Kr

  J. J. Valiente-Dobón, C. E. Svensson, A. V. Afanasjev, I. Ragnarsson, C. Andreoiu, D. E. Appelbe, R. A. E. Austin, G. C. Ball, J. A. Cameron, M. P. Carpenter, [......], G. Mukherjee, A. A. Phillips, W. Reviol, D. Sarantites, M. A. Schumaker, D. Seweryniak, M. B. Smith, J. C. Waddington, R. Wadsworth, D. Ward
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  ABSTRACT: The nucleus 74Kr has been populated in the 40Ca(40Ca,2pα)74Kr fusion-evaporation reaction at a beam energy of 165 MeV and studied using the Gammasphere and Microball multidetector arrays. The lifetimes for low-spin states in the ground-state and two signature-split negative-parity bands were determined using the Doppler-shift attenuation method. These results are discussed together with the lifetimes measured for the high-spin states of these bands and compared with theoretical calculations.
  Phys. Rev. C. 02/2008; 77(2).
• Article: Search for the low-lying (π1g_ {9/2})^{4} 6_ {2}^{+} state in^{94} Ru

  W. J. Mills, J. J. Ressler, R. A. E. Austin, R. S. Chakrawarthy, D. S. Cross, A. Heinz, E. A. McCutchan, M. D. Strange
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  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).
• Article: β decay of^{32} Na

  C. M. Mattoon, F. Sarazin, G. Hackman, E. S. Cunningham, R. A. E. Austin, G. C. Ball, R. S. Chakrawarthy, P. Finlay, P. E. Garrett, G. F. Grinyer, [......], A. A. Phillips, M. A. Schumaker, H. C. Scraggs, J. Schwarzenberg, M. B. Smith, C. E. Svensson, J. C. Waddington, P. M. Walker, B. Washbrook, E. Zganjar
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  ABSTRACT: The β-decay of 32Na has been studied using β-γ coincidences. New transitions and levels are tentatively placed in the level scheme of 32Mg from an analysis of γ-γ and β-γ-γ coincidences. The observation of the indirect feeding of the 2321 keV state in 32Mg removes some restrictions previously placed on the spin assignment for this state. No evidence of a state at 2117 keV in 32Mg is found. Previously unobserved weak transitions up to 5.4 MeV were recorded but could not be placed in the decay scheme of 32Na.
  Phys. Rev. C. 01/2007; 75(1).
• Article: Lifetime measurements in N=Z 72Kr

  C Andreoiu, C E Svensson, R A E Austin, M P Carpenter, D Dashdorj, P Finlay, S J Freeman, P E Garrett, A Görgen, J Greene, [......], F Moore, G Mukherjee, A A Phillips, W Reviol, D G Sarantites, M A Schumaker, D Seweryniak, M B Smith, J J Valiente-Dobón, R Wadsworth
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  ABSTRACT: High-spin states in the N=Z nucleus 72Kr have been populated in the 40Ca(40Ca, 2α)72Kr fusion–evaporation reaction at a beam energy of 165 MeV and using a thin isotopically enriched 40Ca target. The experiment, performed at Argonne National Laboratory close to Chicago, USA, employed the Gammasphere array for γ-ray detection coupled to the Microball array for charged particle detection. The previously observed bands in 72Kr were extended to a higher excitation energy of ~24 MeV and higher angular momentum of 30. Using the Doppler-shift attenuation method, the lifetimes of high-spin states were measured for the first time in order to investigate deformation changes associated with the g9/2 proton and neutron alignments in this N=Z nucleus. An excellent agreement with theoretical calculations including only standard t=1 np pairing was observed.
  Physica Scripta 06/2006; 2006(T125):127. · 1.20 Impact Factor
• Article: Kπ=0+ 2.29 s isomer in neutron-rich 174Tm

  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
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  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).