B.J. Varley

Publications (101)71.96 Total impact

• Article: Simplex s = ±i excitations in 141Xe

  W. Urban, N. Schulz, M. Bentaleb, E. Lubkiewicz, J. L. Durell, M. J. Leddy, M. A. Jones, W. R. Phillips, A. G. Smith, B. J. Varley, I. Ahmad, L. R. Morss
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  ABSTRACT: Excited levels in 141Xe, populated in spontaneous fission of 248Cm, were studied by means of prompt γ-ray spectroscopy, using the EUROGAMM2 array. Level scheme of 141Xe obtained in this work shows patterns characteristic of simplex symmetry with s = +i and s = −i bands present but low value of D 0 moment indicates that octupole correlations in Xe isotopes are systematically lower than in Ba nuclei.
  European Physical Journal A 05/2012; 8(1):5-7. · 2.19 Impact Factor
• Article: Magnetic rotation and quasicollective structures in^{58} Fe: Influence of the νg_ {9/2} orbital

  D. Steppenbeck, R. V. F. Janssens, S. J. Freeman, M. P. Carpenter, P. Chowdhury, A. N. Deacon, M. Honma, H. Jin, T. Lauritsen, C. J. Lister, [......], J. Peng, D. Seweryniak, J. F. Smith, Y. Sun, S. L. Tabor, B. J. Varley, Y.-C. Yang, S. Q. Zhang, P. W. Zhao, S. Zhu
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  ABSTRACT: The structure of 58Fe was investigated at Gammasphere using 48Ca(13,14C,xn) fusion-evaporation reactions at a beam energy of 130 MeV. The level scheme has been revised and extended to J∼17ℏ and an excitation energy of 16.6 MeV. Regular band structures consisting of low-energy ΔJ=1ℏ transitions have been observed at moderate spin (J∼8ℏ–15ℏ) and are candidates for magnetic rotational bands. Self-consistent tilted-axis-cranking calculations within a relativistic mean-field theory were applied to investigate these bands and were found to reproduce the experimental results well. In other parts of the level scheme, quasirotational bands composed of stretched-E2 transitions have been extended to high spin, and other new bands have been identified. Positive-parity experimental states were compared to predictions of the spherical shell model using the GXPF1A, KB3G, and FPD6 effective interactions in the fp model space. The projected shell model, with a deformed quasiparticle basis including the neutron νg9/2 orbital, was applied to interpret regular ΔJ=2ℏ band structures that extend beyond the maximum spin available for π[(f7/2)−2] ⊗ ν[(p3/2f5/2p1/2)4] configurations and exhibit features characteristic of rotational alignment. It is clear that the νg9/2 intruder orbital plays a crucial role in describing the quasirotational structures in this nucleus, even starting as low as J∼5ℏ.
  Physical Review C 04/2012; 85(4). · 3.31 Impact Factor
• Article: New isomers and medium-spin structure of the^{95} Y nucleus

  W. Urban, K. Sieja, G. S. Simpson, H. Faust, T. Rząca-Urban, A. Złomaniec, M. Łukasiewicz, A. G. Smith, J. L. Durell, J. F. Smith, B. J. Varley, F. Nowacki, I. Ahmad
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  ABSTRACT: Excited states in 95Y, populated following the spontaneous fission of 248Cm and 252Cf and following fission of 235U induced by thermal neutrons, were studied by means of γ spectroscopy using the EUROGAM2 and GAMMASPHERE multidetector Ge arrays and the LOHENGRIN fission-fragment separator, respectively. We have found a new (17/2-) isomer in 95Y at 3142.2 keV with a half-life of T1/2=14.9(5) ns. Another isomer was identified in 95Y at 5022.1 keV and it was assigned a spin-parity (27/2-). For this isomer a half-life of T1/2=65(4) ns was determined and four decay branches were found, including an E3 decay. A new E3 decay branch was also found for the known, 1087.5-keV isomer in 95Y, for which we measured a half-life of 51.2(9) μs. The B(E3) and B(E1) transition rates, of 2.0 and 3.8×10-7 W.u., respectively, observed in 95Y are significantly lower than in the neighboring 96Zr core, suggesting that octupole correlations in this region are mainly due to the coupling of proton Δj=3 orbitals. Shell-model calculations indicate that the (27/2-) isomer in 95Y corresponds to the πg9/2ν(g7/2h11/2) maximally aligned configuration and that all three isomers in 95Y decay, primarily, by M2 transitions between proton g9/2 and f5/2 orbitals.
  Phys. Rev. C. 04/2009; 79(4).
• Conference Proceeding: Isomers in Fission Fragments

  W Urban, H Faust, M Jentschel, U Koster, J Krempel, Th. Materna, P Mutti, T Soldner, J Genevey, J A Pinston, [......], J L Durell, A G Smith, B J Varley, I Tsekhanovich, J Jolie, A Linnemann, A Scherillo, R Orlandi, J F Smith, I Ahmad
  Proc.13th Intern.Symposium on Capture Gamma-Ray Spectroscopy and Related Topics; 01/2009
• Conference Proceeding: Fission-Fragment Spectroscopy with STEFF

  A G Smith, I Tsekhanovich, J Dare, D M Cullen, B J Varley, N Lumley, T Materna, U Koster, M Helmecke, G S Simpson
  Proc.4th.Intern.Conf.Fission and Properties of Neutron-Rich Nuclei; 01/2008
• Article: Yrast structures in the neutron-rich isotopes^{59, 60} Fe and the role of the g_ {9/2} orbital

  A. N. Deacon, S. J. Freeman, R. V. F. Janssens, M. Honma, M. P. Carpenter, P. Chowdhury, T. Lauritsen, C. J. Lister, D. Seweryniak, J. F. Smith, S. L. Tabor, B. J. Varley, F. R. Xu, S. Zhu
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  ABSTRACT: The structure of the neutron-rich isotopes 59,60Fe has been studied with the Gammasphere detector array using fusion-evaporation reactions. Level schemes for these nuclei are presented which have been extended to spins of ~20ℏ. Both isotopes exhibit regular, near-yrast γ-decay sequences which are generated by the intrusion of the g9/2 orbital into the fp shell-model space. Lower-spin, natural-parity levels are discussed within the context of shell-model calculations using the GXPF1A interaction in the full fp model space. Experimental features of the high-spin bands are compared with total Routhian surface calculations.
  Phys. Rev. C. 11/2007; 76(5).
• Article: Near-yrast structure of the^{149} La nucleus

  W. Urban, T. Rza¸ca-Urban, A. Syntfeld-Każuch, J. L. Durell, A. G. Smith, B. J. Varley, I. Ahmad
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  ABSTRACT: Excited states in 149La, populated in the spontaneous fission of 248Cm, were studied with the EUROGAM2 array. A new ΔI=2 band found in 149La is interpreted as the α=-1/2 branch of the π3/2-[402] configuration. The bandhead has spin 7/2- because the 3/2- and 5/2- levels are pushed up by the Coriolis interaction. The 7/2- level is located not higher than 30 keV above the ground state and may form a long-lived isomer if spin and parity of the g.s. is 3/2+.
  Phys. Rev. C. 09/2007; 76(3).
• Article: First observation of medium-spin excitations in the 138Cs nucleus

  T. Rzaca-Urban, W. Urban, M. Saha Sarkar, S. Sarkar, J. L. Durell, A. G. Smith, B. J. Varley, I. Ahmad
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  ABSTRACT: Medium-spin, yrast excitations in the 138Cs nucleus, populated in the spontaneous fission of 248Cm, were observed for the first time. 138Cs was studied by means of prompt γ-ray spectroscopy using the EUROGAM2 array. The newly observed yrast cascade, built on the known 6- isomer at 80 keV, was successfully described by shell model calculations. Analogously to the 136I isotone, the 6- isomer in 138Cs has the (pg7/2 4 d5/2 nf7/2)6-\ensuremath{(\pi g_{7/2} ^4 d_{5/2} \nu f_{7/2})_{6^-}} dominating configuration and the 7- excitation, located 175 keV above, corresponds to the (pg7/2 3 d5/22 nf7/2)7-\ensuremath{(\pi g_{7/2} ^3 d_{5/2}^2 \nu f_{7/2})_{7^-}} as dominating configuration. Similarly as in 136I, changing the position of the d 5/2 proton orbital improves the reproduction of the data. However, in 138Cs the energy of this orbital should be increased compared to its energy in 133Sb, to get the best description, in contrast to 136I and 135Sb, where it had to be decreased. The best reproduction of excitation energies in 138Cs is obtained assuming that the πd 5/2 orbital in 138Cs is located about 100 keV higher than in 133Sb. These observations suggest that the lowering of the d 5/2 s.p. energy in 135Sb is not a physical effect due to the appearance of a neutron skin, as proposed by other authors, but rather an artifact due to some deficiency of the input data used in the shell model calculations in the region of the doubly magic 132Sn core.
  European Physical Journal A 03/2007; 32(1):5-9. · 2.19 Impact Factor
• Article: Near-yrast structure of the $^149$La nucleus

  W Urban, T Rzaca-Urban, A Syntfeld-Kazuch, J L Durell, A G Smith, B J Varley, I Ahmad
  Phys.Rev. C. 01/2007; 76:037301.
• Article: First observation of medium-spin excitations in the $^138$Cs nucleus

  T Rzaca-Urban, W Urban, M S Sarkar, S Sarkar, J L Durell, A G Smith, B J Varley, I Ahmad
  Eur.Phys.J. A. 01/2007; 32:5.
• Article: Level structure of the neutron-rich^{56, 58, 60} Cr isotopes: Single-particle and collective aspects

  S. Zhu, A. N. Deacon, S. J. Freeman, R. V. F. Janssens, B. Fornal, M. Honma, F. R. Xu, R. Broda, I. R. Calderin, M. P. Carpenter, [......], S. N. Liddick, C. J. Lister, P. F. Mantica, T. Pawłat, D. Seweryniak, J. F. Smith, S. L. Tabor, B. E. Tomlin, B. J. Varley, J. Wrzesiński
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  ABSTRACT: The structure of the 56,58,60Cr nuclei was investigated at Gammasphere using both deep inelastic and fusion-evaporation reactions. As a result of this work, expanded level schemes are now available for these three neutron-rich, even-even isotopes. Experimental signatures were found for both single-particle and collective excitations whose relative importance varies with neutron number. Together with recent structural information on the odd-A 55,57,59Cr neighbors, the present data highlight the changing role of the g9/2 orbital with neutron number. Comparisons with shell-model calculations using the recently developed GXPF1A interaction and with total Routhian surface calculations are presented.
  Phys. Rev. C. 12/2006; 74(6).
• Article: Near-yrast structure of the^{109} Mo nucleus

  W. Urban, Ch. Droste, T. Rząca-Urban, A. Złomaniec, J. L. Durell, A. G. Smith, B. J. Varley, I. Ahmad
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  ABSTRACT: Excited states in 109Mo, populated in the spontaneous fission of 248Cm, were studied using the EUROGAM2 array. Octupole deformation reported previously in 109Mo was not confirmed. Spin and parity of the ground state were changed. A new band found in this work suggests the 5/2+[402] neutron configuration for the ground state. In the 222.2 keV band, the 110.8 and 138.9 keV transitions are of M1 + E2 instead of E1 multipolarity, as reported previously. The 222.2 keV band is explained as the 7/2-[523] neutron configuration.
  Phys. Rev. C. 03/2006; 73(3).
• Article: Triaxiality in $^105$Mo and $^107$Mo from the low to intermediate spin region

  J A Pinston, W Urban, Ch. Droste, T Rzaca-Urban, J Genevey, G Simpson, J L Durell, A G Smith, B J Varley, I Ahmad
  Phys.Rev.C. 01/2006; 74:064304.
• Article: Structure of the neutron-rich Cr isotopes

  S J Freeman, R V F Janssens, A N Deacon, F Xu, I J Calderin, M P Carpenter, P Chowdhury, S M Fischer, N J Hammond, M Honma, T Lauritsen, C J Lister, T L Khoo, G Mukherjee, D Seweryniak, J F Smith, S L Tabor, B J Varley, S Zhu
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  ABSTRACT: The low-lying levels in 59,60Cr have been populated with 13,14C(48Ca, 2p) reactions using a beam energy of 130 MeV. Prompt electromagnetic radiation was detected using the Gammasphere array, in coincidence with recoiling ions measured with the Fragment Mass Analyzer. The residues were selected and identified on the basis of charge-to-mass ratio, energy-loss and time-of-flight measurements. Preliminary results for 60Cr, when compared to lighter even-even isotopes, indicate a softness in shape which increases with neutron number. The low-lying structure of 59Cr is clearly inconsistent with the results of a spherical shell-model calculation and requires the inclusion of the νg9/2 orbital. The sequence of states can be understood within the Nilsson model assuming a moderate oblate ground-state deformation. This is in contrast to lighter odd-Cr nuclei where there is evidence for prolate deformation after excitation of g9/2 neutrons.
  Journal of Physics G Nuclear and Particle Physics 09/2005; 31(10):S1465. · 4.18 Impact Factor
• Article: Near-yrast, medium-spin structure of the^{107} Mo nucleus

  W. Urban, T. Rząca-Urban, J. A. Pinston, J. L. Durell, W. R. Phillips, A. G. Smith, B. J. Varley, I. Ahmad, N. Schulz
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  ABSTRACT: Excited states in 107Mo, populated in spontaneous fission of 248Cm, were studied by use of the eurogam2 multidetector array. Spins and parities of the ground state and the 66.0-, 152.1-, and 458.5-keV excited levels, reported previously, were changed based on conversion-coefficient and angular-correlation measurements. Octupole deformation reported previously in 107Mo is dismissed, and we explain the near-yrast structure of 107Mo in terms of rotational bands built on the 5/2+[413], 3/2+[411], and 7/2-[523] orbitals.
  Phys. Rev. C. 08/2005; 72(2).
• Article: High-spin structures of 51121, 123, 125, 127Sb nuclei: Single proton and core-coupled states

  M. -G. Porquet, Ts. Venkova, R. Lucas, A. Astier, A. Bauchet, I. Deloncle, A. Prévost, F. Azaiez, G. Barreau, A. Bogachev, [......], A. Minkova, I. Piqueras, N. Redon, A. Roach, M. Rousseau, N. Schulz, A. G. Smith, O. Stézowski, Ch. Theisen, B. J. Varley
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  ABSTRACT: The 121,123,125,127Sb nuclei have been produced as fission fragments in three reactions induced by heavy ions: 12C + 238U at 90 MeV bombarding energy, 18O + 208Pb at 85 MeV, and 31P + 176Yb at 152 MeV. Their level schemes have been built from gamma rays detected using the EUROBALL III and IV arrays. High-spin states of 123,125,127Sb nuclei have been identified for the first time. Moreover isomeric states lying around 2.3 MeV have been established in 123,125,127Sb from the delayed coincidences between the fission fragment detector SAPhIR and the gamma array. All the observed states can be described by coupling a d5/2 or g7/2 proton to an excited Sn core involving either vibrational states or broken neutron pairs.
  European Physical Journal A 01/2005; 24(1):39-49. · 2.19 Impact Factor
• Source

  Available from: Michael Patten Carpenter

  Article: Changes in [nu] g9/2 shape polarisation across the odd neutron-rich Cr isotopes

  A N Deacon, S J Freeman, R V F Janssens, F R Xu, M P Carpenter, I R Calderin, P Chowdhury, N J Hammond, T Lauritsen, C J Lister, D Seweryniak, J F Smith, S L Tabor, B J Varley, S Zhu
  Physics Letters B. 01/2005; 622:151-158.
• Article: Lifetimes of excited states in octupole-collective Ba-142,Ba-144 nuclei

  D C Biswas, A G Smith, R M Wall, D Patel, G S Simpson, D M Cullen, J L Durell, S J Freeman, J C Lisle, J F Smith, [......], M Petit, C Theisen, E Bouchez, M Houry, R Lucas, B Cahan, A Le Coguie, B J P Gall, O Dorvaux, N Schulz
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  ABSTRACT: Lifetimes of excited states have been measured for the positive-parity rotational bands in neutron-rich Ba-142,Ba-144 as well as the 7(-) and 9(-) states of the negative-parity band in Ba-144 using the differential Doppler shift method. The deduced quadrupole moment, Q(t), of the positive-parity band decreases with angular momentum and overall shows good agreement with earlier measurements. The measured lifetimes of 7(-) and 9(-) states are used to determine the electric dipole moment, D-0=0.17(3) and 0.09(1) e fm, respectively, in the negative-parity octupole band of Ba-144.
  Physical Review C. 01/2005; 71(1).
• Article: New spins for ground states and isomers in 115Pd and 117Pd

  W. Urban, A. Złomaniec, G. Simpson, J. A. Pinston, J. Kurpeta, T. Rzaca-Urban, J. L. Durell, A. G. Smith, B. J. Varley, N. Schulz, I. Ahmad
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  ABSTRACT: Levels in 115Pd and 117Pd nuclei, populated in the spontaneous fission of 248Cm were studied by means of prompt gamma spectroscopy using the EUROGAM2 array of Anti-Compton spectrometers. Negative-parity, I = 9/2 excitations were identified, which are associated with the long-lived isomers in these nuclei, reported previously as 11/2- excitations. The new data indicate spin and parity 3/2 + for ground states in 115Pd and 117Pd instead of 5/2 + proposed in previous works. This result implicates changes of spin assignments to other levels in both nuclei.
  European Physical Journal A 10/2004; 22(2):157-161. · 2.19 Impact Factor
• Article: New bands and spin-parity assignments in 111Ru

  W. Urban, T. Rzaca-Urban, Ch. Droste, S. G. Rohoziński, J. L. Durell, W. R. Phillips, A. G. Smith, B. J. Varley, N. Schulz, I. Ahmad, J. A. Pinston
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  ABSTRACT: The 111Ru nucleus, populated in the spontaneous fission of 248Cm has been studied by means of prompt gamma spectroscopy using the EUROGAM2 array. Spin and parity assignments, based on angular correlations, linear polarization, and conversion coefficient measurements differ from those available in the literature. New bands are reported, which incorporate g\gamma transitions seen previously but not placed in the scheme of 111Ru or placed incorrectly. The bands are interpreted as neutron excitations into subshells originating predominantly from the h 11/2, g 7/2 and s 1/2 spherical orbitals. The s 1/2 band, strongly mixed with the d 3/2, d 5/2 and g 7/2 configurations, is observed for the first time in this region.
  European Physical Journal A 10/2004; 22(2):231-239. · 2.19 Impact Factor