W. F. Rogers

Publications (22)31.04 Total impact

• Article: Observation of a low-lying neutron-unbound state in 19C

  M. Thoennessen, S. Mosby, N. S. Badger, T. Baumann, D. Bazin, M. Bennett, J. Brown, G. Christian, P. A. DeYoung, J. E. Finck, M. Gardner, E. A. Hook, B. Luther, D. A. Meyer, M. Mosby, W. F. Rogers, J. K. Smith, A. Spyrou, M. J. Strongman
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  ABSTRACT: Proton removal reactions from a secondary 22N beam were utilized to populate unbound states in neutron-rich carbon isotopes. Neutrons were measured with the Modular Neutron Array (MoNA) in coincidence with carbon fragments. A resonance with a decay energy of 76(14) keV was observed in the system 18C+n corresponding to a state in 19C at an excitation energy of 653(95)keV. This resonance could correspond to the first 5/2+ state which was recently speculated to be unbound in order to describe 1n and 2n removal cross section measurements from 20C.
  05/2013;
• Article: Search for $^{21}$C and constraints on $^{22}$C

  S. Mosby, N. S. Badger, T. Baumann, D. Bazin, M. Bennett, J. Brown, G. Christian, P. A. DeYoung, J. E. Finck, M. Gardner, [......], B. Luther, D. A. Meyer, M. Mosby, G. F. Peaslee, W. F. Rogers, J. K. Smith, J. Snyder, A. Spyrou, M. J. Strongman, M. Thoennessen
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  ABSTRACT: A search for the neutron-unbound nucleus $^{21}$C was performed via the single proton removal reaction from a beam of 22 N at 68 MeV/u. Neutrons were detected with the Modular Neutron Array (MoNA) in coincidence with $^{20}$C fragments. No evidence for a low-lying state was found, and the reconstructed $^{20}$C+n decay energy spectrum could be described with an s-wave line shape with a scattering length limit of |as| < 2.8 fm, consistent with shell model predictions. A comparison with a renormalized zero-range three-body model suggests that $^{22}$C is bound by less than 70 keV.
  04/2013;
• Source

  Available from: N. Frank

  Article: Exploring the Low-$Z$ Shore of the Island of Inversion at $N = 19$

  G. Christian, N. Frank, S. Ash, T. Baumann, D. Bazin, J Brown, P. A. DeYoung, J. E. Finck, A Gade, G. F. Grinyer, [......], G. F. Peaslee, W. F. Rogers, J. K. Smith, J. Snyder, A. Spyrou, M. J. Strongman, M. Thoennessen, M. Warren, D. Weisshaar, A. Wersal
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  ABSTRACT: The technique of invariant mass spectroscopy has been used to measure, for the first time, the ground state energy of neutron-unbound $^{28}\textrm{F},$ determined to be a resonance in the $^{27}\textrm{F} + n$ continuum at $2\underline{2}0 (\underline{5}0)$ keV. States in $^{28}\textrm{F}$ were populated by the reactions of a 62 MeV/u $^{29}\textrm{Ne}$ beam impinging on a 288 $\textrm{mg/cm}^2$ beryllium target. The measured $^{28}\textrm{F}$ ground state energy is in good agreement with USDA/USDB shell model predictions, indicating that $pf$ shell intruder configurations play only a small role in the ground state structure of $^{28}\textrm{F}$ and establishing a low-$Z$ boundary of the island of inversion for N=19 isotones.
  Physical Review Letters 01/2012; 108(3). · 7.37 Impact Factor
• Article: Neutron knockout of^{12} Be populating neutron-unbound states in^{11} Be

  W. A. Peters, T. Baumann, B. A. Brown, J. Brown, P. A. DeYoung, J. E. Finck, N. Frank, K. L. Jones, J.-L. Lecouey, B. Luther, G. F. Peaslee, W. F. Rogers, A. Schiller, M. Thoennessen, J. A. Tostevin, K. Yoneda
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  ABSTRACT: Neutron-unbound resonant states of 11Be were populated in neutron knockout reactions from 12Be and identified by 10Be–n coincidence measurements. A resonance in the decay-energy spectrum at 80(2) keV was attributed to a highly excited unbound state in 11Be at 3.949(2) MeV decaying to the 2+ excited state in 10Be. A knockout cross section of 15(3) mb was inferred for this 3.949(2) MeV state, suggesting a spectroscopic factor near unity for this 0p3/2- level, consistent with the detailed shell model calculations.
  Phys. Rev. C. 05/2011; 83(5).
• Source

  Available from: N. Frank

  Article: Neutron knockout of 12Be populating neutron-unbound states in 11Be

  William A. Peters, T. Baumann, B A Brown, J Brown, P. A. DeYoung, J. E. Finck, N. Frank, K. L. Jones, J. -L. Lecouey, B. Luther, G. F. Peaslee, W. F. Rogers, A. Schiller, M. Thoennessen, J A Tostevin, K Yoneda
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  ABSTRACT: Neutron-unbound resonant states of 11Be were populated in neutron knock-out reactions from 12Be and identified by 10Be-n coincidence measurements. A resonance in the decay-energy spectrum at 80(2) keV was attributed to a highly excited unbound state in 11Be at 3.949(2) MeV decaying to the 2+ excited state in 10Be. A knockout cross section of 15(3) mb was inferred for this 3.949(2) MeV state suggesting a spectroscopic factor near unity for this 0p3/2- level, consistent with the detailed shell model calculations.
  04/2011;
• Source

  Available from: Jill S Berryman

  Article: Doubly-magic nature of 56Ni: measurement of the ground state nuclear magnetic dipole moment of 55Ni

  J. S. Berryman, K. Minamisono, W. F. Rogers, B A Brown, H. L. Crawford, G. F. Grinyer, P. F. Mantica, J. B. Stoker, I. S. Towner
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  ABSTRACT: The nuclear magnetic moment of the ground state of $^{55}$Ni ($I^{\pi}=3/2^{-}, T_{1/2}=204$ ms) has been deduced to be $|\mu$^{55}Ni)$|=(0.976 \pm 0.026)$ $\mu_N$ using the $\beta$-NMR technique. Results of a shell model calculation in the full \textit{fp} shell model space with the GXPF1 interaction reproduce the experimental value. Together with the known magnetic moment of the mirror partner $^{55}$Co, the isoscalar spin expectation value was extracted as $<\sum \sigma_z >=0.91 \pm 0.07$. The $<\sum \sigma_z>$ shows a similar trend as that established in the \textit{sd} shell. The present theoretical interpretations of both $\mu(^{55}$Ni) and $<\sum \sigma_z>$ for the $T=1/2$, A=55 mirror partners support the softness of the $^{56}$Ni core. Comment: 13 pages, 1 figure, accepted for publication in Phys. Rev. C
  05/2009;
• Article: Evidence for a doubly magic $^24O$

  C R Hoffman, T Baumann, D Bazin, J Brown, G Christian, D H Denby, P A DeYoung, J E Finck, N Frank, J Hinnefeld, S Mosby, W A Peters, W F Rogers, A Schiller, A Spyrou, M J Scott, S L Tabor, M Thoennessen, P Voss
  Phys. Lett. B. 01/2009; 672(1):17 - 21.
• Article: Determination of the N=16 shell closure at the oxygen drip line.

  C R Hoffman, T Baumann, D Bazin, J Brown, G Christian, P A DeYoung, J E Finck, N Frank, J Hinnefeld, R Howes, [......], B Rizzo, W F Rogers, G Peaslee, W A Peters, A Schiller, M J Scott, S L Tabor, M Thoennessen, P J Voss, T Williams
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  ABSTRACT: The neutron unbound ground state of (25)O (Z=8, N=17) was observed for the first time in a proton knockout reaction from a (26)F beam. A single resonance was found in the invariant mass spectrum corresponding to a neutron decay energy of 770_+20(-10) keV with a total width of 172(30) keV. The N=16 shell gap was established to be 4.86(13) MeV by the energy difference between the nu1s(1/2) and nu0d(3/2) orbitals. The neutron separation energies for (25)O agree with the calculations of the universal sd shell model interaction. This interaction incorrectly predicts an (26)O ground state that is bound to two-neutron decay by 1 MeV, leading to a discrepancy between the theoretical calculations and experiment as to the particle stability of (26)O. The observed decay width was found to be on the order of a factor of 2 larger than the calculated single-particle width using a Woods-Saxon potential.
  Physical Review Letters 04/2008; 100(15):152502. · 7.37 Impact Factor
• Article: Production of nuclei in neutron unbound states via primary fragmentation of $^48Ca$

  G Christian, W A Peters, D Absalon, D Albertson, T Baumann, D Bazin, E Breitbach, J Brown, P L Cole, D Denby, [......], E Mosby, S Mosby, D Padilla, P V Pancella, G Peaslee, W F Rogers, A Schiller, M J Strongman, M Thoennessen, L O Wagner
  Nuc. Phys. A. 01/2008; 801(3-4):101 - 113.
• Article: Nuclear magnetic moment of 57Cu ground state

  K. Minamisono, P. F. Mantica, T. J. Mertzimekis, A. D. Davies, M. Hass, J. Pereira, J. S. Pinter, W. F. Rogers, J. B. Stoker, B. E. Tomlin, R. R. Weerasiri
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  ABSTRACT: The nuclear magnetic moment of the ground state of 57Cu(Iπ = 3/2-, T1/2 = 196.3 ms) has been measured to be |μ(57Cu)| = (2.00 ±0.05) μN using the β-NMR technique. Together with the known magnetic moment of the mirror partner 57Ni, the spin expectation value was extracted as áåszñ\langle\sum\sigma_z\rangle = -0.78 ± 0.13. Discrepancy between present results and shell model calculations in the full fp shell implies significant shell breaking at 56Ni with the neutron number N = 28.
  The European Physical Journal Special Topics 10/2007; 150(1):145-146. · 1.56 Impact Factor
• Source

  Available from: Rankothge Ranjith Weerasiri

  Article: Nuclear magnetic moment of the 57Cu ground state.

  K Minamisono, P F Mantica, T J Mertzimekis, A D Davies, M Hass, J Pereira, J S Pinter, W F Rogers, J B Stoker, B E Tomlin, R R Weerasiri
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  ABSTRACT: The nuclear magnetic moment of the ground state of (57)Cu(Iota(pi) = 3/2(-), T(1/2) = 196.3 ms) has been measured to be /mu((57)Cu)/ = (2.00 +/- 0.05)mu(N) using the beta-NMR technique. Together with the known magnetic moment of the mirror partner (57)Ni, the spin expectation value was extracted as <Sigmasigma(z)> = -0.078 +/- 0.13. This is the heaviest isospin mirror T = 1/2 pair above the (40)Ca region for which both ground state magnetic moments have been determined. The discrepancy between the present results and shell-model calculations in the full f p shell giving mu((57)Cu) approximately 2.4mu(N) and <Sigmasigma(z)> approximately 0.5 implies significant shell breaking at (56)Ni with the neutron number N = 28.
  Physical Review Letters 03/2006; 96(10):102501. · 7.37 Impact Factor
• Source

  Available from: cern.ch

  Article: Spin polarization of 37K produced in a single-proton pickup reaction at intermediate energies.

  D E Groh, P F Mantica, A E Stuchbery, A Stolz, T J Mertzimekis, W F Rogers, A D Davies, S N Liddick, B E Tomlin
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  ABSTRACT: Spin polarization of 37K nuclei produced via single proton pickup from a 9Be target by a beam of 150 MeV/nucleon 36Ar has been observed. Positive spin polarization with magnitude (8.5+/-0.6)% was deduced near the peak of the 37K momentum distribution. The variation of the spin polarization as a function of outgoing 37K momentum is explained by a classical conservation model, as previously applied to describe the induced spin polarization observed for fragments produced in intermediate-energy heavy-ion reactions, with the condition that the picked-up proton has an average momentum equal to the Fermi momentum and is aligned along the incident beam direction.
  Physical Review Letters 06/2003; 90(20):202502. · 7.37 Impact Factor
• Article: Ground-state magnetic moment of the T= 1 nucleus^{32} Cl using on-line β-NMR spectroscopy

  W. F. Rogers, G. Georgiev, G. Neyens, D. Borremans, N. Coulier, R. Coussement, A. D. Davies, J. L. Mitchell, S. Teughels, B. A. Brown, P. F. Mantica
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  ABSTRACT: The magnetic dipole moment of the 1+ ground state of the T=1 nucleus 1732Cl15 has been measured to be μ=1.114(6)μN using conventional β-NMR spectroscopy. Polarized 32Cl nuclei were produced by fragmentation of a 100 MeV/nucleon 36Ar beam in a 642 mg/cm2 93Nb target, where the beam was incident on the target at an angle 2.5° to the normal beam axis. The desired 32Cl fragments were filtered from other fragmentation products using the A1200 fragment separator and implanted in a NaCl single crystal, maintained at room temperature, at the center of a β-NMR apparatus. The Larmor frequency was determined by measuring the β-decay asymmetry as a function of the applied radio-frequency field. Isoscalar and isovector moments for the A=32, T=1 isospin multiplet are extracted and compared with large-basis shell model calculations.
  Phys. Rev. C. 09/2000; 62(4).
• Article: Disappearance of the N= 14 shell

  M. J. Strongman, A. Spyrou, C. R. Hoffman, T. Baumann, D. Bazin, J. Brown, P. A. DeYoung, J. E. Finck, N. Frank, S. Mosby, W. F. Rogers, G. F. Peaslee, W. A. Peters, A. Schiller, S. L. Tabor, M. Thoennessen
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  ABSTRACT: An excited state of 22N unbound with respect to neutron emission was observed in a stripping reaction from a 85 MeV/nucleon 26F beam. The observed decay energy of 650(50) keV places the level, which is interpreted to be the first 3- state, at an excitation energy of 1.93(22) MeV. Together with the previously measured bound states of 22N, reduction of the N=14 shell gap compared to less neutron-rich nitrogen isotopes at the neutron dripline is observed. Based on the magnitude of the reduction of the shell gap for 22N, a disappearance of the gap and even a level inversion of the ν1s1/2 and the ν0d5/2 levels in the neutron-unbound nucleus 21C seems likely.
  Phys. Rev. C. 80(2).
• Article: Observation of a two-neutron cascade from a resonance in^{24} O

  C. R. Hoffman, T. Baumann, J. Brown, P. A. DeYoung, J. E. Finck, N. Frank, J. D. Hinnefeld, S. Mosby, W. A. Peters, W. F. Rogers, A. Schiller, J. Snyder, A. Spyrou, S. L. Tabor, M. Thoennessen
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  ABSTRACT: A new resonance having a relative decay energy of ~0.6 MeV has been observed above the two-neutron separation energy in 24O at an excitation energy of ~7.5 MeV. The new level was found to directly feed the first excited state in 23O, an E=0.045(2)-MeV resonance, through the measurement of neutron-neutron correlations. Energy level comparisons with 23O suggest that this new level in 24O is dominated by an unpaired neutron in the ν0d3/2 single-particle orbital coupled to a single hole in the ν0d5/2 single-particle orbital. Establishment of this two-neutron discrimination technique provides a means for investigating high-lying excited states in neutron-rich nuclei.
  Phys. Rev. C. 83(3).
• Article: Reply to “Comment on 'Neutron knockout of^{12} Be populating neutron-unbound states in^{11} Be'”

  W. A. Peters, T. Baumann, B. A. Brown, J. Brown, P. A. DeYoung, J. E. Finck, N. Frank, K. L. Jones, J.-L. Lecouey, B. Luther, G. F. Peaslee, W. F. Rogers, M. Thoennessen, J. A. Tostevin
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  ABSTRACT: In the preceding Comment, Fortune argues that, in our original paper [ Peters et al. Phys. Rev. C 83 057304 (2011)], we did not or could not separate the two neutron-unbound states in 11Be near 4 MeV. However, including the suggested contribution of the 3.887-MeV state decaying via 18 keV to the 2+ state in 10Be does not fit the data; neither do any other attempts incorporating any contribution of this decay channel. The best fit was achieved with a single resonance of decay energy 80(2) keV.
  Phys. Rev. C. 86(1).
• Article: Spin Polarization of $^37$K Produced in a Single-Proton Pickup Reaction at Intermediate Energies

  D E Groh, P F Mantica, A E Stuchbery, A Stolz, T J Mertzimekis, W F Rogers, A D Davies, S N Liddick, B E Tomlin
  Phys. Rev. Lett. 90(20):202502-.
• Conference Proceeding: Nuclear magnetic moment of $^57$Cu ground state

  K Minamisono, P F Mantica, T J Mertzimekis, A D Davies, M Hass, J Pereira, J S Pinter, W F Rogers, J B Stoker, B E Tomlin, R R Weerasiri
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  ABSTRACT: The nuclear magnetic moment of the ground state of 57 Cu(I? = 3/2-, T1/2 = 196.3 ms) has been measured to be ?(57Cu) = (2.00 ± 0.05) ?N using the ?-NMR technique. Together with the known magnetic moment of the mirror partner 57Ni, the spin expectation value was extracted as ?? ?z? = -0.78 ± 0.13. Discrepancy between present results and shell model calculations in the full fp shell implies significant shell breaking at 56Ni with the neutron number N = 28. © EDP Sciences/Societe? Italiana di Fisica/Springer-Verlag 2007.
• Article: Nuclear magnetic moment of the $^57$Cu ground state (I=3/2$^-$, T$_1/2$=199.4 ms)

  K Minamisono, P F Mantica, T J Mertzimekis, A D Davies, M Hass, J Pereira, J S Pinter, W F Rogers, J B Stoker, B E Tomlin, R R Weerasiri
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  ABSTRACT: The nuclear magnetic moment of the ground state of Cu57(I?=3/2-,T1/2= 196.3ms) has been measured to be |?(Cu57)|=(2.00±0.05)?N using the ?-NMR technique. Together with the known magnetic moment of the mirror partner Ni57, the spin expectation value was extracted as ??z =-0.78±0.13. This is the heaviest isospin T=1/2 mirror pair above the Ca40 region for which both ground state magnetic moments have been determined. The discrepancy between the present results and shell-model calculations in the full fp shell giving ?(Cu57)?2.4?N and ??z ?0.5 implies significant shell breaking at Ni56 with the neutron number N=28. © 2006 The American Physical Society.
  Phys. Rev. Lett. 96(10):1-4.
• Article: Evidence for 2f$_1/2$ neutron strength in the low-energy structure of $^144,146,148,150Nd isotopes

  J Holden, N Benczer-Koller, G Jakob, G Kumbartzki, T J Mertzimekis, K -H Speidel, A Macchiavelli, M McMahan, L Phair, P Maier-Komor, A E Stuchbery, W F Rogers, A D Davies
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  ABSTRACT: The Bardeen model - the first regular black hole model in General Relativity - is reinterpreted as the gravitational field of a nonlinear magnetic monopole, i.e., as a magnetic solution to Einstein equations coupled to a nonlinear electrodynamics. (C) 2000 Elsevier Science B.V.
  Phys. Lett. B. 493(1-2):7-11.