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Title: Identification of the g{sub (9/2)} proton and neutron band crossing in the N=Z nucleus {sup 76}Sr

Abstract

High-spin states in {sup 76}Sr have been studied using Gammasphere plus Microball detector arrays. The known yrast band has been extended beyond the first band crossing, which involves the simultaneous alignment of pairs of g{sub (9/2)} protons and neutrons, to a tentative spin of 24({Dirac_h}/2{pi}). The data are compared with the results of cranked relativistic mean-field (CRMF) and cranked relativistic Hartree-Bogoliubov (CRHB) calculations. The properties of the band, including the g{sub (9/2)} proton/neutron band crossing frequency and moments of inertia, are found to be well reproduced by the CRHB calculations. Furthermore, the unpaired CRMF calculations show quite good agreement with the data beyond the band crossing region, indicating that pairing is weak at these frequencies. The high spin results suggest that there is little evidence for an isoscalar (t=0) np pair field. Moreover, a systematic study of the band crossings in even-even N=Z nuclei for the first time reveals that there is no evidence to support the existence of the Coulomb antipairing effect caused by the Coulomb exchange term.

Authors:
; ; ; ;  [1];  [2];  [3];  [4];  [5];  [6]; ; ; ; ;  [7];  [8];  [9];  [5];  [4];  [10] more »;  [11]; ;  [12];  [13] « less
  1. Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom)
  2. Department of Physics and Astronomy, Mississippi State University, Mississippi 39762 (United States)
  3. (Latvia)
  4. Department of Physics, University of Guelph, Guelph, Ontario N1G 2W1 (Canada)
  5. (United Kingdom)
  6. Department Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4K1 (Canada)
  7. Physics Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)
  8. North Carolina State University, Rayleigh, North Carolina 27695 (United States)
  9. Physics Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA (United States)
  10. (Canada)
  11. CE Saclay, Daphnia/SphN, F-91191 Gif-sur-Yvette Cedex France (France)
  12. Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
  13. Department of Chemistry, Washington University, St. Louis, Missouri 63130 (United States) (and others)
Publication Date:
OSTI Identifier:
20990924
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevC.75.011302; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; HIGH SPIN STATES; MEAN-FIELD THEORY; MOMENT OF INERTIA; NEUTRONS; PROTONS; RELATIVISTIC RANGE; SPIN; STRONTIUM 76

Citation Formats

Davies, P. J., Wadsworth, R., Jenkins, D. G., Johnston-Theasby, F. L., Joshi, P., Afanasjev, A. V., Laboratory of Radiation Physics, Institute of Solid State Physics, University of Latvia, LV 2169 Salaspils, Miera str. 31, Andreoiu, C., Oliver Lodge Laboratory, University of Liverpool, Liverpool, L69 3BX, Austin, R. A. E., Carpenter, M. P., Greene, J., Moore, F., Mukherjee, G., Seweryniak, D., Dashdorj, D., Freeman, S. J., The School of Physics and Astronomy, University of Manchester, Manchester M15 9PL, Garrett, P. E., TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3, Goergen, A., Macchiavelli, A. O., Ward, D., and Reviol, W. Identification of the g{sub (9/2)} proton and neutron band crossing in the N=Z nucleus {sup 76}Sr. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.011302.
Davies, P. J., Wadsworth, R., Jenkins, D. G., Johnston-Theasby, F. L., Joshi, P., Afanasjev, A. V., Laboratory of Radiation Physics, Institute of Solid State Physics, University of Latvia, LV 2169 Salaspils, Miera str. 31, Andreoiu, C., Oliver Lodge Laboratory, University of Liverpool, Liverpool, L69 3BX, Austin, R. A. E., Carpenter, M. P., Greene, J., Moore, F., Mukherjee, G., Seweryniak, D., Dashdorj, D., Freeman, S. J., The School of Physics and Astronomy, University of Manchester, Manchester M15 9PL, Garrett, P. E., TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3, Goergen, A., Macchiavelli, A. O., Ward, D., & Reviol, W. Identification of the g{sub (9/2)} proton and neutron band crossing in the N=Z nucleus {sup 76}Sr. United States. doi:10.1103/PHYSREVC.75.011302.
Davies, P. J., Wadsworth, R., Jenkins, D. G., Johnston-Theasby, F. L., Joshi, P., Afanasjev, A. V., Laboratory of Radiation Physics, Institute of Solid State Physics, University of Latvia, LV 2169 Salaspils, Miera str. 31, Andreoiu, C., Oliver Lodge Laboratory, University of Liverpool, Liverpool, L69 3BX, Austin, R. A. E., Carpenter, M. P., Greene, J., Moore, F., Mukherjee, G., Seweryniak, D., Dashdorj, D., Freeman, S. J., The School of Physics and Astronomy, University of Manchester, Manchester M15 9PL, Garrett, P. E., TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3, Goergen, A., Macchiavelli, A. O., Ward, D., and Reviol, W. Mon . "Identification of the g{sub (9/2)} proton and neutron band crossing in the N=Z nucleus {sup 76}Sr". United States. doi:10.1103/PHYSREVC.75.011302.
@article{osti_20990924,
title = {Identification of the g{sub (9/2)} proton and neutron band crossing in the N=Z nucleus {sup 76}Sr},
author = {Davies, P. J. and Wadsworth, R. and Jenkins, D. G. and Johnston-Theasby, F. L. and Joshi, P. and Afanasjev, A. V. and Laboratory of Radiation Physics, Institute of Solid State Physics, University of Latvia, LV 2169 Salaspils, Miera str. 31 and Andreoiu, C. and Oliver Lodge Laboratory, University of Liverpool, Liverpool, L69 3BX and Austin, R. A. E. and Carpenter, M. P. and Greene, J. and Moore, F. and Mukherjee, G. and Seweryniak, D. and Dashdorj, D. and Freeman, S. J. and The School of Physics and Astronomy, University of Manchester, Manchester M15 9PL and Garrett, P. E. and TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3 and Goergen, A. and Macchiavelli, A. O. and Ward, D. and Reviol, W.},
abstractNote = {High-spin states in {sup 76}Sr have been studied using Gammasphere plus Microball detector arrays. The known yrast band has been extended beyond the first band crossing, which involves the simultaneous alignment of pairs of g{sub (9/2)} protons and neutrons, to a tentative spin of 24({Dirac_h}/2{pi}). The data are compared with the results of cranked relativistic mean-field (CRMF) and cranked relativistic Hartree-Bogoliubov (CRHB) calculations. The properties of the band, including the g{sub (9/2)} proton/neutron band crossing frequency and moments of inertia, are found to be well reproduced by the CRHB calculations. Furthermore, the unpaired CRMF calculations show quite good agreement with the data beyond the band crossing region, indicating that pairing is weak at these frequencies. The high spin results suggest that there is little evidence for an isoscalar (t=0) np pair field. Moreover, a systematic study of the band crossings in even-even N=Z nuclei for the first time reveals that there is no evidence to support the existence of the Coulomb antipairing effect caused by the Coulomb exchange term.},
doi = {10.1103/PHYSREVC.75.011302},
journal = {Physical Review. C, Nuclear Physics},
number = 1,
volume = 75,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}
  • No abstract prepared.
  • Excited states in the T{sub z}=(1)/(2) nucleus {sup 75}Rb were observed for the first time using the {sup 40}Ca({sup 40}Ca,{alpha}p) reaction at 128 MeV. Identification was achieved using events detected by the Daresbury recoil separator in coincidence with {gamma} rays detected in the 45 element EUROGAM I Ge-detector array. Threefold events were used to build a decay scheme which consists of two rotational bands observed to I{sup {pi}}=((45)/(2){sup +}) and I{sup {pi}}=((33)/(2){sup {minus}}). The positive parity band in {sup 75}Rb behaves similarly to a negative-parity band in {sup 74}Kr and contains a region of alignment at {h_bar}{omega}{approx}0.75 MeV. These data,more » and those of {sup 77}Sr, can be interpreted by treating protons and neutrons separately in a cranked shell model approach despite a recent suggestion for the presence of T=1 neutron-proton pairing correlations in the neighboring self-conjugate, odd-odd {sup 74}Rb ground state band. Our study suggests that some experimental observables such as the energy levels and moments of inertia, may not be able to differentiate between different T=1 pairing phases in these T{sub z}=(1)/(2) nuclei. {copyright} {ital 1997} {ital The American Physical Society}« less
  • Excited states in the odd-A {sup 71,73,75,77}Ga nuclei have been populated in deep-inelastic reactions of a {sup 76}Ge beam at 530 MeV with a thick {sup 238}U target. High-spin sequences built upon the 9/2{sup +}, 5/2{sup -}, and 3/2{sup -} states were identified in all four isotopes. A comparison of the observed structures with the yrast positive-parity states in the neighboring even-even Zn cores indicates that the newly identified levels may be regarded as arising from the relatively weak coupling of the odd proton to the core states. However, significant contributions from broken pairs are expected to be present inmore » this region of excitation energy. The present data set also provides clarification of previously reported decay paths of the low-energy levels in {sup 71,73,75,77}Ga.« less
  • Excited states in the odd-A {sup 71,73,75,77}Ga nuclei have been populated in deep-inelastic reactions of a {sup 76}Ge beam at 530 MeV with a thick {sup 238}U target. High-spin sequences built upon the 9/2{sup +}, 5/2{sup -}, and 3/2{sup -} states were identified in all four isotopes. A comparison of the observed structures with the yrast positive-parity states in the neighboring even-even Zn cores indicates that the newly identified levels may be regarded as arising from the relatively weak coupling of the odd proton to the core states. However, significant contributions from broken pairs are expected to be present inmore » this region of excitation energy. The present data set also provides clarification of previously reported decay paths of the low-energy levels in {sup 71,73,75,77}Ga.« less
  • The crystal structure, electronic structure, and photoluminescence properties of Eu{sub x}Si{sub 6-z}Al{sub z-x}O{sub z+x}N{sub 8-z-x} (x=0-0.1, 0<z<1) and Eu{sub x}M{sub y}Si{sub 6-z}Al{sub z-x-y}O{sub z+x+y}N{sub 8-z-x-y} (M=2Li, Mg, Ca, Sr, Ba) have been studied. Single-phase Eu{sub x}Si{sub 6-z}Al{sub z-x}O{sub z+x}N{sub 8-z-x} can be obtained in very narrow ranges of x{<=}0.06 (z=0.15) and z<0.5 (x=0.3), indicating that limited Eu{sup 2+} ions can be incorporated into nitrogen-rich Si{sub 6-z}Al{sub z}O{sub z}N{sub 8-z}. The Eu{sup 2+} ion is found to occupy the 2b site in a hexagonal unit cell (P6{sub 3}/m) and directly connected by six adjacent nitrogen/oxygen atoms ranging 2.4850-2.5089 A. The calculatedmore » host band gaps by the relativistic DV-X{alpha} method are about 5.55 and 5.45 eV (without Eu{sup 2+} 4f5d levels) for x=0 and 0.013 in Eu{sub x}Si{sub 6-z}Al{sub z-x}O{sub z+x}N{sub 8-z-x} (z=0.15), in which the top of the 5d orbitals overlap with the Si-3s3p and N-2p orbitals within the bottom of the conduction band of the host. Eu{sub x}Si{sub 6-z}Al{sub z-x}O{sub z+x}N{sub 8-z-x} shows a strong green emission with a broad Eu{sup 2+} band centered at about 530 nm under UV to near-UV excitation range. The excitation and emission spectra are hardly modified by Eu concentration and dual-doping ions of Li and other alkaline-earth ions with Eu. Higher Eu concentrations can significantly quench the luminescence of Eu{sup 2+} and decrease the thermal quenching temperature. In addition, the emission spectrum can only be slightly tuned to the longer wavelengths ({approx}529-545 nm) by increasing z within the solid solution range of z<0.5. Furthermore, the luminescence intensity of Eu{sub x}Si{sub 6-z}Al{sub z-x}O{sub z+x}N{sub 8-z-x} can be improved by increasing z and the dual-doping of Li and Ba. - Graphical abstract: Excitation and emission spectra of Eu{sub x}Si{sub 6-z}Al{sub z-x}O{sub z+x}N{sub 8-z-x} with the project of a 2x2x2 supercell crystal structure viewed along (001), in which red spheres are the Eu atoms.« less