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Title: Nuclear shape and structure in neutron-rich {sup 110,111}Tc

Abstract

The high-spin nuclear structure of Tc isotopes is extended to more neutron-rich regions based on the measurements of prompt {gamma} rays from the spontaneous fission of {sup 252}Cf at the Gammasphere. The high-spin level scheme of N=67 neutron-rich {sup 110}Tc (Z=43) is established for the first time, and that of {sup 111}Tc is extended and expanded. The ground band of {sup 111}Tc reaches the band-crossing region, and the new observation of the weakly populated {alpha}=-1/2 member of the band provides important information on signature splitting. The systematics of band crossings in the isotopic and isotonic chains and a CSM calculation suggest that the band crossing of the ground band of {sup 111}Tc is due to alignment of a pair of h{sub 11/2} neutrons. The best fit to signature splitting, branching ratios, and excitations of the ground band of {sup 111}Tc by the rigid triaxial rotor plus particle model calculations result in a shape of {epsilon}{sub 2}=0.32 and {gamma}=-26 deg. for this nucleus. Its triaxiality is larger than that of {sup 107,109}Tc, which indicates increasing triaxiality in Tc isotopes with increasing neutron number. The identification of the weakly populated K+2 satellite band provides strong evidence for the large triaxiality of {supmore » 111}Tc. In {sup 110}Tc, the four lowest-lying levels observed are very similar to those in {sup 108}Tc. At an excitation of 478.9 keV above the lowest state observed, ten states of a {delta}I=1 band are observed. This band of {sup 110}Tc is very analogous to the {delta}I=1 bands in {sup 106,108}Tc, but it has greater and reversal signature splitting at higher spins.« less

Authors:
 [1];  [2]; ; ; ; ; ;  [1]; ;  [3];  [4];  [5];  [1];  [6];  [2];  [7];  [3];  [2];  [8]; more »;  [9];  [10];  [11];  [12] « less
  1. Physics Department, Vanderbilt University, Nashville, Tennessee 37235 (United States)
  2. (United States)
  3. Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
  4. KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200D, B-3001 Leuven (Belgium)
  5. Physics Department, Tsinghua University, Beijing 100084 (China)
  6. (China)
  7. Department of Physics, National Tsing Hua University, Hsinchu, Taiwan (China)
  8. Mississippi State University, Drawer 5167, Mississippi State, Mississippi 39762 (United States)
  9. Flerov Laboratory for Nuclear Reactions, JINR, Dubna (Russian Federation)
  10. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
  11. Universidade Federal do Rio de Janeiro, CP 68528, RG (Brazil)
  12. Institut fuer Kernphysik, Universitaet zu Koeln, D-50937, Cologne (Germany)
Publication Date:
OSTI Identifier:
20863704
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 74; Journal Issue: 2; Other Information: DOI: 10.1103/PhysRevC.74.024308; (c) 2006 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; BRANCHING RATIO; CALIFORNIUM 252; ENERGY LEVELS; EXCITATION; GAMMA RADIATION; KEV RANGE; NEUTRONS; NUCLEAR STRUCTURE; PARTICLE-CORE COUPLING MODEL; SPIN; SPONTANEOUS FISSION; TECHNETIUM 108; TECHNETIUM 109; TECHNETIUM 110; TECHNETIUM 111

Citation Formats

Luo, Y. X., Lawrence Berkeley National Laboratory, Berkeley, California 94720, Hamilton, J. H., Ramayya, A. V., Hwang, J. K., Gore, P. M., Jones, E. F., Fong, D., Rasmussen, J. O., Lee, I. Y., Stefanescu, I., Che, X. L., Zhu, S. J., Physics Department, Tsinghua University, Beijing 100084, Joint Institute for Heavy Ion Research, Oak Ridge, Tennessee 37831, Wu, S. C., Ginter, T. N., National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, Ma, W. C., Ter-Akopian, G. M., Daniel, A. V., Stoyer, M. A., Donangelo, R., and Gelberg, A. Nuclear shape and structure in neutron-rich {sup 110,111}Tc. United States: N. p., 2006. Web. doi:10.1103/PHYSREVC.74.024308.
Luo, Y. X., Lawrence Berkeley National Laboratory, Berkeley, California 94720, Hamilton, J. H., Ramayya, A. V., Hwang, J. K., Gore, P. M., Jones, E. F., Fong, D., Rasmussen, J. O., Lee, I. Y., Stefanescu, I., Che, X. L., Zhu, S. J., Physics Department, Tsinghua University, Beijing 100084, Joint Institute for Heavy Ion Research, Oak Ridge, Tennessee 37831, Wu, S. C., Ginter, T. N., National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, Ma, W. C., Ter-Akopian, G. M., Daniel, A. V., Stoyer, M. A., Donangelo, R., & Gelberg, A. Nuclear shape and structure in neutron-rich {sup 110,111}Tc. United States. doi:10.1103/PHYSREVC.74.024308.
Luo, Y. X., Lawrence Berkeley National Laboratory, Berkeley, California 94720, Hamilton, J. H., Ramayya, A. V., Hwang, J. K., Gore, P. M., Jones, E. F., Fong, D., Rasmussen, J. O., Lee, I. Y., Stefanescu, I., Che, X. L., Zhu, S. J., Physics Department, Tsinghua University, Beijing 100084, Joint Institute for Heavy Ion Research, Oak Ridge, Tennessee 37831, Wu, S. C., Ginter, T. N., National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, Ma, W. C., Ter-Akopian, G. M., Daniel, A. V., Stoyer, M. A., Donangelo, R., and Gelberg, A. Tue . "Nuclear shape and structure in neutron-rich {sup 110,111}Tc". United States. doi:10.1103/PHYSREVC.74.024308.
@article{osti_20863704,
title = {Nuclear shape and structure in neutron-rich {sup 110,111}Tc},
author = {Luo, Y. X. and Lawrence Berkeley National Laboratory, Berkeley, California 94720 and Hamilton, J. H. and Ramayya, A. V. and Hwang, J. K. and Gore, P. M. and Jones, E. F. and Fong, D. and Rasmussen, J. O. and Lee, I. Y. and Stefanescu, I. and Che, X. L. and Zhu, S. J. and Physics Department, Tsinghua University, Beijing 100084 and Joint Institute for Heavy Ion Research, Oak Ridge, Tennessee 37831 and Wu, S. C. and Ginter, T. N. and National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824 and Ma, W. C. and Ter-Akopian, G. M. and Daniel, A. V. and Stoyer, M. A. and Donangelo, R. and Gelberg, A.},
abstractNote = {The high-spin nuclear structure of Tc isotopes is extended to more neutron-rich regions based on the measurements of prompt {gamma} rays from the spontaneous fission of {sup 252}Cf at the Gammasphere. The high-spin level scheme of N=67 neutron-rich {sup 110}Tc (Z=43) is established for the first time, and that of {sup 111}Tc is extended and expanded. The ground band of {sup 111}Tc reaches the band-crossing region, and the new observation of the weakly populated {alpha}=-1/2 member of the band provides important information on signature splitting. The systematics of band crossings in the isotopic and isotonic chains and a CSM calculation suggest that the band crossing of the ground band of {sup 111}Tc is due to alignment of a pair of h{sub 11/2} neutrons. The best fit to signature splitting, branching ratios, and excitations of the ground band of {sup 111}Tc by the rigid triaxial rotor plus particle model calculations result in a shape of {epsilon}{sub 2}=0.32 and {gamma}=-26 deg. for this nucleus. Its triaxiality is larger than that of {sup 107,109}Tc, which indicates increasing triaxiality in Tc isotopes with increasing neutron number. The identification of the weakly populated K+2 satellite band provides strong evidence for the large triaxiality of {sup 111}Tc. In {sup 110}Tc, the four lowest-lying levels observed are very similar to those in {sup 108}Tc. At an excitation of 478.9 keV above the lowest state observed, ten states of a {delta}I=1 band are observed. This band of {sup 110}Tc is very analogous to the {delta}I=1 bands in {sup 106,108}Tc, but it has greater and reversal signature splitting at higher spins.},
doi = {10.1103/PHYSREVC.74.024308},
journal = {Physical Review. C, Nuclear Physics},
number = 2,
volume = 74,
place = {United States},
year = {Tue Aug 15 00:00:00 EDT 2006},
month = {Tue Aug 15 00:00:00 EDT 2006}
}
  • Isomeric states in {sup 112}Tc and {sup 113}Tc, with half-lives of 150(17) ns and 500(100) ns, respectively, have been observed following the relativistic fission of {sup 238}U. The fission fragments have been separated in a fragment separator and identified by means of energy-loss and time-of-flight techniques. In both nuclei, the ground-state configuration is calculated to have an oblate shape and the isomerism is proposed to arise due to transitions from a triaxial excited state to a low-lying oblate state.
  • The shell structure underlying shape changes in neutron-rich nuclei near N=28 has been investigated by a novel application of the transient-field technique to measure the first-excited-state g factors in {sup 38}S and {sup 40}S produced as fast radioactive beams. There is a fine balance between proton and neutron contributions to the magnetic moments in both nuclei. The g factor of deformed {sup 40}S does not resemble that of a conventional collective nucleus because spin contributions are more important than usual.
  • The structure of Tc nuclei is extended to the moreneutron-rich regions based on measurements of prompt gamma rays from thespontaneous fission of 252Cf at Gammasphere. The level scheme of N=67neutron-rich (Z=43) 110Tc is established for the first time and that of111Tc is expanded. The ground-state band of 111Tc reaches theband-crossing region and the new observation of the weakly populatedalpha = -1/2 member of the band provides important information ofsignature splitting. The systematics of band crossings in the isotopicand isotonic chains and a CSM calculation suggest that the band crossingof the gs band of 111Tc is due to alignment of amore » pair of h11/2 neutrons.The best fit to signature splitting, branching ratios, and excitations ofthe ground-state band of 111Tc by RTRP model calculations result in ashape of epsilon2 = 0.32 and gamma = -26 deg. for this nucleus. Itstriaxiality is larger than that of 107Tc, to indicate increasingtriaxiality with increasing neutron number. The identification of theweakly-populated "K+2 satellite" band provides strong evidence for thelarge triaxiality of 111Tc. In 110Tc the four lowest-lying levelsobserved are very similar to those in 108Tc. At an excitation of 478.9keV above the lowest state observed, ten states of a delta I = 1 band areobserved. This band is very analogous to the delta I = 1 bands in106,108Tc, but it has greater signature splitting at higherspins.« less
  • The decays of three new neutron-rich nuclides /sup 111/Tc, /sup 113/Ru, and /sup 113/Rh have been observed at an on-line isotope separator facility. In addition, the beta decays of several other n-rich isotopes with A>100 have been studied for the first time. The new half-lives reported in this work include: /sup 111/Tc (T/sub 1/2/ = 0.30(3) s), /sup 111/Ru (2.12(7) s), /sup 112/Ru (1.75(7) s), /sup 113/Ru (0.80(10) s), /sup 113/Rh (2.72(22) s), and /sup 118/Pd (2.24(17) s). In general, these results support the microscopic theoretical half-life predictions below Z = 50.
  • The low-lying structure of {sup 188,190,192}W has been studied following {beta} decays of the neutron-rich mother nuclei {sup 188,190,192}Ta produced following the projectile fragmentation of a 1-GeV-per-nucleon {sup 208}Pb primary beam on a natural beryllium target at the GSI Fragment Separator. The {beta}-decay half-lives of {sup 188}Ta, {sup 190}Ta, and {sup 192}Ta have been measured, with {gamma}-ray decays of low-lying states in their respective W daughter nuclei, using heavy-ion {beta}-{gamma} correlations and a position-sensitive silicon detector setup. The data provide information on the low-lying excited states in {sup 188}W, {sup 190}W, and {sup 192}W, which highlight a change in nuclearmore » shape at {sup 190}W compared with that of lighter W isotopes. This evolution of ground-state structure along the W isotopic chain is discussed as evidence for a possible proton subshell effect for the A{approx}190 region and is consistent with maximization of the {gamma}-softness of the nuclear potential around N{approx}116.« less