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Title: Structures of the neutron-rich nuclei observed in fission of {sup 252}Cf

Abstract

Analysis of high statistics triple coincidence fission γ data from {sup 252}Cf at Gammasphere including angular correlations yielded well-expanded high-spin level schemes with more complete and reliable spin/parity assignments for {sup 82}Ge, {sup 118,120,122}Cd and {sup 114,115}Rh. Both the quasi-particle/hole couplings and quasi-rotational degrees of freedom are implied to play roles in these Cd isotopes. Evidence for triaxial shapes and octupole components in the Cd isotopes is presented. These Cd isotopes may have triaxial deformations. High-spin level schemes of {sup 114,115}Rh have been established for the first time. The existence of a relatively large signature splitting and an yrare band shows typical features of a triaxially deformed nucleus. Possible excited deformed rotational bands are observed, for the first time, in {sup 82}Ge. From the multipole mixing ratio measurement, the ground state configurations of {sup 109,111}Ru, as well as excited states in {sup 103,107}Mo and {sup 111}Ru were determined.

Authors:
; ; ; ;  [1];  [2];  [3]; ;  [4];  [5];  [6];  [7]
  1. Department of Physics, Vanderbilt University, Nashville, Tennessee 37235 (United States)
  2. Department of Physics, Vanderbilt University, Nashville, Tennessee 37235 USA and Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
  3. Department of Physics, Vanderbilt University, Nashville, Tennessee 37235 USA and UNRIB/Oak Ridge Associated Universities, Oak Ridge, Tennessee 37831 (United States)
  4. Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
  5. Department of Physics, Oxford University, Oxford OX1 3PU (United Kingdom)
  6. Flerov Laboratory of Nuclear Reactions, JINR, Dubna (Russian Federation)
  7. Department of Physics, Tsinghua University, Beijing 100084 (China)
Publication Date:
OSTI Identifier:
22308424
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1609; Journal Issue: 1; Conference: FIG12: International conference on frontiers in gamma-ray spectroscopy 2012, New Delhi (India), 5-7 Mar 2012; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ANGULAR CORRELATION; CADMIUM 122; CALIFORNIUM 252; DEFORMED NUCLEI; FISSION; GERMANIUM 82; GROUND STATES; MIXING RATIO; MOLYBDENUM 107; NEUTRON-RICH ISOTOPES; RHODIUM 115; ROTATIONAL STATES; RUTHENIUM 111; SPIN

Citation Formats

Ramayya, A. V., Hamilton, J. H., Goodin, C. J., Brewer, N. T., Hwang, J. K., Luo, Y. X., Liu, S. H., Rasmussen, J. O., Lee, I. Y., Stone, N. J., Daniel, A. V., and Zhu, S. J. Structures of the neutron-rich nuclei observed in fission of {sup 252}Cf. United States: N. p., 2014. Web. doi:10.1063/1.4893263.
Ramayya, A. V., Hamilton, J. H., Goodin, C. J., Brewer, N. T., Hwang, J. K., Luo, Y. X., Liu, S. H., Rasmussen, J. O., Lee, I. Y., Stone, N. J., Daniel, A. V., & Zhu, S. J. Structures of the neutron-rich nuclei observed in fission of {sup 252}Cf. United States. doi:10.1063/1.4893263.
Ramayya, A. V., Hamilton, J. H., Goodin, C. J., Brewer, N. T., Hwang, J. K., Luo, Y. X., Liu, S. H., Rasmussen, J. O., Lee, I. Y., Stone, N. J., Daniel, A. V., and Zhu, S. J. Thu . "Structures of the neutron-rich nuclei observed in fission of {sup 252}Cf". United States. doi:10.1063/1.4893263.
@article{osti_22308424,
title = {Structures of the neutron-rich nuclei observed in fission of {sup 252}Cf},
author = {Ramayya, A. V. and Hamilton, J. H. and Goodin, C. J. and Brewer, N. T. and Hwang, J. K. and Luo, Y. X. and Liu, S. H. and Rasmussen, J. O. and Lee, I. Y. and Stone, N. J. and Daniel, A. V. and Zhu, S. J.},
abstractNote = {Analysis of high statistics triple coincidence fission γ data from {sup 252}Cf at Gammasphere including angular correlations yielded well-expanded high-spin level schemes with more complete and reliable spin/parity assignments for {sup 82}Ge, {sup 118,120,122}Cd and {sup 114,115}Rh. Both the quasi-particle/hole couplings and quasi-rotational degrees of freedom are implied to play roles in these Cd isotopes. Evidence for triaxial shapes and octupole components in the Cd isotopes is presented. These Cd isotopes may have triaxial deformations. High-spin level schemes of {sup 114,115}Rh have been established for the first time. The existence of a relatively large signature splitting and an yrare band shows typical features of a triaxially deformed nucleus. Possible excited deformed rotational bands are observed, for the first time, in {sup 82}Ge. From the multipole mixing ratio measurement, the ground state configurations of {sup 109,111}Ru, as well as excited states in {sup 103,107}Mo and {sup 111}Ru were determined.},
doi = {10.1063/1.4893263},
journal = {AIP Conference Proceedings},
number = 1,
volume = 1609,
place = {United States},
year = {Thu Aug 14 00:00:00 EDT 2014},
month = {Thu Aug 14 00:00:00 EDT 2014}
}
  • High spin excited states in neutron-rich nuclei [sup 112,114,116]Pd have been investigated by measuring prompt [gamma] rays emitted from a [sup 252]Cf spontaneous fission source. Two different measurements were performed. First, [gamma]-[gamma] coincidence data, necessary to determine the decay schemes, were obtained by using an array of 20 Compton-suppressed Ge detectors. Second, [ital Z] identification and the enhancement of a desired neutron channel were carried out using a [ital x]-[ital n]-[gamma] multiplicity spectrometer. Ground state bands have been extended to [ital J][sup [pi]]=10[sup +] for [sup 112]Pd, and [ital J][sup [pi]]=12[sup +] for [sup 114]Pd and [sup 116]Pd. Band crossingsmore » were observed in all three isotopes. It was found from cranked shell model calculations that these backbends are due to the alignment of two [ital g][sub 9/2] protons. The measured energy levels were also compared with predictions of the interacting boson model.« less
  • In this paper we present research that has been carried out using the Euroball and Eurogam arrays to detect {gamma} rays emitted from spontaneously fissioning {sup 248}Cm and {sup 252}Cf. The paper focuses on three sub-areas of current activity, namely, the measurement of yields of secondary fragment pairs, the measurement of state lifetimes at around spin 10, and recent measurements of g-factors of excited states in fission fragments. (c) 1999 American Institute of Physics.
  • The high selectivity and sensitivity offered by large detector arrays such as Gammasphere and Eurogam enable one to identify gamma rays from individual neutron-rich nuclei produced in the spontaneous fission (SF) of {sup 252}Cf and {sup 248}Cm. We have identified new {gamma} transitions in {sup 101,102,103}Nb, {sup 98,100}Y, {sup 103,107,109}Mo and {sup 109,111}Ru. In Nb nuclei we observed pairing-free rotational bands with J{sub exp}/J{sub rigid}{approx_equal}1. In {sup 103}Mo and {sup 109,111}Ru we identified bands with close doublet structures which may be a general consequence of rotation alignment for configurations of half-filled j-shells, which are weakly coupled to the deformed shapes.more » In addition, rare processes such as cold neutronless binary fission, {alpha}-accompanied ternary fission and {sup 10}Be-accompanied ternary fission are observed.« less
  • New neutron-rich isotopes of several rare-earth elements have been identified using on-line mass separation. The observed decay rates of K x rays in the mass separated fractions for which 153less than or equal toAless than or equal to162, together with the associated ..gamma..-decay spectra, provided direct isotopic identifications. New isotopes observed, with values of their half lives given in parentheses, are /sup 153/Pr (4.3 +- 0.2 s), /sup 155/Nd (8.9 +- 0.2 s), /sup 156/Nd (5.47 +- 0.11 s), /sup 157/Pm (10.90 +- 0.20 s), /sup 158/Pm (4.8 +- 0.5 s), and /sup 162/Eu (10.6 +- 1.0 s). In addition,more » we have confirmed recent reports of the observation of /sup 153/Nd (28.9 +- 0.4 s), /sup 154/Nd (25.9 +- 0.2 s), /sup 156/Pm (26.70 +- 0.10 s), /sup 159/Sm (11.37 +- 0.15 s), and /sup 160/Sm (9.6 +- 0.3 s). These half-life values are compared to the reuslts of theoretical predictions.« less
  • Spontaneous fission provides a very natural production mechanism for neutron-rich nuclei. The large excesses of neutrons over protons in heavy systems near the valley of stability, coupled with the tendency for the charge-to-mass ratio to be preserved in the fission process, results in fission fragments that lie well to the neutron-rich side of stability. The excitation energy of the primary fragments produced at scission results in the evaporation of neutrons (Fig 1) to produce secondary fragments whose excitation energy is dissipated through {gamma}-ray emission. In the last few years the study of such {gamma} rays has produced a dramatic increasemore » in the available information on the structure of neutron-rich nuclei. This renaissance in fission-fragment spectroscopy has been due primarily to the much increased resolving power of large arrays of germanium {gamma}-ray detectors such as Euroball and Gammasphere. Through the improved detection efficiency and high granularity, these arrays have made it possible to obtain reasonable rates for the detection of three coincident {gamma} rays out of the cascades of multiplicity ten that are typically produced in spontaneous fission. In addition to the determination of the energies of excited levels, developments in spectroscopic techniques have allowed for information to be deduced regarding the spins and parities [1,2] and lifetimes [3,4] of such states of extreme isospin. In this paper we present research that has been carried out using the Euroball and Eurogam arrays to detect {gamma} rays emitted from spontaneously fissioning {sup 248}Cm and {sup 252}Cf. The paper focuses on three sub-areas of current activity, namely, the measurement of yields of secondary fragment pairs, the measurement of state lifetimes at around spin 10, and recent measurements of g-factors of excited states in fission fragments.« less