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Title: E3 strength of the 11{sup -} to 8{sup +} isomeric decays in {sup 194}Pb and {sup 196}Pb and oblate deformation

Abstract

The E3 decays of the 11{sup -} isomers in the isotopes {sup 194}Pb and {sup 196}Pb have been studied experimentally and evaluated in terms of configuration mixing due to the development of oblate deformation. New results include a remeasurement of the lifetime of the 11{sup -} isomer in {sup 194}Pb and clarification of the intensities of its main decay branches including the known 496 keV E3 branch. Its intensity is an order of magnitude weaker than previously reported, leading to an E3 transition strength of 29(4) W.u. Limits are placed on possible E3 decays of the 11{sup -} isomer in {sup 196}Pb to a previously assigned 8{sup +} two-proton state. Neither the branch, nor the state is observed. An alternative 562 keV transition to a new state at 2630 keV is proposed, with an E3 strength of 26(2) W.u. The approximately constant E3 strength for the range of even-even isotopes {sup 190-196}Pb is consistent with an oblate deformation for the 11{sup -} state of similar magnitude. This is supported by K-constrained potential-energy-surface calculations for the 11{sup -} and 8{sup +} configurations.

Authors:
; ; ; ; ;  [1]; ;  [2];  [3];  [4]
  1. Department of Nuclear Physics, RSPhysSE, Australian National University, Canberra ACT 0200 (Australia)
  2. Department of Physics, Faculty of Science, Australian National University, Canberra ACT 0200 (Australia)
  3. (Australia)
  4. School of Physics, Peking University, Beijing 100871 (China)
Publication Date:
OSTI Identifier:
20771095
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 72; Journal Issue: 6; Other Information: DOI: 10.1103/PhysRevC.72.064319; (c) 2005 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; CONFIGURATION MIXING; E3-TRANSITIONS; ISOMERIC NUCLEI; KEV RANGE; LEAD 194; LEAD 196; LIFETIME; NUCLEAR DECAY; NUCLEAR DEFORMATION; POTENTIAL ENERGY; PROTONS; SURFACES

Citation Formats

Dracoulis, G.D., Lane, G.J., Peaty, T.M., Baxter, A.M., Davidson, P.M., Kibedi, T., Byrne, A.P., Wilson, A.N., Department of Nuclear Physics, RSPhysSE, Australian National University, Canberra ACT 0200, and Xu, F.R. E3 strength of the 11{sup -} to 8{sup +} isomeric decays in {sup 194}Pb and {sup 196}Pb and oblate deformation. United States: N. p., 2005. Web. doi:10.1103/PhysRevC.72.064319.
Dracoulis, G.D., Lane, G.J., Peaty, T.M., Baxter, A.M., Davidson, P.M., Kibedi, T., Byrne, A.P., Wilson, A.N., Department of Nuclear Physics, RSPhysSE, Australian National University, Canberra ACT 0200, & Xu, F.R. E3 strength of the 11{sup -} to 8{sup +} isomeric decays in {sup 194}Pb and {sup 196}Pb and oblate deformation. United States. doi:10.1103/PhysRevC.72.064319.
Dracoulis, G.D., Lane, G.J., Peaty, T.M., Baxter, A.M., Davidson, P.M., Kibedi, T., Byrne, A.P., Wilson, A.N., Department of Nuclear Physics, RSPhysSE, Australian National University, Canberra ACT 0200, and Xu, F.R. Thu . "E3 strength of the 11{sup -} to 8{sup +} isomeric decays in {sup 194}Pb and {sup 196}Pb and oblate deformation". United States. doi:10.1103/PhysRevC.72.064319.
@article{osti_20771095,
title = {E3 strength of the 11{sup -} to 8{sup +} isomeric decays in {sup 194}Pb and {sup 196}Pb and oblate deformation},
author = {Dracoulis, G.D. and Lane, G.J. and Peaty, T.M. and Baxter, A.M. and Davidson, P.M. and Kibedi, T. and Byrne, A.P. and Wilson, A.N. and Department of Nuclear Physics, RSPhysSE, Australian National University, Canberra ACT 0200 and Xu, F.R.},
abstractNote = {The E3 decays of the 11{sup -} isomers in the isotopes {sup 194}Pb and {sup 196}Pb have been studied experimentally and evaluated in terms of configuration mixing due to the development of oblate deformation. New results include a remeasurement of the lifetime of the 11{sup -} isomer in {sup 194}Pb and clarification of the intensities of its main decay branches including the known 496 keV E3 branch. Its intensity is an order of magnitude weaker than previously reported, leading to an E3 transition strength of 29(4) W.u. Limits are placed on possible E3 decays of the 11{sup -} isomer in {sup 196}Pb to a previously assigned 8{sup +} two-proton state. Neither the branch, nor the state is observed. An alternative 562 keV transition to a new state at 2630 keV is proposed, with an E3 strength of 26(2) W.u. The approximately constant E3 strength for the range of even-even isotopes {sup 190-196}Pb is consistent with an oblate deformation for the 11{sup -} state of similar magnitude. This is supported by K-constrained potential-energy-surface calculations for the 11{sup -} and 8{sup +} configurations.},
doi = {10.1103/PhysRevC.72.064319},
journal = {Physical Review. C, Nuclear Physics},
number = 6,
volume = 72,
place = {United States},
year = {Thu Dec 15 00:00:00 EST 2005},
month = {Thu Dec 15 00:00:00 EST 2005}
}
  • The de-excitations of the 2+ second excited states of Pt/sup 194/ and Pt/ sup 196/ have been studied to compare crossover transition intensities to the 0+ ground states relative to the known cascade transitions to the 2+ first excited states. An intermediate-image beta-ray spectrometer was used to measure the internal-conversion electron spectra occurring in the decay of Au/sup 194/ and Au/ sup 196/ line is found in the decay of Au/sup 194/ corresponding to n O.618-Mev crossover having a transition intensity of 25% relative to the 0.290Mev cascade, provided the latter is assumed to be E2. In possible crossover transitionmore » compared with the 0.331Mev cascade. Au/sup 194/ exhihits the internal-conversion lines of 36 gamma-ray transitions which fit energetically into a proposed energy level seheme for Pt/sup 194/. A search in the electron spectrum of Au/sup 198/ showed no gamma-ray transitions other than the three already known. (auth)« less
  • Evidence for collective oblate behavior in [sup 196]Pb is presented. One irregular and two regular bands of [ital M]1 transitions have been observed following the [sup 170]Er([sup 30]Si,4[ital n]) and [sup 176]Yb([sup 26]Mg,6[ital n]) reactions. Transitions linking the most intense regular band to the low-lying negative-parity yrast levels are observed, establishing excitation energies, spins, and probable parities of the band members. In contrast, no such transitions have been found for the irregular band and the weaker regular band. The bands are interpreted as corresponding to collective oblate rotation, arising mainly from deformation-aligned high-[ital j], shape-driving quasiproton excitations across the [italmore » Z]=82 shell gap, coupled to rotation-aligned quasineutrons.« less
  • High-spin states in the nucleus [sup 196]Hg were populated in the reaction [sup 192]Os([sup 9]Be,5[ital n]) at a beam energy of 65 MeV. A regular rotational-like [Delta][ital I]=1 band has been observed up to an excitation energy of [ital E][sup *][approx]8.7 MeV and spin [ital I][approx]30[h bar]. This is the second observation of a band of this character in a mercury isotope. The experimental results are compared with mean field calculations and semiclassical estimates based on the Doenau-Frauendorf formalism. The mercury bands show significantly lower [ital B]([ital M]1)/[ital B]([ital E]2) branching ratios as compared with similar bands in light leadmore » nuclei. This difference may be more readily explained by a difference in single-particle structure rather than by large differences in deformation between the lead and mercury configurations.« less