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Title: Nuclear structure of {sup 229}Th

Abstract

Lifetimes of excited states in {sup 229}Th, populated in the {beta} decay of {sup 229}Ac, have been measured using the advanced time-delayed {beta}{gamma}{gamma}(t) method. Half-lives of 14 states have been determined including 11 of them for the first time. Twenty-seven new {gamma} lines have been introduced into the {beta}-decay scheme of {sup 229}Ac based on results of {gamma}{gamma} coincidence measurements. Reduced transition probabilities have been determined for more than 70 {gamma} transitions in {sup 229}Th. Average |D{sub 0}| values of 0.029(1), 0.077(3), and 0.024(5) e fm have been deduced for the lowest K{sup {pi}}=1/2{sup {+-}},3/2{sup {+-}}, and 5/2{sup {+-}} parity partner bands, respectively. Excited states in {sup 229}Th and experimental transition rates have been interpreted within the quasiparticle-plus-phonon model. The half-life of the 3.5-eV, 3/2{sup +} isomeric state is predicted to be about 10 h. Potential energy surfaces on the ({beta}{sub 2},{beta}{sub 3}) plane for the lowest single quasiparticle configurations in {sup 229}Th have been calculated using the Strutinsky method.

Authors:
; ; ; ;  [1]; ;  [2]; ;  [3];  [4]; ; ;  [5]; ;  [6]; ; ; ;  [7];  [8]
  1. Andrzej Soltan Institute for Nuclear Studies, PL 05-400 Swierk (Poland)
  2. Institute of Experimental Physics, University of Warsaw, PL 00-681 Warsaw (Poland)
  3. Department of Radiation Sciences, University of Uppsala, SE-751 21 Uppsala (Sweden)
  4. Department of Nuclear Physics, Charles University, CZ-18000 Prague 8 (Czech Republic)
  5. Instituto de Fizica Corpuscular, CSIC-University Valencia, E-46100 Burjassot (Spain)
  6. Oliver Lodge Laboratory, University of Liverpool, Liverpool L69 3BX (United Kingdom)
  7. Physics Department, Royal Institute of Technology, SE-106 91 Stockholm (Sweden)
  8. Instituto de Estructura de la Materia, CSIC, E-28006 Madrid (Spain) (and others)
Publication Date:
OSTI Identifier:
20771452
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 73; Journal Issue: 4; Other Information: DOI: 10.1103/PhysRevC.73.044326; (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; ACTINIUM 229; BETA DECAY; EV RANGE; EXCITED STATES; HALF-LIFE; LIFETIME; NUCLEAR STRUCTURE; PARITY; PHONONS; POTENTIAL ENERGY; PROBABILITY; QUASIPARTICLE-PHONON MODEL; THORIUM 229; TIME DELAY

Citation Formats

Ruchowska, E., Plociennik, W.A., Kaczarowski, R., Syntfeld, A., Wasilewski, A.A., Zylicz, J., Kurcewicz, W., Mach, H., Fogelberg, B., Kvasil, J., Algora, A., Nacher, E., Rubio, B., Amzal, N., Butler, P.A., Baeck, T., Cederwall, B., Kerek, A., Lagergren, K., and Borge, M.G. Nuclear structure of {sup 229}Th. United States: N. p., 2006. Web. doi:10.1103/PhysRevC.73.044326.
Ruchowska, E., Plociennik, W.A., Kaczarowski, R., Syntfeld, A., Wasilewski, A.A., Zylicz, J., Kurcewicz, W., Mach, H., Fogelberg, B., Kvasil, J., Algora, A., Nacher, E., Rubio, B., Amzal, N., Butler, P.A., Baeck, T., Cederwall, B., Kerek, A., Lagergren, K., & Borge, M.G. Nuclear structure of {sup 229}Th. United States. doi:10.1103/PhysRevC.73.044326.
Ruchowska, E., Plociennik, W.A., Kaczarowski, R., Syntfeld, A., Wasilewski, A.A., Zylicz, J., Kurcewicz, W., Mach, H., Fogelberg, B., Kvasil, J., Algora, A., Nacher, E., Rubio, B., Amzal, N., Butler, P.A., Baeck, T., Cederwall, B., Kerek, A., Lagergren, K., and Borge, M.G. Sat . "Nuclear structure of {sup 229}Th". United States. doi:10.1103/PhysRevC.73.044326.
@article{osti_20771452,
title = {Nuclear structure of {sup 229}Th},
author = {Ruchowska, E. and Plociennik, W.A. and Kaczarowski, R. and Syntfeld, A. and Wasilewski, A.A. and Zylicz, J. and Kurcewicz, W. and Mach, H. and Fogelberg, B. and Kvasil, J. and Algora, A. and Nacher, E. and Rubio, B. and Amzal, N. and Butler, P.A. and Baeck, T. and Cederwall, B. and Kerek, A. and Lagergren, K. and Borge, M.G.},
abstractNote = {Lifetimes of excited states in {sup 229}Th, populated in the {beta} decay of {sup 229}Ac, have been measured using the advanced time-delayed {beta}{gamma}{gamma}(t) method. Half-lives of 14 states have been determined including 11 of them for the first time. Twenty-seven new {gamma} lines have been introduced into the {beta}-decay scheme of {sup 229}Ac based on results of {gamma}{gamma} coincidence measurements. Reduced transition probabilities have been determined for more than 70 {gamma} transitions in {sup 229}Th. Average |D{sub 0}| values of 0.029(1), 0.077(3), and 0.024(5) e fm have been deduced for the lowest K{sup {pi}}=1/2{sup {+-}},3/2{sup {+-}}, and 5/2{sup {+-}} parity partner bands, respectively. Excited states in {sup 229}Th and experimental transition rates have been interpreted within the quasiparticle-plus-phonon model. The half-life of the 3.5-eV, 3/2{sup +} isomeric state is predicted to be about 10 h. Potential energy surfaces on the ({beta}{sub 2},{beta}{sub 3}) plane for the lowest single quasiparticle configurations in {sup 229}Th have been calculated using the Strutinsky method.},
doi = {10.1103/PhysRevC.73.044326},
journal = {Physical Review. C, Nuclear Physics},
number = 4,
volume = 73,
place = {United States},
year = {Sat Apr 15 00:00:00 EDT 2006},
month = {Sat Apr 15 00:00:00 EDT 2006}
}
  • The electromagnetic transition between the almost degenerate 5/2{sup +} and 3/2{sup +} states in {sup 229}Th is deemed to be very sensitive to potential changes in the fine structure constant {alpha}. State of the art Hartree-Fock and Hartree-Fock-Bogoliubov calculations are performed to compute the difference in Coulomb energies of the two states that determines the sensitivity of the transition frequency {nu} on variations in {alpha}. The kinetic energies are also calculated that reflect a possible variation in the nucleon or quark masses. As the two states differ mainly in the orbit occupied by the last unpaired neutron the Coulomb energymore » difference results from a change in the nuclear polarization of the proton distribution. This effect turns out to be rather small and to depend on the nuclear model. The sensitivity q{sub s} of the frequency shift {delta}{nu} on {delta}{alpha}/{alpha}({delta}{nu}=q{sub s}{delta}{alpha}/{alpha}) varies for the different models between about +10{sup 20} Hz and -10{sup 20} Hz. Therefore, much more effort must be put into the improvement of the nuclear models before one can draw conclusions from a measured drift in the transition frequency on the size of a temporal drift of {alpha}.« less
  • We consider the excitation of the nuclear transition {sup 229g}Th-{sup 229m}Th near 7.6 eV in singly ionized thorium via an electronic bridge process. The process relies on the excitation of the electron shell by two laser photons whose sum frequency is equal to the nuclear transition frequency. This scheme allows us to determine the nuclear transition frequency with high accuracy. Based on calculations of the electronic level structure of Th{sup +} which combine the configuration-interaction method and many-body perturbation theory, we estimate that a nuclear excitation rate in the range of 10 s{sup -1} can be obtained using conventional lasermore » sources.« less
  • Energy distributions and yields of ternary particles (TP's) emitted in the thermal neutron induced fission of {sup 229}Th, {sup 233}U and {sup 239}Pu have been determined. Special emphasis was put on the study of heavy ternary particles. The measurements were performed at the high flux reactor of the Institut Laue-Langevin (ILL). For identification of particles the mass separator Lohengrin and a {delta}E-E ionisation chamber were used. In the case of {sup 233}U(n{sub th},f) it was possible to detect 25 different TP's, with 19 of them having never been detected before in this reaction. For {sup 229}Th(n{sub th},f) all 17 TP'smore » that were observed were new. From the reaction {sup 239}Pu(n{sub th},f) 21 out of 34 detected TP's were new. The energy distributions and yields of the TP's are given. The yields of TP's as a function of mass number depend on the mass of the decaying compound nucleus. Heavy TP's are increasingly favored in the decay of heavy mother nuclei.« less
  • We have considered an effect of atomic electrons on the nuclear {sup 229m}Th-{sup 229g}Th transition in {sup 229}Th{sup 3+} due to the electronic bridge process. Based on a recent experimental result we assumed the energy difference between the isomeric and the ground nuclear states to be equal to 7.6 eV. We have calculated the ratios of the electronic bridge process probability ({Gamma}{sub EB}) to the probability of the nuclear radiative transition ({Gamma}{sub N}) for the electronic 5f{sub 5/2{yields}}6d{sub 3/2},6d{sub 5/2},7s and the 7s{yields}7p{sub 1/2},7p{sub 3/2} transitions and found {Gamma}{sub EB}/{Gamma}{sub N{approx}}0.01-0.1 for the former and {Gamma}{sub EB}/{Gamma}{sub N{approx}}20 for themore » latter.« less