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Title: Isospin purity of T=1 states in the A=38 nuclei studied via lifetime measurements in {sup 38}K

Abstract

The Doppler Shift Attenuation Method was used to measure lifetimes for levels in {sup 38}K at excitation energies of 1698, 2404, 2830, 2996, and 3671 keV, populated using the {sup 40}Ca(d, {alpha}){sup 38}K reaction at a beam energy of 4.5 MeV. Values of 109(29), 95(22), 457(63), 130(40), and 160(50) fs, respectively, were measured and are compared with previous values obtained using different stopping powers. The matrix element for the transition between the J{sup {pi}}=2{sub T=1}{sup +} and 0{sub T=1}{sup +} states in this T{sub z}=0 nucleus is compared with the analogous transition in the other nuclei in the T=1 triplet, {sup 38}Ca (T{sub z}=-1) and {sup 38}Ar (T{sub z}=+1), and with the results of shell-model calculations.

Authors:
; ;  [1]; ; ; ;  [2];  [3]; ;  [4]
  1. School of Engineering, University of Brighton, Brighton BN2 4GJ (United Kingdom)
  2. Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520 (United States)
  3. CLRC Daresbury Laboratory, Daresbury, Warrington WA4 4AD (United Kingdom)
  4. School of Chemistry and Physics, Keele University, Staffordshire ST5 5BG (United Kingdom)
Publication Date:
OSTI Identifier:
20990948
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.75.014309; (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; ARGON 38; CALCIUM 38; CALCIUM 40; DSA METHOD; EXCITATION; IMPURITIES; ISOSPIN; KEV RANGE; LIFETIME; MATRIX ELEMENTS; MEV RANGE; POTASSIUM 38; S STATES; SHELL MODELS; STOPPING POWER; TRIPLETS

Citation Formats

Prados Estevez, F. M., Bruce, A. M., Taylor, M. J., Amro, H., Beausang, C. W., Casten, R. F., Ressler, J. J., Barton, C. J., Chandler, C., and Hammond, G. Isospin purity of T=1 states in the A=38 nuclei studied via lifetime measurements in {sup 38}K. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.014309.
Prados Estevez, F. M., Bruce, A. M., Taylor, M. J., Amro, H., Beausang, C. W., Casten, R. F., Ressler, J. J., Barton, C. J., Chandler, C., & Hammond, G. Isospin purity of T=1 states in the A=38 nuclei studied via lifetime measurements in {sup 38}K. United States. doi:10.1103/PHYSREVC.75.014309.
Prados Estevez, F. M., Bruce, A. M., Taylor, M. J., Amro, H., Beausang, C. W., Casten, R. F., Ressler, J. J., Barton, C. J., Chandler, C., and Hammond, G. Mon . "Isospin purity of T=1 states in the A=38 nuclei studied via lifetime measurements in {sup 38}K". United States. doi:10.1103/PHYSREVC.75.014309.
@article{osti_20990948,
title = {Isospin purity of T=1 states in the A=38 nuclei studied via lifetime measurements in {sup 38}K},
author = {Prados Estevez, F. M. and Bruce, A. M. and Taylor, M. J. and Amro, H. and Beausang, C. W. and Casten, R. F. and Ressler, J. J. and Barton, C. J. and Chandler, C. and Hammond, G.},
abstractNote = {The Doppler Shift Attenuation Method was used to measure lifetimes for levels in {sup 38}K at excitation energies of 1698, 2404, 2830, 2996, and 3671 keV, populated using the {sup 40}Ca(d, {alpha}){sup 38}K reaction at a beam energy of 4.5 MeV. Values of 109(29), 95(22), 457(63), 130(40), and 160(50) fs, respectively, were measured and are compared with previous values obtained using different stopping powers. The matrix element for the transition between the J{sup {pi}}=2{sub T=1}{sup +} and 0{sub T=1}{sup +} states in this T{sub z}=0 nucleus is compared with the analogous transition in the other nuclei in the T=1 triplet, {sup 38}Ca (T{sub z}=-1) and {sup 38}Ar (T{sub z}=+1), and with the results of shell-model calculations.},
doi = {10.1103/PHYSREVC.75.014309},
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}
}
  • Isospin is a good quantum number under the assumption that the nuclear interaction is charge independent. An analogous structure of excited states is expected for nuclei with the same mass number A but with different z components T{sub z} of the isospin T, where T{sub z}=(N-Z)/2. The analogous structure has been studied for the isobaric nuclei {sup 58}Ni and {sup 58}Cu by comparing the transitions from the {sup 58}Ni ground state (initial isospin T{sub i}=1 and J{sup {pi}}=0{sup +}) to the M1 and the Gamow-Teller (GT) states (J{sup {pi}}=1{sup +}) in {sup 58}Ni and {sup 58}Cu, respectively. For this purpose,more » proton inelastic scattering (p,p{sup '}) at E{sub p}=160 MeV and the charge-exchange ({sup 3}He,t) reaction at 140 MeV/nucleon were both measured at 0 deg., exciting final states with isospin T{sub f}=1 and 2 and T{sub f}=0, 1, and 2, respectively. High energy and scattering-angle resolutions were achieved by applying complete beam matching techniques. On the basis of the correspondence between excitation energies and transition strengths, isospin values T{sub f}=1 and 2 of analog GT and M1 states were identified. The distribution of T{sub f}=2 states was also compared with results of {sup 58}Ni(d,{sup 2}He), {sup 58}Ni(t,{sup 3}He), and {sup 58}Ni(n,p) experiments, in which only T{sub f}=2 states are excited. The obtained GT strength distribution is compared with the results of shell-model calculations.« less
  • The /sup 38/Ar(/sup 3/He,t) /sup 38/K reaction has been studied using a 40 MeV /sup 3/He beam. Angular distributions for 26 levels are presented and theoretical analysis of the results has been carried out. Firstly, the conclusions of a macroscopic study of the /sup 38/K level spectrum are presented. Secondly, the difficulties encountered using a one-step microscopic model to describe the five lowest states of /sup 38/K are discussed. Thirdly, the improvements obtained by including two-step contributions in our microscopic model are shown and the importance of the transitions occurring via the ((/sup 3/He,..cap alpha..) + (..cap alpha..,t)) channel ismore » emphasized.« less