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Title: First observation of medium-spin excitations in the {sup 138}Cs nucleus.

Abstract

Medium-spin, yrast excitations in the {sup 138}Cs nucleus, populated in the spontaneous fission of {sup 248}Cm, were observed for the first time. {sup 138}Cs was studied by means of prompt {gamma}-ray spectroscopy using the EUROGAM2 array. The newly observed yrast cascade, built on the known 6- isomer at 80 keV, was successfully described by shell model calculations. Analogously to the {sup 136}I isotone, the 6- isomer in {sup 138}Cs has the ({pi} g{sub 7/2}{sup 4} d{sub 5/2}{nu} f{sub 7/2}){sub 6-} dominating configuration and the 7{sup -} excitation, located 175 keV above, corresponds to the ({pi} g{sub 7/2}{sup 3} d{sup 2}{sub 5/2}{nu} f{sub 7/2}){sub 7-} as dominating configuration. Similarly as in {sup 136}I, changing the position of the d{sub 5/2} proton orbital improves the reproduction of the data. However, in {sup 138}Cs the energy of this orbital should be increased compared to its energy in {sup 133}Sb, to get the best description, in contrast to {sup 136}I and {sup 135}Sb, where it had to be decreased. The best reproduction of excitation energies in {sup 138}Cs is obtained assuming that the {pi}d{sub 5/2} orbital in {sup 138}Cs is located about 100 keV higher than in {sup 133}Sb. These observations suggest that themore » lowering of the d{sub 5/2} s.p. energy in {sup 135}Sb is not a physical effect due to the appearance of a neutron skin, as proposed by other authors, but rather an artifact due to some deficiency of the input data used in the shell model calculations in the region of the doubly magic {sup 132}Sn core.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
914986
Report Number(s):
ANL/PHY/JA-58868
Journal ID: ISSN 1434-6001; TRN: US0804865
DOE Contract Number:  
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Eur. Phys. J. A; Journal Volume: 32; Journal Issue: 1 ; Apr. 2007
Country of Publication:
United States
Language:
ENGLISH
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; CONFIGURATION; EXCITATION; ISOMERS; NEUTRONS; PROTONS; REPRODUCTION; SHELL MODELS; SPECTROSCOPY; SPONTANEOUS FISSION

Citation Formats

Rzaca-Urban, T., Urban, W., Saha Sarkar, M., Sarkar, S., Durell, J. L., Smith, A. G., Varley, B. J., Ahmad, I., Physics, Warsaw Univ., Saha Inst. of Nuclear Physics, Bengal Engineering and Science Univ., and Univ. of Manchester. First observation of medium-spin excitations in the {sup 138}Cs nucleus.. United States: N. p., 2007. Web. doi:10.1140/epja/i2007-10362-1.
Rzaca-Urban, T., Urban, W., Saha Sarkar, M., Sarkar, S., Durell, J. L., Smith, A. G., Varley, B. J., Ahmad, I., Physics, Warsaw Univ., Saha Inst. of Nuclear Physics, Bengal Engineering and Science Univ., & Univ. of Manchester. First observation of medium-spin excitations in the {sup 138}Cs nucleus.. United States. doi:10.1140/epja/i2007-10362-1.
Rzaca-Urban, T., Urban, W., Saha Sarkar, M., Sarkar, S., Durell, J. L., Smith, A. G., Varley, B. J., Ahmad, I., Physics, Warsaw Univ., Saha Inst. of Nuclear Physics, Bengal Engineering and Science Univ., and Univ. of Manchester. Sun . "First observation of medium-spin excitations in the {sup 138}Cs nucleus.". United States. doi:10.1140/epja/i2007-10362-1.
@article{osti_914986,
title = {First observation of medium-spin excitations in the {sup 138}Cs nucleus.},
author = {Rzaca-Urban, T. and Urban, W. and Saha Sarkar, M. and Sarkar, S. and Durell, J. L. and Smith, A. G. and Varley, B. J. and Ahmad, I. and Physics and Warsaw Univ. and Saha Inst. of Nuclear Physics and Bengal Engineering and Science Univ. and Univ. of Manchester},
abstractNote = {Medium-spin, yrast excitations in the {sup 138}Cs nucleus, populated in the spontaneous fission of {sup 248}Cm, were observed for the first time. {sup 138}Cs was studied by means of prompt {gamma}-ray spectroscopy using the EUROGAM2 array. The newly observed yrast cascade, built on the known 6- isomer at 80 keV, was successfully described by shell model calculations. Analogously to the {sup 136}I isotone, the 6- isomer in {sup 138}Cs has the ({pi} g{sub 7/2}{sup 4} d{sub 5/2}{nu} f{sub 7/2}){sub 6-} dominating configuration and the 7{sup -} excitation, located 175 keV above, corresponds to the ({pi} g{sub 7/2}{sup 3} d{sup 2}{sub 5/2}{nu} f{sub 7/2}){sub 7-} as dominating configuration. Similarly as in {sup 136}I, changing the position of the d{sub 5/2} proton orbital improves the reproduction of the data. However, in {sup 138}Cs the energy of this orbital should be increased compared to its energy in {sup 133}Sb, to get the best description, in contrast to {sup 136}I and {sup 135}Sb, where it had to be decreased. The best reproduction of excitation energies in {sup 138}Cs is obtained assuming that the {pi}d{sub 5/2} orbital in {sup 138}Cs is located about 100 keV higher than in {sup 133}Sb. These observations suggest that the lowering of the d{sub 5/2} s.p. energy in {sup 135}Sb is not a physical effect due to the appearance of a neutron skin, as proposed by other authors, but rather an artifact due to some deficiency of the input data used in the shell model calculations in the region of the doubly magic {sup 132}Sn core.},
doi = {10.1140/epja/i2007-10362-1},
journal = {Eur. Phys. J. A},
number = 1 ; Apr. 2007,
volume = 32,
place = {United States},
year = {Sun Apr 01 00:00:00 EDT 2007},
month = {Sun Apr 01 00:00:00 EDT 2007}
}