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Title: Evidence for octupole vibration in the triaxial superdeformed well of {sup 164}Lu.

Abstract

High-spin states in {sup 164}Lu were populated in the {sup 121}Sb({sup 48}Ca,5n) reaction at 215 MeV and {gamma}-ray coincidences were measured with the Gammasphere spectrometer. Through this experiment the eight known triaxial superdeformed bands in {sup 164}Lu could be confirmed. Some of these bands were extended to higher as well as to lower spins. Evidence is reported for the first time for weak {delta}I=1,E1 transitions linking TSD3 and TSD1. This observation may imply coupling to octupole vibrational degrees of freedom. The decay mechanism is different from the one observed in the neighboring even-N isotopes, which exhibit wobbling excitations built on the {pi}i{sub 13/2} structure with E2(M1),{delta}I=1 interband decay. An additional sequence decaying at high spin into TSD1 was observed up to I{sup {pi}}=(50{sup -}). This band has a constant dynamic moment of inertia of {approx}70({Dirac_h}/2{pi}){sup 2}MeV{sup -1} and an alignment that is {approx}2({Dirac_h}/2{pi}) larger than that found for TSD1. A revision of the assumed spin-parity-assignment of TSD2 is based on the observed decay-out to normal-deformed structures. The parity and signature quantum numbers of TSD2 are now firmly assigned as ({pi},{alpha})=(+,0), in disagreement with the former assignment of ({pi},{alpha})=(-,1), which was based on the assumption that TSD2 is the signature partnermore » of TSD1. TSD1 and TSD2 show an alignment gain at ({Dirac_h}/2{pi}){omega}{approx}0.67 and 0.60 MeV, respectively. In TSD1 the involvement of the j{sub 15/2} neutron orbital is suggested to be responsible for the high-frequency crossing.« less

Authors:
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Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC); Danish Science Foundation; German BMPF
OSTI Identifier:
914957
Report Number(s):
ANL/PHY/JA-58626
Journal ID: ISSN 0556-2813; PRVCAN; TRN: US0804858
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys. Rev. C; Journal Volume: 75; Journal Issue: 2007
Country of Publication:
United States
Language:
ENGLISH
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ALIGNMENT; DECAY; DEGREES OF FREEDOM; MOMENT OF INERTIA; NEUTRONS; OCTUPOLES; PARITY; QUANTUM NUMBERS; SPIN

Citation Formats

Bringel, P., Engelhardt, C., Hubel, H., NeuBer-Neffgen, A., Odegard, S. W., Hagemann, G. B., Hansen, C. R., Herskind, B., Sletten, G., Carpenter, M. P., Janssens, R. V. F., Khoo, T. L., Lauritsen, T., Seweryniak, D., Ma, W. C., Roux, D. G., Chowdhury, P., Physics, Univ. Bonn, Univ. of Oslo, Niels Bohr Inst., Mississippi State Univ., and Univ. of Massachusetts. Evidence for octupole vibration in the triaxial superdeformed well of {sup 164}Lu.. United States: N. p., 2007. Web. doi:10.1103/PhysRevC.75.044306.
Bringel, P., Engelhardt, C., Hubel, H., NeuBer-Neffgen, A., Odegard, S. W., Hagemann, G. B., Hansen, C. R., Herskind, B., Sletten, G., Carpenter, M. P., Janssens, R. V. F., Khoo, T. L., Lauritsen, T., Seweryniak, D., Ma, W. C., Roux, D. G., Chowdhury, P., Physics, Univ. Bonn, Univ. of Oslo, Niels Bohr Inst., Mississippi State Univ., & Univ. of Massachusetts. Evidence for octupole vibration in the triaxial superdeformed well of {sup 164}Lu.. United States. doi:10.1103/PhysRevC.75.044306.
Bringel, P., Engelhardt, C., Hubel, H., NeuBer-Neffgen, A., Odegard, S. W., Hagemann, G. B., Hansen, C. R., Herskind, B., Sletten, G., Carpenter, M. P., Janssens, R. V. F., Khoo, T. L., Lauritsen, T., Seweryniak, D., Ma, W. C., Roux, D. G., Chowdhury, P., Physics, Univ. Bonn, Univ. of Oslo, Niels Bohr Inst., Mississippi State Univ., and Univ. of Massachusetts. Mon . "Evidence for octupole vibration in the triaxial superdeformed well of {sup 164}Lu.". United States. doi:10.1103/PhysRevC.75.044306.
@article{osti_914957,
title = {Evidence for octupole vibration in the triaxial superdeformed well of {sup 164}Lu.},
author = {Bringel, P. and Engelhardt, C. and Hubel, H. and NeuBer-Neffgen, A. and Odegard, S. W. and Hagemann, G. B. and Hansen, C. R. and Herskind, B. and Sletten, G. and Carpenter, M. P. and Janssens, R. V. F. and Khoo, T. L. and Lauritsen, T. and Seweryniak, D. and Ma, W. C. and Roux, D. G. and Chowdhury, P. and Physics and Univ. Bonn and Univ. of Oslo and Niels Bohr Inst. and Mississippi State Univ. and Univ. of Massachusetts},
abstractNote = {High-spin states in {sup 164}Lu were populated in the {sup 121}Sb({sup 48}Ca,5n) reaction at 215 MeV and {gamma}-ray coincidences were measured with the Gammasphere spectrometer. Through this experiment the eight known triaxial superdeformed bands in {sup 164}Lu could be confirmed. Some of these bands were extended to higher as well as to lower spins. Evidence is reported for the first time for weak {delta}I=1,E1 transitions linking TSD3 and TSD1. This observation may imply coupling to octupole vibrational degrees of freedom. The decay mechanism is different from the one observed in the neighboring even-N isotopes, which exhibit wobbling excitations built on the {pi}i{sub 13/2} structure with E2(M1),{delta}I=1 interband decay. An additional sequence decaying at high spin into TSD1 was observed up to I{sup {pi}}=(50{sup -}). This band has a constant dynamic moment of inertia of {approx}70({Dirac_h}/2{pi}){sup 2}MeV{sup -1} and an alignment that is {approx}2({Dirac_h}/2{pi}) larger than that found for TSD1. A revision of the assumed spin-parity-assignment of TSD2 is based on the observed decay-out to normal-deformed structures. The parity and signature quantum numbers of TSD2 are now firmly assigned as ({pi},{alpha})=(+,0), in disagreement with the former assignment of ({pi},{alpha})=(-,1), which was based on the assumption that TSD2 is the signature partner of TSD1. TSD1 and TSD2 show an alignment gain at ({Dirac_h}/2{pi}){omega}{approx}0.67 and 0.60 MeV, respectively. In TSD1 the involvement of the j{sub 15/2} neutron orbital is suggested to be responsible for the high-frequency crossing.},
doi = {10.1103/PhysRevC.75.044306},
journal = {Phys. Rev. C},
number = 2007,
volume = 75,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • High-spin states in {sup 164}Lu were populated in the {sup 121}Sb({sup 48}Ca,5n) reaction at 215 MeV and {gamma}-ray coincidences were measured with the Gammasphere spectrometer. Through this experiment the eight known triaxial superdeformed bands in {sup 164}Lu could be confirmed. Some of these bands were extended to higher as well as to lower spins. Evidence is reported for the first time for weak {delta}I=1,E1 transitions linking TSD3 and TSD1. This observation may imply coupling to octupole vibrational degrees of freedom. The decay mechanism is different from the one observed in the neighboring even-N isotopes, which exhibit wobbling excitations built onmore » the {pi}i{sub 13/2} structure with E2(M1),{delta}I=1 interband decay. An additional sequence decaying at high spin into TSD1 was observed up to I{sup {pi}}=(50{sup -}). This band has a constant dynamic moment of inertia of {approx}70({Dirac_h}/2{pi}){sup 2}MeV{sup -1} and an alignment that is {approx}2({Dirac_h}/2{pi}) larger than that found for TSD1. A revision of the assumed spin-parity-assignment of TSD2 is based on the observed decay-out to normal-deformed structures. The parity and signature quantum numbers of TSD2 are now firmly assigned as ({pi},{alpha})=(+,0), in disagreement with the former assignment of ({pi},{alpha})=(-,1), which was based on the assumption that TSD2 is the signature partner of TSD1. TSD1 and TSD2 show an alignment gain at ({Dirac_h}/2{pi}){omega}{approx}0.67 and 0.60 MeV, respectively. In TSD1 the involvement of the j{sub 15/2} neutron orbital is suggested to be responsible for the high-frequency crossing.« less
  • An experiment using the Eurogam phase II {gamma}-ray spectrometer confirms the existence of an excited superdeformed (SD) band in {sup 190}Hg and its very unusual decay into the lowest SD band over 3--4 transitions. The energies of the transitions linking the two SD bands have been firmly established, and their angular distributions are consistent with a dipole character. Comparisons with calculations using random-phase approximation indicate that the excited SD band can be interpreted as an octupole-vibrational structure.
  • An excited superdeformed (SD) band has been observed in {sup 19O}Hg which decays to the lowest-energy (yrast) SD band rather than to the less deformed states as observed in most known SD bands in the A{approximately}150 and A{approximately}190 regions. The band exhibits properties which are in good agreement with predictions of collective octupole vibrations in the SD well of {sup 19O}Hg.
  • Gammasphere experiments in 1993-94 brought to light the existence of an excited superdeformed (SD) band in {sup 190}Hg with the unusual property of decaying entirely to the lowest (yrast) SD band over 3-4 transitions, rather than to the normally deformed states as is usually the case in the A {approximately} 150 and A {approximately} 190 regions of superdeformation. Although M1 transitions between signature-partner SD bands were previously observed in {sup 193}Hg, no such mechanism was available to explain the situation in the even-even nucleus {sup 190}Hg, whose yrast SD band has no signature partner. The best explanation appears to liemore » in long-standing theoretical predictions that the SD minimum in the potential energy surface would be quite soft with respect to octupole vibrations. This would lead to enhanced E1 transitions connecting the one-phonon and zero-phonon states. The data and this interpretation were published. A shortcoming of the Gammasphere experiments was that they did not allow the definitive measurement of the energies of the gamma-ray transitions connecting the two bands, due to the very weak population of the excited band ({approximately}0.05% of the {sup 190}Hg channel) and also partly, we believed, to the angular distributions of the transitions, which were peaked near 90 degrees, where Gammasphere had few detectors.« less
  • A Comment on the Letter by Cullen {ital et} {ital al}., Phys. Rev. Lett. 65, 1547 (1990).