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Title: Fragmentation of two-phonon {gamma}-vibrational strength in deformed nuclei

Abstract

Rotational and vibrational modes of collective motion. are very useful in classifying the low-lying excited states in deformed nuclei. The rotational mode of collective motion is characterized by rotational bands having correlated level energies and strongly-enhanced E2 matrix elements. The lowest intrinsic excitation with I,K{sup {pi}} = 2,2{sup +} in even-even deformed nuclei, typically occurring at {approx}1 MeV, is classified as a one-phonon {gamma}-vibration state. In a pure harmonic vibration limit, the expected two-phonon {gamma}-vibration states with I,K{sup {pi}} = 0,0{sup +} and 4,4{sup +} should have excitation energies at twice that of the I,K{sup {pi}} = 2,2{sup +} excitation, i.e. {approx}2 MeV, which usually is above the pairing gap leading to possible mixing with two-quasiparticle configurations. Therefore, the question of the localization of two-phonon {gamma}-vibration strength has been raised because mixing may lead to fragmentation of the two-phonon strength over a range of excitation energy. For several well-deformed nuclei, an assignment of I,K{sup {pi}}=4,4{sup +} states as being two-phonon vibrational excitations has been suggested based on the excitation energies and the predominant {gamma}-ray decay to the I,K{sup {pi}}=2,2{sup +} state. However, absolute B(E2) values connecting the presumed two- and one-phonon states are the only unambiguous measure of double phononmore » excitation. Such B(E2) data are available for {sup 156}Gd, {sup 160}Dy, {sup 168}Er, {sup 232}Th, and {sup 186,188,190,192}Os. Except for {sup 160}Dy, the measured B(E2) values range from 2-3 Weisskopf units in {sup 156}Gd to 10-20 Weisskopf units in osmium nuclei; enhancement that is consistent with collective modes of motion.« less

Authors:
;  [1]
  1. Univ. of Rochester, NY (United States)
Publication Date:
Research Org.:
Argonne National Lab., IL (United States)
OSTI Identifier:
458928
Report Number(s):
ANL/PHY-97/1; CONF-9607156-
ON: DE97003376; TRN: 97:007001
Resource Type:
Conference
Resource Relation:
Conference: Conference on nuclear structure at the limits, Argonne, IL (United States), 22-26 Jul 1996; Other Information: PBD: 1996; Related Information: Is Part Of Proceedings of the conference on nuclear structure at the limits; PB: 391 p.
Country of Publication:
United States
Language:
English
Subject:
66 PHYSICS; DEFORMED NUCLEI; OSCILLATION MODES; COLLECTIVE EXCITATIONS; NUCLEAR MODELS; OSCILLATOR STRENGTHS; FRAGMENTATION; ROTATION; PHONONS; VIBRATIONAL STATES

Citation Formats

Wu, C Y, and Cline, D. Fragmentation of two-phonon {gamma}-vibrational strength in deformed nuclei. United States: N. p., 1996. Web.
Wu, C Y, & Cline, D. Fragmentation of two-phonon {gamma}-vibrational strength in deformed nuclei. United States.
Wu, C Y, and Cline, D. Tue . "Fragmentation of two-phonon {gamma}-vibrational strength in deformed nuclei". United States. https://www.osti.gov/servlets/purl/458928.
@article{osti_458928,
title = {Fragmentation of two-phonon {gamma}-vibrational strength in deformed nuclei},
author = {Wu, C Y and Cline, D},
abstractNote = {Rotational and vibrational modes of collective motion. are very useful in classifying the low-lying excited states in deformed nuclei. The rotational mode of collective motion is characterized by rotational bands having correlated level energies and strongly-enhanced E2 matrix elements. The lowest intrinsic excitation with I,K{sup {pi}} = 2,2{sup +} in even-even deformed nuclei, typically occurring at {approx}1 MeV, is classified as a one-phonon {gamma}-vibration state. In a pure harmonic vibration limit, the expected two-phonon {gamma}-vibration states with I,K{sup {pi}} = 0,0{sup +} and 4,4{sup +} should have excitation energies at twice that of the I,K{sup {pi}} = 2,2{sup +} excitation, i.e. {approx}2 MeV, which usually is above the pairing gap leading to possible mixing with two-quasiparticle configurations. Therefore, the question of the localization of two-phonon {gamma}-vibration strength has been raised because mixing may lead to fragmentation of the two-phonon strength over a range of excitation energy. For several well-deformed nuclei, an assignment of I,K{sup {pi}}=4,4{sup +} states as being two-phonon vibrational excitations has been suggested based on the excitation energies and the predominant {gamma}-ray decay to the I,K{sup {pi}}=2,2{sup +} state. However, absolute B(E2) values connecting the presumed two- and one-phonon states are the only unambiguous measure of double phonon excitation. Such B(E2) data are available for {sup 156}Gd, {sup 160}Dy, {sup 168}Er, {sup 232}Th, and {sup 186,188,190,192}Os. Except for {sup 160}Dy, the measured B(E2) values range from 2-3 Weisskopf units in {sup 156}Gd to 10-20 Weisskopf units in osmium nuclei; enhancement that is consistent with collective modes of motion.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1996},
month = {12}
}

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