Two-quasiproton states in 168Er studied by the reaction |
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Authors: | D.G. Burke W.F. Davidson J.A. Cizewski Ronald E. Brown J.W. Sunier |
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Affiliation: | Tandem Accelerator Laboratory, McMaster University, Hamilton, Ontario, Canada, L8S 4K1;Division of Physics, National Research Council, Ottawa, Ontario, Canada, K1A 0R6;A.M. Wright Nuclear Structure Laboratory, Yale University, New Haven, CT 06511, USA;Los Alamos National Laboratory, Los Alamos, NM 87545, USA |
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Abstract: | The reaction has been studied using 17 MeV polarized tritons from the Los Alamos National Laboratory tandem Van de Graaff accelerator. The α-spectra were analyzed with a Q3D magnetic spectrometer. The overall energy resolution was typically ~ 15 keV (FHWM) and angular distributions of cross sections and analyzing powers were obtained for levels up to ~ 2.7 MeV. The fact that spins and parities for all levels up to ? 2 MeV were previously known from an extensive series of (n, γ) studies made it possible to determine specific two-quasiproton structures for many bands from the present results. The Kπ = 2+ γ-vibrational band was found to have a large admixture, consistent with the predicted microscopic composition of this phonon, but no component was observed. The Kπ = 04+ band at 1833 keV has ~ 25% of the two-quasiproton strength. This is in excellent agreement with the Soloviev model but is inconsistent with the interacting boson model, in which the Kπ = 04+ band is composed almost completely of multiphonon configurations that should not be populated in a single-nucleon transfer reaction. The two-quasiproton and the two-quasineutron states are mixed strongly with each other, but the two Kπ = 3? bands composed of antiparallel couplings of the same particles are not. A good qualitative explanation of this mixing pattern is provided in terms of the effective neutron-proton interaction. |
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Keywords: | Nuclear reactions |
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