Shape transitional aspects of odd-AEu isotopes studied by the (p, t) reaction

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Abstract
The abrupt shape transition as is observed around N≃88−90 in even nuclei has been examined for the odd-A Eu isotopes Eu88151 and Eu86149 by the (p, t) reaction at 18.5 and 19.0 MeV with an average resolution of 10 keV. Angular distributions, taken from 10 to 70°, enabled unambiguous indentification of many L=0 (Jfπ=52+) transitions in both residual nuclei; seven for Eu151 and seven or eight for Eu149. The summed L=0 cross sections are close to those of the (p, t) reactions for the neighboring even-A Sm isotopes connecting the same neutron numbers. A number of new levels have been found in both isotopes. We have obtained markedly different level structures for the two neighboring isoptopes. In Eu151, whose ground state and low-lying states below 200 keV can be described in terms of spherical shell-model configurations, two deformed bands have been tentatively identified. One of these is a 52+[413] band with members at 261 keV, 52+; 414 keV, (72+); and possibly a 597 keV, (92+) member. In addition a 52+[413] β band is postulated with members at 654 keV, 52+; 801 keV, (72+). These deformed states, coexisting with the spherical states, have been strongly excited while the spherical low-lying states have shown vanishingly small (p, t) cross sections. The (p, t) cross sections to the Eu151 states were found to be in strong anticorrelation with B(E2) values from Coulomb excitation and (