Collectivity in ‘‘spherical’’ Eu143,144 nuclei

Long cascades of stretched E2 transitions have been observed in Eu-143 and Eu-144 nuclei which at low excitation exhibit spherical shape. Lifetime experiments demonstrate high collectivity values up to B(E2)approximate to 100 W.u. among these E2 cascades. The total Routhian surface calculations indicate many crossing rotational bands of the nucleus with triaxial shape at beta(2) approximate to 0.25 and gamma approximate to 30 degrees. The E2 cascades in Eu-143 are proposed to represent the nu h(11/2)(2) pi h(11/2)(n) configurations with an additional nu(3/2)(-1)i(13/2) excitation at the highest states.