First Measurement of Collectivity of Coexisting Shapes Based on Type II Shell Evolution: The Case of Zr96.

Background: Type II shell evolution has recently been identified as a microscopic cause for nuclear shape coexistence. Purpose: Establish a low-lying rotational band in Zr96. Methods: High-resolution inelastic electron scattering and a relative analysis of transition strengths are used. Results: The B(E2;0+1→2+2) value is measured and electromagnetic decay strengths of the 2+2 state are deduced. Conclusions: Shape coexistence is established for Zr96. Type II shell evolution provides a systematic and quantitative mechanism to understand deformation at low excitation energies. [ABSTRACT FROM AUTHOR]