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

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 ^{96}Zr. 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 ^{96}Zr. Type II shell evolution provides a systematic and quantitative mechanism to understand deformation at low excitation energies.