First Measurement of Collectivity of Coexisting Shapes based on Type II Shell Evolution: The Case of $^{96}$Zr

TL;DR

This paper reports the first measurement of shape coexistence in 96-Zr, demonstrating how Type II shell evolution explains nuclear deformation and establishing a low-lying rotational band through electron scattering experiments.

Contribution

It provides the first experimental evidence linking Type II shell evolution to shape coexistence in 96-Zr, offering a systematic understanding of nuclear deformation.

Findings

Shape coexistence confirmed in 96-Zr.

Measured B(E2) transition strength for 0_1^+ to 2_2^+.

Electromagnetic decay strengths of the second 2^+ state deduced.

Abstract

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 secdond 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.