Remeasuring the anomalously enhanced B(E2; 2⁺ → 1⁺) in ⁸Li

2021/09/13 by Henderson, S. L., Ahn, T., Fasano, P. J. +14
#FOS: Physical sciences #Nuclear Experiment (nucl-ex) #Nuclear Theory (nucl-th)

paper · doi:10.48550/arxiv.2109.06081

Abstract

The large reported E2 strength between the 2⁺ ground state and 1⁺ first excited state of \isotope[8]Li, B(E2; 2⁺ → 1⁺)= 55(15) e²\fm⁴, presents a puzzle. Unlike in neighboring A=7--9 isotopes, where enhanced E2 strengths may be understood to arise from deformation as rotational in-band transitions, the 2⁺→1⁺ transition in ⁸Li cannot be understood in any simple way as a rotational in-band transition. Moreover, the reported strength exceeds ab initio predictions by an order of magnitude. In light of this discrepancy, we revisited the Coulomb excitation measurement of this strength, now using particle-γ coincidences, yielding a revised B(E2; 2⁺ → 1⁺) of 19(⁺⁷_-6)(2)~e²fm⁴. We explore how this value compares to what might be expected in the limits of rotational models. While the present value is about a factor of three smaller than previously reported, it remains anomalously enhanced.

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