High-spin alpha formation beyond 208Pb: Revealing interference phases in quartetting and alpha clustering

The complexity of microscopic nuclear many-body wave functions hindered a deeper understanding of nucleon clustering driven by complex nucleon-nucleon correlations. To address this, a universal four-fermion formation framework (U4F) is developed within the configuration-interaction shell model. The U4F enables microscopic analysis of the α component in mixed quartet configurations and reveals the correlation between α formation and the underlying nucleon-nucleon interaction, with consideration of full many-body correlations within a model space. The α formation in the α -decaying yrast band and high-spin isomer of 212 Po is investigated using the U4F. Theoretical results agree with the α formation amplitude extracted from the measured α decay half-life and decay energy. The analysis shows that the reduction of α formation with increasing spin in the yrast band arises from the competition between the growing purity of quartet configurations and the diminishing realistic α component within them. Finally, the α -decaying 18 + isomer of 212 Po is suggested as an α -reducing phase generated by the mixing of the 18 1 + and 18 2 + states.