利用核共振荧光技术研究$^{68}$Zn低自旋态下的核心破裂
Core Breaking at Low Spin in $^{68}$Zn from Nuclear Resonance Fluorescence
AI总结：
本研究借助HIγS的NRF技术与Clover Array，确定$^{68}$Zn低自旋态的自旋-宇称等参数，发现~5 MeV以上激发能处总M1强度演化需核心破裂机制，为该核结构研究提供关键实验与理论依据。
AI中文摘要：
本研究在高强度伽马射线源（HIγS），采用核共振荧光技术（NRF）和新研发的四极阵列（Clover Array），对$^{68}$Zn的低自旋激发态从基态到粒子发射阈值展开研究。利用2.90-9.79 MeV的线偏振光子束激发低自旋能级，对观测到的158个态中的大部分，确定了自旋-宇称量子数及相关的M1和E1衰变强度。此外，在9.46和9.79 MeV开展的长时符合测量，可对基态附近的能级纲图进行研究。研究结果采用壳模型计算解释，使用了两种不同模型空间及多个常用于描述该质量区原子核的有效相互作用。基态附近的结构可仅通过价核子激发来理解，而要解释~5 MeV以上激发能处总M1强度的演化，则需引入核心破裂机制。
英文摘要：
Low-spin excited states in $^{68}$Zn have been studied at the High Intensity Gamma-Ray Source (HI$γ$S) from the ground state up to the particle emission threshold using the nuclear resonance fluorescence technique (NRF) and the newly developed Clover Array. Low-spin levels were excited by linearly-polarized, $2.90 - 9.79$ MeV photon beams. Spin-parity quantum numbers as well as associated $M1$ and $E1$ decay strengths were determined for a large fraction of the 158 states observed. In addition, long-duration coincidence measurements at 9.46 and 9.79 MeV enabled the investigation of the level scheme near the ground state. The results have been interpreted with shell-model calculations using two different model spaces and several effective interactions often used to describe nuclei in this mass region. While the structure near the ground state can be understood in terms of excitations involving solely valence nucleons, core breaking is required to account for the evolution of the total $M1$ strength at excitation energies above $\sim5$ MeV.
