基于协变密度泛函理论研究原子核低激发态中的对振动效应

Nuclear low-lying excited spectra is nowadays one of the most important frontiers of nuclear physics. The model of nuclear low-lying excitation not only include shape vibration excitation,rotation excitation, but also include pairing vibration excitation. Collective Hamiltonian based on covariant density functional theory can research nuclear low-lying spectra systematic, providing a powerful tool for nuclear low-lying spectra research. The Collective Hamiltonian don’t include pairing vibration degree of freedom. In this project, starting from covariant density functional theory, the Collective Hamiltonian including degree of freedom of pairing fluctuation will be established, and this method will be subsequently applied to study the influence of nuclear pairing vibration to nuclear low-laying excited spectra and heavy-ion fusion reaction cross section. The implementation of this project will, on one hand, study the influence of nuclear pairing vibration to nuclear low-laying spectra, especially to 0+ low-laying excited state, by comparing including pairing vibration and not including pairing vibration collective Hamiltonian calculation. On the other hand, calculate the heavy-ion fusion reaction cross section，with the nuclear low-lying excited spectra as input from the collective Hamiltonian including pairing vibration. Comparing the reaction cross section, which input from axial symmetry collective Hamiltonian calculation, the role of nuclear pairing vibration to the heavy-ion fusion reaction cross sections will be described.

原子核低激发谱是当今原子核研究的重要前沿之一。原子核低能激发模式不但包括形状振动激发、转动激发，还包括对振动激发。基于协变密度泛函的集体哈密顿量理论可系统研究原子核低激发谱，为原子核低激发谱研究提供了有力的理论工具。但目前的集体哈密顿量没有包含对振动自由度。项目拟基于协变密度泛函理论发展包含对振动的集体哈密顿量，开展原子核对振动对原子核低激发谱及重离子融合反应截面影响的研究。本项目的实施，一方面，通过比较是否包含对振动自由度的集体哈密顿量计算得到的低激发谱，研究原子核对振动对原子核低激发谱，尤其是对0+激发态的影响。另一方面，利用包含对振动的集体哈密顿量计算融合反应靶核的低激发谱为输入量，计算重离子融合反应截面，并与以轴对称集体哈密顿量计算结果为输入量的计算结果比较，研究原子核对振动对重离子融合反应的影响。

对振动对原子核低激发谱及无中微子双beta衰变矩阵元等物理量的描述有重要影响。基于协变密度泛函的集体哈密顿量理论可系统研究原子核低激发谱，为原子核低激发谱研究提供了有力的理论工具。但目前的集体哈密顿量没有包含对振动自由度。本项目基于协变密度泛函理论发展了包含对振动的集体哈密顿量，实现了对原子核低激发谱中对振动效应的统一、微观、自洽描述。采用新发展的理论模型研究了N=92稀土区同中子素链低激发谱中的对振动效应，指示考虑对振动自由度以后，0+激发态能量及其电单极跃迁强度均降低，同时与实验值符合更好。同时，我们构建了基于协变密度泛函理论的包含三轴自由度与对振动自由度的相互作用玻色子模型，并用于对gamma-软 Xe、Os及Pt同位素链低激发谱中对振动效应的研究。基于项目的支持，我们还对原子核形状演化，形状共存、气泡结构开展了原创性的研究工作。