g玻色子对^(100)Pd核高自旋态能谱的影响

Effect of g-Boson on Spectra of High-Spin States in ^(100)Pd Nucleus

以新近的实验单粒子能量为输入,应用唯象sdgIBM理论的两种微观实现——微观sdgIBM-2方案和sdgIBM-Fmax方案,仔细研究100Pd的核能谱和B(E2)跃迁。计算结果表明:sdgIBM-2方案成功地再现了100Pd核的较复杂的基态带和γ带的高角动量态能谱以及已知的B(E2)跃迁,其再现角动量达Jπ=16+、Ex≈7.00 MeV,比通常IBM理论再现的Jπ=6+~8+、Ex≈2.00 MeV高出很多;指认直到16+的yrast态都是基态,很可能目前观测到的yrast带中根本就不存在玻色子破对后的准粒子态。理论分析和数值计算进一步表明,为了能在IBM理论框架下描述好核的高角动量基态,需要平权地引入g玻色子,以便提供较强的十六极对相互作用,抵抗住高速转动下玻色子的破对趋势。用g玻色子数为0~3的弱耦合sdgIBM-Fmax方案的计算结果对此作了进一步说明。按照微观sdgIBM-2方案,解释了实验上3个14+态的异常:141+态是由于1个中子g玻色子在转变为中子d玻色子的量子相变中辐射出1对光子的结果,142+是161+态退耦的中间态,而143+是真正的基态。

By using a microscopic sdgIBM-2 approach which is the accomplishment of the phenomenological sdgIBM theory and the experimental single-particle energies, the levels of the more complex ground-state band and the high-angular momentum states of y-band on ^100 Pd nucleus are successfully reproduced. The ground-state band and γ-band are described well up to J^n=16＋ and Ex≈7.00 MeV, and that is larger than that J^n= 6^＋-8^＋, Ex ≈2.00 MeV can be successfully reproduced in IBM theory. It has been proved that its yrast states up to the 16^＋ state are ground states, there may not exist any broken pair quasi-particle state by boson in yrast states. Theoretical analysis and numerical calculation show that to describe successfully spectra on ^100 Pd nucleus under the boson approach in IBM theory, it is impossible that the g-boson has been not considered in one. According to the microscopic sdgIBM-2 approach, the 14^＋ state is understood as a result that a neutron g-boson transites into a neutron d-boson and a pair of photos is radiated at same time, and the 14^＋ state is the decoupling state of the 16^＋ state, while the 14^＋ state is the actual ground state.