Unified studies of chemical bonding structures and resonant scattering in light neutron-excess systems, 10,12Be
Unified studies of chemical bonding structures and resonant scattering in light neutron-excess systems, 10,12Be
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DOI：
10.1088/0034-4885/77/9/096301
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发表时间：
2014-09
影响因子：
18.1
通讯作者：
Makoto Ito;K. Ikeda
中科院分区：
文献类型：
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作者：
Makoto Ito;K. Ikeda
在微观团簇模型的基础上，建立了广义双中心团簇模型，该模型可以处理一般双惰性核+价核子体系的共价组态、离子组态和原子组态。在该模型中，由分子轨道(MO)方法构建的共价组态和由价键(VB)方法得到的原子(或离子)组态可以以一致的方式处理。将该方法应用于轻丰中子系统10，12Be=α+α+Xn(X=2，4)。在绝热能面中可以清楚地观察到中子轨道从共价MO态到离子VB态的连续而平滑的变化，这是随着α-α距离的变化而得到的能量曲线。从俄歇电子能谱获得的能级很好地再现了最近在大范围能量区域内的观测结果。根据对其本征波函数的分析，用类化学键的结构来表征各个光谱，如共价MO结构或离子VB结构。从俄歇电子能谱的分析出发，研究了10，12Be的神秘态的形成，这些态的激发能比朴素的壳层模型预测的要小。在从基态MO态到离子α+6，8He VB态的单极跃迁中发现了很大的增强，这似乎与最近的观察一致。在非束缚区，将α+α+Xn(X=2，4)体系作为束缚态或准束缚态处理的结构问题，以及由α+6，8He的渐近VB态碰撞引起的反应问题，用广义量子模型结合起来。结合反应机理讨论了非束缚共振态的性质，并在反应可观测值中预测了一些源于本征态性质的增强因子。
The generalized two-center cluster model (GTCM), which can treat covalent, ionic and atomic configurations in general systems with two inert cores plus valence nucleons, is formulated in the basis of the microscopic cluster model. In this model, the covalent configurations constructed by the molecular orbital (MO) method and the atomic (or ionic) configuration obtained by the valence bonding (VB) method can be handled in a consistent manner. The GTCM is applied to the light neutron-rich system 10,12Be = α + α + Xn (X = 2, 4). The continuous and smooth changes of the neutron orbits from the covalent MO states to the ionic VB states are clearly observed in the adiabatic energy surfaces (AESs), which are the energy curves obtained with a variation of the α–α distance. The energy levels obtained from the AESs nicely reproduce the recent observations over a wide energy region. The individual spectra are characterized in terms of chemical-bonding-like structures, such as the covalent MO or ionic VB structures, according to analysis of their intrinsic wave functions. From the analysis of AESs, the formation of the mysterious states in 10,12Be, which have anomalously small excitation energies in comparison to a naive shell-model prediction, is investigated. A large enhancement in a monopole transition from a ground MO state to an ionic α + 6,8He VB state is found, which seems to be consistent with a recent observation. In the unbound region, the structure problem, which handles the total system of α + α + Xn (X = 2, 4) as a bound or quasi-bound state, and the reaction problem, induced by the collision of an asymptotic VB state of α + 6,8He, are combined by the GTCM. The properties of unbound resonant states are discussed in close connection to the reaction mechanism, and some enhancement factors originating from the properties of the intrinsic states are predicted in the reaction observables.