分类： 物理学 >> 核物理学 提交时间： 2024-04-01
摘要： Using two nuclear models, i) the relativistic continuum Hartree-Bogoliubov (RCHB) theoryand ii) the Weizs acker-Skyrme (WS) model WS$^ ast$,the performances of nine kinds of kernel functions in the kernel ridge regression (KRR) methodare investigated by comparing the accuracies of describing the experimental nuclear chargeradii and the extrapolation abilities.It is found that, except the inverse power kernel, other kernels can reach the same levelaround 0.015-0.016~fm for these two models with KRR method.The extrapolation ability for the neutron rich region of each kernel depends on the trainning data.Our investigation shows that the performances of the power kernel and Multiquadric kernel arebetter in the RCHB+KRR calculation, and the Gaussian kernel is better in the WS$^ ast$+KRR calculation.In addition, the performance of different basis functions inthe radial basis function method is also investigated for comparison.The results are similar to the KRR method.The influence of different kernels on the KRR reconstruct function is discussedby investigating the whole nuclear chart.At last, the charge radii of some specific isotopic chains have been investigatedby the RCHB+KRR with power kernel and the WS$^ ast$+KRR with Gaussian kernel.The charge radii and most of the specific features in these isotopic chainscan be reproduced after considering the KRR method.
分类： 物理学 >> 核物理学 提交时间： 2023-12-13
摘要： The extended kernel ridge regression (EKRR) method with odd-even effects was adopted to improve the de charge radius using five commonly used nuclear models.These are: (i) the isospin dependent $A^{1/3}$ formula(ii) relativistic continuum Hartree-Bogoliubov (RCHB) theory(iii) Hartree-Fock-Bogoliubov (HFB) model HFB25(iv) the Weizs acker-Skyrme (WS) model WS$^ ast$,(v) HFB25$^ ast$ model.In the last two models, the charge radii were calculated using a five-parameter formulawith the nuclear shell corrections and deformations obtained from the WS and HFB25 models, respectively.For each model, the resultant root-mean-square deviation for the 1014 nucleiwith proton number $Z geq 8$ can be significantly reducedto 0.009-0.013~fm after considering the modification with the EKRR method.The best among them was the RCHB model, with a root-mean-square deviation of 0.0092~fm.The extrapolation abilities of the KRR and EKRR methods for the neutron-rich region were examined and it was found that afterconsidering the odd-even effects,the extrapolation power was improved compared with that of the original KRR method.The strong odd-even staggering of nuclear charge radii of Ca and Cu isotopesand the abrupt kinks across the neutron $N=126$ and 82 shell closures were alsocalculated and could be reproduced quite well by calculations using the EKRR method.
分类： 物理学 >> 核物理学 提交时间： 2017-08-22
摘要： The recently observed high-spin rotational bands in odd-A nuclei 247,249Cm and 249Cf [Tandel et al., Phys. Rev. C 82 (2010) 041301R] are investigated by using the cranked shell model (CSM) with the pairing correlations treated by a particle-number conserving (PNC) method in which the blocking effects are taken into account exactly. The experimental moments of inertia and alignments and their variations with the rotational frequency ω are reproduced very well by the PNC-CSM calculations. By examining the ω-dependence of the occupation probability of each cranked Nilsson orbital near the Fermi surface and the contributions of valence orbitals to the angular momentum alignment in each major shell, the level crossing and upbending mechanism in each nucleus is understood clearly.
分类： 物理学 >> 核物理学 提交时间： 2017-08-22
摘要： The rotational bands in nuclei with Z ≈ 100 are investigated systematically by using a cranked shell model (CSM) with the pairing correlations treated by a particle-number conserving (PNC) method, in which the blocking effects are taken into account exactly. By fitting the experimental single-particle spectra in these nuclei, a new set of Nilsson parameters (κ and μ) and deformation parameters (ε2 and ε4) are proposed. The experimental kinematic moments of inertia for the rotational bands in even-even, odd-A and odd-odd nuclei, and the bandhead energies of the 1- quasiparticle bands in odd-A nuclei, are reproduced quite well by the PNC-CSM calculations. By analyzing the ω-dependence of the occupation probability of each cranked Nilsson orbital near the Fermi surface and the contributions of valence orbitals in each major shell to the angular momentum alignment, the upbending mechanism in this region is understood clearly.
分类： 物理学 >> 核物理学 提交时间： 2017-07-30
摘要： The effects of nuclear superfluidity on antimagnetic rotation bands in 105Cd and 106Cd are in- vestigated by the cranked shell model with the pairing correlations and the blocking effects treated by a particle-number conserving method. The experimental moments of inertia and the reduced B(E2) transition values are excellently reproduced. The nuclear superfluidity is essential to repro- duce the experimental moments of inertia. The two-shears-like mechanism for the antimagnetic rotation is investigated by examining the shears angle, i.e., the closing of the two proton hole angular momenta, and its sensitive dependence on the nuclear superfluidity is revealed.
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