We apply the no-core shell model to the nuclear structure of odd-mass nuclei straddling $^{48}$Ca. Starting with the NN interaction, that fits two-body scattering and bound state data we evaluate the nuclear properties of $A = 47$ and $A = 49$ nuclei while preserving all the underlying symmetries. Due to model space limitations and the absence of 3-body interactions, we incorporate phenomenological interaction terms determined by fits to $A = 48$ nuclei in a previous effort. Our modified Hamiltonian produces reasonable spectra for these odd mass nuclei. In addition to the differences in single-particle basis states, the absence of a single-particle Hamiltonian in our no-core approach complicates comparisons with valence effective NN interactions. We focus on purely off-diagonal two-body matrix elements since they are not affected by ambiguities in the different roles for one-body potentials and we compare selected sets of $fp$-shell matrix elements of our initial and modified Hamiltonians in the harmonic oscillator basis with those of a recent model $fp$-shell interaction, the GXPF1 interaction of Honma, Otsuka, Brown and Mizusaki. While some significant differences emerge from these comparisons, there is an overall reasonably good correlation between our off-diagonal matrix elements and those of GXPF1.
By using a phenomenologically successful Woods-Saxon potential, I study the shape and shell structure of (A) neutron drip line nuclei with 10 \leq N \leq 60, (B) neutron-rich nuclei related to the r- process with 40 \leq N \leq 90, and (C) one-particle spectra in the potential provided by the nucleus 70Fe as a representative of so-called N=40 "island of inversion (IoI)" nuclei. First, the shell structure that is unique in very weakly-bound neutrons is systematically studied, and the approximate neutron number of odd-N nuclei at which spherical (or deformed) halos can be found is pinned down. S…
In this work we present $ab~initio$ shell-model calculations for electric quadrupole moments and magnetic dipole moments of $sd$ shell nuclei using valence-space Hamiltonians derived with two $ab~initio$ approaches: the in-medium similarity renormalization group (IM-SRG) and the coupled-cluster effective interaction (CCEI). Results are in a reasonable agreement with the available experimental data as well as with the results from the phenomenological USDB effective interaction. This work will add more information to the available $ab~initio$ results for the spectroscopy of $sd$ shell nuclei.
Shell-model calculation with density-dependent interaction for $pf$-shell nuclei
Graduate School of Science and Technology, University of Tsukuba（筑波大学科学技术研究院）；Center for Computational Sciences and Institute of Pure and Applied Sciences, University of Tsukuba（筑波大学计算科学中心及纯应用科学研究所）；RIKEN Nishina Center（理化学研究所仁科研究中心）
The shell corrections and shell gaps in nuclei are systematically studied with the latest Weizsäcker-Skyrme (WS4) mass model. We find that most of asymmetric nuclei with (sub)-shell closures locate along the shell stability line (SSL), $N=1.37Z+13.5$, which might be due to a strong correlation between neutrons and protons near Fermi surface. The double magicity of nuclei $^{46}$Si and $^{78}$Ni is predicted according to the corresponding shell gaps, shell corrections and nuclear deformations. The unmeasured super-heavy nuclei $^{296}$118 and $^{298}$120, with relatively large shell gaps and sh…
We merge two successful ab initio nuclear-structure methods, the no-core shell model (NCSM) and the multi-reference in-medium similarity renormalization group (IM-SRG) to define a new many-body approach for the comprehensive description of ground and excited states of closed and open-shell nuclei. Building on the key advantages of the two methods---the decoupling of excitations at the many-body level in the IM-SRG and the access to arbitrary nuclei, eigenstates, and observables in the NCSM---their combination enables fully converged no-core calculations for an unprecedented range of nuclei and…
Spectroscopic factors involving well bound nucleons in light nuclei are calculated with standard shell model, no-core shell model and Gamow shell model. Continuum coupling is included exactly in the Gamow shell model, due to the use of the Berggren basis, which contains bound, resonance and scattering states. Conversely, it is absent from standard and no-core shell models, where a basis of harmonic oscillator states is used. As the A - 1 nuclei for which spectroscopic factors are calculated are either weakly bound or unbound, coupling to continuum is prominent, even though the A nuclei are wel…
The basic version of the semi-microscopic particle-hole dispersive optical model is implemented to describe main properties of the Gamow-Teller and charge-exchange giant spin-monopole resonances in medium-heavy closed-shell parent nuclei. Calculation results obtained for $^{48}Ca$, $^{90}Zr$, $^{132}Sn$, and $^{208}Pb$ are compared with available experimental data.
The one- plus two-body isospin nonconserving nuclear interactions are included in the prediction of ground state energies of fp shell nuclei using spectral distribution theory. This in turn is used to calculate the linear term in the isobaric mass-multiplet equation and the predictions are then compared to experimental values after the addition of the Coulomb contribution. The agreement is found to be reasonable as observed for sd shell nuclei earlier. One also sees that in this method the contribution to the linear term comes almost completely from the one body isovector Hamiltonian and that …
Gamow-Teller strength distributions in fp-shell nuclei
我们使用壳模型蒙特卡罗方法计算完整的0 f1 p壳响应函数的Gamow-Teller（GT）运营商，并获得相应的强度分布，使用最大熵技术。对48 Ti的直接对角化验证了该方法。计算的GT强度分布与A=48-64的核（n，p）和（p，n）反应的数据吻合得很好。我们还计算了代表性核的GT+分布的温度演化，发现随着温度的升高，GT+分布变宽，质心向低能移动。
We introduce a hybrid many-body approach that combines the flexibility of the No-Core Shell Model (NCSM) with the efficiency of Multi-Configurational Perturbation Theory (MCPT) to compute ground- and excited-state energies in arbitrary open-shell nuclei in large model spaces. The NCSM in small model spaces is used to define a multi-determinantal reference state that contains the most important multi-particle multi-hole correlations and a subsequent second-order MCPT correction is used to capture additional correlation effects from a large model space. We apply this new ab initio approach for t…
