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In this contribution, we give a brief overview over the historical development of shell-model-related experimental and theoretical nuclear physics activities at KTH Royal Institute of Technology that benefited from the classic Kuo–Brown interaction and the fundamental insight of Kuo on the core polarization effect. [ABSTRACT FROM AUTHOR]

In this paper, we discuss isospin analogues of the tetraneutron resonance and their possible manifestations in nuclear structure and reactions. [ABSTRACT FROM AUTHOR]

The possibilities of using modern ab initio approaches to describe various cluster and decay characteristics of light nuclei and nuclear reactions induced by their collisions, the limits of these possibilities and prospects for expanding these boundaries are discussed. The quality of the description of the spectra of nuclear energy levels, the probabilities of emission of nucleons and clusters by resonant states, the amplitudes of the reduced decay widths of these states and the asymptotic normalization coefficients of bound states are analyzed. It is demonstrated that the results of ab initio calculations of the above characteristics can in many cases be useful for describing and predicting cross-sections for resonant nuclear reactions and analyzing the results of their measurements. [ABSTRACT FROM AUTHOR]

In this paper, the nuclear structure and some prospective decay properties of the 128−208Sm62 elements are studied. This is accomplished by using an axially deformed oscillator basis and the Relativistic Mean Field model (RMF) with PK1 and NL-SH force parameters. The bulk characteristics are carefully examined, including the binding energy (B.E./A), nuclear radii,quadrupole deformation parameter(β2), two neutron separation energy (S2n), and differential change of two neutron separation energy (dS2n). Estimates are also made for the half-lives of the Sm isotopes for α-decay, β-decay and spontaneous fission (SF). Both our computed Q-values and empirically measurable Q-values are used to determine the α-decay half-life periods using the MUDL and AKRE formulae. The results we anticipate could be useful for experiments and future perspective. [ABSTRACT FROM AUTHOR]

The positive and negative parity rotational band structures of odd–odd Nb isotopes with atomic masses 90, 92 and 94 are investigated using the theoretical framework of the projected shell model. These odd–odd nuclei are found to be ideal for investigating the significant structural changes occurring in the region situated far from the valley of stability. This is the first time that such comprehensive theoretical data for both positive and negative parities together for the odd–odd 9 0 − 9 4 Nb isotopes have been disclosed. The g-factor and electromagnetic transition probabilities are among the various nuclear structure quantities that are examined for the first time. Using a broad configuration space for both protons and neutrons, the computed data have been anticipated up to high spin values. [ABSTRACT FROM AUTHOR]

The microscopic variant of the Grodzins relation and the Quasiparticle Phonon Model are applied to predict the excitation energies of the 2 1 + states of neutron-deficient U and Pu isotopes. The P-factor systematics is used to determine the quadrupole deformation of nuclei under consideration. The excitation energies of the 4 1 + states are predicted based on the simple universal anharmonic vibrator-type relation. [ABSTRACT FROM AUTHOR]

Role of effective interaction potential in shears band structure in 2 0 4 At has been investigated in more detail than in previous studies. A semi-classical geometric model is used to obtain the interaction strengths between valence protons and neutron holes constituting the shears blades. The value produces overall good agreement with this region's nuclei. Band crossing is observed in the spin-parity range 1 6 + – 2 3 + . Configurations of the Magnetic Rotational (MR) band are assigned in the light of the Shears mechanism with the Principal Axis Cranking (SPAC) model. Experimental rotational frequencies and the deduced ratio of B (M 1) / B (E 2) are well reproduced by SPAC calculations, suggesting the dipole band in 2 0 4 At can undoubtedly be interpreted as the MR band resulting from the effective interaction of repulsive potential. [ABSTRACT FROM AUTHOR]

The cluster radioactivity of 2 2 2 , 2 2 4 , 2 2 6 Ra, 2 2 3 , 2 2 5 Ac, 2 3 2 , 2 3 4 , 2 3 5 , 2 3 6 U, 2 3 6 , 2 3 8 Pu, 2 3 4 , 2 3 6 U, 2 3 2 , 2 3 3 , 2 3 4 , 2 3 5 , 2 3 6 U and 2 3 0 , 2 3 2 Th isotopes which emitted 1 4 C, 2 4 Ne, 2 8 Mg, 2 6 Ne, 2 8 Mg, 2 4 Ne, respectively, has been analyzed with the help of fractional calculus for investigating the connection between order of the fractional derivative and nuclear structure. When the neutron number of daughter nuclei is equal to magic number, order of the fractional derivative shows a maximum. It is shown that there is a relationship between the order of fractional derivative and shell effect. This order has a similar role to the preformation factor in cluster radioactivity. [ABSTRACT FROM AUTHOR]

Since Mayer and Jensen employed the single-particle shell model to interpret the magic numbers, various microscopic nuclear models have been developed to study the nuclear force and structure. The configuration–interaction shell model (CISM), performed in truncated model space with the inclusion of the residual interaction, is one widely-used nuclear structure model. In the last decade, CISM has progressed in investigating the cross-shell excitation in exotic light nuclei, the similarity and difference in mirror nuclei, and the isomerism and seniority conservation in medium and heavy nuclei. Additionally, researchers have attempted to construct effective Hamiltonians for nuclei near 1 3 2 Sn and 2 0 8 Pb through a unified way in the CISM framework. In parallel, related models, including the nucleon-pair approximation (NPA) approach, the Monte Carlo shell model (MCSM), the projected shell model (PSM), the Gamow shell model (GSM), etc., have also been extensively developed and validated in the last decade. This paper reviews the recent progress in CISM and some related models. [ABSTRACT FROM AUTHOR]

In this paper, the interacting boson model (IBM-1) with intrinsic coherent state is used to study the O(6) shapes in Se isotopes. The Hamiltonian is written in the annihilation and creation form with one and two body terms. For each nucleus, a fitting procedure is adopted to get the best model parameters by fitting selected experimental energy levels, B(E2), B(M1) transition rates and mixing ratio with the calculated ones. The O(6) IBM potential energy surfaces (PESs) are analyzed. [ABSTRACT FROM AUTHOR]

Reflection asymmetric, octupole shapes in nuclei are a prominent aspect of nuclear structure, and have been recurrently studied over the decades. Recent experiments using radioactive-ion beams have provided evidence for stable octupole shapes. A variety of nuclear models have been employed for the related theoretical analyses. We review recent studies on the nuclear octupole shapes and collective excitations within the interacting boson model. A special focus is placed on the microscopic formulation of this model by using the mean-field method that is based on the framework of nuclear density functional theory. As an illustrative example, a stable octupole deformation, and a shape phase transition as a function of nucleon number that involves both quadrupole and octupole degrees of freedom are shown to occur in light actinides. Systematic spectroscopic studies indicate enhancement of the octupole collectivity in a wide mass region. Couplings between the octupole and additional degrees of freedom are incorporated in a microscopic manner in the boson system, and shown to play a crucial role in the description of the related intriguing nuclear structure phenomena such as the shape coexistence. [ABSTRACT FROM AUTHOR]

The normal deformed bands of 1 6 7 , 1 6 9 , 1 7 1 Lu isotopes have been studied by using projected shell model approach. The band head spins, configurations and energies of all the normal deformed bands are reproduced well by the above said approach. The present calculations have predicted I = 7 ∕ 2 − band head spin for [523]7/2− bands of 1 6 9 , 1 7 1 Lu. The observed systematics of aligned angular momenta and the experimental differences in frequencies around the backbends for all the normal deformed bands are reproduced well by the theoretical results. Besides this, the observed backbends or upbends in these isotopes may be ascribed to the alignment of a pair of neutrons in the neutron 1 i 1 3 ∕ 2 orbital. Although the theoretical B (E 2) values obtained from the projected shell model wavefunctions overestimate the experimental B (E 2) values in 1 6 7 Lu, yet they are close to the measured values, considering the precision of measurement. The reduction in the theoretical B (E 2) values around the band crossing region may be ascribed to change in nuclear structure of yrast bands due to neutron pair alignment in 1 i 1 3 ∕ 2 orbital. [ABSTRACT FROM AUTHOR]

A systematic study of the super-deformed (SD) bands in A ∼ 1 5 0 mass region is carried out by using two different approaches, namely, the Principal-axis Cranking (PAC) and the Variable Moment of Inertia (VMI). Both these approaches not only support each other's results but also their hand-in-hand calculations help us in establishing the prominent features, like the band-head spin, parity, quadrupole moment and excitation energy, of the observed SD bands. Since the rotational frequency in the PAC model depends on angular momentum, parity, and quadrupole moment, by identifying the most common rotational frequency between the calculations and the experimentally observed ones, the band-head spin, and parity are likely to be extracted. On the other hand, the VMI model calculations are quite simple and are capable of predicting the threshold limits of band-head spin, the quadrupole moment, and the excitation energy, which in turn are significantly useful for deciding an appropriate configuration assignment in the PAC model calculations of the existing as well as upcoming SD bands. Further, the VMI model calculations involve the variation of the moment of inertia with angular momentum, which in turn is quite helpful in understanding the mechanism of the observed identical SD bands between a pair of neighboring nuclei. [ABSTRACT FROM AUTHOR]

Recently, from the study of the absolute B (E 2) values for the (γ – g) E 2 transitions, the different roles of the triaxiality parameter γ = (0 ∘ – 2 0 ∘) and γ = (2 0 ∘ – 3 0 ∘) parts were pointed out. Here, the use of the triaxial rotor model expressions for the B (E 2)s in producing the bell-shaped curve of B (E 2 , 2 γ − 0 1 +) is illustrated. The variation of certain (γ – g) B (E 2) ratios versus γ for the states 2 γ and 3 γ are illustrated, reflecting the two regions of γ. The inter relation of the γ and β variables is illustrated for the Os isotopes. [ABSTRACT FROM AUTHOR]

Higher-order approximation based on Taylor expansion over the saddle point is employed to approach the partition function of a hot nucleus in the presence of the like-particle pairing correlations. Analytical expressions have been derived for the correction terms of different thermodynamic quantities such as energy, entropy and heat capacity. Furthermore, the theory has been applied to the schematic and realistic models. It is found that the correction terms are temperature-dependent functions and are more deeply sensitive to the pairing gap in the vicinity of the critical temperature. [ABSTRACT FROM AUTHOR]

The interaction of dark matter particles (weakly interacting massive particles (WIMPs)) with the odd-mass 7 3 Ge and 1 3 1 Xe target nuclei, that is, the recoil rates corresponding to the elastic scattering of WIMPs by these nuclei, is analyzed in the context of the minimal extensions of the supersymmetry model. The BCS+QRPA technique plus the quasiparticle–phonon coupling scheme is used to describe the nuclear structure part of the calculations. The resulting values for the nuclear spin content of both nuclei are compared to values previously reported in the literature. [ABSTRACT FROM AUTHOR]

The nuclear structure and thermal quantities of the superheavy nucleus of 2 9 2 1 2 0 1 7 2 are studied in a recent developed framework of the Finite-Temperature Hartree–Fock–Bogoliubov (FT-HFB) by using a zero-range pairing and including the continuum effects. Analyzing the shell structure of this nucleus at both zero and finite temperature shows a dependence on the various Skyrme-type forces used and a shell closure occurrence at Z = 120 for protons and N = 172 for neutrons with a large gap energy where the pseudo-spin-orbit effects play a primordial role in the shell sequence at finite temperature which confirm the double magicity of 2 9 2 1 2 0 1 7 2 . Thermodynamic quantities are also studied in the same framework where the results are qualitatively similar to what are obtained in case of the hot ordinary nuclei. [ABSTRACT FROM AUTHOR]

The shapes of the A = 70, T = 1 triplet nuclei 7 0 Se, 7 0 Br and 7 0 Kr have been investigated by Total Routhian Surface (TRS) calculations in the microscopic–macroscopic formalism. A Woods–Saxon potential with global set of parameters was used for obtaining the shell correction energy and the Strutinsky method has been applied to calculate the TRS. The β 2 and γ shape parameters, determined from the minimum of the TRS, show a structural change between mirror pairs 7 0 Se and 7 0 Kr. This is in support of the recent measurements performed at RIKEN. [ABSTRACT FROM AUTHOR]

L. Y. Jia recently proposed an algorithm that applies the variational method directly to coherent-pair condensates (VDPC) [L. Jia, Phys. Rev. C (2019).] Now I'll make changes to the VDPC algorithm that applies it to the Constraint Hatree–Fock theory. I derived expressions of the mean energy extremum with linear constraints and the analytic form of the Lagrangian multiplier. In addition, I acquire an angle through the inverse tangent of the energy minimum to the electric quadrupole moment in Fig. 3, which describes the unconstrained energy under an equivalent rotating system. I demonstrate the new algorithm in a semirealistic example using the realistic V low − k interaction in the large model spaces (up to 15 harmonic-oscillator major shells). In this work, I am interested in a wave function | ψ (Q) 〉 , which minimizes the total energy under the constraint that has a fixed expectation Q = 〈 ψ | Q ̂ | ψ 〉. I graphed the results as just an energy extreme versus electric quadrupole moment graph. The result shows that Fig. 3 is similar to Fig. 7.2 in [P. Ring and P. Schuck, The Nuclear Many-body Problem (Springer Science & Business Media, 2004)]. [ABSTRACT FROM AUTHOR]

In this paper, odd-mass isotopic chain of 1 2 3 − 1 2 9 Sn has been studied within the framework of nucleon-pair shell model (NPSM) with the noncollective pair originating from the alignment of two neutrons in the ν h11/2 orbit included. It was found that NPSM can reproduce the properties of the yrast bands satisfactorily, it is crucial to include the noncollective pair in the NPSM. The band structure can be explained as the backbending or the phase transition from vibrational limit to the rotational limit. The mechanism of the yrast band can be explained as band crossing between the ground state band and the S band constructed from the neutron alignment in the ν h11/2 orbit. Our results also suggest that the mechanism of the band structure of those four Sn isotopes can also be interpreted as the competition and transition between collective and noncollective phase. [ABSTRACT FROM AUTHOR]

We have performed a systematic study for the nuclear structure of superheavy nuclei with a special emphasis on the nuclei with possible central depletion of proton and neutron density in the mass region A ∼ 3 0 0 using the Relativistic Hartree–Bogoliubov (RHB) framework. It has been observed that in the case of neutron density distribution, the occurrence of central depletion is related to the occupancy of 4s orbital and it is found to decrease with increasing occupancy of the 4s orbital. On the other hand, in the case of proton density distribution, the central density depletion is mainly due to the lowering of weakly bound p-orbital states close to the continuum as it is energetically favored to lower the Coulomb repulsion in the case of superheavy nuclei. Also, occupation probability of the lower angular momentum states (p-orbitals) lying near the Fermi level is strongly suppressed due to the weak centrifugal barrier and strong Coulomb repulsion in comparison to large angular momentum states (contributing to surface region mainly), resulting in central density depletion. Among the considered cases in the present work, the maximum depletion is observed for 2 9 2 1 2 0 and for 2 9 4 Og under spherically symmetric and axially deformed cases, respectively. [ABSTRACT FROM AUTHOR]

The problem of mismatching of the level energies, in the ground band and the K π = 2 + γ -band of triaxially deformed atomic nuclei, as predicted in the rigid triaxial rotor (RTR) approximation of Davydov and Filippov (DF) model, with experiment, is well known. Here, we illustrate the solutions suggested in the literature, and the deviations observed in the converted energy values, from the experiment. We analyze the source of problem of this mismatch with experiment. This enables a physical picture of the DF (or RTR) model spectra. Our analysis will help in understanding the merits and the limitation of the RTR model in this respect. [ABSTRACT FROM AUTHOR]

Level density ρ (E , N , Z) is derived for a nuclear system with a given energy E , neutron N , and proton Z particle numbers, within the semiclassical extended Thomas–Fermi and periodic-orbit theory beyond the Fermi-gas saddle-point method. We obtain ρ ∝ I ν (S) / S ν , where I ν (S) is the modified Bessel function of the entropy S , and ν is related to the number of integrals of motion, except for the energy E. For small shell structure contribution one obtains within the micro–macroscopic approximation (MMA) the value of ν = 2 for ρ (E , N , Z). In the opposite case of much larger shell structure contributions one finds a larger value of ν = 3. The MMA level density ρ reaches the well-known Fermi gas asymptote for large excitation energies, and the finite micro-canonical limit for low excitation energies. Fitting the MMA ρ (E , N , Z) to experimental data on a long isotope chain for low excitation energies, due mainly to the shell effects, one obtains results for the inverse level density parameter K , which differs significantly from that of neutron resonances. [ABSTRACT FROM AUTHOR]

This work theoretically analyzed the role played by intrinsic degrees of freedom of the colliding partners and/or nucleon transfer channel in the fusion dynamics of 1 2 C + 9 2 Zr and 1 2 C + 1 9 4 , 1 9 8 Pt reactions. The theoretical calculations for the chosen reactions have been done by using symmetric–asymmetric Gaussian barrier distribution (SAGBD) model, coupled channel code CCFULL and one-dimensional Wong formula. The fusion excitation functions for these reactions are enhanced at energies lying in the sub-barrier regions with respect to calculations based on one-dimensional Wong formula. Such enhancement can be ascribed to the involvement of the low-lying inelastic surface excitations of the colliding systems and some other favored channels. The CCFULL calculations consider the couplings to low lying vibrational states of target isotopes and hence intimate the dominance of the collective excitations associated with the fusing partners. For all the studied reactions, the SAGBD model adequately addresses the sub-barrier fusion dynamics and thus the impacts of nuclear structure degrees of freedom associated with the collision partners are intrinsically incorporated via single Gaussian type of weight function. In the SAGBD approach, the nuclear structure effects are analyzed in terms of channel coupling parameter (λ) and percentage reduction of effective fusion barrier V CBRED with reference to the Coulomb barrier. The larger values for λ and V CBRED imply that the channel couplings due to internal structure of participants are significant at below barrier energies. The CCFULL calculations and SAGBD predictions consistently explain the fusion dynamics of chosen systems and hence reveal that both models have almost similar predictive power with respect to reported fusion data. [ABSTRACT FROM AUTHOR]

The negative- and positive-parity states and electromagnetic transitions for 2 0 1 − 2 0 9 Rn and 2 0 3 − 2 1 1 Fr nuclei have been studied by using the Interacting Boson–Fermion Approximation (IBFM-1). Based on our calculations, the spin assignments for some states with uncertain spin have been done. Energy spectra, electromagnetic transition probabilities and branching ratios in these isotopes are calculated and compared with available experimental data. The wave functions are analyzed to understand the nuclear structure. In addition, some predictions of levels that have no experimental data are presented such as spin and electromagnetic transitions. Good results were obtained with a decrease in the collectivity properties, especially for the most neutron-deficient isotopes. [ABSTRACT FROM AUTHOR]

In this work, we calculate the level density parameter for several nuclei by deploying the semiclassical trace formula for spherically symmetric harmonic oscillator potential with spin-orbit interactions, which describes the quantum shell effects in terms of the classical periodic orbits. With the usage of recently proposed Laplace like formula of level density parameter by Canbula et al., the effects of collective rotations and vibrations as well as deformations in nuclei are incorporated. The comparison of our results with the experimental ones show a good agreement. Later on, the study is also extended to the calculation of nuclear level density and survival probability in several superheavy nuclei (SHN). [ABSTRACT FROM AUTHOR]

The validity of the extended Grodzins product rule (GPR) for higher spins in the ground bands of even Z , even N nuclei of the light mass region of Cd to Zn chain of isotopes is studied. The plots of B (E 2, I → I − 2) versus [1/ E γ (I → I − 2) ] ( I π = 4 1 + , 6 1 +) provide test of the linear relationship of the two entities. There seems to be a good correlation of the two entities at these higher spin states for most of the nuclei studied here. The deviations from linearity in specific cases are found to be useful for studying the variations in the nuclear structures involved. From these linearity plots, the structural change at higher spin in some nuclei involving subshell gaps, as reflected in the anomalous rise or saturation, leads to further insight into the under lying microscopic structure. [ABSTRACT FROM AUTHOR]

We have studied systematically the alpha decay and cluster radioactivity half-life of heavy 2 4 5 − 2 6 0 Mendelevium (Z = 1 0 1) isotopes. The alpha decays from Md isotopes have been studied within the framework of Coulomb and proximity potential model using 14 different versions of nuclear potentials. Also, we have studied the half-lives of alpha decay of Md nuclei within the nuclear potentials generalized liquid drop model (GLDM) and also within GLDM with modified different nuclear potentials, namely proximity potential 2010, 1977, 1988, 2000 and 2002. Moreover, the half-lives of the α -decay and cluster radioactivity calculated using the Universal formula for cluster decay (UNIV) of Poenaru et al., the Universal decay law (UDL) of Qi et al. and the Unified formula of half-lives for both the α -decay and cluster radioactivity (UFADCR) of Ni et al. and found to be in good agreement. Our results have been compared with experimental data and demonstrate the acceptability of the approach. Among the different proximity potentials, GLDM with proximity 1977 version (GLDM + P77) (σ = 0. 8 5 0 9) provides the best description for alpha decay studies with low deviation. [ABSTRACT FROM AUTHOR]

The nuclear shell model with the Skyrme–Hartree–Fock (SHF), as a nonrelativistic approach, and the Relativistic Hartree–Fock–Bogoliubov (RHFB) methods have been used to study the nuclear structure of some exotic nuclei at the proton and neutron drip lines. Different Skyrme parametrizations, in particular SkM*, SkX, SkO, SLy4, Skxs25 and Z, have been used in the nonrelativistic region. In the relativistic region, the density-dependence meson-exchange models and density-dependence point-coupling models are used. Both methods are used to study ground state properties such as binding energy, mass radial density distribution and the corresponding root mean square (rms) mass radii. The fragmentation reaction cross-section is used as an important property to investigate the halo structure. Strong evidence for existence of a neutron halo in 1 1 Li and 1 4 Be and proton halo in 1 7 Ne, 2 3 Al and 2 7 P are found using the SHF model and reaction cross-section. The ability of the SHF model to study the exotic structure with shell model occupation probability is confirmed. [ABSTRACT FROM AUTHOR]

The charge, proton and neutron density distributions along with nuclear properties were calculated by Hartree–Fock approach with Skyrme force interaction for isotopic Pb chain (8 8 ≤ N ≤ 1 8 4). The effects of correlation on neutron skin thicknesses by obtaining bulk and surface contributions were analyzed by three different approaches. The occurrence of the nuclei with bubble structure due to central depletion in nucleonic was investigated for Pb isotopes as a function of relative neutron excess I = (N − Z) / A. The important role of the bubble effect in heavy region was explained by the relation between Coulomb and nn-interaction. The single particle energy levels were determined by each j = l ∓ 1 2 state of stable Pb isotopes, as well as charge form factors F ch (k). Besides, the average neutron–proton δ V np and residual neutron–proton δ np interactions of the Pb isotopes were calculated by the theoretical binding energies. The fluctuations in the obtained results were considered in detail because its variation may give a good criterion for the mass model approaches. [ABSTRACT FROM AUTHOR]

Experimental observation of 3 4 Si as a proton bubble nuclei has heated up the interest in the study of exotic bubble shaped nuclei. In this work, some of the potential doubly bubble-like (for proton as well as neutron both simultaneously) cases have been explored using relativistic Hartree–Bogoliubov (RHB) in light mass region, specially around N or Z = 1 4. Further, the role of pairing and the evolution of new shell gaps around N or Z = 3 2 and 34 have been investigated, as one moves toward drip lines. This study suggests that the occupancies/vacancies of neutron/proton orbitals for lower angular momentum state plays major role in nuclear structure to create bubble-like structure and 8 2 2 O 1 4 , 1 2 2 0 Mg8 and 1 4 4 8 Si 3 4 may have dual bubble-like structures. [ABSTRACT FROM AUTHOR]

We demonstrate that pairing phase transition (superfluid to normal) can be described quite generally in terms of the thermodynamical properties after verifying the obtained level densities with the available experimental data for 1 1 8 , 1 2 2 S n - isotopes. Periodic-orbit theory conveniently connects the oscillatory part of level density to the underlying classical periodic orbits and hence, leads to the shell effects in the single-particle level density. Such methods incorporated with pairing effects can be used effectively to study the phase transitions in S n -isotopes. In addition to this, an interplay between pairing correlations and the shell effects has been understood by analyzing the results obtained for the critical temperatures and shell structure energies for 1 0 2 − 1 3 8 S n isotopes. A relation between variation in critical temperatures caused by shell effects and the shell structure energies determined with and without pairing effects has been established. Furthermore, the systematics of the heat capacity (giving a clear signature of pairing phase transition) as function of temperature for these nuclei are investigated as well. [ABSTRACT FROM AUTHOR]

The Kr isotopes lying in between the lighter isotopes of (Zn, Ge and Se) and the heavier isotopes of (Sr and Zr) in the A = 7 0 –80 region exhibit very interesting spectral features. The spectra of 7 2 − 8 4 Kr isotopes display a striking contrast from those of Zn, Ge and Se isotopes. The role of spherical and oblate and prolate deformed subshell gaps at specific Z and N and the resulting re-inforcement are strikingly evident in these contrasting features, with variation in Z or N. The evolution of the spectral features in Kr isotopes with N as reflected in the quadrupole deformation, K -band structures, E 0 decay, B (E 2) values, β -softness of the nuclear core and odd–even staggering in K π = 2 + γ -bands is studied to explore the role of the under lying nuclear interactions. The correlations with odd– A isotopes are explored. The shape co-existence displayed in some Kr isotopes is studied. The large deformation observed in the ground bands of 7 4 , 7 6 Kr, as exhibited in the B (E 2) values, is especially interesting. [ABSTRACT FROM AUTHOR]

Shell model calculations have been performed in f 5 / 2 p g 9 / 2 model space using two different interactions viz. jj44bpn and jun45pn to explore nuclear structure in 6 3 , 6 5 , 6 7 Ga. Calculated excitation energies are compared with previously reported experimental values and a good agreement has been observed. Transitions strengths are also calculated using two sets of effective charges for proton and neutron and are compared with nearby 6 2 , 6 4 , 6 6 Zn isotopes. Occupation probabilities of protons and neutrons corresponding to individual orbitals (namely f 5 / 2 , p 3 / 2 , p 1 / 2 and g 9 / 2 orbital), and dominant particle configurations for individual spin states have been presented as well. Calculations suggest major role of intruder 1 g 9 / 2 orbital in constructing the wave functions of higher angular momentum states, whereas, the lower excited states are mainly dominated by contributions from f p orbitals. [ABSTRACT FROM AUTHOR]

The well known, one-parameter Davydov–Filippov model (DFM) or its variants have been used often to study the inter band γ -g B(E2) ratios for the triaxially deformed nuclei. Here, its application for the axially deformed nuclei with γ less than 2 0 ∘ is illustrated, which has not received attention so far. Instead of the usual practice of studying the gamma-ground B(E2) ratios, we focus on the absolute B(E2) values in DFM. It offers a wholly new role of the γ -variable in explaining the spectral features of the axially deformed nuclei. Further, it illustrates the intimate relationship of the γ variable and the quadrupole deformation variable β. Additionally, a unified view of the various differing patterns of the variation of the γ -g B(E2) ratios versus γ is presented. [ABSTRACT FROM AUTHOR]

The accurate knowledge of the nuclear level density is crucial for understanding the nuclear structure and for numerous applications including astrophysical reactions. In this review paper, we discuss the shell-model description of the nuclear level density, the use of the statistical moments method and underlying physics. The level density found with the moments method is shown to agree with the results of the exact diagonalization of the Hamiltonian matrix. The statistical approach is also compared to other standard methods for deriving level densities. The role of specific interaction matrix elements is reviewed in connection to the behavior of the level densities as these evolve. Chaotization and thermalization processes, collective enhancement and phase transitions are discussed with changing strengths of specific groups of two-body interaction matrix elements. The popular phenomenological constant temperature model is compared to the moments method and the effective temperature parameter of the model for different isotopes is discussed. [ABSTRACT FROM AUTHOR]

This work emphasized the role of the projectile breakup channel by studying the complete fusion (CF) and incomplete fusion (ICF) dynamics of 6 , 7 Li + 1 4 4 , 1 5 2 Sm reactions. The theoretical calculations for the chosen reactions have been done by opting for the coupled channel approach and the energy dependent Woods–Saxon potential (EDWSP) model. The below barrier fusion enhancements of the studied reactions are reasonably addressed by the outcomes of the adopted models, which in turn can be attributed to the couplings of nuclear structure degrees of freedom of the collision partners to their relative motion. In contrast, at above barrier energies, the CF cross-section data of the chosen reactions are found to be suppressed significantly when compared with the predictions made by using the present models. Interestingly, the fusion suppression factors of the given reactions can be minimized considerably with respect to the reported value when it is analyzed within the framework of the EDWSP model. For instance, in case of 6 Li + 1 4 4 Sm ( 6 Li + 1 5 2 Sm) reaction, the magnitude of fusion suppression factor is minimized up to 7% (13%) relative to the reported value whereas for 7 Li + 1 4 4 Sm ( 7 Li + 1 5 2 Sm) reaction, the fusion suppression factor is found to be less by 7% (8%) with reference to the reported value. Such suppression effects can be correlated with the low breakup threshold of alpha breakup channel associated with the loosely bound projectile. The projectiles being weakly bound systems split into two charged fragments and either of the breakup components is absorbed by the target resulting in the reduction of incoming flux going into fusion channel. The flux lost from the CF channel appears in the form of ICF yields. For 6 Li + 1 5 2 Sm , total fusion (TF) cross-sections that are sum of CF and ICF cross-sections are also analyzed in conjunction with the EDWSP model and thus reasonably explained by the model calculations. In order to identify the ICF contribution, the ratio of ICF/TF cross-section data of 6 Li + 1 5 2 Sm reaction has been examined and thus properly addressed by using the EDWSP model. The presence of ICF component in TF cross-section clearly pointed out the breakup of projectile due to its loosely bound nature prior to the Coulomb barrier. Although ICF data of other systems are not available in the literature, a similar behavior is expected for ICF and TF data for 6 Li + 1 4 4 Sm and 7 Li + 1 4 4 , 1 5 2 Sm reactions. [ABSTRACT FROM AUTHOR]

1 4 C is a beta decay isotope, its beta decay is very slow reflecting the stability of this nucleus and emitted from medium and heavy mass nuclei. The 1 4 C result is in excellent agreement with the favored ground-state-to-ground-state transition according to the cluster model of Blendowske et al. We study nuclear structure properties of spin-1/2 heavy nuclei in the relativistic core-cluster model, that its cluster is 1 4 C. According to this model for spin-1/2 heavy nuclei and for obtaining its wave function, we solve the Dirac equation with the new phenomenological potential by parametric Nikiforov–Uvarov method and then calculate the binding energy and charge radius. [ABSTRACT FROM AUTHOR]

Energy levels and electromagnetic transition probabilities of odd-mass 1 2 9 − 1 3 5 Pr and 1 2 7 − 1 3 3 Ce isotopes have been calculated using the interacting boson fermion model. The even–even 1 2 8 − 1 3 4 Ce isotopes have been used as the cores. In the model space, the bosons have angular momentum, L = 0 (s -boson) and L = 2 (d -boson) have been considered, while the nine protons for 1 2 9 − 1 3 5 Pr and 19–25 neutrons for 1 2 7 − 1 3 3 Ce are allowed to occupy the 1 g 7 / 2 , 2 d 5 / 2 , 2 d 3 / 2 , 3 s 1 / 2 and 1 h 1 1 / 2 single particle orbitals. The quasi-particle energies and occupation probabilities have been obtained by solving the BCS equation. According to the model space, the wave function for low-lying states has been investigated. The calculated results are in good agreement with the available experimental data. [ABSTRACT FROM AUTHOR]

The structure of exotic nuclei sheds new light on the linkage of the nuclear structure to the nucleonic interaction. The self-consistent mean-field (SCMF) theories are useful to investigate this linkage, which are applicable to many nuclei covering almost the whole range of the nuclear chart without artificial truncation of model space. For this purpose, it is desired to develop effective interaction for the SCMF calculations well connected to the bare nucleonic interaction. Focusing on ground-state properties, I show the results of SCMF calculations primarily with the Michigan-three-range-Yukawa (M3Y)-type semi-realistic interaction, M3Y-P6 and M3Y-P6a to be precise, and discuss in detail how the nucleonic interaction affects the structure of nuclei including those far off the β -stability. The central channels of the effective interaction are examined by the properties of the infinite nuclear matter up to the spin dependence and the isospin dependence. While experimental information of the infinite matter is obtained by extrapolating systematic data on finite nuclei in principle, it is not easy to constrain the spin dependence and the isospin dependence without connection to the bare nucleonic interaction. The noncentral channels play important roles in the shell structure of the finite nuclei. The tensor force is demonstrated to affect Z - or N -dependence of the shell structure and the magic numbers, on which the spin–isospin channel in the central force often acts cooperatively. By using the M3Y-P6 interaction, the prediction of magic numbers is given in a wide range of the nuclear chart, which is consistent with almost all the available data. In relation to the erosion of magic numbers in unstable nuclei, effects of the tensor force on the nuclear deformation are also argued, being opposite between nuclei at the ℓ s - and the j j -closed magicities. Qualitatively consistent with the 3 N -force effect on the ℓ s -splitting suggested from the chiral effective field theory, the density-dependent LS channel, which is newly introduced in M3Y-P6a, reproduces the observed kinks in the differential charge radii at the j j -closed magic numbers and predicts anti-kinks at the ℓ s -closed magic numbers. The pairing correlation has significant effects on the halos near the neutron drip line. A new mechanism called "unpaired-particle haloing" is disclosed. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is to rigorously establish the Strutinsky method from the least squares principle. Thus, it is the mathematical basis of this method (aspect often neglected) which is revisited in an extensive way. Some formulas previously given without demonstration or in a simplified way are set out here with all the details. In this respect, the most important mathematical properties of the averaging functions are also established in this paper. When some conditions are met, it turns out that Strutinsky's method is nothing more than a polynomial moving average of the semi-classical level density. [ABSTRACT FROM AUTHOR]

The low-lying positive and negative parity states of even–even 1 4 4 − 1 5 4 Nd isotopes are studied using the interacting boson model (IBM). The negative parity states are involved within the IBM model by adding a single angular momentum (L = 3) boson with intrinsic negative parity f -boson to s and d -bosons model space. For these nuclei, the potential energy surfaces V (β , γ) , transition probability B (E 1) , B (E 2) and B (E 3) are calculated. Phase transition from the U (5) limit to the S U (3) limit is observed in the chain and the critical point has been determined for 1 5 0 Nd isotope. It is found that the calculated positive and negative parity energy spectra of Nd-isotopes agree well with the experimental data. [ABSTRACT FROM AUTHOR]

Shell model and core polarization (CP) effects have been used to calculate the transverse and longitudinal electron scattering form factors for 7Li and 1 0 B nuclei. The calculations considered one particle–one hole excitation up to 12 ℏ ω. This manner seems to be essential for obtaining the best explanation for empirical results. Therefore, adding the excited states up to 12 ℏ ω gives a reasonable description for transverse and longitudinal form factors. Furthermore, with these calculations, it is possible to get a very close location of diffraction minimum, and the behavior of the momentum transfer is described properly at the high configuration for 7Li compared with 6 ℏ ω energy. [ABSTRACT FROM AUTHOR]

The well-known Grodzins product B (E 2, 0 1 + → 2 1 +) × E (2 1 +) constancy rule was generalized to the Grodzins linearity relation in our recent work in the form of B (E 2) versus [ 1 / E (2 1 +) ] linear plots. In this form, besides testing the linear relation of B (E 2) and kinetic moment of inertia, it also served as a tool for the study of the spectral details of the nuclei, and for the study of the variation of nuclear structure with N and Z. We now study its extension to the intra band E 2 transition from the higher spins of the ground bands of even Z even N nuclei of the mid-mass region of Xe–Pt chain of isotopes. We use the plots of B (E 2, I → I − 2) versus [ 1 / E γ (I → I − 2) ] (I π = 4 + and 6 +) to test their linear relationship. There seems to be a good correlation of the two entities even at the higher spins for all the nuclei studied here. The deviations from linearity in specific cases can be used for studying the nuclear structures involved. [ABSTRACT FROM AUTHOR]

By using a nonrelativistic independent particle model, we investigate the mechanism promoting 34 as new magic number. We carried out Hartree–Fock plus Bardeen–Cooper–Schrieffer and Quasi-particle Random Phase Approximation calculations by consistently using the same finite-range interaction in all the three steps of our approach. We used four Gogny-like interactions, with and without tensor terms. We find that the shell closure for N = 3 4 neutrons appears in isotones with Z < 2 6 protons. The smaller the proton number, the more evident is the shell closure at N = 3 4. An ideal nucleus to investigate this effect should be 4 8 Si, as it has been recently suggested. However, some discrepancies occur between the results obtained with the four effective interactions we used concerning the position of the two-neutron drip line and, therefore, the existence of 4 8 Si. The experimental identification of this nucleus could shed light about the shell evolution in nuclei far from the stability valley and put stringent tests on nuclear structure theories. [ABSTRACT FROM AUTHOR]

We have examined the binding energy, root-mean-square radii and two neutrons separation energies for the recently accepted super-heavy element Z = 1 1 8 established as Og using the axially deformed relativistic mean field (RMF) model with NL3 force parameter set. The calculation is extended to various isotopes of Z = 1 1 8 element, starting from A = 2 9 0 till A = 3 1 0. The most stable isotope is found to be at N ∼ 1 7 4 (A = 2 9 2 , Z = 1 1 8). Also, the α -decay energy Q α and hence the half-lives T α is carried out by taking three different empirical formulae for the α -decay chains of Z = 1 1 8 supporting the possible shell closure at daughter nuclei N = 1 7 0 and/ or 184 and at parent nucleus of N = 1 9 2 with Z = 1 1 8. [ABSTRACT FROM AUTHOR]

This work examined the fusion dynamics of 1 6 O + 7 6 Ge and 1 8 O + 7 4 Ge reactions within the framework of the static Woods–Saxon potential model, the energy dependent Woods–Saxon potential (EDWSP) model and coupled channel formulation. The effects of inelastic surface excitations, static deformation of colliding pairs and /or neutron transfer channels on fusion process are investigated through the coupled channel method. The calculations based upon static Woods–Saxon potential in conjunction with one-dimensional Wong formula strongly under predict the fusion data of 1 6 O + 7 6 Ge and 1 8 O + 7 4 Ge reactions at sub-barrier energies. However, such discrepancies are removed if one uses couplings to nuclear structure degrees of freedom of reacting nuclei. The coupled channel calculations obtained by considering the vibrational nature of the colliding nuclei fairly reproduce the fusion data of 1 8 O + 7 4 Ge reactions. For this reaction, the neutron transfer channels, which are expected to influence strongly the fusion yields at below barrier energies, in reality contribute very weakly to fusion process. While in case of 1 6 O + 7 6 Ge reaction, the consideration of vibrational couplings as well as the rotational couplings for target provides a reasonable explanation to the fusion cross-section data at near and above barrier energies. In distinction, the energy dependence in the nucleus–nucleus potential causes barrier modulation effects and subsequently modifies the barrier profile of the interaction barrier in such a way that the effective fusion barrier between the colliding pair reduces. This ultimately brings larger fusion cross-sections over the outcomes of one-dimensional barrier penetration model and the EDWSP model based calculations appreciably explained the fusion dynamics of chosen reaction at energy spanning around the Coulomb barrier. Both models (EDWSP and coupled channel model) lead to barrier lowering effects and modeled quantum tunneling in different way, henceforth, adequately explore the fusion dynamics of the studied reactions in near and above barrier energy regions. [ABSTRACT FROM AUTHOR]

In the 35 years since the European Muon Collaboration announced the astonishing result that the valence structure of a nucleus was very different from that of a free nucleon, many explanations have been suggested. The first of the two most promising explanations is based upon the different effects of the strong Lorentz scalar and vector mean fields known to exist in a nucleus on the internal structure of the nucleon-like clusters which occupy shell model states. The second links the effect to the modification of the structure of nucleons involved in short-range correlations, which are far off their mass shell. We explore some of the methods which have been proposed to give complementary information on this puzzle, especially the spin-dependent EMC effect and the isovector EMC effect, both proposed by Cloët, Bentz and Thomas. It is shown that the predictions for the spin-dependent EMC effect, in particular, differ substantially within the mean-field and short-range correlation approaches. Hence, the measurement of the spin-dependent EMC effect at Jefferson Lab should give us a deeper understanding of the origin of the EMC effect and, indeed, of the structure of atomic nuclei. [ABSTRACT FROM AUTHOR]

The nuclei in the A = 1 3 0 , 1 0 0 and 8 0 regions, lying on both sides of the β -stability line, continue to be of interest for their complex nuclear structures. The Grodzins product rule (GPR) viz. [ E (2 1 +) × B (E 2 , 0 1 + → 2 1 +) = constant × Z 2 A − 2 / 3 ] , for the ground bands of even- Z even- N nuclei provides a useful approach to study these structures. The utility of our method, displaying the linear relation of B (E 2) to [ 1 / E (2 1 +) ] , is illustrated for the Z = 3 0 Zn to Z = 4 8 Cd series of isotopes. The spread of the data on the linear plots enables a quick view of the shape phase transitions. The role of the shells and the subshells, at spherical and deformed shell gaps for neutrons and protons, with their mutual re-inforcement and the shape phase transition are vividly visible on our plots. The development of collectivity in this region is also linked to the effective number of valence nucleons above the magic number of Z = 2 0 , and 28 rather than Z = 4 0 , for Mo to Cd isotopes for a microscopic calculation. [ABSTRACT FROM AUTHOR]

The spectroscopic properties play a crucial role in understanding the structure of nuclei, in particular, the shape and shape transitions of nuclei. In recent years, the exotic shapes of nuclear systems, such as the rod and pear shapes, have attracted a lot of attention. Covariant density functional theory (CDFT) has become a standard tool for nuclear structure calculations, and it provides a global and accurate description of nuclear ground states and excitations. In the present paper, we briefly review the recent progress in covariant density functional theory (DFT) for spectroscopic properties of the rod- and pear-shaped nuclei with the cranking calculations in a rotating mean field and the collective Hamiltonian method beyond mean field. The novel linear-chain structure of alpha clustering is discussed with the cranking approach, and low lying spectra of pear-shaped nuclei are illustrated with the quadrupole–octupole collective Hamiltonian. [ABSTRACT FROM AUTHOR]