Search

In this brief report, we make a short review of progress in developing the microscopic optical potential in recent years. In particular, we present our current studies and plans on building the microscopic optical potential based on the so-called nuclear structure models at low energies.

The present paper reports on the spin-parities and the magnetic moments for the ground states of 44 proton-rich isotopes with Z = 21–30 and A = 36–57, which are important for studies of either reaction rates in X-ray bursts or nuclear structure. These nuclear properties were calculated based on the single-particle shell model. The spins of the concerned nuclei were compared to available experimental data adopted from the NuDat database to evaluate the variations in the astrophysical rates of the rp-process reactions. We found discrepancies, due to the deformed nuclear structure, between the present results and those reported in the NuDat database. The spin uncertainties result in large variations, 13%–200%, in the astrophysical rates of the rp-process reactions. In particular, the spin uncertainties of the 44V and the 46–49Mn isotopes significantly affect the astrophysical rates of the reverse reactions of the proton captures 43Ti(p, γ)44V(p, γ)45Cr, 45Cr(p, γ)46Mn(p, γ)47Fe, 47Mn(p, γ)48 Fe, 47Cr(p, γ)48 Mn(p, γ)49 Fe, and 48Cr(p, γ)49 Mn(p, γ)50 Fe. Moreover, the magnetic moments of most of the isotopes were predicted for the first time. The results show that the magnetic moments are in the order of μp(1f7/2) > μp(2p3/2) > μn(1d3/2) > μp (1f7/2)for thenuclei having an unpaired nucleon in the proton/neutron shells. The present study suggests that reliable calculations and/or measurements for the properties of proton-rich nuclei are highly demanded.

The properties of the scattering solutions obtained as poles of the $S$ and $K$ matrices are analyzed in terms of pairing effects in the framework of the Hartree-Fock-Bogoliubov (HFB) Jost function. As a result of our analysis, we found the following: in order for the poles of the $S$ matrix to form a resonance, there must be a pole of the $K$ matrix nearby. Within the framework of HFB theory, there are three types of resonance states; shape resonances, particle-type, and hole-type quasiparticle resonances. Other scattering states that can be classified are independent $K$- and $S$-matrix poles. It is shown both numerically and qualitatively using the Jost function that the pair-correlation effect is hardly observed in the shape resonance state, and that the appearance of the pair-correlation effect is different in the particle-type and hole-type quasiparticle resonance. We also found a noteworthy correlation effect that independent $K$-matrix poles break the metastable structure of the wave function of the quasiparticle resonance and turn it into an independent $S$-matrix pole. The correlation effect that the poles of the independent $S$ matrix break the metastable structure of the inner wave function without breaking the resonance structure of the outer wave function when a pole of the independent $S$ matrix is near the hole-type resonance state was also revealed. This is considered to be another aspect of the Fano effect.

In this paper, nanostructured Ni-doped LaFeO3 materials were prepared via a simple co-precipitation method involving the hydrolysis of La(III), Fe(III), and Ni(II) cations in hot water with 5% KOH as a precipitating agent. To evaluate the effects of Ni substitution in these products, their structural phases, lattice parameters, crystallite and grain sizes, and magnetic properties were determined. As the Ni content in the LaFe1-xNixO3 (x = 0–0.25) materials increased, the average crystallite size and lattice parameters decreased. Moreover, across the range of Ni-substitution ratios, all magnetic properties correspondingly changed: the coercive force (Hc) value rose from 42.53 to 173.98 Oe. In contrast, the remanent magnetization (Mr) and saturation magnetization (Ms) values decreased from 1.0· × 10⁻2 to 3.8· × 10⁻4 emu g⁻1, and from 0.24· × 10° to 0.74· × 10⁻4 emu g⁻1, respectively. These predictable changes provide a sound foundation for the fabrication and application of magnetic materials based on nanostructured Ni-doped LaFeO3 substrates.

A fully microscopic model for the description of nuclear level density (NLD) in spherical nuclei is proposed. The model is derived by combining the partition function of the exact pairing solution plus the independent-particle model at finite temperature (EP+IPM) with that obtained by using the collective vibrational states calculated from the self-consistent Hartree-Fock mean field with MSk3 interaction plus the exact pairing and random-phases approximation (SC-HFEPRPA). Two important factors are taken into account in a fully microscopic way, namely the spin cut-off and vibrational enhancement factors are, respectively, calculated using the statistical thermodynamics and partition function of the SC-HFEPRPA without any fitting parameters. The numerical test for two spherical $^{60}$Ni and $^{90}$Zr nuclei shows that the collective vibrational enhancement is mostly dominated by the quadrupole and octupole excitations. This is the first microscopic model confirming such an effect, which was phenomenologically predicted long time ago and widely employed in several NLD models. In addition, the influence of collective vibrational enhancement on nuclear thermodynamic quantities such as excitation energy, specific heat capacity and entropy is also studied by using the proposed model., 7 pages, 3 figures, accepted in Phys. Lett. B

Elastic scattering of a series of doubly closed-shell nuclei at low energy has been described in the framework of optical potential model generated from the particle-vibration coupling approach on top of the collective excited states obtained from the random-phase approximation. We focus on the effects of the spin-orbit and velocity-dependent interaction on the angular distributions and analyzing powers by comparing these observables with experimental data. It has been found that the contribution of the two-body velocity-dependent and two-body spin-orbit terms are important to improve results for $^{16}\mathrm{O},\phantom{\rule{0.16em}{0ex}}^{40}\mathrm{Ca},\phantom{\rule{0.16em}{0ex}}^{48}\mathrm{Ca}$, and $^{208}\mathrm{Pb}$. The velocity-dependent interactions strongly reduce the absorption on the surface while the spin-orbit interactions sightly increase the absorption in the interior.

By focusing on the asymmetric shape of cross section, we analyze the pairing effect on the partial wave components of cross section for neutron elastic scattering off stable and unstable nuclei within the Hartree-Fock-Bogoliubov (HFB) framework. Explicit expressions for Fano parameters $q_{lj}$ and $\epsilon_{lj}$ have been derived and the pairing effects have been analyzed in term of these parameters, and the Fano effect was found on the neutron elastic scattering off the stable nucleus in terms of the pairing correlation. Fano effect was appeared as the asymmetric line-shape of the cross section caused by the small absolute value of $q_{lj}$ due to the small pairing effect on the deep-lying hole state of the stable nucleus. In the case of the unstable nuclei, the large $q_{lj}$ value is expected because of the small absolute value of the Fermi energy. The quasiparticle resonance with the large $q_{lj}$ forms the Breit-Wigner type shape in the elastic scattering cross section., Comment: Submitted to Physical Review C

At low-energy nuclear physics facilities, the in-flight fragmentation method is often employed to produce radioactive ion beams. This technique often involves a stable ion beam at high intensity and a gas cell target. Since the parameters for the production reaction are usually chosen to take advantage of a large cross section of the resonance reaction, a slight change in the center-of-mass energy due to the reduced target density may significantly affect the rare isotope production rate. Therefore, to estimate the heating effect due to beam particles on the target thickness, a new and more comprehensive semi-empirical model is developed by employing a heating factor function. The estimated heating factors were consistent with experimental data, which were obtained from various reaction measurements at wide ranges of heat densities.

We conducted a measurement of 18Ne + α scattering in inverse kinematics , in order to search for experimental evidence of α -cluster structure in 22Mg above the alpha threshold ( E thr = 8 . 14 MeV ) and determine the astrophysical rates of the 18Ne( α , p)21Na reaction under the conditions of break-out from the Hot-CNO cycle. A high intensity 18 Ne beam at 2.54 AMeV was successfully produced at CRIB (CNS Radioactive Ion Beam separator) of the Center for Nuclear Study, the University of Tokyo. This paper presents the in-flight production of the radioactive 18Ne beam by using the production reaction 3He(16O, 18Ne)n with a windowed cryogenic gas target, which was employed in the mentioned resonant α -scattering experiment.

Gamma spectrum measured by an NaI(Tl) detector is known to be unstable with the in situ temperature. In the present work, an advanced method has been applied to stabilize the gamma spectrum measured by the NaI(Tl) detector at environmental radiation monitoring (ERM) stations. The method is based on experimental data obtained under controlled conditions in laboratory. In the temperature range from 4 to 45°C, the relative deviation of the peak positions within the stabilized gamma spectrum is less than 2%. To test this method in a real scenario, it has been integrated into the ERM station at the Military Institute of Chemical and Environmental Engineering in Hanoi, Vietnam. The results show that the proposed method is ready for a real application.

We formulate the Jost function formalism based on the Hartree-Fock-Bogoliubov (HFB) theory which has been used to represent the nature of nuclear superfluidity. By using the Jost function based on the HFB, the $S$-matrix for the neutron elastic scattering by the open-shell nucleus can be represented analytically. Adopting the Woods-Saxon potential, we calculate the $S$-matrix poles and their trajectories by varying the pairing strength using the Jost function in order to see the pairing effect on the complex energy-momentum plane. The total cross sections of neutron elastic scattering are also analyzed, and some sharp or asymmetrical resonances (from the configuration mixing) due to the pairing effect are found in the cross section.

In this paper, we estimated half-lives using semi-empirical formulae for isotopes with Z = 100 − 126 in four α-decay chains, which can appear in the syntheses of the 309−312126 nuclei. The spontaneous fission half-lives were calculated using the Anghel, Karpov, and Xu models, whereas the α-decay ones were predicted using the Viola-Seaborg, Royer, Akrawy, Brown, modified formulae of Royer, Ni, and Qian approaches. We found that there are large differences among the spontaneous fission half-lives estimated using the Xu model and those calculated using the others, which are up to 50 orders of magnitude. The α-decay half-lives also have large uncertainties due to difference in either methods or uncertainties in nuclear mass and spin-parities. Subsequently, there is an argument in determination of α-emitters, especially for the 312126 isotope. On the other hand, the α-decay half-lives are in the range from a few microseconds (309−312126) to thousands of years (257−260Fm) in the decay chains. It was found that the half-lives are very sensitive to not only the shell closure but also the angular momentum in the α decay. For experiments, with relatively long half-lives (a few milliseconds), the 289−292Lv isotopes can be observed as evidences for syntheses of the unknown super-heavy 309−312126 nuclei. Furthermore, measurements for precise mass, fission barrier, and spin-parity are necessary to improve accuracy of half-life predictions for super-heavy nuclei.

In this work, we present a derivation of cross sections for single ionization and electron capture processes within the Classical Trajectory Monte Carlo (CTMC) approach. Specifically, we have used a potential stemming from an ab initio calculation in Green et al.’s framework to describe the dynamics of the water molecule system. Proposing a modified version of the Classical Over-Barrier (COB) potential, we have found that a cut-off of roughly 28 a.u. on the initial distance of the projectile produced a reasonable accuracy. A global agreement has been obtained in our calculations compared to experimental and other theoretical results for C6+ ion energies ranging from 10 keV/u to 10 MeV/u.

In this study the classical three-dimensional ensemble model is utilized for investigating the role of final state electron-electron repulsion in forming the ultimate correlated two-electron momentum distribution. For the first time, a comprehensive analysis has been made to thoroughly understand such repulsive force associating with each microscopic mechanism of nonsequential double ionization. The helium exposed to 800-nm laser with two representative intensities of 3.5×1014 W/cm2 and 4.5×1014 W/cm2 is used for illustration. The results indicate the dominance of electron-electron repulsion in direct and recollision-induced excitation with subsequential ionizations. While its contribution in case of exchanging-state mechanism gradually emerges as the laser intensity increases.

In this paper, we applied the method developed by Santhosh and Safoora in [Phys. Rev. C 94 (2016) 024623; 95 (2017) 064611] to theoretically investigate the fusion, evaporation-residue (ER) and fission cross-sections of the synthesis of the unknown superheavy [Formula: see text]126 nuclei produced by using the [Formula: see text]Ni + [Formula: see text]Cf and [Formula: see text]Zn + [Formula: see text]Cm combinations. The charge asymmetry, mass asymmetry and fissility of the DiNuclear System (DNS) in the synthesis of the mentioned combinations are also estimated. The calculated results show that the ER cross-sections for the synthesis of the [Formula: see text]126 nuclei are predicted to be much less than 1.0[Formula: see text]fb. In particular, it has been found that there may exist a valley of the ER cross-sections in the synthesis of a superheavy [Formula: see text] element, which produces the [Formula: see text]126 isotope. Subsequently, a model for the mass dependence of the ER cross-section in the synthesis of the [Formula: see text]126 isotopes has been proposed for the first time. On the other hand, the quasi-fission process strongly dominates over the fusion in the two concerned interacting systems. The present results, together with those reported in the previous studies, indicate that the investigated projectile–target combinations are not capable for the synthesis of the [Formula: see text]126 isotopes due to tiny fusion cross-sections (about 2–3[Formula: see text]zb), which go beyond the limitations of available facilities. Further studies are thus recommended to search for alternative interacting systems. In conclusion, this work provides useful information for the synthesis of the gap isotopes [Formula: see text]126, which have not been well studied up to date.

Background: Fission barriers of actinide nuclei have been mostly and for long been microscopi- cally calculated for even-even fissioning systems. Calculations in the case of odd nuclei have been performed merely within a so-called equal-filling approximation (EFA) as opposed to an approach taking explicitly into account the time reversal breaking properties at the mean field level- and for only one single-particle configuration. Purpose: We study the dependence of the fission barriers on various relevant configurations (e.g. to evaluate the so-called specialization energy). Besides, we want to assess the relevance as a func- tion of the deformation of the EFA approach which has been already found out at ground state deformation. Methods: Calculations within the Hartree-Fock plus BCS with self-consistent particle blocking have been performed using the SkM* Skyrme effective interaction in the particle-hole channel and a seniority force in the particle-particle channel. Axial symmetry has been imposed throughout the whole fission path while the intrinsic parity symmetry has been allowed to be broken in the outer fission barrier region. Results: Potential energy curves have been determined for six different configurations in U-235 and four in Pu-239. Inner and outer fission barriers have been calculated along with some spectroscopic properties in the fission isomeric well. These results have been compared with available data. The influence of time-reversal breaking mean fields on the solutions has been investigated. Conclusions: A sizeable configuration dependence of the fission barrier (width and height) has been demonstrated. A reasonable agreement with available systematic evaluations of fission barrier heights has been found. The EFA approach has been validated at the large elongations occurring at the outer barrier region., 25 pages, 11 figures, accepted for publication in PRC

In this contribution we make a short review of recent progress on topics of current interest in nuclear physics and nuclear astrophysics. In particular, we discuss a re-analysis of the extraction of the dipole response of the pigmy resonance in $^{68}$Ni based on a continuum discretized coupled-channels calculation in relativistic Coulomb excitation experiments. We also discuss the forthcoming progresses made by our group on the Alt-Sandhas-Grassberber approach to (d,p) reactions and future expectations. The role of separable potentials in solving such equations with a test case based on applications of such potentials to phase-shift analysis is also presented., Carpathian Summer School of Physics 2016,Exotic Nuclei and Nuclear/Particle Physics VI, "Physics with small accelerators", eds. L. Trache et al. 9 pages, 6 figures

The dipole excitations for calcium and zirconium isotopes are studied within the fully self-consistent Hartree-Fock mean field incorporated with the renormalized random-phase approximation (RRPA) using the Skyrme interaction SLy5. The RRPA takes into account the effect of ground-state correlations beyond RPA owing to the Pauli principle between the particle-hole pairs that form the RPA excitations as well as the correlations due to the particle-particle and hole-hole transitions, whose effects are treated here in an effective way. By comparing the RPA results with the RRPA ones, which are obtained for isoscalar (IS) and isovector (IV) dipole excitations in $^{48, 52, 58}$Ca and $^{90, 96, 110}$Zr, it is shown that ground-state correlations beyond the RPA reduce the IS transition strengths. They also shift up the energy of the lowest IV dipole state and slightly push down the peak energy of the IV giant dipole resonance. As the result, the energy-weighted sums of strengths of both IS and IV modes decrease, causing the violation of the corresponding energy-weight sum rules (EWSR). It is shown that this sum rule violation can be eliminated by taking into account the contribution of the particle-particle and hole-hole excitations together with the particle-hole ones in a simple and perturbative way. Consequently, the ratio of the energy-weighted sum of strengths of the pygmy dipole resonance to that of the giant dipole resonance increases., Comment: 23 pages, 2 figures, accepted in Physical Review C

Nucleon–nucleus (NA) optical potentials are microscopically generated from a fully self-consistent framework of the particle-vibration coupling (PVC), in which the nucleon–nucleon (NN) effective interaction of the Skyrme type is consistently used to describe the Hartree–Fock (HF) mean-field, the small amplitude collective motions of the target, and the particle-collective states coupling. For the first time, a systematic calculation of low-energy NA elastic scattering off a series of doubly closed-shell nuclei is carried out without ad hoc adjusted parameters. Angular distributions obtained using the present optical potentials are in good agreement with the experimental data. This will be a major step forward in the applications of the Skyrme energy-density-functional theory to build up the global microscopic optical potentials, which are expected to be a powerful tool for the study of unstable (exotic) nuclei at low-incident nucleon energies.

In four well-deformed heavy odd nuclei, the energies of low-lying rotational band heads have been determined microscopically within a self-consistent Hartree-Fock-plus-BCS approach with blocking. A Skyrme nucleon-nucleon effective interaction has been used together with a seniority force to describe pairing correlations. Only such states which are phenomenologically deemed to be related to single-particle excitations have been considered. The polarization effects, including those associated with the genuine time-reversal symmetry breaking have been fully taken into account within our model assumptions. The calculated spectra are in reasonably good qualitative agreement with available data for the considered odd-neutron nuclei. This is not so much the case for the odd-proton nuclei. A potential explanation for such a difference in behavior is proposed.

Using the $R$-matrix approach we calculate the radiative width for a resonance decaying to a bound state through electric dipole, $E1$, transitions. The total radiative width is determined by the interference of the nuclear internal and external radiative width amplitudes. For a given channel radius the external radiative width amplitude is model independent and is determined by the asymptotic normalization coefficient (ANC) of the bound state to which the resonance decays. It also depends on the partial resonance width. To calculate the internal radiative width amplitude we show that a single particle potential model is appropriate. We compare our results with a few experimental data., Comment: Version accepted for publication in Phys. Rev. C

International audience; Gold nanoparticles have been reported as a possible radio-sensitizer agent in radiation therapy due totheir ability to increase energy deposition and subsequent direct damage to cells and DNA within theirlocal vicinity. Moreover, this increase in energy deposition also results in an increase of the radiochemicalyields. In this work we present, for the first time, an in silico investigation, based on the general purposeMonte Carlo simulation toolkit Geant4, into energy deposition and radical species production around aspherical gold nanoparticle 50 nm in diameter via proton irradiation. Simulations were preformed forincident proton energies ranging from 2 to 170 MeV, which are of interest for clinical proton therapy.

The description of nucleons scattering off doubly closed-shell nuclei $^{16}\mathrm{O}$ and $^{208}\mathrm{Pb}$ at energies below 50 MeV is carried out in a fully self-consistent framework of the particle-vibration coupling approach. The applications are performed with commonly used Skyrme-type effective interactions. Nucleon-nucleus optical potentials are thus calculated without ad hoc adjusted parameters. These potentials are then solved with standard optical model codes (dwba98 in the present case). Empirical nucleon-nucleus elastic angular distributions are thus successfully reproduced.

The restoration of parity symmetry has been performed in the framework of the highly truncated diagonalization approach, which is suited to treat correlations in an explicitly particle-number-conserving microscopic approach. To do so we have assumed axial symmetry and used a generalized Wick's theorem attributable to L\"owdin in a projection-after-variation scheme. We have chosen the Skyrme SkM${}^{*}$ energy-density functional for the particle-hole channel and a density-independent $\ensuremath{\delta}$ force for the residual interaction. We have applied this approach in the region of the outer fission barrier of the ${}^{240}$Pu nucleus. As a result, we have shown that the ${K}^{\ensuremath{\pi}}={0}^{+}$ fission isomeric state is statically unstable against intrinsic parity-breaking modes, while the projection does not affect the energy at the top of the intrinsic outer fission barrier. Altogether, this leads to an increase of the height of the outer fission barrier, with respect to the fission isomeric state, by about 350 keV, thus affecting significantly the spontaneous-fission half-life of the considered fission isomer.

Two systematic sources of error in most current microscopic evaluations of fission-barrier heights are studied. They are concerned with an approximate treatment of the Coulomb exchange terms (known as the Slater approximation) in the self-consistent mean-fields and the projection on good parity states (e.g., of positive parity for the spontaneous fission of an even–even nucleus) of left–right reflection asymmetric intrinsic solutions (e.g., around the second barrier). Approximate or unprojected solutions are shown to lead each to an underestimation of the barrier heights by a few hundred keV.

The left–right asymmetric deformation of normal deformed (ND) and superdeformed (SD) states of 194 Pb has been investigated in the framework of the parity-symmetry projection of the highly truncated diagonalization approach (HTDA), which is suited to treat the correlations in an explicitly particle-number conserving microscopic approach. A Skyrme energy density functional using the SIII and SkM* interactions has been considered to treat the particle–hole channel, whereas a density-independent δ force has been adopted for the residual interaction. The obtained results are compared with previous approaches. The calculated octupole phonon excitation energy is found to be in good qualitative agreement with available data in the ND state.