Combinedatomic–nuclear decay

We analyzed in details the combined decay of the atomic-nuclear state, which consists of the excited 3/2⁺ level of ₆₃¹⁵³Eu and K hole, formed in the K capture by ¹⁵³Gd. This decay proceeds in two stages. First, the nucleus transfers its energy to 2p electron, which flies into the continuum spectrum, and then returns into 1s hole, emitting γ quantum with the energy equal to the sum of energies of the nuclear and atomic transitions. We estimated the decay probability to be 2.2 × 10^?13, that is much less than the recent experimental findings.     

Saturation of nuclear partons: Fermi statistics or nuclear opacity?

We derive the two-plateau momentum distribution of final state (FS) quarks produced in deep inelastic scattering (DIS) off nuclei in the saturation regime. The diffractive plateau, which dominates for small p, measures precisely the momentum distribution of quarks in the beam photon; the role of the nucleus is simply to provide an opacity. The plateau for truly inelastic DIS exhibits a substantial nuclear broadening of the FS momentum distribution. We discuss the relationship between the FS quark densities and the properly defined initial state (IS) nuclear quark densities. The Weizsäcker-Williams glue of a nucleus exhibits a substantial nuclear dilution, still soft IS nuclear sea saturates because of the anti-collinear splitting of gluons into sea quarks.     

Symmetries in nuclear β decay

A summary is presented of experiments which test time reversal invariance in nuclear beta decay. The principal measurements are of the angular correlation for which in neutron and¹⁹Ne beta decay one finds an upper limit of D10^–3. As a second topic we also summarize the status of certain angular correlation measurements that bear on the question of second class currents.     

New nuclear three-body clusters φNN

Binding energies of three-body systems of the type φ + 2N are estimated. Due to the strong attraction between φ-meson and nucleon, suggested in different approaches, bound states can appear in systems like φ + np (singlet and triplet), φ + nn and φ + pp. This indicates the principal possibility of the formation of new nuclear clusters.     

Semi-gross theory of nuclear β-decay

The gross theory of β-decay is refined to take into account shell effects of the parent nuclei, and the resulting theory is named semi-gross theory. In this theory, the one-particle energy distribution in the parent nucleus is taken to have structures, and the one-particle strength function is assumed to depend on the quantum numbers of the initial state of the decaying nucleon. β-decay (partial) half-lives are calculated for 1659 nuclides, and the results are compared with experimental data as well as with those calculated by the gross theory. The β-decay strength functions are shown for two selected nuclides, and briefly discussed. These numerical studies confirm that the semi-gross theory includes some part of the shell effects correctly, although there still remain deviations of the theoretical results from experimental data, which should, at least partly, be due to shell effects of the daughter nuclei. Comparison of the present results with microscopic theories shows that the overall accuracy of the semi-gross theory is comparable with those of the microscopic theories.     

Superfluid states in β-stable nuclear matter

Two superfluid states of nuclear matter, which are supposed to play an important role in neutron stars, are discussed: the first one due to the proton-proton ¹ S ₀ pairing in β-equilibrium nuclear matter; the second one due to the anisotropic neutron-neutron ³ PF ₂ pairing in neutron matter. Since the two phases appear at high density of nuclear matter, the three-body forces were added to the pairing interaction and the strong correlation effects in the single-paricle spectrum. The energy gaps, obtained solving the extended BCS equations, significantly deviate from the values without medium effects so as to limit the role of these two superfluid states in the interpretation of phenomena occurring in the neutron-star core.     

Proton radioactivity half-lives with nuclear asymmetry factor

The dependence of proton emission half-lives on the nuclear asymmetry parameter is investigated using the WKB method and two types of empirical formula.Using the single-folding formalism with asymmetry-depend-ent nuclear radius and surface diffuseness of nuclear matter,the nuclear potential and consequently the half-life are functions of the asymmetry factor.Despite small values of asymmetry in neutron-deficient proton emitters,notice-able changes in the half-lives are observed.The addition of an asymmetry parameter term to the two forms of empir-ical formulas leads to a reduction in the rms error for ground state and isomeric transitions.A noticeable reduction of about 43%is obtained for isomeric transitions in the second form of the empirical formula.Considering ground state transitions in two categories,odd-even and odd-odd emitters,and adopting deformation and asymmetry-dependent empirical formulas,the rms decreases remarkably.The low est values of rms errors,viz.0.1492,0.2312,and 0.1999,are obtained for the aforementioned empirical formulas for ground state transitions of odd-even and odd-odd emit-ters and for all isomeric transitions,respectively.     

The NUBASE2012 evaluation of nuclear properties

This paper presents the Nubase2012 evaluation that contains the recommended values for nuclear and decay properties of nuclides in their ground and excited isomeric(T1/2>100 ns) states.All nuclides for which some experimental information is known are considered.NUBASE2012 covers all up to date experimental data published in primary(journal articles) and secondary(mainly laboratory reports and conference proceedings) references,together with the corresponding bibliographical information.During the development of NUBASE2012,the data available in the "Evaluated Nuclear Structure Data File"(Ensdf) database were consalted,and critically assessed of their validity and completeness.Furthermore,a large amount of new and somewhat older experimental results that were missing in Ensdf were compiled,evaluated and included in NUBASE2012.The atomic mass values were taken from the "Atomic Mass Evaluation"(AME2012,second and third parts of the present issue).In cases where no experimental data were available for a particular nuclide,trends in the behavior of specific properties in neighboring nuclei(TNN) were examined.This approach allowed to estimate,whenever possible,values for a range of properties,and are labeled in NUBASE2012 as "non-experimental"(lagged "#").Evaluation procedures and policies that were used during the development of this database are presented,together with a detailed table of recommended values and their uncertainties.     

Nonextensive nuclear liquid–gas phase transition

We study an effective relativistic mean-field model of nuclear matter with arbitrary proton fraction at finite temperature in the framework of nonextensive statistical mechanics, characterized by power-law quantum distributions. We investigate the presence of thermodynamic instability in a warm and asymmetric nuclear medium and study the consequent nuclear liquid–gas phase transition by requiring the Gibbs conditions on the global conservation of baryon number and electric charge fraction. We show that nonextensive statistical effects play a crucial role in the equation of state and in the formation of mixed phase also for small deviations from the standard Boltzmann–Gibbs statistics.     

Isospin dependence of the nuclear binding energy

In this paper,we study the symmetry energy and the Wigner energy in the binding energy formula for atomic nuclei.We simultaneously extract the I2 symmetry energy and Wigner energy coefficients using the double difference of "experimental" symmetry-Wigner energies,based on the binding energy data of nuclei with A≥16.Our study of the triple difference formula and the "experimental" symmetry-Wigner energy suggests that the macroscopic isospin dependence of binding energies is explained well by the I2 symmetry energy and the Wigner energy,and further consideration of the I4 term in the binding energy formula does not substantially improve the calculation result.     

Density-functional theory calculation of the nuclear magnetic resonance indirect nuclear spin—spin coupling constants in C60

Density-functional theory is used to study the nuclear magnetic resonance (NMR) indirect nuclear spin-spin coupling constants in C₆₀. Knowledge of these coupling constants may help in the analysis of future experimental NMR studies of ¹³C-enriched C₆₀. At the Becke 3-parameter Lee-Yang-Parr (B3LYP) Kohn-Sham level, the one-bond couplings within pentagons and between pentagons are 62 Hz and 77 Hz, respectively; the corresponding geminal couplings are 7 Hz and 1 Hz, respectively. Except for the vicinal couplings (about 4 Hz), the long-range couplings are all 1 Hz or smaller. This is the largest theoretical calculation to date of the complete set of indirect nuclear spin-spin coupling constants of a molecular system; it has been made possible by solving the response equations only for the perturbing operators related to one nuclear magnetic moment, making the calculation feasible.     

New nuclear quadrupole resonance technique in β-NMR

The -NMR technique has been modified in order to detect efficiently the nuclear quadrupole effects in the NMR spectra. -NMR is detected as a function of coupling frequency; all RFs that correspond to the coupling frequency were applied simultaneously.     

The NUBASE2020 evaluation of nuclear physics properties

The NUBASE2020 evaluation contains the recommended values of the main nuclear physics properties for all nuclei in their ground and excited,isomeric(T1/2≥100 ns)states.It encompasses all experimental data published in primary(journal articles)and secondary(mainly laboratory reports and conference proceedings)references,together with the corresponding bibliographical information.In cases where no experimental data were available for a particular nuclide,trends in the behavior of specific properties in neighboring nuclei were examined and estimated values are proposed.Evaluation procedures and policies that were used during the development of this evaluated nuclear data library are presented,together with a detailed table of recommended values and their uncertainties.     

Width of the ? meson in nuclear matter

The ratios of the cross sections for ?-meson production induced by 2.83-GeV protons on Cu, Ag, and Au nuclei to the respective cross section for C nuclei were measured at the ANKE-COSY facility in the momentum range of 0.6?C1.6 GeV/c and the angular range of 0°?C8°. The product ? mesons were identified by their decay ? ?? K ⁺ K ^?. The procedure used to separate kaon pairs was described in detail, and all sources of the background and their contribution to the resulting error in the values found for the above cross-section ratios were analyzed. The A dependence of the cross section for ?-meson production was shown to obey the A ^0.56±0.03 law. The total width of the ? meson at a normal nuclear density was extracted from a comparison of the measured cross-section ratios with the results of calculations based on two theoretical models. The resulting width value exceeds substantially both the vacuum width and the width expected in the absence of the nuclear-matter effect on the properties of the ? meson.     

Whence the odd-even staggering in nuclear binding?

We explore the systematics of odd-even mass staggering with a view to identifying the physical mechanisms responsible. The BCS pairing and mean-field contributions have A - and number parity dependences which can help disentangle the different contributions. This motivates the two-term parametrization c ₁ + c ₂/A as a theoretically based alternative to the inverse-power form traditionally used to fit odd-even mass differences. Assuming that the A -dependence of the BCS pairing is weak, we find that mean-field contributions are dominant below mass number A ∼ 40 while BCS pairing dominates in heavier nuclei.     

Mass shift of σ-meson in nuclear matter

The propagation of σ-meson in nuclear matter is studied in the Walecka model, by assuming that the sigma couples to a pair of nucleon–antinucleon states and to particle–hole states. The in-medium effect of σ–ω mixing is also studied. For completeness, the coupling of sigma to two virtual pions was also considered. It is found that the σ-meson mass decreases with respect to its value in vacuum and that the contribution of the σ–ω mixing effect on the mass shift is relatively small.     

Template identification technology of nuclear warheads and components

Template identification technology （TIT） is designed for the scenarios where a batch of disarmed nuclear weapons or components would be dismantled to observe a nuclear disarmament treaty. The core function played by the TIT is to make a judgment on whether the verified item belongs to a certain kind of nuclear weapons or component （NW/NC） or to which kind the verified item belongs. This paper analyses the functions played by the TIT in the process of NW/NC dismantlement, and proposes that two phases would be followed when applying the TIT： firstly to establish NW/NC templates with a sample of size n drawn from a certain kind of disarmament NW; secondly to authenticate NW/NC by means of the TIT. This paper also expatiates some terms related to the concept of the TIT and investigates on the development status of NW/NC TIT based on radiation signatures. The study concludes that the design of template structure is crucial to the establishment of an effective TIT and that starting from different research angles and aiming at the same goal of classification different template structures and corresponding template identification methods can be built up to meet specific identification requirements.     

Parameterization of the nuclear Hulthén potentials

Within the formalism of supersymmetry-inspired factorization method, a two-term nuclear Hulthén potential has been developed and parameterized to reproduce the nucleon–nucleon scattering phase shifts for P and D partial wave states.     

Density-functional calculations of the nuclear magnetic shielding and indirect nuclear spin–spin coupling constants of three isomers of C20

The parameters of the nuclear magnetic resonance (NMR) spectrum – shielding constants and indirect spin–spin coupling constants – of three isomers of C₂₀ are studied using density-functional theory. The performance of different exchange–correlation functionals is analysed by optimising the geometry for the ring, bowl and cage isomers, followed by a computation of the NMR constants at the optimised structure. The results are analysed and rationalised by performing comparisons of the three isomers with one another and with related systems such as polyynes (for the ring), o-benzyne (for the bowl) and C₆₀ (for the cage). The shielding and spin–spin parameters calculated using the Perdew–Burke–Ernzerhof (PBE) exchange–correlation functional are sufficiently reliable to assist in future experimental NMR studies of C₂₀ and, in particular, the identification of its isomers.     

Fragmentation of ^16O nuclei in nuclear emulsion

We present the topology of 16O fragmentation at 60A GeV in reactions with emulsion nuclei.We discuss the multiplicity distributions of projectile fragments.charged secondaries and their dependence on the target residues.