Elastic proton scattering from Be, C, and O isotopes has been investigated in the relativistic impulse approximation (RIA). In the calculations, the nucleon-nucleus optical potentials are obtained using ground state nuclear matter densities, which are computed using the relativistic mean field model with the FSU parameter set. The scattering observables, including differential cross section, analyzing power, and spin-rotation function, are analyzed. It is found that the scattering observables for O isotopic chains display a clear mass dependence, for instance, the minimum analyzing power shifts to a low scattering angle with increasing mass number. While for the Be isotopic chain, the emergence of a neutron halo in ^(14) Be breaks this trend, i.e., the minimum analyzing powers for ^(12) Be and ^(14) Be are almost the same as each other.
The allowed Gamow-Teller β-decay information of Li,Be,B,C,and N isotopes under the frame work of nuclear shell model is calculated herein.Theoretical results of Q values,half-lives,excitation energies,log ft values,branching fractions,and β-delayed proton/neutron emission probabilities are tabulated and compared with experimental data.The deviations from the observations are also analyzed.The 11Be nucleus is well known for its anomaly ground state Jπ=1/2+.Thus,we compared the theoretical energy levels with the experimental data and the agreements for low excitation states are consistent.The quenching factor is also evaluated and discussed.
Very neutron-deficient nuclei are investigated with Woods-Saxon potentials,especially the newly measured A =2Z-1 nucleus ^(65)As [X.L.Tu et al.,Phys.Rev.Lett.106,112501(2011)],where the experimental proton separation energy is obtained as-90(85) keV for the first time.Careful consideration is given to quasibound protons with outgoing Coulomb wave boundary conditions.The observed proton halos in the first excited state of ^(17)F and in the ground states of ^(26,27,28)P are reproduced well,and predictions of proton halos are made for the ground states of ^(56,57)Cu and ^(65)As.The sensitivity of the results to the proton separation energy is discussed in detail,together with the effect of the l=1 centrifugal barrier on proton halos.
The charge form factors of elastic electron scattering for isotones with N=20 and N=28 are calculated using the phase-shift analysis method,with corresponding charge density distributions from relativistic mean-field theory.The results show that there are sharp variations at the inner parts of charge distributions with the proton number decreasing.The corresponding charge form factors are divided into two groups because of the unique properties of the s-states wave functions,though the proton numbers change uniformly in two isotonic chains.Meanwhile,the shift regularities of theminima are also discussed,and we give a clear relation between theminima of the charge form factors and the corresponding charge radii.This relation is caused by the diffraction effect of the electron.Under this conclusion,we calculate the charge density distributions and the charge form factors of the A=44 nuclei chain.The results are also useful for studying the central depression in light exotic nuclei.
Nuclear double β--decay with two neutrinos is an important decay mode for some unstable nuclei. Based on the available experimental data of nuclear double β--decay, we propose that there is a law between the logarithm of double β--decay half-lives and the reciprocal of the decay energy. The physics behind the law is discussed and it is found that this is associated with the universal properties of the weak interaction. This doubleβ--decay law is similar to the famous Geiger-Nuttall law of α-decay. The law is applied to predictions of the nuclear double β--decay half-lives for six even-even nuclei from Z = 84 to Z = 98 and we found that232 Th is very interesting for future experiments. The branching ratios between double β--decay and α-decay are also estimated for the six even-even nuclei and this is useful for future experimental search of new emitters of doubleβ--decay.
The neutron-rich even-even nuclei26–40Mg,28–46Si,30–48S,and32–56Ar are calculated with the RMF model and the phase-shift electron scattering method.Results show that level inversion of the 2s1/2and 1d3/2proton states may occur for the magnesium,silicon,sulphur,and argon isotopes with more neutrons away from the stability line.Calculations show that the variation of the central charge densities for30–48S,and32–56Ar are very sensitive to the 2s1/2and 1d3/2proton state level inversion,and the level inversion can lead to a large measurable central charge depletion to the charge density distributions for the neutron-rich isotopes.Calculations also show that the charge density diferences between the isotopes with and without central charge depletion can reveal not only the level inversion of the 2s1/2and 1d3/2proton states but also the behavior of the proton wave functions of both states.The results can provide references for the possible study of the nuclear level inversion and nuclear bubble phenomenon with electron scattering of short-lived nuclei at RIKEN or/and GSI in the future.In addition,direct nuclear reaction44S(n,d)43P or44S(3H,α)43P might also be a possible way to study the 2s1/2and 1d3/2proton state level inversion.
Nuclear doubleβ--decays with two neutrinos were observed for many years and a systematic law describing the relation between their half-lives and decay energies was also proposed recently[Phys Rev C,2014,89:064603].However,doubleβ+-decay(β+β+)with emission of both two positrons and two neutrinos has not been observed up to date.In this article,we perform a systematic analysis on the candidates of doubleβ+-decay,based on the 2012 nuclear mass table.Eight nuclei are found to be the good candidates for doubleβ+-decay and their half-lives are predicted according to the generalization of the systematic law to doubleβ+-decay.As far as we know,there is no theoretical result on doubleβ+-decay of nucleus154Dy and our result is the first prediction on this nucleus.This is also the first complete research on eight doubleβ+-decay candidates based on the available data of nuclear masses.It is expected that the calculated half-lives of doubleβ+-decay in this article will be useful for future experimental search of doubleβ+-decay.
A new version of the generalized density-dependent cluster model (GDDCM) is de-veloped to describe an α particle tunneling through a deformed potential barrier.The microscopic deformed potential is numerically constructed in the double-folding model using the multipole ex-pansion method.The decay width of an α-cluster state is evaluated using the integral of the quasi-bound state wave function,the scattering state wave function,and the difference of poten-tials.We perform a systematic calculation of α-decay half-lives for favored transitions in even-even nuclei ranging from Z=52 to Z=104.The calculated half-lives are in good agreement with the experimental values.The relation between nuclear deformations and α-decay half-lives is also discussed in details.
Nuclear binding energies,charge radii and the charge distributions of even-even tin (Sn) isotopes are calculated using relativistic mean field theory,and the theoretical results are found to be in accordance with the experimental data.The nuclear charge form factors for Sn isotopes are calculated using the phase-shift analysis method.It is shown that the minima of the charge form factors shift upward and inward with an increase in the neutron number of the Sn isotopes.
We investigate the half-lives of β + /EC(electron capture) decay using the proton-neutron quasiparticle random-phase approximation(pnQRPA) with a δ-form Gamow-Teller residual interaction.Both particle-hole and particle-particle residual interactions are consistently introduced in dealing with the pnQRPA matrix equation.The sensitivity of the calculated half-lives to some physical quantities used in the calculations is examined.Calculations are performed for even-even neutron-deficient isotopes ranging from Z = 10 to Z = 76.Good agreement between experiment and theory is achieved especially for the nuclei far from stability,and the results of our calculations are discussed with comparison with other theoretical results.Predictions on the β-decay half-lives of some very neutron-deficient nuclei are also given for reference in future experiments.
