Nuclear shape evolution of neutron-deficient Au and kink structure of Pb isotopes

Recent experiments using advanced laser spectroscopy technique revealed that the charge radii of neutron-deficient gold (Au) isotopes exhibit significant changes in ground state deformation: odd-even shape staggering in the $N = 98 \sim 100$ region and abrupt change of charge radii from $N =$ 108. In this study, we examine the abnormal shape evolution of the nuclear charge radii. To understand the nuclear structure underlying this phenomenon, we exploit the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc). The significant change in mean-squared charge radii ($\delta {}$) turns out to originate from nuclear shape transitions between prolate deformation and small oblate deformation due to the shape coexistence possibility. We elucidate the nuclear shape evolution by analyzing the evolution of occupation probability for single-particle states. In addition, the abrupt kink structure in the nuclear charge radius of lead (Pb) isotopes near the $N =$ 126 shell is also investigated and reproduced quite well

Nuclear structure in Parity Doublet Model

Using an extended parity doublet model with the hidden local symmetry, we study the properties of nuclei in the mean field approximation to see if the parity doublet model could reproduce nuclear properties and also to estimate the value of the chiral invariant nucleon mass $m_0$ preferred by nuclear structure. We first determined our model parameters using the inputs from free space and from nuclear matter properties. Then, we study some basic nuclear properties such as the nuclear binding energy with several different choices of the chiral invariant mass. We observe that our results, especially the nuclear binding energy, approach the experimental values as $m_0$ is increased until $m_0=700$ MeV and start to deviate more from the experiments afterwards with $m_0$ larger than $m_0=700$ MeV, which may imply that $m_0=700$ MeV is preferred by some nuclear properties.Comment: 8 pages, 2 figure

Effects of pair freeze-out on photon distributions in BBN epoch

We investigate the evolution of non-extensivity in the photon distribution during the Big Bang Nucleosynthesis (BBN) epoch using Tsallis statistics. Assuming a minimal deviation from the Planck distribution, we construct the perturbed Boltzmann equation for photons, including the collision terms for pair creation and annihilation processes. We analyze the possibility that these collisions could cause a slight increase in the number of high-frequency photons within the BBN era, and consequently, the primordial plasma might be temporarily placed in a state of chemical non-equilibrium. We also discuss the restoration of the photon distribution to an equilibrium state as the Universe enters the matter-dominated era. These findings, which suggest possible changes in the photon distribution during the epoch between the BBN and the recombination, offer insights that support the previously proposed ansatz solution to the primordial lithium problem in arXiv:1812.09472.Comment: 9 pages, 2 figure

Possible production of neutron-rich Md isotopes in multinucleon transfer reactions with Cf and Es targets

The possibilities for production of yet unknown neutron-rich isotopes Md261-265 are explored in the multinucleon transfer reactions with stable beams bombarding on Cf and Es targets. The production of a given isotope of neutron-rich Md is optimized by appropriate choices of projectile-target combinations and bombarding energies. The production cross sections of neutron-rich Md isotopes in the 0n and 1n evaporation channels of multinucleon transfer reactions are compared. The prospects for the use of radioactive beams in the production of new Md isotopes are discussed

Study of production cross section of neutron-rich Md isotopes in multinucleon transfer reactions

The multi-nucleon transfer reactions have recently attracted attention as a possible path to the synthesis of new neutron- rich heavy nuclei. We predicted the possibilities of production of new neutron-rich isotopes of Md at bombarding energies around the Coulomb barriers. In order to synthesize neutron-rich nuclei, a variety of multi-nucleon transfer reactions were used. The optimal choice of projectile-target combinations and bombarding energies for their production are suggested for future experiments

Possible production of neutron-rich No isotopes

We investigate possible production of neutron-rich isotopes of nobelium. We calculate the production cross sections of No-261(-2)66 in the multinucleon transfer reactions of the same projectiles (S-36, Ca-48, and Ti-50) and targets (Es-254 and Cf248-251) that were used in the previous study for the possible production of neutron-rich isotopes of Md. We find that the production cross sections of neutron-rich No isotopes are about an order of magnitude smaller than those for neutron-rich Md isotopes. By combining the results for the production of neutron-rich No and Md isotopes, we suggest simple expressions which can trace the isotopic trends of the production cross sections of heavy neutron-rich isotopes. The logarithm of the production cross section is proportional to isospin of projectile or target and the Q value

Odd-even staggering and kink structures of charge radii of Hg isotopes by the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) theory

We examine odd-even staggering (OES) of relative charge radii of some Hg isotopes, which has been first measured 1977 and recently confirmed by advanced laser techniques. To understand the nuclear structure underlying this phenomenon, we utilize the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) theory. Our analyses reveal that the OES observed in 180-186Hg isotopes can be attributed to the coexistence of different nuclear shapes in the Hg isotopes. Specifically, we find that prolate shapes of 181,183,185Hg result in an increase in the charge radii compared to oblate even-even 180,182,184,186Hg isotopes. We explain the OES due to the change of the deformation in terms of the evolution of nucleon single particle-states of the Hg isotopes. We also investigate the kink structure of the charge radii of the Hg isotopes in the vicinity of the N=126 shell

Possibilities of production of neutron-rich Md isotopes in multi-nucleon transfer reactions

The possibilities of production of yet unknown neutron-rich isotopes of Md are explored in several multi-nucleon transfer reactions with actinide targets and stable and radioactive beams. The projectile-target combinations and bombarding energies are suggested to produce new neutron-rich isotopes of Md in future experiments