Search

Our study showed that the inner electron excitation contributes significantly to the electronic stopping power of palladium for protons.

The multinucleon transfer (MNT) process and radioactive beam induced fusion-evaporation (FE) reactions are the considered routines to explore the island of stability. We make the first direct comparison of the two approaches for producing neutron-rich superheavy nuclei, especially the predicted double magic isotope $^{298}$Fl. The radioactive beams $^{49−59}$Ca induced hot FE reactions with actinide targets and the MNT reaction $^{238}$U + $^{252}$Cf are investigated within the framework of the dinuclear system model. Based on the beam intensities proposed by Argonne Tandem Linac Accelerator System, we find that the MNT and FE processes are comparable for producing $^{298}$Fl. The influence of the shell structures uncertainties on the production cross section of $^{298}$Fl is evaluated. It is found that the shell structures weakly influence the production cross sections of $^{298}$Fl around the optimal incident energy, although, the double shell closures could strongly enhance the stability of $^{298}$Fl. We also quantitatively estimated the relative proportion of shell effects on cross sections in the transfer stage of the MNT reaction $^{238}$U + $^{252}$Cf. It is demonstrated that the shell effects on production cross section of $^{298}$Fl are mainly from de-excitation process. The general conclusion of this work is that the radioactive beam induced FE reactions show advantages for the excursion toward N=184 from current status.

The progresses on production cross-sections of unknown nuclei in fusion evaporation (FE) reactions and multinucleon transfer (MNT) reactions are reviewed. The synthesis of the superheavy nuclei (SHN) with [Formula: see text], 119, 120, 121, and 122 in FE reactions is presented. As a promising pathway to produce neutron-rich nuclei, the MNT reactions near the Coulomb barrier are applied to investigate the generation of neutron-rich heavy nuclei and the transuranium nuclei. The predicted production cross-sections of unknown neutron-rich nuclei in MNT reactions are summarized. We make a comparison of the radioactive beam-induced FE reactions and MNT process for producing the predicted double magic nuclei [Formula: see text]Fl, which provides a possible pathway to approach the island of stability.

We study the earliest steps in the radiolysis of a water pentamer in an intense, 800 nm, linearlypolarized fs laser field [I = (0.1 − 50) ∙ 1014 W/cm2] through a real-space, real-time implementation of time-dependent density functional theory nonadiabatically coupled to molecular dynamics. The ionization is enhanced with increasing laser intensity, resulting in the continuous emergence of higher charge states and an increase in the ionization ratio of the deepest levels. Two different reaction pathways of the water pentamer are presented by analyzing the degree of ionization, the level depletion, the probabilities of ionic states, the time-resolved electron density, the bond lengths, and the vibrational frequencies. Both pathways exhibit fluctuations and rearrangement dynamics of the hydrogen bonding network under irradiation. The cyclic structure of the pentamer formed via five oxygen ions is distorted and opened after ionization and tends to maintain a hydronium H3O+ configuration. Proton transfer is accompanied by an oxygen–oxygen contraction and the first proton transfer rate ranges over 6–22 fs.

The multinucleon transfer process in the reaction 238U + 251Cf is investigated by the dinuclear system model with GEMINI++ code. The time evolution of the fragment probability is studied. For the fragments with larger proton number, the time needed to reach the maximum probability is larger. The isotopic distributions become wider at larger evolution time, and more neutron-rich and proton-rich nuclei can be produced. On the neutron-rich side, the ΔU values becomes higher at larger incident angular momentum, resulting in lower cross sections of neutron-rich nuclei. New neutron-rich isotopes with Z = 98–104 are produced with cross sections larger than 1 nb. Three unknown Db isotopes and two unknown Sg isotopes are generated with cross sections larger than 1 pb.

The multinucleon transfer (MNT) reaction is one promising way to produce neutron-rich heavy nuclei and even super heavy nuclei and attracts more and more attentions theoretically and experimentally. A low energy nuclear structure spectrometer called LENSHIAF specific to the MNT reactions will be designed and constructed in the ongoing big project HIAF in China. In the LENSHIAF spectrometer, the most challenge part is how to collect and stop efficiently the high-energy MNT products into the gas cell. By using Monte-Carlo method, the geometry of the gas cell, the thickness of the titanium window/degrader, and the optimal gas pressure filled in the gas cell have been calculated and estimated. For neutron-rich nuclei around N = 126 from 136Xe + 198Pt reaction, with a titanium window/degrader with a thickness of 2.5–3.5 μ m, a cylindrical helium gas cell with a length of 0.6 m and a diameter of 1.2 m can satisfy the requirements to stop the target-like fragments. For heavier and super heavy nuclei from 238U + 238U reaction, with a 5–8 μ m thick titanium window/degrader, the cylindrical gas cell has to be as big as a length of at least 1.6 m and a diameter of 1.6 m.

Transport models are the main method to obtain physics information from low to relativistic-energy heavy-ion collisions. The Transport Model Evaluation Project (TMEP) has been pursued to test the robustness of transport model predictions in reaching consistent conclusions from the same type of physical model. Calculations under controlled conditions of physical input and set-up were performed with various participating codes. These included both calculations of nuclear matter in a box with periodic boundary conditions, and more realistic calculations of heavy-ion collisions. In this intermediate review, we summarize and discuss the present status of the project. We also provide condensed descriptions of the 26 participating codes, which contributed to some part of the project. These include the major codes in use today. We review the main results of the studies completed so far. They show, that in box calculations the differences between the codes can be well understood and a convergence of the results can be reached. These studies also highlight the systematic differences between the two families of transport codes, known as BUU and QMD type codes. However, when the codes were compared in full heavy-ion collisions using different physical models, as recently for pion production, they still yielded substantially different results. This calls for further comparisons of heavy-ion collisions with controlled models and of box comparisons of important ingredients, like momentum-dependent fields, which are currently underway. We often indicate improved strategies in performing transport simulations and thus provide guidance to code developers. Results of transport simulations of heavy-ion collisions from a given code will have more significance if the code can be validated against benchmark calculations such as the ones summarized in this review., 114 pages, 14 figures, 479 references, accepted for publication in Progress of Particle and Nuclear Phsics

The charge exchange spin-dipole (SD) excitations of Zr are studied using the Skyrme Hartee-Fock plus proton-neutron random phase approximation with SAMi-J interactions. The experimental value of the model-independent sum rule obtained from the SD strength distributions of Zr(p, n) Nb and Zr(n, p) Y is used to deduce the neutron skin thickness. The neutron skin thickness of Zr is extracted as fm, which is similar to the results of other studies. Based on the correlation analysis of the neutron skin thickness and the nuclear symmetry energy J as well as its slope parameter L, a constraint from the extracted leads to the limitation of J to MeV and L to MeV.

To investigate the collision processes of proton with the water dimer (H2O)2 at 50 eV, the time-dependent density functional theory coupled with molecular dynamics nonadiabatically is applied. Six specific collision orientations with various impact parameters are considered. The reaction channels, the mass distribution and the fragmentation mass spectrum are explored. Among all launched samples, the probability of the channel of non-charge transfer scattering and charge transfer scattering is about 80%, hinting that the probability of fragmentation is about 20%. The reaction channel of proton exchange process 2 is taken as an example to exhibit the detailed microscopic dynamics of the collision process by inspecting the positions, the respective distance, the number of loss of electrons and the evolution of the electron density. The study of the mass distribution and the fragmentation mass spectrum shows that among all possible fragments, the fragment with mass 36 has the highest relative abundance of 65%. The relative abundances of fragments with masses 1, 35, and 34 are 20%, 13%, and 1.5%, respectively. For the total electron capture cross section, the present calculations agree with the available measurements and calculations over the energy range from 50 eV to 12 keV.

Effect of linear chirp frequency on the process of electron–positron pairs production from vacuum is investigated by the computational quantum field theory. With appropriate chirp parameters, the number of electrons created under combined potential wells can be increased by two or three times. In the low frequency region, frequency modulation excites interference effect and multiphoton processes, which promotes the generation of electron–positron pairs. In the high frequency region, high frequency suppression inhibits the generation of electron–positron pairs. In addition, for a single potential well, the number of created electron–positron pairs can be enhanced by several orders of magnitude in the low frequency region.

Pronounced changes of nuclear charge radii provide a stringent benchmark on the theoretical models and play a vital role in recognizing various nuclear phenomena. In this work, the systematic evolutions of nuclear charge radii along even $Z$=84-120 isotopic chains are firstly investigated by the recently developed new ansatz under the covariant density functional. The calculated results show that the shell closure effects of nuclear charge radii are remarkably shown at the neutron numbers $N=126$ and 184. Interestingly, the arch-like shapes of charge radii between these two strong neutron closed shells are naturally observed. Across the $N=184$ shell closure, the abrupt increase in charge radii is still evidently emerged. In addition, the rapid raise of nuclear charge radii from the neutron numbers $N=138$ to $N=144$ is also disclosed clearly in superheavy regions due to the enhanced shape deformation., 23 pages, 3 figures

Fluorine is one of the most interesting elements in nuclear astrophysics, where the ^{19}F(p,α)^{16}O reaction is of crucial importance for Galactic ^{19}F abundances and CNO cycle loss in first generation Population III stars. As a day-one campaign at the Jinping Underground Nuclear Astrophysics experimental facility, we report direct measurements of the essential ^{19}F(p,αγ)^{16}O reaction channel. The γ-ray yields were measured over E_{c.m.}=72.4-344 keV, covering the Gamow window; our energy of 72.4 keV is unprecedentedly low, reported here for the first time. The experiment was performed under the extremely low cosmic-ray-induced background environment of the China JinPing Underground Laboratory, one of the deepest underground laboratories in the world. The present low-energy S factors deviate significantly from previous theoretical predictions, and the uncertainties are significantly reduced. The thermonuclear ^{19}F(p,αγ)^{16}O reaction rate has been determined directly at the relevant astrophysical energies.

DNA sequence has important biological significance, its effect on groove size affects the expression of protein specific and non-specific binding groove. In liquid environments, different solvents interact with DNA differently. In this chapter, we will focus on the microscopic mechanism of internal bases and external solvents on DNA conformation. In the ordinary water solvent, with the increase of G base content, the DNA structure is transformed by B form—(A-B)—A form. In glycol solvents, DNA maintains B-form configuration, while in ethanol solvent and low activity water solvent, DNA exhibits a shorter and denser A-form.

We reanalyze the problems in the assignment of $3^{3}{S}_{1}$ and $4^{3}{S}_{1}$ light mesons, which have not yet been well established with the $q\overline{q}$ quark model. Regge trajectories and the $^{3}{P}_{0}$ decay model are used, respectively, to study the mass and width of the observed states and predict the missing ones. By comparing our calculations with the latest experiments, we suggest that the inconsistent data of $\ensuremath{\rho}(2150)$ may include two similar structures, $\ensuremath{\rho}(4{^{3}S}_{1})$ and $\ensuremath{\omega}(4{^{3}S}_{1})$. In addition, the problem of the ${K}^{*}(2{^{3}S}_{1})$ assignment, with two observed states ${K}^{*}(1410)$ and ${K}^{*}(1680)$, is investigated, with several possible explanations.

The electronic stopping power of zinc oxide for protons is presented over a wide range of velocities by using real-time time-dependent density functional theory. We calculated the electronic stopping power of energetic protons for both channeling and off-channeling trajectories, and revealed the microcosmic mechanism of semicore $3d$-electron excitation in ZnO. In the low-energy regime, the stopping power obtained from channeling geometry is in a quantitative agreement with the measured data, which reproduced not only the experimental threshold velocity of the stopping power, but also the deviation from velocity-proportional electronic stopping power which is considered to be caused by excitation of the tightly bound $3d$ electrons. In the high-energy regime, we examined the impact parameter dependence of semicore $3d$-electron excitation of ZnO, and showed that the stopping power obtained from off-channeling geometry greatly improves the simulation results in comparison with the channeling results. We also demonstrated that the electronic energy loss of protons is not only related to the number of electrons excited, but also associated with the energy distribution of excited electrons and holes after collisions.

Based on the isospin-dependent Boltzmann–Langevin model, the dynamical fluctuations in the fragmentation reaction of 112Sn+112Sn are investigated. The quadrupole moment and octupole moment with zero magnetic quantum number have large fluctuations in the early time of the collisions. The dynamical fluctuations in momentum space show a strong dependence on the incident energy. The effects of using different fluctuations on the fragment cross sections are also studied in the fragmentation reactions. The results by using Q 20 + Q 30 fluctuation have a better agreement with the experimental data. Calculations using Q 20 + Q 30 fluctuation produce more proton-rich and neutron-rich nuclei than those using Q 20 fluctuation only. Besides, the difference between the production cross sections of fragments calculated by using Q 20 and Q 20 + Q 30 fluctuations is larger in the vicinity of the projectile. These results present that the dynamical fluctuations may affect the whole dynamical process of fragmentation reactions including the production of fragments, due to the nonlinear nature of the Boltzmann–Langevin equation.

In the framework of the time-dependent density-functional theory, applied to valence electrons, coupled non-adiabatically to molecular dynamics of ions, the collision dynamics of cytosine impacted by proton is studied. We especially focus on the effect of the collision orientations on the damage of cytosine by choosing two collision orientations taking the oxygen atom on the double bond CO as the collision site with the incident energy of proton ranging from 150 eV to 1000 eV. First, two collision dynamical processes are explored by analyzing the molecular ionization, the ionic position and the kinetic energy, the energy loss of proton and the electronic density evolution. The results show that the damage process of cytosine induced by proton impact is mainly the capture of electrons by proton, the departments of ions and groups as well as the opening of ring. It is found that the orientation has little effect on the loss of the kinetic energy of proton, which is about 21.5[Formula: see text] of the incident energy of proton. Although the scattering angle [Formula: see text] has a polynomial relationship with [Formula: see text] in both cases, it is greatly affected by the orientation. When [Formula: see text] eV, the scattering angle of proton colliding with O along the [Formula: see text]-axis is greater than that of proton colliding with O along the [Formula: see text]-axis. The orientation also has a great effect on the mass distribution of the fragments and the fragmentation route. When proton moves along the [Formula: see text]-axis, the fragmentation route is that O leaves the cytosine and the rest keeps on vibration, while products are not only related to the incident kinetic energy, but also show diversity when proton moves along the [Formula: see text]-axis.

Within the transport model evaluation project (TMEP) of simulations for heavy-ion collisions, the mean-field response is examined here. Specifically, zero-sound propagation is considered for neutron-proton symmetric matter enclosed in a periodic box, at zero temperature and around normal density. The results of several transport codes belonging to two families (BUU-like and QMD-like) are compared among each other and to exact calculations. For BUU-like codes, employing the test particle method, the results depend on the combination of the number of test particles and the spread of the profile functions that weight integration over space. These parameters can be properly adapted to give a good reproduction of the analytical zero-sound features. QMD-like codes, using molecular dynamics methods, are characterized by large damping effects, attributable to the fluctuations inherent in their phase-space representation. Moreover, for a given nuclear effective interaction, they generally lead to slower density oscillations, as compared to BUU-like codes. The latter problem is mitigated in the more recent lattice formulation of some of the QMD codes. The significance of these results for the description of real heavy-ion collisions is discussed.

Using time-dependent density-functional theory, we investigate the electronic stopping power of self-irradiated silicon through non-adiabatic dynamics simulations. For specific velocities above 0.5 atom units, electronic stopping shows a generally assumed metallic behavior that is velocity-scaling. While in the lower velocity regime, the slope of electronic stopping power versus velocity changes and the overall magnitude are significantly greater than expectations, leading to the complete vanishing of hard threshold. An analysis of the electron localization function allows us to arrive at the following conclusion: the relative long duration of encounter process between the host atoms and the projectiles with low velocities makes possible the formation of chemical bonds. The continuous formation and breaking of chemical bonds provides an additional effective energy loss channel.

Niobium Arsenic (NbAs), presenting some novel properties, is a high-profile topological material in condensed matter physics. Our study focuses on the NbAs after hydrogen (H) and helium (He) radiation. There are a variety of defects induced. We investigate into the electronic properties of defects by analyzing electronic dispersion curves and density of states based on the DFT method. Meanwhile the formation energy of these defects are calculated. The impacts of radiation are various in different defects. Defects of interstitial H and He atom do not affect the topological properties of NbAs at low defect concentration. However, the other defects destruct part of the Weyl points, especially in the defects of vacancy and substitution As for Nb. In addition, Fermi levels of these defects shift and the degenerate bands are separate. From the perspective of formation energy, the defect of H interstitial is the easiest one to be formed in all the defects.

Molecular dynamics simulations are performed for mixtures of ethylene glycol (EG) and water with EG mass fraction of C i = 0%, 20%, 40%, 60%, 80%, 100%. The extensively studied ethanol (EA) and water mixed solutions are also calculated for comparison. Both structure and dynamics properties are analyzed. When the C i increase from 0% to 100%, the intermolecular structure of solvent-solvent exhibits different degrees of clustering except for EG-EG. The intermolecular structure of EG-EG is not obvious affected by the EG mass fraction until the C i is increased to 80%. Intramolecular structure of EG is represented by the dihedral angular probability distribution of OCCO and HOCC, which is mainly determined by the force field rather than the EG mass fraction. In this paper, using General Amber force field, OCCO and HOCC angles show agreement with available experimental data and OPLS-AA-SEI-M force field. EG mass fraction do not affect the probability distribution of OCCO and have a small influence on the t/g probability distribution of HOCC. The dynamics properties of hydrogen bond (HB) breaking is found to decelerate with EG mass fraction increases. The different mechanisms of the longer scale HB lifetimes for EG and EA are also discussed.

Within the framework of the dinuclear system model, the production cross sections for producing the new neutron-rich Lr isotopes in the multinucleon transfer reactions with 249Bk and 254Es targets were predicted. The results show that the 124Sn + 254Es reaction has the highest production cross sections, followed by the 130Te + 249Bk reaction. As far as the existing experimental techniques are concerned, 130Te + 249Bk is the most suitable choice. With experimental techniques developing in the future, 124Sn + 254Es is preferable when the thick 254Es target can be prepared. The optimal energy for producing the new neutron-rich Lr isotopes is 1.1 times the Coulomb barrier for both reaction systems, and both reactions produced 263–265,267–269Lr isotopes. The production mechanism of Lr isotopes has been investigated in the 130Te + 249Bk reaction. It is found that the production of Lr isotopes mainly originates from the contribution of quasifission. And the contribution of quasifission gradually decreases with the increase of the incident angular momentum. The final production cross sections for 263–265,267–269Lr in 130Te + 249Bk reaction at E c.m. = 1.10V C are 0.22 μb, 0.13 μb, 0.15 μb, 4.45 nb, 0.62 nb, and 0.03 nb, respectively