The total cross sections of the neutron radiative capture on 12B at astrophysical energies to the ground state of 13B have been calculated in the energy range of 10E-8 to 10 MeV within the framework of a modified potential cluster model with the classification of orbital states according to Young diagrams. Reaction rates in the temperature range of 0.01 to 10 T9 and their analytical parameterization were obtained. The calculated rates of 12B(n,gamma)13B excess the previous results by approximately to one order. Cross sections and reaction rates of 12C(n,gamma)13C are calculated and compared to the n10B, n11B, n12B, and p12C reaction rates. It is proposed that obtained rates of the 12B(n,gamma)13B reaction should be taken into account in novel scenarios of stable isotope 13C synthesis without of 12C hydrogen burning.
Nuclear reactions in stars are difficult to measure directly in the laboratory at the small astrophysical energies. In recent years indirect methods with rare isotopes have been developed and applied to extract low-energy astrophysical cross sections.
The observation and prediction of unusually depressed first excited 2^+_1 states in even-A neutron - rich isotopes of semi-magic Sn above 132Sn provide motivations for reviewing the problems related to the nuclear astrophysics in general. In the present work, the beta-decay rates of the exotic even Sn isotopes (134,136Sn) above the 132Sn core have been calculated as a function of temperature (T). In order to get the necessary ft values, B(GT) values corresponding to allowed Gamow Teller (GT-) beta-decay have been theoretically calculated using shell model. The total decay rate shows decrease w…
A project of using a target consisting of the mixture of (249-252)Cf isotopes to be bombarded with the 48Ca beam, aimed to synthesize new isotopes of the heaviest known element Z = 118, is under way at the FLNR in Dubna. In the present work excitation functions for all the reactions: 249Cf(48Ca,xn)(297-x)118, 250Cf(48Ca,xn)(298-x)118, 251Cf(48Ca,xn)(299-x)118 and 252Cf(48Ca,xn)(300-x)118 have been calculated in the framework of the fusion-by-diffusion model, assuming fission barriers, ground-state masses and shell effects of the superheavy nuclei predicted by Kowal et al. Energy dependence of …
Four groups (even-even, even-odd, odd-even and odd-odd) of heavy and super-heavy nuclei are of interest for the synthesis of the isotopes with $Z=119, 120$. We report calculations of $α$~decay half-lives using four models: AKRA (Akrawy); ASAF (Analytical Super-Asymmetric Fission); UNIV (Universal Formula), and semFIS (Semi-empirical formula based on Fission Theory). We compare the experimental $Q_α$ values either with AME16 atomic mass evaluation (whenever available) and with the theoretical model WS4, able to give masses of not yet measured nuclides. For $^{92,94}$Sr cluster radioactivity of …
We calculate the reaction and the fusion cross-sections of neutron-rich heavy nuclei taking light exotic isotopes as projectiles. Results of neutron-rich Pb and U isotopes are demonstrated as the representative targets and He, B as the projectiles. The Gluaber Model and the Coupled Channel Formalism are used to evaluate the reaction and the fusion cross-sections for the cases considered.Based on the analysis of these cross-sections, we predict the formation of heavy, superheavy and super-superheavy elements through rapid neutron/light nuclei capture r-process of the nucleosynthesis in astrophy…
In the framework of the dinuclear system model, the synthesis mechanism of the superheavy nuclides with atomic number $Z=112, 114, 115$ in the reactions of projectiles $^{40,48}$Ca bombarding on targets $^{238}$U, $^{242}$Pu, and $^{243}$Am at a wide incident energies (excitation energy from 0-100 MeV) have been investigated systematically. Based on the available experimental excitation functions, the dependence of calculated synthesis cross sections on collision orientations has been studied thoroughly. The TKEs of these collisions with the fixed collision orientation show its orientation dep…
The connection between neutrino physics, nucleosynthesis of elements in astrophysical sites, laboratory measurements with rare exotic nuclei and astronomical observations is discussed. The key role played by neutrinos is emphasized and the close connection between neutrino physics and nucleosynthesis is highlighted.
Using the Sao Paulo potential and the barrier penetration formalism we have calculated the astrophysical factor S(E) for 946 fusion reactions involving stable and neutron-rich isotopes of C, O, Ne, and Mg for center-of-mass energies E varying from 2 MeV to 18-30 MeV (covering the range below and above the Coulomb barrier). We have parameterized the energy dependence S(E) by an accurate universal 9-parameter analytic expression and present tables of fit parameters for all the reactions. We also discuss the reduced 3-parameter version of our fit which is highly accurate at energies below the Cou…
Beta-decay properties of even and odd-A neutron-rich Ge, Se, Kr, Sr, Ru, and Pd isotopes involved in the astrophysical rapid neutron capture process are studied within a deformed proton-neutron quasiparticle random-phase approximation. The underlying mean field is described self-consistently from deformed Skyrme Hartree-Fock calculations with pairing correlations. Residual interactions in the particle-hole and particle-particle channels are also included in the formalism. The isotopic evolution of the various nuclear equilibrium shapes and the corresponding charge radii are investigated in all…
We study Gamow-Teller strength distributions in some selected nuclei of particular Astrophysical interest within the iron mass region. The theoretical framework is based on a proton-neutron Quasiparticle Random Phase Approximation built on a deformed selfconsistent mean field basis obtained from two-body density-dependent Skyrme forces. We compare our results to available experimental information obtained from (n,p) and (p,n) charge exchange reactions.
Constraining cross sections for unstable $^{153,159}$Gd$(n,γ)$ and their astrophysical implications
School of nuclear Science and Technology, University of South China（南华大学核科学与技术学院）；Key Laboratory of Advanced Nuclear Energy Design and Safety, Ministry of Education（教育部先进核能设计与安全重点实验室）；Office of the Financial Commission, CPC Hunan Provincial Committee（中共湖南省委金融工作委员会）
Nuclear reactions leading to formation of new superheavy elements and isotopes are discussed in the paper. ``Cold'' and ``hot'' synthesis, fusion of fission fragments, transfer reactions and reactions with radioactive ion beams are analyzed along with their abilities and limitations. Several most promising reactions are proposed for experimental study.
The total cross sections of the radiative proton capture on 8Li at astrophysical energies were considered in the framework of the modified potential cluster model with forbidden states, with the classification of the orbital cluster states according to Young diagrams. The recalculation of total cross sections for the 9Be(γ,p0)8Li photodisintegration was used as experimental data. In whole, it is possible to obtain the available data on cross sections at energies to 7.0 MeV. Astrophysical S-factors and reaction rates at the temperature range of 0.01 to 10 T9 were calculated. It was shown that t…
Gamow-Teller transitions in isotopes of chromium play a consequential role in the presupernova evolution of massive stars. $β$-decay and electron capture rates on chromium isotopes significantly affect the time rate of change of lepton fraction ($\dot{Y_{e}}$). Fine-tuning of this parameter is one of the key for simulating a successful supernova explosion. The (anti)neutrinos produced as a result of electron capture and $β$-decay are transparent to stellar matter during presupernova phases. They carry away energy and this result in cooling the stellar core. In this paper we present the calcula…
The properties of recently predicted thermally fissile Th and U isotopes are studied within the framework of relativistic mean field (RMF) approach using axially deformed basis. We calculated the ground, first intrinsic excited state and matter density for highly neutron-rich thorium and uranium isotopes. The possible modes of decay like $α$-decay and $β$-decay are analyzed. We found that the neutron-rich isotopes are stable against $α$-decay, however they are very much unstable against $β$-decay. The life time of these nuclei predicted to be tens of second against $β$-decay. If these nuclei u…
Gamow-Teller (GT) strength distributions (B(GT)) in electron-capture (EC) daughters stemming from the parent ground state are computed with the shell-model in the full pf-shell space, with quasi-particle random-phase approximation (QRPA) in the formalism of Krumlinde and Möller and with an Approximate Method (AM) for assigning an effective B(GT). These are compared to data available from decay and charge-exchange (CE) experiments across titanium isotopes in the pf-shell from A=43 to A=62, the largest set available for any chain of isotopes in the pf-shell. The present study is the first to exa…
We present here a robust analytical model based on nuclear reaction theory for non-resonant fusion cross sections near Coulomb barrier. The astrophysical $S$-factors involving stable and neutron rich isotopes of C, O, Ne, Mg and Si for fusion reactions have been calculated in the centre of mass energy range of 2-30 MeV. The model is based on the tunneling through barrier arising out of nuclear, Coulomb and centrifugal potentials. Our formalism predicts precisely the suppression of $S$-factor at sub-barrier energies which are of astrophysical interest. The cross sections can be convoluted with …
First-forbidden (FF) charge-changing transitions become relatively important for nuclei as their proton number increases. This is because the strength of allowed Gamow-Teller (GT) transitions decreases with increasing Z. The FF transitions play an important role in reducing the half-lives as against those calculated from taking the GT transitions alone into account. In this paper we calculate allowed GT as well as $0^{+} \rightarrow 0^{-}$ and $0^{+} \rightarrow 2^{-}$ transitions for neutron-rich Zn and Ge isotopes. Two different pn-QRPA models were used with a schematic separable interaction…
The production cross sections of heaviest isotopes of superheavy nuclei with charge numbers 112--118 are predicted in the $xn$--, $pxn$--, and $αxn$--evaporation channels of the $^{48}$Ca-induced complete fusion reactions for future experiments. The estimates of synthesis capabilities are based on a uniform and consistent set of input nuclear data. Nuclear masses, deformations, shell corrections, fission barriers, and decay energies are calculated within the macroscopic-microscopic approach for even-even, odd-Z, and odd-N nuclei. For odd systems, the blocking procedure is used. To find, the gr…
Present theoretical investigations aim to explore the fusion characteristics of various isotopes of Z=120 within the relativistic mean-field (RMF) formalism. We predict the most suitable projectile-target combination for the synthesis of element Z=120. The microscopic nucleon-nucleon R3Y interaction and the RMF density distributions for targets and projectiles are used to calculate the nuclear interaction potential using the double folding approach. 17 different projectile-target combinations that allow a high $N$/$Z$ ratio are considered in the present analysis to calculate the capture and/or…
The synthesis of isotopes is possible under conditions of power electric discharge in the atmosphere. Knowledge of the radioactive 14C yield under flash conditions (as additional channel of 14C production relative to the main - cosmogenic one) is important for radiocarbon analysis. It is proposed the gross model for evaluation of the upper limit of the 14C yield, which creation was simulated for the altitudes up to 15 km. It is presented the results for yield of radioactive isotope 41Ar which synthesis goes along with 14C creation under thunderstorm conditions. It was obtained that the possibl…
The study of the $^{48}$Ca+$^{249,250,251,252}$Cf reactions in a wide energy interval around the external barrier has been achieved with the aim of investigating the dynamical effects of the entrance channel via the $^{48}$Ca induced reactions on the $^{249-252}$Cf targets and to analyze the influence of odd and even neutron composition in target on the capture, quasifission and fusion cross sections. Moreover, we also present the results of the individual evaporation residue excitation functions obtained from the de-excitation cascade of the various even-odd and even-even $^{297-300}$118 supe…
Within the framework of the dinuclear system model, the reaction mechanisms for synthesizing target-like isotopes from Bk to compound nuclei Lv are thoroughly investigated in complete and incomplete fusion reaction of $^{48}$Ca +$^{248}$Cm around Coulomb barrier energies. Production cross-section of $^{292,293}$Lv as a function of excitation energy in fusion-evaporation reactions and target-like isotopic yields in multinucleon transfer reactions are evaluated, in which a statistical approach is used to describe the decay process of excited nuclei. The available experimental data can be reprodu…
When muons travel through matter, their energy losses lead to nuclear breakup ("spallation") processes. The delayed decays of unstable daughter nuclei produced by cosmic-ray muons are important backgrounds for low-energy astrophysical neutrino experiments, e.g., those seeking to detect solar neutrino or Diffuse Supernova Neutrino Background (DSNB) signals. Even though Super-Kamiokande has strong general cuts to reduce these spallation-induced backgrounds, the remaining rate before additional cuts for specific signals is much larger than the signal rates for kinetic energies of about 6 -- 18 Me…
Radio-isotopes produced via proton induced reaction holds special significance regarding nuclear medicine, astrophysical p-process, theragnostic and diagnostic processes. $^{76}$Br, $^{80m}$Br and $^{61}$Cu are positron emitter and they are useful in the functional studies via Positron Emission Tomography (PET), whereas $^{77}$Br bears the potential for the application in Single Photon Emission Computed Tomography (SPECT) which involves electron capture process. PET and SPECT have been in high application in medical physics, diagnostics, therapy and nuclear medicine. $^{99m}$Tc and $^{64}$Cu a…
A semi-microscopic model for the low-energy photodisintegration of the 9Be nucleus is constructed, and the experimental data are analyzed with its help. The older radioactive isotope data are supported by this analysis. The theoretical photodisintegration cross section is derived. The astrophysical rates for the reaction alpha + alpha + n -> 9Be + gamma and the reverse photodisintegration of 9Be are calculated. The new reaction rate for alpha + alpha + n -> 9Be + gamma is compared with previous estimations.
Isotopes with low-lying long-lived isomers can behave very differently from other isotopes in astrophysical environments. In particular, the assumption of thermal equilibrium in computing the temperature-dependent $β$-decay rates of such isotopes can fail below certain temperatures. We focus on the $β$-decay of $^{26}$Al since it is one of the most important isotopes in observational astrophysics and has a low-lying isomeric state; we compare and contrast these results with $^{34}$Cl. We rule out recently reported $^{26}$Al effective $β$-decay rates that showed large differences from previous …
This is an exciting time for the study of r-process nucleosynthesis. Recently, a neutron star merger GW170817 was observed in extraordinary detail with gravitational waves and electromagnetic radiation from radio to gamma rays. The very red color of the associated kilonova suggests that neutron star mergers are an important r-process site. Astrophysical simulations of neutron star mergers and core collapse supernovae are making rapid progress. Detection of both, electron neutrinos and antineutrinos from the next galactic supernova will constrain the composition of neutrino-driven winds and pro…
We have computed dipole strength distributions for nickel and tin isotopes within the Relativistic Quasiparticle Time Blocking approximation (RQTBA). These calculations provide a good description of data, including the neutron-rich tin isotopes $^{130,132}$Sn. The resulting dipole strengths have been implemented in Hauser-Feshbach calculations of astrophysical neutron capture rates relevant for r-process nucleosynthesis studies. The RQTBA calculations show the presence of enhanced dipole strength at energies around the neutron threshold for neutron rich nuclei. The computed neutron capture rat…
Experimental studies of hypernuclear dynamics, besides being essential for the understanding of strong interactions in the strange sector, have important astrophysical implications. The observation of neutron stars with masses exceeding two solar masses poses a serious challenge to the models of hyperon dynamics in dense nuclear matter, many of which predict a maximum mass incompatible with the data. In this article, it is argued that valuable new insight may be gained extending the experimental studies of kaon electro production from nuclei to include the $\isotope[208][]{\rm Pb}(e,e^\prime K…
We investigate the possibilities of producing neutron-rich nuclides in projectile fission of heavy beams in the energy range of 20 MeV/nucleon expected from low-energy facilities. We report our efforts to theoretically describe the reaction mechanism of projectile fission following a multinucleon transfer collision at this energy range. Our calculations are mainly based on a two-step approach: the dynamical stage of the collision is described with either the phenomenological Deep-Inelastic Transfer model (DIT), or with the microscopic Constrained Molecular Dynamics model (CoMD). The deexcitati…
Examination of promising reactions with $^{241}$Am and $^{244}$Cm targets for the synthesis of new superheavy elements within the dinuclear system model with a dynamical potential energy surface
Captures of alpha particles on the proton-richest Barium isotope, 130Ba, have been studied in order to provide cross section data for the modeling of the astrophysical gamma process. The cross sections of the 130Ba(alpha,gamma)134Ce and 130Ba(alpha,n)133Ce reactions have been measured with the activation technique in the center-of mass energy range between 11.6 and 16 MeV, close above the astrophysically relevant energies. As a side result, the cross section of the 132Ba(alpha,n)135Ce reaction has also been measured. The results are compared with the prediction of statistical model calculation…
We study here the onset of thermal equilibrium affecting the lifetimes of 26Al and 34Cl nuclei within a hot astrophysical photon gas. The 26Al isotope is of prime interest for gamma ray astronomy with the observation of its delayed (t_1\2=0.74 My) 1.809MeV gamma-ray line. Its nucleosynthesis is complicated by the presence of a short lived (t_1\2=6.34s) spin isomer. A similar configuration is found in 34Cl where the decay of its isomer (34mCl, t_1\2=32m) is followed by delayed gamma-ray emission with characteristic energies. The lifetimes of such nuclei are reduced at high temperature by the th…
We present our recent study of cross sections and angular distributions of projectile fragments from heavy-ion reactions at beam energy of 15 MeV/nucleon. We studied the production cross sections and the angular distributions of neutron-rich nuclides from collisions of a 86 Kr (15 MeV/nucleon) beam with heavy targets ( 64 Ni, 124 Sn and 238 U). Experimental data from our previous work at Texas A & M were compared with model calculations. Our calculations were based on a two-step approach: the dynamical stage of the collision was described with, first, the phenomenological Deep-Inelastic Transf…
The doubly-magic nucleus $^{16}$O has a small neutron capture cross section of just a few tens of microbarn in the astrophysical energy region. Despite of this, $^{16}$O plays an important role as neutron poison in the astrophysical slow neutron capture ($s$) process due to its high abundance. We present in this paper a re-evaluation of the available experimental data for $^{16}$O($n,γ$)$^{17}$O and derive a new recommendation for the Maxwellian-averaged cross sections (MACS) between $kT$= 5$-$100 keV. Our new recommendations are lower up to $kT$= 60 keV compared to the previously recommended …
In astrophysical environments, allowed Gamow-Teller (GT) transitions are important, particularly for $β$-decay rates in presupernova evolution of massive stars, since they contribute to the fine-tuning of the lepton-to-baryon content of the stellar matter prior to and during the collapse of a heavy star. In environments where GT transitions are unfavored, first-forbidden transitions become important especially in medium heavy and heavy nuclei. Particularly in case of neutron-rich nuclei, first-forbidden transitions are favored primarily due to the phase-space amplification for these transition…
A single terbium foil was irradiated with 800 MeV protons to ascertain the potential for production of lanthanide isotopes of interest in medical, astrophysical, and basic science research and to contribute to nuclear data repositories. Isotopes produced in the foil were quantified by gamma spectroscopy. Cross sections for 36 isotopes produced in the irradiation are reported and compared with predictions by the MCNP6 transport code using the CEM03.03, Bertini, and INCL+ABLA event generators. Our results indicate the need to accurately consider fission and fragmentation of relatively light targ…
We use an underground counting lab with an extremely low background to perform an activity measurement for the $^{12}$C+$^{13}$C system with energies down to $E\rm_{c.m.}$=2.323 MeV, at which the $^{12}$C($^{13}$C,$p$)$^{24}$Na cross section is found to be 0.22(7) nb. The $^{12}$C+$^{13}$C fusion cross section is derived with a statistical model calibrated using experimental data. Our new result of the $^{12}$C+$^{13}$C fusion cross section is the first decisive evidence in the carbon isotope systems which rules out the existence of the astrophysical S-factor maximum predicted by the phenomeno…
The prediction of cross sections for nuclei far off stability is crucial in the field of nuclear astrophysics. We calculate direct neutron capture on the even-even isotopes $^{124-145}$Sn and $^{208-238}$Pb with energy levels, masses, and nuclear density distributions taken from different nuclear-structure models. The utilized structure models are a Hartree-Fock-Bogoliubov model, a relativistic mean field theory, and a macroscopic-microscopic model based on the finite-range droplet model and a folded-Yukawa single-particle potential. Due to the differences in the resulting neutron separation a…
Carbon burning is a crucial process for a number of important astrophysical scenarios. The lowest measured energy is around E$_{\rm c.m.}$=2.1 MeV, only partially overlapping with the energy range of astrophysical interest. The currently adopted reaction rates are based on an extrapolation which is highly uncertain because of potential resonances existing in the unmeasured energy range and the complication of the effective nuclear potential. By comparing the cross sections of the three carbon isotope fusion reactions, ${}^{12}$C+${}^{12}$C, ${}^{12}$C+${}^{13}$C and ${}^{13}$C+${}^{13}$C, we h…
