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 Coulomb barrier, and outline the procedure for calculating the reaction rates. The results can be easily converted to thermonuclear or pycnonuclear reaction rates to simulate various nuclear burning phenomena, in particular, stellar burning at high temperatures and nucleosynthesis in high density environments.
Spectral lines belonging to the short-lifetime heavy radioactive elements up to Es ($Z$=99) have been found in the spectra of the Przybylski's star. We suggest that these unstable elements may be decay products of a "magic" metastable nucleus belonging to the the island of stability where the nuclei have a magic number of neutrons $N=184$. The laboratory-produced nuclei have a significantly smaller number of neutrons. To identify spectra of the $N=184$ isotopes of these nuclei and their neutron-reach superheavy decay products in astrophysical data we calculate the isotope shift which should be…
Fusion data for $^{13}$C+$^{13}$C, $^{12}$C+$^{13}$C and $^{12}$C+$^{12}$C are analyzed by coupled-channels calculations that are based on the M3Y+repulsion, double-folding potential. The fusion is determined by ingoing-wave-boundary conditions (IWBC) that are imposed at the minimum of the pocket in the entrance channel potential. Quadrupole and octupole transitions to low-lying states in projectile and target are included in the calculations, as well as mutual excitations of these states. The effect of one-neutron transfer is also considered but the effect is small in the measured energy regi…
Since the discovery of molecular resonances in $^{12}$C+$^{12}$C in the early sixties a great deal of research work has been undertaken to study $α$-clustering and resonant effects of the fusion process at sub-Coulomb barrier energies. The modified astrophysical $S^{*}$ factors of $^{12}$C+$^{12}$C fusion have been extracted from direct fusion measurements at deep sub-barrier energies near the Gamow window. They were also obtained by the indirect Trojan horse method (THM). A comparison of direct measurements and the THM, which elucidates problems in the analysis of the THM, is discussed in thi…
We consider the production and deposition on Earth of isotopes with half-lives in the range 10$^{5}$ to 10$^{8}$ years that might provide signatures of nearby stellar explosions, extending previous analyses of Core-Collapse Supernovae (CCSNe) to include Electron-Capture Supernovae (ECSNe), Super-Asymptotic Giant Branch (SAGBs) stars, Thermonuclear/Type Ia Supernovae (TNSNe), and Kilonovae/Neutron Star Mergers (KNe). We revisit previous estimates of the $^{60}$Fe and $^{26}$Al signatures, and extend these estimates to include $^{244}$Pu and $^{53}$Mn. We discuss interpretations of the $^{60}$Fe…
Numerous nuclear reactions in the crust of accreting neutron stars are strongly affected by dense plasma environment. Simulations of superbursts, deep crustal heating and other nuclear burning phenomena in neutron stars require astrophysical S-factors for these reactions (as a function of center-of-mass energy E of colliding nuclei). A large database of S-factors is created for about 5000 non-resonant fusion reactions involving stable and unstable isotopes of Be, B, C, N, O, F, Ne, Na, Mg, and Si. It extends the previous database of about 1000 reactions involving isotopes of C, O, Ne, and Mg. …
Microscopic description of $^{12}$C+$^{12,13}$C fusion reactions at nuclear astrophysical energies
Department of Physics, Kyoto University（京都大学）；Institute for Liberal Arts and Sciences, Kyoto University（京都大学人文学部）；RIKEN Nishina Center for Accelerator-based Science, RIKEN（理化学研究所仁科加速器科学中心）；Nuclear Data Center, Japan Atomic Energy Agency（日本原子力机构核数据中心）
Proton-to-Alpha branching ratio in the $^{12}$C+$^{12}$C fusion reaction at astrophysical energies
Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-sen University（中山大学中法核工程与技术学院）；Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）；School of Nuclear Science and Technology, University of Chinese Academy of Sciences（中国科学院大学核科学与技术学院）；China Institute of Atomic Energy（中国原子能科学研究院）；University of Notre Dame（圣母大学）
The synthesis of heavy, proton rich isotopes is a poorly understood astrophysical process. Thermonuclear (type Ia) supernova explosions are among the suggested sites and the abundance of some isotopes present in the early solar system may be used to test the models. 92Nb is such an isotope and one of the reactions playing a role in its synthesis is 91Zr(p,gamma)92Nb. As no experimental cross sections were available for this reaction so far, nucleosynthesis models had to solely rely on theoretical calculations. In the present work the cross section of 91Zr(p,gamma)92mNb has been measured at ast…
Past and ongoing research activities at the Heidelberg heavy-ion storage-ring TSR are reviewed which aim at providing accurate absolute rate coefficients and cross sections of atomic collision processes for applications in astrophysics and magnetically confined fusion. In particular, dielectronic recombination and electron impact ionization of iron ions are discussed as well as dielectronic recombination of tungsten ions.
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…
The $^{12}$C+$^{12}$C fusion reaction plays a crucial role in stellar evolution and explosions. Its open reaction channels mainly include $α$, $p$, $n$, and ${}^{8}$Be. Despite more than a half century of efforts, large discrepancies remain among the experimental data measured using various techniques. In this work, we analyze the existing data using the statistical model. Our calculation shows: 1) the relative systematic uncertainties of the predicted branching ratios get smaller as the predicted ratios increase; 2) the total modified astrophysical S-factors (S$^*$ factors) of the $p$ and $α$…
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…
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 …
Background: The density dependence of nuclear symmetry energy is crucial in determining several properties of finite nuclei to the neutron stars with mass $\sim$ 1.4 $M_\odot$. The values of neutron skin thickness, isovector giant dipole resonances energies and various nuclear reaction cross-sections in asymmetric nuclei have been utilized to determine the slope of symmetry energy ($L_0$) at the saturation density. Recent PREX-II and CREX measurements of neutron skin thickness in $^{208}$Pb and $^{48}$Ca nuclei yield very different values of $L_0$ which overlap marginally within 90$\%$ confide…
Radioactive isotopes produced in core-collapse supernovae (CCSNe) provide useful insights into the underlying processes driving the collapse mechanism and the origins of elemental abundances. Their study generates a confluence of major physics research, including experimental measurements of nuclear reaction rates, astrophysical modeling, and $γ$-ray observations. Here we identify the key nuclear reaction rates to the nucleosynthesis of observable radioactive isotopes in explosive silicon-burning during CCSNe. Using the nuclear reaction network calculator SkyNet and current REACLIB reaction ra…
Type Ia supernovae (SNe Ia) are thought to be thermonuclear explosion of white dwarfs (WDs). Their progenitors are not well understood. One popular scenario is the double-degenerate (DD) scenario, which attributes SNe Ia to WD-WD binary mergers. The fates of the WD mergers depend on the rate of $^{12}$C+$^{12}$C reaction. Recently, the $^{12}$C+$^{12}$C cross sections have been measured and the analysis of the data using the Trojan Horse Method suggested that the astrophysical reaction rate is larger than conventional rates at astrophysical temperatures due to possible resonances. The resonanc…
