Evidence for nucleosynthesis in the supernova gamma process: universal scaling for p nuclei

Analyzing the solar system abundance, we find two universal scaling laws concerning the p and s nuclei. They indicate that the gamma process in supernova (SN) explosions is the most probable origin of the p nuclei that has been discussed with many possible nuclear reactions and sites in about 50 years. In addition, the scalings lead to new concepts: a universality of the gamma process and a new nuclear cosmochronometer. We carry out gamma-process nucleosynthesis calculations for typical core-collapse SN explosion models, and the results satisfy the observed scalings.     

Neutrino-induced fission of neutron-rich nuclei

We calculate neutrino-induced fission cross sections for selected nuclei with Z=84-92. We show that these reactions populate the daughter nucleus at excitation energies where shell effects are significantly washed out, effectively reducing the fission barrier. If the r process occurs in the presence of a strong neutrino fluence, and electron neutrino average energies are sufficiently high, perhaps as a result of matter-enhanced neutrino flavor transformation, then neutrino-induced fission could lead to significant alteration in the r-process flow in slow outflow scenarios.     

Calculation of the quadrupole deformation of nuclei in the mass region A>16

The method for calculating the nuclear-quadrupole-deformation parameter on the basis of a self-consistent anisotropic oscillator potential is modified in such a way that it becomes possible to take phenomenologically into account the resistance of closed nucleon shells against changes in the spherical shape of the nuclear surface. This approach enables one to describe satisfactorily the deformation of beta-stable nuclei in the mass region A>16. The possibility of performing such calculations for nuclei occurring far from the beta-stability valley is also considered.     

Beta decay rates for nuclei with 115<A<140 for r-process nucleosynthesis

For r-process nucleosynthesis the β-decay rates for a number of neutron-rich intermediate heavy nuclei are calculated. The model for the β-strength function is able to reproduce the observed half-lives quite well.     

R-process nucleosynthesis and nuclei far from the region of β-stability

The gross theory of β-decay is applied to make improved estimates of the absolute magnitude of β-decay half-lives and related variables in the r-process calculation. The time necessary for synthesis seems to be considerably longer than assumed in some of the recent studies of the dynamic r-process. This means the necessity of suitable re-scaling of the expansion rates in the dynamics. Although the application of the improvements to the dynamics is most interesting, the present paper has limited itself to the classical quasi-static model of Seeger, Fowler and Clayton in performing the abundance calculation. The calculation method of the final abundance curve can allow several nuclear processes to interrupt β-decay cascades before the β-stability region is reached. The sudden freezing of neutron flux and temperature is assumed to precede these processes. In particular, the effect of β-delayed neutron emission after freezing is extensively studied. The β-delayed fission is also discussed. The calculated β-strength functions are compared with the recent experimental data obtained at the ISOLDE and OSIRIS facilities.     

Toward precision mass measurements of neutron-rich nuclei relevant to r-process nucleosynthesis

The open question of where, when, and how the heavy elements beyond iron enrich our Universe has triggered a new era in nuclear physics studies. Of all the relevant nuclear physics inputs, the mass of very neutron-rich nuclides is a key quantity for revealing the origin of heavy elements beyond iron. Although the precise determination of this property is a great challenge, enormous progress has been made in recent decades, and it has contributed significantly to both nuclear structure and astrophysical nucleosynthesis studies. In this review, we first survey our present knowledge of the nuclear mass surface, emphasizing the importance of nuclear mass precision in r-process calculations. We then discuss recent progress in various methods of nuclear mass measurement with a few selected examples. For each method, we focus on recent breakthroughs and discuss possible ways of improving the weighing of r-process nuclides.     

Analytical solutions for the slow neutron capture process of heavy element nucleosynthesis

In this paper, the network equation for the slow neutron capture process (s-process) of heavy element nucleosynthesis is investigated. Dividing the s-process network reaction chains into two standard forms and using the technique of matrix decomposition, a group of analytical solutions for the network equation are obtained. With the analytical solutions, a calculation for heavy element abundance of the solar system is carried out and the results are in good agreement with the astrophysical measurements.     

Analysis of the 4p 64d 7-(4p 64d 64f + 4p 54d 8) transitions in the Sn VIII spectrum

The spectrum of the 4p ⁶4d ⁷-(4p ⁶4d ⁶4f + 4p ⁵4d ⁸) transitions in Sn VIII occurring in the wavelength range 140–170 Å and excited in a vacuum spark plasma was investigated. For the first time, 113 spectral lines of these transitions were classified and the energies of 38 levels of the 4d ⁶4f and 4p ⁵4d ⁸ configurations were experimentally determined. The semiempirical energy parameters determined by least-squares fitting of the experimental energies of Sn VIII are in good agreement with the parameters of the corresponding configurations obtained previously in the analysis of the Sn VI and Sn VII spectra.