Nuclidic Mass Formula on a Spherical Basis with an Improved Even-Odd Term

Abstract

A nuclidic mass formula composed of a gross term, an even-odd term and a shell term is presented as a revised version of the mass formula constructed by the present authors and published in 2000. The gross term has almost the same functional form as in the previous formula, but the parameter values in it are somewhat different. The even-odd term is treated more carefully, and a considerable improvement is realized. The shell term is exactly the same as the previous one; it was obtained using spherical single-particle potentials and by treating the deformed nucleus as a superposition of spherical nuclei. The new mass formula is applicable to nuclei with Z ≥ 2 and N ≥ 2. The root-mean-square deviation from experimental masses is 666.7 keV, which is less than that of the previous mass formula, 689.8 keV. §1. IntroductionNuclear masses are important quantities to determine the ground state properties and reactions. Since the formulation of the Weizsäcker-Bethe nuclear mass formula, 1), 2) many mass predictions have been made. At the present time, the main purpose of the study of mass formulas is to predict reliable masses of unknown nuclides, especially neutron-rich nuclides and the superheavy nuclides. Some recent mass formulas have been applied to calculations of fission barriers and r-process nucleosyntheses.One way to reproduce the known nuclear mass values is to use mass systematics. For example, the mass formulas presented by Comay et al. and Jänecke et al. 3) are based on Garvey-Kelson-like systematics, 4) which take into consideration particle-hole configurations and yield accurate predictions of known experimental masses, though it is rather difficult to apply these formulas to unknown nuclei far from known ones. In the last decade, some mass predictions designed for wide nuclidic regions have been presented. Among these, we specifically mention two sophisticated mass formulas that give not only nuclear masses but also nuclear shapes

Beta-Decay Rates for Exotic Nuclei and R-Process Nucleosynthesis up to Th and U

“…The half-life for Z =78 obtained here is fairly consistent with the experimental value [4]. Results obtained with global β halflives (GT2-KTUY) [5] are also fairly in good agreement with the present ones within a factor of 2-3. We use the present SM half-lives, which are short compared to the conventional ones of FRDM [3], to study r-process nucleosynthesis in various astrophysical conditions to obtain possible hints for the r-process site which is still under controversy.…”

The equation of state and composition of hot, dense matter in core-collapse supernovae

“…The limited range of low T ∼ 2 MeV and high ρ ∼ 10 13 g/cm 3 is because we consider the nuclear interaction and the convergence of iterations. We show at first the general behaviour of equation of state in the current framework with the mass formula by Koura et al (2005) in Sect. 3.1.…”

“…Our code is not new: we have already compared our NSE results with the kinetic approach in the paper (Panov et al 2001), but the code has not been described in detail. Another motivation for our work is the availability of new mass formulae as in Koura et al (2005) and Möller et al (1995) and detailed EOS tables such as those given in Shen et al (1998b). Our aim is to develop and to test a practical and reliable tool for predictions of NSE composition at subnuclear densities.…”

“…comm. ) for the KTUY mass formula (Koura et al 2005) and ∼9000 nuclides for the FRDM mass formula (Möller et al 1995) as an extra option.…”

Deformation and orientation effects in heavy-particle radioactivity of Z=115

“…With this discovery, a big hunt for more and more cluster emitters was stimulated and as a result today we have a family of cluster radioactive decays leading to 12,14 C, 15 N, 18,20 O, 23 F, 22,24−26 Ne, 28,30 Mg, and 32,34 Si emissions. To date, 34 Si is the heaviest cluster observed with the longest decay half-life (log 10 T 1/2 (s) = 29.04) from 238 U parent, and the smallest branching ratio of cluster w.r.t.…”