Calculation of Beta Decay Half-Lives and Delayed Neutron Branching Ratio of Fission Fragments with Skyrme-QRPA

Abstract

Abstract. Nuclear β-decay and delayed neutron (DN) emission is important for the rprocess nucleosynthesis after the freeze-out, and stable and safe operation of nuclear reactors. Even though radioactive beam facilities have enabled us to measure β-decay and branching ratio of neutron-rich nuclei apart from the stability line in the nuclear chart, there are still a lot of nuclei which one cannot investigate experimentally. In particular, information on DN is rather scarce than that of T 1/2 . To predict T 1/2 and the branching ratios of DN for next JENDL decay data, we have developed a method which comprises the quasiparticle-random-phase-approximation (QRPA) and the Hauser-Feshbach statistical model (HFSM). In this work, we calculate fission fragments with T 1/2 ≤ 50 sec. We obtain the rms deviation from experimental half-life of 3.71. Although the result is still worse than GT2 which has been adopted in JENDL decay data, DN spectra are newly calculated. We also discuss further subjects to be done in future for improving the present approach and making next generation of JENDL decay data.

Development of a Reference Database for Beta-Delayed Neutron Emission

“…Finally, we mention the self-consistent models for spherical and deformed nuclei in the GT approximation [169][170][171][172][173][174] which have been used in selected isotopic regions. Ref.…”

“…Ref. [170] in particular is dedicated to the next generation of JENDL evaluated decay data, including β-decay half-lives, β-delayed neutron branching ratios, as well as neutron energy spectra. A detailed review of the self-consistent models of β decay can be found in Refs.…”

“…Within the CRP, we performed similar calculations of DN spectra by using a Hartree-Fock-BCS model (SHF-BCS) -instead of the FRDM -combined with QRPA to obtain the β-decay properties. The DN emission part was calculated using the HF model [170]. In this SHFBCS+QRPA+HF model, the pairing correlation is treated by the BCS approximation with a zerorange volume-type force.…”

Toward next JENDL Fission Yield Data and Decay Data

“…This model gives a reasonable agreement with experimental data in half-lives, delayed neutron branching ratios, and average β and γ emission energies in a wide range of nuclei. Another promising model is a quasiparticle random-phase-approximation (QRPA) on the basis of non-relativistic Skyrme energy density functional (Skyrme EDF) [16] and covariant density functional [17]. We have calculated half-lives and delayed neutron branching ratios of FPs using QRPA+Skyrme EDF [16].…”

“…Another promising model is a quasiparticle random-phase-approximation (QRPA) on the basis of non-relativistic Skyrme energy density functional (Skyrme EDF) [16] and covariant density functional [17]. We have calculated half-lives and delayed neutron branching ratios of FPs using QRPA+Skyrme EDF [16]. We developed the model considering a finite-range proton-neutron isospin T = 0 force.…”