Application of the Gross Theory of β-Decay to Delayed Neutron Emissions

Abstract

Delayed neutron emission is investigated theoretically. First, the strength functions for the allowed and first-forbidden {.1-decays of delayed neutron precursors are calculated by the gross theory of {.1-decay developed by Takahashi, Koyama and Yamada. It is shown that the strengths obtained by the sum rule considerations of the gross theory are less energy-dependent than those used by other investigators. Next, the absolute magnitudes of the delayed neutron emission rates are calculated for the first time without takirig into account the angular momentum. The general trends of the observed emission rates for many nuclides can be well explained. Furthermore, the energy spectra of delayed neutrons are calculated for several examples in consideration of the angular momentum. These results show that the gross theory of {.1-decay is favorably applicable to the study of delayed neutrons.

β-Delayed Neutron Spectroscopy Using Trapped Radioactive Ions

“…For these decays, the lepton momenta were generated from an allowed distribution and γ-ray cascades were approximated as consisting of 1 or 2 isotropically emitted γ rays for decays to excited states above the neutron-separation energy of 137 Xe. Prior experimental results [47] are consistent with calculations based on the gross theory of β decay [55] that indicate that for 137 I, ≈ 75-80% are expected to be allowed. For these allowed decays, no correlation between the β particle and neutron momentum is expected.…”

βdecay of nuclei around90Se: Search for signatures of aN=56subshell closure relevant to theQuinn1, Aprahamian2, Pereira3 et al. 2012Phys. Rev. C

“…In the first (QRPA97 [40]) and second (QRPA03 [44]) calculations (solid and dashed lines, respectively), the nuclear-deformation parameters were determined using the Finite-range droplet model (FRDM) of Möller et al [41]. In addition, QRPA03 includes first-forbidden transition rates obtained from the statistical gross theory [45,46]. The third calculation (QRPAsph) (Fig.…”

β-decay half-lives andβ-delayed neutron emission probabilities of nuclei in the regionA≲110, relevant for the r process

“…The solid lines are the results taken from Ref. [41] (QRPA03), in which the allowed Gamow-Teller transition rates are calculated in a microscopic QRPA approach and in which the first-forbidden transition rates are obtained from the statistical gross theory [86,87]. The second calculation (henceforth referred to as QRPA06), represented by the dashed lines, gives results from an identical model, but with the theoretical Q β values which enter in the phase-space integrals obtained from the improved finite-range liquid-drop model (FRLDM) of Ref.…”