β decay of neutron-richCa53−56

Abstract

β-decay properties of neutron-rich Ca isotopes have been obtained. Half-life values were determined for the first time for 54 Ca (86 ± 7 ms), 55 Ca (22 ± 2 ms), and 56 Ca (11 ± 2 ms). The half-life of 230 ± 60 ms deduced for 53 Ca is significantly longer than reported previously, where the decay chain 53 K → 53 Ca → 53 Sc was considered. A delayed γ ray with energy 247 keV was identified following β decay of 54 Ca, and is proposed to depopulate the 1 + 1 level in 54 Sc. The β-decay properties compare favorably with the results of shell model calculations completed in the full pf -space with the GXPF1 interaction. The half-lives of the neutron-rich Ca isotopes are also compared with gross β-decay theory. The systematic trend of the neutron-rich Ca half-lives is consistent with the presence of a subshell gap at N = 32.

Production cross sections from82Se fragmentation as indications of shell effects in neutron-rich isotopes close to the drip-line

“…Recently, it was shown that the beta-decay half-lives of the neutron-rich Ca isotopes [25] compare favorably with the results of shell-model calculations performed in the full pf model space using the GXPF1 effective interaction [26]. The systematic trend of these half-lives is consistent with the presence of a subshell gap at N = 32 as predicted by this interaction and confirmed by a variety of experiments.…”

“…A similar trend had already been pointed out by Mantica et al [25] where they deduce that the effective energy gap between the adjacent neutron single-particle orbitals f 5/2 and p 1/2 is overestimated by the GXPF1 and GXPF1A effective interactions. Based on this, the GXPF1B interaction has been modified to correct this 0.5 MeV shift and is referred to as GXPF1B5 here.…”

“…Indeed, recent measurements at the NSCL [1,[4][5][6] have demonstrated that the fragmentation of 48 Ca and 76 Ge beams can be used to produce new isotopes in the proximity of the neutron dripline. Continuing this work, we report here the next step with a newly developed 82 Se beam towards the fundamental goal of defining the absolute mass limit for chemical elements in the region of calcium.…”

Discovery of the calcium, indium, tin, and platinum isotopes

“…''This work gives evidence for three new K and Ca isotopes and provides further information on half-lives and P n values''. The measured half-life of 90(15) ms is somewhat smaller than the recent measurement of 230(60) ms [30]. Mantica et al analyzed their data with both half-life values and found the fit for the longer half-life slightly better based on the R 2 regression analysis.…”

“…Mantica et al analyzed their data with both half-life values and found the fit for the longer half-life slightly better based on the R 2 regression analysis. In addition, the authors mentioned that a second β-decaying state could have contributed to the longer half-life value [30]. [54][55][56] Ca 54 Ca, 55 Ca, and 56 Ca were first observed by Bernas et al in 1997, reported in ''Discovery and cross-section measurement of 58 new fission products in projectile fission of 750.A MeV 238 U'' [31].…”