Beta-decay properties of the neutron-rich 94–99Kr and 142–147Xe isotopes

Abstract

Beta-decay half-lives and delayed-neutron emission probabilities of the neutron-rich noble-gas isotopes 94−99 Kr and 142−147 Xe have been measured at the PSB-ISOLDE facility at CERN. The results are compared to QRPA shell-model predictions and are used in dynamic calculations of r-process abundances of Kr and Xe isotopes.

β -decay half-lives of 55 neutron-rich isotopes beyond the N=82 shell gap

“…3. The experimental results are compared with literature values [23,[29][30][31][32][33][34][35][36][37][38] and five theoretical predictions: finite-range droplet-model FRDM-1995 mass formula [46] with quasiparticle-randomphase approximation (QRPA) (2003) [39] as well as the new version (2019) [40] with FRDM-2012 masses [47], Koura-Tachibana-Uno-Yamada (KTUY) with the second generation of β-decay gross theory (GT2) [41,42], Relativistic Hartree-Bogoliubov (RHB) with the proton-neutron relativistic quasiparticle random-phase approximation (pn-RQRPA) [43], and the energy density functional (DF) with continuum quasiparticle random-phase approximation (CQRPA) [44,45].…”

“…One reason for the discrepancy is that the Q β values in this calculation do not include pairing effects. The DF+CQRPA are only applicable for nearly spherical nuclei, so they fit well [23,[29][30][31][32][33][34][35][36][37][38]. The measurements are compared to predictions of five theoretical models: FRDM+QRPA (2003) [39] (brown), FRDM+QRPA (2019) [40] (green), KTUY+GT2 [41,42] (red), RHB+pn-RQRPA [43] (blue), and DF+CQRPA [44,45] (magenta).…”

Discovery of the krypton isotopes

“…It should be mentioned that an estimated half-life of 1-2 s for 97 Kr had been reported during the Manhattan Project [37]. However, this observation was later questioned [42], which is supported by the most recent half-life measurement of 68 (7) ms [45].…”

“…In 1976, Ahrens et al extracted the half-life of 95 Kr (T 1/2 = 0.78(3) s) from its long-lived decay products using a gas-flow method [44]. However, in 2003 Bergmann et al [45] measured a significantly shorter half-life of 114(3) ms which raises doubt about the Ahrens measurement: "In particular, the half-lives from the earlier indirect radiochemical measurements ... (quoted by nuclear data evaluators for 95 Kr ...) deviate considerably from our results, indicating that these identifications probably were not correct." Thus, we credit the discovery to 96 Kr in 1994 at GSI, Germany, as reported in Projectile Fission at Relativistic Velocities: A Novel and Powerful Source of Neutron-Rich Isotopes Well Suited for In-Flight Isotopic Separation [43].…”

Discovery of palladium, antimony, tellurium, iodine, and xenon isotopes

“…According to the HFB-14 model [15], 179 Xe should be the last odd-even particle stable neutron-rich nucleus while the even-even particle stable neutron-rich nuclei should continue through 184 Xe. At the proton dripline one more isotope ( 108 Xe) is predicted to be particle stable.…”