A nuclear spectroscopy experiment was conducted to study α-decay chains stemming from isotopes of flerovium (element Z=114). An upgraded TASISpec decay station was placed behind the gas-filled ...separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. The fusion-evaporation reactions ^{48}Ca+^{242}Pu and ^{48}Ca+^{244}Pu provided a total of 32 flerovium-candidate decay chains, of which two and eleven were firmly assigned to ^{286}Fl and ^{288}Fl, respectively. A prompt coincidence between a 9.60(1)-MeV α particle event and a 0.36(1)-MeV conversion electron marked the first observation of an excited state in an even-even isotope of the heaviest man-made elements, namely ^{282}Cn. Spectroscopy of ^{288}Fl decay chains fixed Q_{α}=10.06(1) MeV. In one case, a Q_{α}=9.46(1)-MeV decay from ^{284}Cn into ^{280}Ds was observed, with ^{280}Ds fissioning after only 518 μs. The impact of these findings, aggregated with existing data on decay chains of ^{286,288}Fl, on the size of an anticipated shell gap at proton number Z=114 is discussed in light of predictions from two beyond-mean-field calculations, which take into account triaxial deformation.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
The radioactive decay properties of \(^{242}\)Es were studied with significantly improved statistics compared to available literature data. This isotope was produced in the 3n evaporation channel of ...the fusion reaction of \(^{48}\)Ca+\(^{197}\)Au. A half-life of 16.9(8)~s was deduced from 662 \(\alpha\) decays of \(^{242}\)Es, resulting in an \(\alpha\)-decay branching of 41(3)\%. Twenty-six fission events with a half-life of 18.2\(^{+4.5}_{-3.0}\)~s were assigned to originate from the electron-capture delayed fission of \(^{242}\)Es. The probability for the electron-capture delayed fission was measured to be 0.015(4), which improves and resolves ambiguities in available experimental data. We discuss all known cases for electron-capture delayed fission in Es, Bk, and Am isotopes and compare experimental data with predictions from a recent semi-empirical model. A cross section of 27(3)~nb was measured for the production of \(^{242}\)Es.
Flerovium isotopes (element Z = 114) were produced in the fusion-evaporation reactions 48Ca+242,244Pu and studied with an upgraded TASISpec decay station placed in the focal plane of the gas-filled ...separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Twenty-nine flerovium decay chains were identified by means of correlated implantation, α decay, and spontaneous fission events. Data analysis aspects and statistical assessments, primarily based on measured rates of various events, which laid the foundation for the comprehensive spectroscopic information on the flerovium decay chains, are presented in detail. Various decay scenarios of an excited state observed in 282Cn are examined in depth with the help of GEANT4 simulations and assessed by predictions of beyond mean-field calculations including triaxial shape degrees of freedom. Previous, revised, and newly derived fission probabilities of even-even superheavy nuclei are compared with various theoretical predictions.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
PDF
