α -decay properties of Fr200,202

Abstract

Background:The neutron-deficient lead region provides a range of nuclear phenomena, including isomerism at low energies. This phenomenon can be studied by α decay because the degree of hindrance of α decay provides information on the change in nuclear structure of connected states. Purpose: The aim of this work was to investigate the α-decay properties of 200,202 Fr and daughter products. Method: Neutron-deficient francium nuclei are produced at ISOLDE-CERN bombarding a UC x target with 1.4 GeV protons. Surface ionization and mass-separation techniques were employed to provide a pure radioactive ion beam at a radiation-detection setup. Results: Due to the very high statistics and the high beam purity, improved decay data for 202 Fr and its daughters were obtained. In particular, this data set allowed us to identify many fine-structure α lines with a relative reduced α-decay width up to five orders of magnitude lower as the strongest ground-to-ground state or isomericto-isomeric state α-decay transition. In addition, several half-life values were extracted with similar or better precision as compared with the literature. Conclusions: The observation of crossover transitions positioned the isomeric high-spin level of 198 At at an excitation energy of 265(3) keV. Half-life values of 4.47(5) s and 1.28(10) s were extracted for the ground state and isomeric state of 198 At and 52(3) ms for the ground-state decay of 200 Fr. Furthermore, α-decay schemes for 202 Fr and its daughter 198 At could be constructed.

Laser-assisted decay spectroscopy for the ground states of Au180,182

“…After selective ionization, the ions were accelerated by a 30-kV electrostatic potential, and mass separated according to their mass-to-charge ratio using the General Purpose Separator (GPS). The pure ion beam of the isotope of interest was then transported either to the Windmill (WM) decay station [27] or the ISOLTRAP Multi-Reflection Time-of-flight Mass Spectrometer (MR-ToF MS) [17,28]. The WM detection system was utilized for detailed αand β-decay studies of 180 Au, while both setups were used for taking hfs scans for 180,182 Au, either via α-decay tagging in the case of the WM or photo-ion counting using the high-resolution mass-selective MR-ToF MS, see Refs.…”

“…1 of Ref. [27], here only a short description is given. The ion beam passes through a central hole of an annular surface-barrier silicon detector (Si1) and is implanted into one of ten thin carbon foils of 20 μg/cm 2 thickness, mounted on a rotatable wheel.…”