First high-precision direct determination of the atomic mass of a superheavy nuclide

Abstract

We present the first direct measurement of the atomic mass of a superheavy nuclide. Atoms of ${}^{257}$Db ($Z$=105) were produced online at the RIKEN Nishina Center for Accelerator-Based Science using the fusion-evaporation reaction ${}^{208}$Pb(${}^{51}$V, 2n)${}^{257}$Db. The gas-filled recoil ion separator GARIS-II was used to suppress both the unreacted primary beam and some transfer products, prior to delivering the energetic beam of ${}^{257}$Db ions to a helium gas-filled ion stopping cell wherein they were thermalized. Thermalized ${}^{257}$Db${}^{3+}$ ions were then transferred to a multi-reflection time-of-flight mass spectrograph for mass analysis. An alpha particle detector embedded in the ion time-of-flight detector allowed disambiguation of the rare ${}^{257}$Db${}^{3+}$ time-of-flight detection events from background by means of correlation with characteristic $\alpha$-decays. The extreme sensitivity of this technique allowed a precision atomic mass determination from 11 events. The mass excess was determined to be $100063(231{)}_{\text{stat}}(132{)}_{\text{sys}}$~keV/c${}^2$. Comparing to several mass models, we show the technique can be used to unambiguously determine the atomic number as $Z$=105 and should allow similar evaluations for heavier species in future work.

arXiv commentSubmitted to PRC as Rapid Comm., 5 pages, 4 figures

References in corpus (15)

• Nuclear ground-state masses and deformations: FRDM(2012)
• Microscopic mass formulae
• Further explorations of Skyrme-Hartree-Fock-Bogoliubov mass formulas. XII: Stiffness and stability of neutron-star matter
• New Result in the Production and Decay of an Isotope, 278[113], of the 113th Element
• Nuclear mass predictions with radial basis function approach
• Dawning of the N=32 shell closure seen through precision mass measurements of neutron-rich titanium isotopes
• Have Superheavy Elements been Produced in Nature?
• First direct mass measurements of nuclides around $Z=100$ with a Multireflection Time-of-Flight Mass Spectrograph
• Single-reference high-precision mass measurement with a multi-reflection time-of-flight mass spectrograph
• The anatomy of the simplest Duflo-Zuker mass formula
• Improving wide-band mass measurements in a multi-reflection time-of-flight mass spectrograph by usage of a concomitant measurement scheme
• New mass anchor points for neutron-deficient heavy nuclei from direct mass measurements of radium and actinium isotopes
• Design of a Multiple-Reflection Time-of-Flight Mass-Spectrometer for Barium-tagging
• Production cross section and decay study of ${}^{243}$Es and ${}^{249}$Md
• Development of an "$\alpha$-ToF" detector for correlated measurement of atomic masses and decay properties