Q value and half-life of double-electron capture in Os-184

Os-184 has been excluded as a promising candidate for the search of neutrinoless double-electron capture. High-precision mass measurements with the Penning-trap mass spectrometer TRIGA-TRAP resulted in a marginal resonant enhancement with = -8.89(58) keV excess energy to the 1322.152(22) keV 0+ excited state in W-184. State-of-the-art energy density functional calculations are applied for the evaluation of the nuclear matrix elements to the excited states predicting a strong suppression due to the large deformation of mother and daughter states. The half-life of the transition in Os-184 exceeds T_{1/2} > 1.3 10^{29} years for an effective neutrino mass of 1 eV.Comment: accepted in Phys. Rev.

Research of the NUSTAR departments : SHE departments and HIM SHE section

The SHE departments devoted to the research of superheavy elements, operate the recoil separators SHIP and TASCA and their ancillary installations including SHIPTRAP and a laser spectroscopy setup at SHIP as well as chemistry and nuclear spectroscopy setups at TASCA. In 2019, the activities at GSI focused on the UNILAC beamtime within the FAIR Phase-0 program and on the analysis of data obtained in prior beamtimes. At HIM, the advancement of actinide sample preparation, manipulation, and characterization for various applications was most central. In addition, technical developments, for example for single-ion mass measurements, have been performed

Fusion reaction 48Ca+249Bk leading to formation of the element Ts (Z=117)

The heaviest currently known nuclei, which have up to 118 protons, have been produced in 48Ca induced reactions with actinide targets. Among them, the element tennessine (Ts), which has 117 protons, has been synthesized by fusing 48Ca with the radioactive target 249Bk, which has a half-life of 327 d. The experiment was performed at the gas-filled recoil separator TASCA. Two long and two short α decay chains were observed. The long chains were attributed to the decay of 294Ts. The possible origin of the short-decay chains is discussed in comparison with the known experimental data. They are found to fit with the decay chain patterns attributed to 293Ts. The present experimental results confirm the previous findings at the Dubna Gas-Filled Recoil Separator on the decay chains originating from the nuclei assigned to Ts

On the diffusion of adsorbed particles on single crystal surfaces: Dynamical investigations with the Scanning Tunneling Microscope

Subject of the present work is the diffusion of adsorbed particles on single crystal planes, which is investigated by scanning tunneling microscopy (STM) and analyzed quantitatively. By evaluation of the atomic motion of oxygen atoms on Ru(0001) it is demonstated, how the transition from the microscopic to the macroscopic description of diffusion can be realized experimentally. Computer-aided image processing permits the statistical evaluation of long sequences of several thousands of atomic configurations, which were recorded with a fast STM system that allows frame rates of up to 20 frames per second. On the one hand, this enables the measurement of the jump rate of isolated oxygen atoms at room temperature as well as the influence of the mutual O-O interaction on that rate over distances of up to 3 lattice constants; from these data the pair potential can be derived. On the other hand the chemical diffusion coefficients were directly determined at various coverages by analysis of the particle number fluctuations. These are found to be in agreement with the microscopic jump rates under consideration of the mutual O-O interaction. Additionally, variable-temperature measurements on the diffusion of sulfur on Pt(111) with coadsorption of CO are reported. For the diffusion of sulfur an activation energy of 550 meV is found. Coadsorption of CO leaves this activation energy unchanged, however, the prefactor is increased by two orders of magnitude by coadsorption of half a monolayer of CO. Various models for this behavior are discussed