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

Direct demonstration of the two-phonon structure of the Jπ=14742keV− state of Sr88

We have studied the decay pattern of the Jπ=1−4742keV state of 88Sr to probe its quadrupole-octupole coupled two-phonon structure. In particular, a unique fingerprint to prove the two-phonon nature is the E2 decay strength of the 1−4742keV→3−1 transition into the one-octupole-phonon state. γ-ray spectroscopy was performed after the β decay of 88Rb to obtain the necessary sensitivity for this weak-intensity decay branch. Sufficient amounts of 88Rb (T1/2=17.8 min) were produced by neutron activation of natural Rb in the TRIGA Mark II reactor. The results show that the B(E2) value of the 1−4742keV→3−1 transition is equal to the B(E2) of the 2+1→0+1 transition, directly demonstrating the quadrupole-octupole coupled two-phonon nature of the 1− state. A comparison of the results with energy-density functional plus quasiparticle-phonon model calculations shows remarkable agreement, corroborating this assignment

Implementation of an aerodynamic lens for TRIGA-SPEC

We report on the optimization of the gas-jet system employed to couple the TRIGA-SPEC experiment to the research reactor TRIGA Mainz. CdI₂ aerosol particles suspended in N₂ as carrier gas are used for an effective transport of fission products from neutron induced ²³⁵235U fission from the target chamber to a surface ion source. Operating conditions of the gas-jet were modified to enable the implementation of an aerodynamic lens, fitting into the limited space available in front of the ion source. The lens boosts the gas-jet efficiency by a factor of 4–10. The characterization of the gas-jet system as well as the design of the aerodynamic lens and efficiency studies are presented and discussed