Mass measurements of very neutron-deficient Mo and Tc isotopes and their impact on rp process nucleosynthesis

The masses of ten proton-rich nuclides, including the N=Z+1 nuclides 85-Mo and 87-Tc, were measured with the Penning trap mass spectrometer SHIPTRAP. Compared to the Atomic Mass Evaluation 2003 a systematic shift of the mass surface by up to 1.6 MeV is observed causing significant abundance changes of the ashes of astrophysical X-ray bursts. Surprisingly low alpha-separation energies for neutron-deficient Mo and Tc are found, making the formation of a ZrNb cycle in the rp process possible. Such a cycle would impose an upper temperature limit for the synthesis of elements beyond Nb in the rp process.Comment: Link to online abstract: http://link.aps.org/doi/10.1103/PhysRevLett.106.12250

Direct mass measurements beyond the proton drip-line

First on-line mass measurements were performed at the SHIPTRAP Penning trap mass spectrometer. The masses of 18 neutron-deficient isotopes in the terbium-to-thulium region produced in fusion-evaporation reactions were determined with relative uncertainties of about $7\cdot 10^{-8}$, nine of them for the first time. Four nuclides ($^{144, 145}$Ho and $^{147, 148}$Tm) were found to be proton-unbound. The implication of the results on the location of the proton drip-line is discussed by analyzing the one-proton separation energies

GABRIELA : a new detector array for gamma-ray and conversion electron spectroscopy of transfermium elements

With the aid of the Geant4 Monte Carlo simulation package a new detection system has been designed for the focal plane of the recoil separator VASSILISSA situated at the Flerov Laboratory of Nuclear Reactions, JINR, Dubna. GABRIELA (Gamma Alpha Beta Recoil Investigations with the Electromagnetic Analyser VASSILISSA) has been optimised to detect the arrival of reaction products and their subsequent radioactive decays involving the emission of alpha- and beta-particles, fission fragments, gamma- and X-rays, and conversion electrons. The new detector system is described and the results of the first commissioning experiments are presented.Comment: 24 pages, Submitted to NIM

Alpha decay of 176Au

International audienceThe isotope Au176 has been studied in the complete fusion reaction Ca40+Pr141 → 176Au+5n at the velocity filter SHIP (GSI, Darmstadt). The complex fine-structure α decay of two isomeric states in Au176 feeding several previously unknown excited states in the daughter nucleus Ir172 is presented. An α-decay branching ratio of bα=9.5(11)% was deduced for the high-spin isomer in Ir172

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

alpha-decay chains of Z=114, A=289 and Z=118, A=293 in the relativistic mean-field model

A comparison of calculated and experimental Q_alpha values of superheavy even-even nuclei and a few selected odd-N nuclei is presented in the framework of the relativistic mean-field model with the parameterization NL-Z2. Blocking effects are found to be important for a proper description of Q_alpha of odd mass nuclei. The model gives a good overall description of the available experimental data. The mass and charge assignment of the recently measured decay chains from Dubna and Berkeley is in agreement with the predictions of the model. The analysis of the new data does not allow a final conclusion about the location of the expected island of spherical doubly-magic superheavy nuclei.Comment: 4 pages REVTeX, 4 eps figures, accepted for publication in Phys. Rev.

Beta-Delayed fission of 230Am

The exotic decay process of β-delayed fission (βDF) has been studied in the neutron-deficient isotope Am230. The Am230 nuclei were produced in the complete fusion reaction Pb207(Al27,4n)Am230 and separated by using the GARIS gas-filled recoil ion separator. A lower limit for the βDF probability PβDF(Am230)>0.30 was deduced, which so far is the highest value among all known βDF nuclei. The systematics of βDF in the region of Am230 will be discussed