Yuliia Hrabar

The production cross sections of neutron-rich nuclides near the N = 126 neutron shell closure have been measured for the elements ranging from tungsten ( Z = 74 ) to gold ( Z = 79 ) in the fragmentation of a 1000 MeV / u Pb 208 beam on a Be 9 target. Several cross sections, namely those for W 196 − 199 , Re 199 − 201 , and Os 202 − 203 , were determined for the first time with this projectile-target combination. The results are compared with the predictions of several nuclear reaction models and semiempirical parametrizations; special attention is devoted to multiple proton-removal channels and the formation of nuclides with neutron number N = 127 .

Excited states in the proton drip line nucleus Ga 61 were populated via the fusion-evaporation reaction Mg 24 ( Ca 40 , p 2 n ) Ga 61 . The experimental setup at Argonne National Laboratory comprised a novel combination of the Gammasphere array with two CD-shaped double-sided Si-strip detectors inside the Microball CsI(Tl) charged-particle detection array, as well as the Neutron-Shell liquid scintillators and the Fragment Mass Analyzer. Owing to the setup’s unprecedented in-beam proton spectroscopy and tracking capabilities, a coincidence between a 957.6(5)-keV γ ray and a 1.876(24)-MeV proton line was observed, which identifies the quasibound proton π g 9 / 2 single-particle state in Ga 61 at E x = 2150 ( 34 ) keV . This probes isospin symmetry at the limit of nuclear binding by providing a unique challenge for the shell-model interpretation of mirror nuclei beyond doubly magic Ni 56 .

Deuteron evaporation was observed from the N = Z compound nuclei Fe ★ 52 , Ni ★ 56 , and Ge ★ 64 in an experiment conducted at Argonne National Laboratory, USA. The experiment included a novel combination of two highly pixelated double-sided Si-strip detectors inside the Microball charged-particle detection array, allowing for unequivocal discrimination of evaporated deuterons from protons and α particles. In conjunction with the Gammasphere array, Neutron Shell, and additional ancillary detectors, decay paths into various residual nuclei were investigated. The study provides insights into the competition of deuteron vs proton-neutron evaporation as a function of available excitation energy and populated angular momentum. Results are interpreted using a statistical evaporation formalism for multiple subsequent particle emissions. The decisive factor in the comparison appears to be the available excitation energy in the residual system, with single nucleon evaporation preferred over deuteron evaporation for higher excitation energies. Published by the American Physical Society 2025