Quasifree (p, 2p) Reactions on Oxygen Isotopes: Observation of Isospin Independence of the Reduced Single-Particle Strength

Quasifree one-proton knockout reactions have been employed in inverse kinematics for a systematic study of the structure of stable and exotic oxygen isotopes at the R3B/LAND setup with incident beam energies in the range of 300-450 MeV/u. The oxygen isotopic chain offers a large variation of separation energies that allows for a quantitative understanding of single-particle strength with changing isospin asymmetry. Quasifree knockout reactions provide a complementary approach to intermediate-energy one-nucleon removal reactions. Inclusive cross sections for quasifree knockout reactions of the type OA(p,2p)NA-1 have been determined and compared to calculations based on the eikonal reaction theory. The reduction factors for the single-particle strength with respect to the independent-particle model were obtained and compared to state-of-the-art ab initio predictions. The results do not show any significant dependence on proton-neutron asymmetry

Activity determination of 60Co and the importance of its beta spectrum

21st International Conference on Radionuclide Metrology and its Applications (ICRM), Argentinian Comis Nacl Energia Atomica, Buenos Aires, ARGENTINA, MAY 15-19, 2017. Organizer: Argentinian Comision Nacional Energia AtomicaInternational audienceThe activity concentration of a $^{60}$Co solution was measured by means of two 4$\pi\beta$-$\gamma$ coincidence counting systems using a liquid scintillation counter and a proportional counter (PC) in the beta channel, respectively. Additional liquid scintillation measurements were carried out and CIEMAT/NIST efficiency tracing as well as the triple-to double coincidence ratio (TDCR) methods were applied to analyse the data. The last two methods require computed beta spectra to determine the counting efficiencies. The results of both 4$\pi\beta$-$\gamma$ coincidence counting techniques are in very good agreement and yield a robust reference value. The initial activity concentration determined with liquid scintillation counting was found to be significantly lower than the results from 4$\pi\beta$-$\gamma$ a coincidence counting. In addition, the results from TDCR and CIEMAT/NIST show some inconsistency. The discrepancies were resolved by applying new beta spectrum calculations for the dominant allowed beta transition of $^{60}$Co. The use of calculations which take screening effects as well as the atomic exchange effect into account leads to good agreement between all four methods; the combination of these techniques delivers an important validation of beta spectra

Unveiling the Two-Proton Halo Character of 17Ne: Exclusive Measurement of Quasi-free Proton-Knockout Reactions

The proton drip-line nucleus 17Ne is investigated experimentally in order to determine its two-proton halo character. A fully exclusive measurement of the 17Ne(p,2p)16F->15O+p quasi-free one-proton knockout reaction has been performed at GSI at around 500 MeV/nucleon beam energy. All particles resulting from the scattering process have been detected. The relevant reconstructed quantities are the angles of the two protons scattered in quasi-elastic kinematics, the decay of 16F into 15O (including gamma decays from excited states) and a proton, as well as the 15O+p relative-energy spectrum and the 16F momentum distributions. The latter two quantities allow an independent and consistent determination of the ratio of l=0 and l=2 motion of the valence protons in 17Ne. With a resulting relatively small l=0 component of only around 35(3)%, it is concluded that 17Ne exhibits a rather modest halo character only. The quantitative agreement of the two values deduced from the energy spectrum and the momentum distributions supports the theoretical treatment of the calculation of momentum distributions after quasi-free knockout reactions at high energies by taking into account distortions based on the Glauber theory. Moreover, the experimental data allow the separation of valence-proton knockout and knockout from the 15O core. The latter process contributes with 11.8(3.1) mb around 40% to the total proton-knockout cross section of 30.3(2.3) mb, which explains previously reported contradicting conclusions derived from inclusive cross sections

Probing the Z=6 spin-orbit shell gap with (p,2p) quasi-free scattering reactions

The evolution of the traditional nuclear magic numbers away from the valley of stability is an active field of research. Experimental efforts focus on providing key spectroscopic information that will shed light into the structure of exotic nuclei and understanding the driving mechanism behind the shell evolution. In this work, we investigate the Z = 6 spin-orbit shell gap towards the neutron dripline. To do so, we employed N-A(p,2p)CA-1 quasi-free scattering reactions to measure the proton component of the 2(1)(+) state of C-16,C-18,C-20. The experimental findings support the notion of a moderate reduction of the proton 1p(1/2) - 1p(3/2) spin-orbit splitting, at variance to recent claims for a prevalent Z = 6 magic number towards the neutron dripline. (C) 2020 The Authors. Published by Elsevier B.V

List of publications Peer-reviewed original articles [1] Quasifree (p, 2p) Reactions on Oxygen Isotopes: Observation of Isospin Independence of the Reduced Single-Particle Strength

[3] Accurate isotopic fission yields of electromagnetically induced fission of U-238 measured in inverse kinematics at relativistic energies