Advances in Radioactive Isotope Science

Quasi-free Proton Knockout Reactions on the Oxygen Isotopic Chain

1 Jun 2017, 17:50

15m

Quandry Peak

Invited Presentation Breakout 2

Speaker

Dr Leyla Atar (TU Darmstadt, GSI and University of Guelph)

Description

According to the Independent Particle Model (IPM) single-particle (SP) states are fully occupied up to the Fermi energy with spectroscopic factors (SF) of one. However, it is well known from electron-induced proton knockout that the SP strength is reduced to about 60-70% for stable nuclei, which has been attributed to the presence of short- and long-range correlations[1]. This finding has been confirmed by nuclear knockout reactions using stable and exotic beams, however, with a strong dependency on the proton-neutron asymmetry [2]. The observed strong reduction of SP cross sections for the deeply bound valence nucleons in asymmetric nuclei is theoretically not understood. To understand this dependency quantitatively a complementary approach, quasi-free (QF) knockout reactions, is introduced. QF knockout reactions in inverse kinematics at relativistic energies provide a direct way to investigate the SP structure of stable and exotic nuclei [3]. We have performed a systematic study of spectroscopic strength of oxygen isotopes using QF (p,2p) knockout reactions in complete kinematics at the R3B/LAND setup at GSI with secondary beams containing 13−24O. The oxygen isotopic chain covers a large variation of separation energies, which allow a systematic study of SF with respect to neutron-proton asymmetry. We will present results on the (p,2p) cross sections for the entire oxygen isotopic chain obtained from a single experiment. By comparison with the Eikonal reaction theory [4] the SF and reduction factors as a function of separation energy have been extracted and will be compared to existing data in literature. The results include total and partial cross sections extracted by means of gamma-coincidence measurements as well as momentum distributions. The latter are sensitive to the angular momentum of the knocked-out nucleon in the projectile. Finally, a brief report will be given on a pioneer experiment performed at RIKEN where the QF (p,2p)-fission reaction was employed for the first time on 238U as a benchmark test for future applications to determine fission barriers of neutron-rich exotic nuclei near 208Pb and 214Bi. This work is supported by the GSI-TU Darmstadt cooperation agreement and the BMBF Verbundforschung under contract 05P15RDFN1. References: [1] L.Lapikas NPA 553,297c (1993). [2] J.A.Tostevin, A.Gade PRC 90,057602 (2014). [3] V.Panin et al. PLB 753,204-210 (2016). [4] T.Aumann, C.Bertulani, J.Ryckebusch PRC 88,064610 (2013).