One-proton and one-neutron knockout reactions from $N = Z = 28$ $^{56}$Ni to the $A = 55$ mirror pair $^{55}$Co and $^{55}$Ni
M. Spieker, A. Gade, D. Weisshaar, B. A. Brown, J. A. Tostevin, B. Longfellow, P. Adrich, D. Bazin, M. A. Bentley, J. R. Brown, C. M. Campbell, C. Aa. Diget, B.… 展开作者
M. Spieker, A. Gade, D. Weisshaar, B. A. Brown, J. A. Tostevin, B. Longfellow, P. Adrich, D. Bazin, M. A. Bentley, J. R. Brown, C. M. Campbell, C. Aa. Diget, B. Elman, T. Glasmacher, M. Hill, B. Pritychenko, A. Ratkiewicz, D. Rhodes
We present a high-resolution in-beam $γ$-ray spectroscopy study of excited states in the mirror nuclei $^{55}$Co and $^{55}$Ni following one-nucleon knockout from a projectile beam of $^{56}$Ni. The newly determined partial cross sections and the $γ$-decay properties of excited states provide a test of state-of-the-art nuclear structure models and probe mirror symmetry in unique ways. A mirror asymmetry for the partial cross sections leading to the two lowest $3/2^-$ states in the $A = 55$ mirror pair was identified as well as a significant difference in the $E1$ decays from the $1/2^+_1$ state to the same two $3/2^-$ states. The mirror asymmetry in the partial cross sections cannot be reconciled with the present shell-model picture or small mixing introduced in a two-state model. The observed mirror asymmetry in the $E1$ decay pattern, however, points at stronger mixing between the two lowest $3/2^-$ states in $^{55}$Co than in its mirror $^{55}$Ni.
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 t…
The $α$-decay phenomennon has been studied for more than a century but the mechanism of the $α$ particle formation and its tunneling process have not yet been fully understood. As an alternative to the $α$-decay lifetime measurement, we propose the proton-induced $α$ knockout reaction, ($p$,$pα$), as a new probe for the surface $α$ formation probability of $α$-decay nuclei. The $^{210,212}$Po($p$,$pα$)$^{206,208}$Pb reaction is described by the distorted-wave impulse approximation framework. It shows that the $^{212}$Po/$^{210}$Po ratio of the $α$ knockout cross sections agrees with that of th…
Background. Knockout reactions with proton targets provide an invaluable tool to access the properties of two-neutron halo nuclei. Recently, experimental results for the average opening angle as a function of the intrinsic neutron momentum in 11Li have shown a localization of dineutron correlations on the nucleus surface. Purpose. Study the model dependence and the effect of distortion and absorption on the opening angle distributions to assess the reliability of this observable to extract properties of Borromean two-neutron halo nuclei. Method. A quasifree sudden model is used to describe the…
Nucleon Correlations in Unstable Nuclei via Knockout Reactions
East Texas A&M University（东德克萨斯农工大学）；Technische Universität Darmstadt（达姆施塔特工业大学）；ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH（极端物质研究所EMMI，GSI重离子研究中心有限公司）
Investigation of Continuum States in the Unbound Neutron-Rich N=7 & 9 Isotones via Breakup and Knockout
利用中能11Be和14，15 B束的分裂和质子敲除技术，研究了~ 9 He，~（10）Li和~（13）Be的结构。在两个N=7的情况下，虚拟s波强度观察到阈值附近与更高的说谎共振。在12 Be +n相对能谱中的阈值处的一个非常窄的结构被证明是由14 Be *（2+）的衰变引起的，而不考虑早期报道的13 Be中的强虚s波态。
Probing the Size of Neutron and Proton Single-Particle Orbitals from Nucleon Knockout Reactions
Technische Universität Darmstadt（达姆施塔特工业大学）；ETH Zürich（苏黎世联邦理工学院）；Institut für Kernphysik, Technische Universität Darmstadt（达姆施塔特工业大学核物理研究所）；Institute of Particle Physics and Astrophysics, ETH Zürich（苏黎世联邦理工学院粒子物理与天体物理研究所）；IRFU, CEA, Université Paris-Saclay（巴黎萨克雷大学CEA IRFU）；RIKEN Nishina Center（理化学研究所仁科加速器科学研究中心）；Dipartimento di Fisica “Aldo Pontremoli”, Università degli Studi di Milano（米兰大学阿尔多·蓬特莫利物理系）；INFN, Sezione di Milano（意大利国家核物理研究所米兰分部）；ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH（GSI重离子研究中心极端物质研究所EMMI）；Max-Planck-Institut für Kernphysik（马克斯·普朗克核物理研究所）；National Center for Computational Sciences, Oak Ridge National Laboratory（橡树岭国家实验室国家计算科学中心）；Department of Physics, Osaka Metropolitan University（大阪公立大学物理系）；Nambu Yoichiro（南部阳一郎）
The structure of $^{33}$Mg was investigated by means of two knockout reactions, one-neutron removal from $^{34}$Mg and one-proton removal from $^{34}$Al. Using comparative analysis of the population of observed excited states in the residual $^{33}$Mg, the nature of these states can be deciphered. In addition, the long-standing controversy about the parity of the $^{33}$Mg ground state is resolved using momentum distribution analysis, showing a clear signature for negative parity. Partial cross section measurements are compared with the results of eikonal reaction theory combined with large-sc…
Single neutron- and proton-removal cross sections have been systematically measured for 72 medium-mass neutron-rich nuclei around Z=50 and energies around 900A MeV using the FRagment Separator (FRS) at GSI. Neutron-removal cross sections are described by considering the knock-out process together with initial- and final-state interactions. Proton-removal cross sections are, however, significantly smaller than predicted by the same calculations. The observed difference can be explained as due to the knockout of short-correlated protons in neutron-proton dominating pairs.
Single-nucleon knockout reaction studies of the proton-dripline nuclei $^9$C and $^{13}$O suggest an appreciable suppression of spectroscopic factors. In this work, we calculate the one-neutron and one-proton spectroscopic factors for the mirror pair $^9$C-$^9$Li and $^{13}$O using two variants of the continuum shell model: the complex-energy Gamow Shell Model and the real-energy Shell Model Embedded in the Continuum. Our results indicate that the continuum effects strongly suppress the spectroscopic factors of well-bound orbits in the dripline systems, but have less impact on the spectroscopi…
Difference in proton radii of mirror nuclei as a possible surrogate for the neutron skin
最近有人提出，镜像核电荷半径的差异与丰中子核的中子皮厚度和对称能$L$的斜率成正比[B.A. Brown Phys. Rev. Lett. 119，122502（2017）]。中子皮的确定对核物理和天体物理有重要意义。虽然电弱探针的使用提供了一个很大程度上与模型无关的中子皮的测定，实验的挑战是巨大的。因此，镜像核的电荷半径的差异可以被用作中子皮的替代物的可能性是一个受欢迎的替代方案。为了检验这一假设的有效性，我们进行计算的基础上，一组相对论能量密度泛函，跨越一个广泛的区域的值的$L$。我们的研究结果证实，不同的缺中子镍同位素和它们相应的镜像核的电荷半径的差异确实是强烈相关的中子皮厚度和$L$。此外，考虑到中子星的各种性质也对$L$敏感，镜像核的电荷半径差与低质量中子星的半径之间出现了数据对数据的关系。
Mechanisms of mirror energy difference for states exhibiting Thomas-Ehrman shift: Gamow shell model case studies of $^{18}$Ne/$^{18}$O and $^{19}$Na/$^{19}$O
Background: The nucleus $^{32}$Mg ($N=20$ and $Z=12$) plays a central role in the so-called "island of inversion" where in the ground states $sd$-shell neutrons are promoted to the $fp$-shell orbitals across the shell gap, resulting in the disappearance of the canonical neutron magic number $N=20$. Purpose: The primary goals of this work are to extend the level scheme of $^{32}$Mg, provide spin-parity assignments to excited states, and discuss the microscopic structure of each state through comparisons with theoretical calculations. Method: In-beam $γ$-ray spectroscopy of $^{32}$Mg was perform…
In this review article we discuss the present status of direct nuclear reactions and the nuclear structure aspects one can study with them. We discuss the spectroscopic information we can assess in experiments involving transfer reactions, heavy-ion-induced knockout reactions and quasifree scattering with (p,2p), (p,pn), and (e,e'p) reactions. In particular, we focus on the proton-to-neutron asymmetry of the quenching of the spectroscopic strength.
