用碎裂和敲除方法研究未束缚丰中子N= 7&9同位素的连续态

Strong neutron pairing in core+4n nuclei

The emission of neutron pairs from the neutron-rich $N\!=\!12$ isotones $^{18}$C and $^{20}$O has been studied by high-energy nucleon knockout from $^{19}$N and $^{21}$O secondary beams, populating unbound states of the two isotones up to 15~MeV above their two-neutron emission thresholds. The analysis of triple fragment-$n$-$n$ correlations shows that the decay $^{19}$N$(-1p)^{18}$C$^*\!\rightarrow^{16}$C+$n$+$n$ is clearly dominated by direct pair emission. The two-neutron correlation strength, the largest ever observed, suggests the predominance of a $^{14}$C core surrounded by four valence…

26 O的基态共振的证据

Evidence for the ground-state resonance of 26O

在82 MeV/u ~（27）F束流的单质子敲除反应中，首次观察到了未束缚中子的~（26）O核的基态。中子测量符合24 O碎片。根据低能中子的观测，26 O被确定为在150+50-150 keV的能量下未结合。这一结果与最近的壳模型计算的基础上微观两个和三个核子力。

Shell structure of $^{43}$S and collapse of the $N=28$ shell closure

The single-particle structure of the $N=27$ isotones provides insights into the shell evolution of neutron-rich nuclei from the doubly-magic $^{48}$Ca toward the drip line. $^{43}$S was studied employing the one-neutron knockout reaction from a radioactive $^{44}$S beam. Using a combination of prompt and delayed $γ$-ray spectroscopy the level structure of $^{43}$S was clarified. Momentum distributions were analyzed and allowed for spin and parity assignments. The deduced spectroscopic factors show that the $^{44}$S ground-state configuration has a strong intruder component. The results were co…

中子滴线附近非束缚核衰变谱中的准粒子共振

Quasiparticle resonance in decay spectrum of unbound nuclei near neutron drip-line

本研究利用 HFB 形式体系分析 ${}^{21}$C 衰变为 ${}^{20}$C 加中子的谱形，证明核子敲除反应可产生低能准粒子共振峰，为实验探测丰中子核配对关联提供途径。

$N=29$同中子素中的$g_{9/2}$中子强度与$^{52}$Cr($d,p$)$^{53}$Cr反应

$g_{9/2}$ neutron strength in the $N=29$ isotones and the $^{52}$Cr($d,p$)$^{53}$Cr reaction

本研究通过16 MeV下的$^{52}$Cr$(d,p)^{53}$Cr反应测量修正并补充了$^{53}$Cr能态的$L$值指认，发现$N=29$同中子素中$g_{9/2}$中子强度远低于求和规则，结合理论计算推测其轨道可能非束缚，并提出后续探测方案。

Single-neutron knockout from $^{20}\textrm{C}$ and the structure of $^{19}\textrm{C}$

The low-lying unbound level structure of the halo nucleus $^{19}\textrm{C}$ has been investigated using single-neutron knockout from $^{20}\textrm{C}$ on a carbon target at 280 MeV/nucleon. The invariant mass spectrum, derived from the momenta of the forward going beam velocity $^{18}\textrm{C}$ fragment and neutrons, was found to be dominated by a very narrow near threshold ($E_\textrm{rel}$ = 0.036(1) MeV) peak. Two less strongly populated resonance-like features were also observed at $E_\textrm{rel}$ = 0.84(4) and 2.31(3) MeV, both of which exhibit characteristics consistent with neutron $p…

12 Be的结构：N=8时的侵入d波强度

Structure of 12Be: intruder d-wave strength at N=8

12 Be基态中N=8壳模型幻数的破缺被确定为包括入侵者d波轨道的显著占据。这与所有其他N=8的同位素形成鲜明对比，它们比12 Be更奇特。通过测量高能12 Be束流中的中子去除量，导出了0毫巴Ω中子p ~（12）轨道和1毫巴Ω中子d ~（5/2）侵入轨道的占位率，并由此导出了11Be的束缚态和非束缚态。

~（24）O中0 d ~（5/2）轨道的中子占有率和N=16壳层闭合

Neutron occupancy of the 0d5/2 orbital and the N=16 shell closure in 24O

在能量为62 MeV/核子的质子靶上，测量了~（24）O到~（23）O第一激发态的单中子敲除。根据22 O碎片和发射中子的四个动量，重建了23 O中子非束缚态的衰变能谱。在E衰变=50 $\pm$ 3 keV处发现了一个尖锐的峰，对应于在2.78 $\pm$ 0.11 MeV处的23 O激发态，正如在以前的测量中观察到的。这种状态的纵向动量分布与d -波中子敲除一致，为Jπ分配5/2+提供了支持。通过将测量的截面（查看MathML源）与畸变波脉冲近似计算进行比较，推导出相关的光谱因子为C2 S（0 d 5/2）=4.1 $\pm$ 0.4。中子0 d 5/2轨道的如此大的占有率与24 O的N=16壳层闭合是一致的。

The Structure of $^{33}$Si and the magicity of the N=20 gap at Z=14

The structure of $^{33}$Si was studied by a one-neutron knockout reaction from a $^{34}$Si beam at 98.5 MeV/u incident on a $^{9}$Be target. The prompt $γ$-rays following the de-excitation of $^{33}$Si were detected using the GRETINA $γ$-ray tracking array while the reaction residues were identified on an event-by-event basis in the focal plane of the S800 spectrometer at NSCL (National Superconducting Cyclotron Laboratory). The presently derived spectroscopic factor values, $C^2S$, for the 3/2$^+$ and 1/2$^+$ states, corresponding to a neutron removal from the $0d_{3/2}$ and $1s_{1/2}$ orbita…

半魔O-23第一激发态的选择布居和中子衰变

Selective population and neutron decay of the first excited state of semi-magic O-23

我们首次在丰中子半魔核O-23中观察到了一个激发态。在以前使用伽马射线光谱的搜索中没有发现这样的状态。在n-碎片符合测量中观察到的共振证实了文献中的推测，即最低的激发态是中子未结合的，并建立了O-23中第一个激发态激发能为2.8（1）MeV的积极证据。假设内壳敲除反应的选择性，解释了预测的第二激发态的非观测。

一次探测两个中子的中子滴线：26 O和16 Be基态共振的首次观测

Exploring the neutron dripline two neutrons at a time: The first observations of the 26O and 16Be ground state resonances

利用$^{27}$ F和$^{17}$ B束的单质子敲除反应，填充了$^{26}$ O和$^{16}$ Be的双中子非束缚基态共振。通过对三体系统（碎片+ n + n）的符合测量，重建了未束缚核的衰变能。在$^{24}$ O + n + n系统中首次观察到一个低能共振$<$ 200 keV，归属于$^{26}$ O的基态.在1.35 MeV处观察到$^{16}$ Be的基态共振。将$^{14}$ Be + n + n系统的三体关联与相空间、序贯和双中子衰变的模拟进行了比较。从实验数据中得到的n-n系统中的强相关性只能通过双中子衰变模拟来再现，这为双中子衰变提供了第一个证据。

First observation of unbound $^{11}$O, the mirror of the halo nucleus $^{11}$Li

The structure of the extremely proton-rich nucleus $^{11}_{~8}$O$_3$, the mirror of the two-neutron halo nucleus $^{11}_{~3}$Li$_8$, has been studied experimentally for the first time. Following two-neutron knockout reactions with a $^{13}$O beam, the $^{11}$O decay products were detected after two-proton emission and used to construct an invariant-mass spectrum. A broad peak of width $\sim$3\,MeV was observed. Within the Gamow coupled-channel approach, it was concluded that this peak is a multiplet with contributions from the four-lowest $^{11}$O resonant states: $J^π$=3/2$^-_1$, 3/2$^-_2$, 5…

Effective proton-neutron interaction near the drip line from unbound states in $^{25,26}$F

Background: Odd-odd nuclei, around doubly closed shells, have been extensively used to study proton-neutron interactions. However, the evolution of these interactions as a function of the binding energy, ultimately when nuclei become unbound, is poorly known. The $^{26}$F nucleus, composed of a deeply bound $\pi0d\_{5/2}$ proton and an unbound $\nu0d\_{3/2}$ neutron on top of an $^{24}$O core, is particularly adapted for this purpose. The coupling of this proton and neutron results in a $J^π = 1^{+}\_1 - 4^{+}\_1$ multiplet, whose energies must be determined to study the influence of the proxi…

中子滴线之外：未结合氧同位素25 O和26 O

Beyond the Neutron Drip-Line: The Unbound Oxygen Isotopes 25O and 26O

本文从实验和理论上研究了极丰中子氧同位素25 O和26 O。在这第一个R3 B-LAND实验中，在GSI通过质子敲除反应从26 F和27 F在相对论能量约450 MeV/核子填充未结合态。从运动学上完整的测量衰变到24 O加上一个或两个中子，25 O基态的能量和寿命被确定，和上限为26 O基态提取。此外，结果提供了一个激发态在26 O在4 MeV左右的证据。实验结果进行了比较，理论壳模型计算的基础上手征的两个和三个核子（3 N）的力量，包括第一次剩余的3 N部队，这是被放大的价中子被添加。

富中子钙同位素中深束缚轨道的光谱学研究

Spectroscopy of deeply bound orbitals in neutron-rich Ca isotopes

本文通过测量$^{53}$Ca和$^{55}$Ca的非束缚态，首次实验证实了富中子钙同位素中$ν0f_{7/2}$深束缚空穴轨道的单粒子强度，结果与壳模型和从头计算一致。

从$^{30}$F的研究看$^{28}$O附近的幻数性与超流性

Magicity versus superfluidity around $^{28}$O viewed from the study of $^{30}$F

首次观测到不稳定同位素$^{30}$F并测得其单中子分离能，证实$^{28}$O附近$N=20$壳层间隙未恢复，揭示了轨道简并与重排导致的超流性及晕核特征。