在考虑$α$ -粒子角动量和子核激发几率的广义液滴模型（GLDM）框架下，计算了$α$ -衰变到偶偶核基态转动带和0 $^{+}$激发态的分支比.计算涵盖了质量区域$180< A <202$和A $\geq 224$中从Hg到Fm的同位素链。计算的$α$ -跃迁的分支比与实验数据符合得很好，并为今后的实验提供了一些有用的预测。
英文摘要：
Branching ratios of $α$-decay to members of the ground state rotational band and excited 0$^{+}$ states of even-even nuclei are calculated in the framework of the generalized liquid drop model (GLDM) by taking into account the angular momentum of the $α$-particle and the excitation probability of the daughter nucleus. The calculation covers isotopic chains from Hg to Fm in the mass regions $180< A <202$ and A$\geq 224$. The calculated branching ratios of the $α$-transitions are in good agreement with the experimental data and some useful predictions are provided for future experiments.
Study of cluster structures of excited states for the light nuclei He, Li and Be in three-body photodisintegration processes. Application for the excited states of the 6He* nucleus
The fragmentation of quasi-projectiles from the nuclear reaction 40Ca + 12C at 25 MeV/nucleon was used to produce alpha-emission sources. From a careful selection of these sources provided by a complete detection and from comparisons with models of sequential and simultaneous decays, strong indications in favour of $α$-particle clustering in excited 16O, 20Ne and 24}Mg are reported.
A novel method for simultaneous measurement of masses, Q-values, isomer excitation energies, half-lives and decay branching ratios of exotic nuclei has been demonstrated. The method includes first use of a stopping cell as an ion trap, combining containment of precursors and decay-recoils for variable durations in a cryogenic stopping cell (CSC), and afterwards the identification and counting of them by a multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). Feasibility has been established by recording the decay and growth of $^{216}$Po and $^{212}$Pb (alpha decay) and of $^{119m2…
Using a fully quantum mechanical post-form finite-range distorted-wave Born approximation theory of Coulomb breakup, I study the parallel momentum distribution of the core in the Coulomb breakup of suggested excited-state one-neutron halo nuclei considered in their different bound excited states. Narrow momentum distributions obtained in the present calculations for some cases indicate the possibilities of the excited-state halo structure in the nuclei under consideration and therefore favor the previous predictions.
The determination of absolute branching ratios for high-energy states in light nuclei is an important and useful tool for probing the underlying nuclear structure of individual resonances: for example, in establishing the tendency of an excited state towards $α$-cluster structure. Difficulty arises in measuring these branching ratios due to similarities in available decay channels, such as ($\mathbf{^{18}}$O,$\mathbf{n}$) and ($\mathbf{^{18}}$O,$\mathbf{2n}$), as well as differences in geometric efficiencies due to population of bound excited levels in daughter nuclei. Methods are presented us…
A search for alpha and double beta decays of ytterbium isotopes was performed with an ultra-low background high purity germanium detector at Gran Sasso Underground Laboratory (Italy). A 194.7 g Yb$_2$(C$_2$O$_4$)$_3$ powder sample was measured for 11.3~d with a total Yb exposure of 1.25 kg$\times$d. Half-life limits for $α$-decay modes of $^{168}$Yb, $^{170}$Yb, $^{171}$Yb, $^{172}$Yb, $^{173}$Yb, $^{174}$Yb and $^{176}$Yb into the first excited states have been obtained between $6\times10^{14}$ yr and $2\times10^{16}$ yr. These are the first experimental constraints of these decay modes. Doub…
The spin and parity ($J^π$) assignments in even-even nuclei were reviewed across the nuclear chart using the Evaluated Nuclear Structure Data File (ENSDF). The prevalence of 2$^+_1$ first or lowest excited states is confirmed. The properties of 0$^+_2$, 1$^-_1$, and 3$^-_1$ lowest excited states were reexamined using the ENSDF data evaluation procedures. The $J^π$ systematic trends and correlations between level quantum numbers and nuclear physics phenomena are discussed.
Starting from experimental studies on alpha-clustering in excited self-conjugate nuclei (from $^{16}$O to $^{28}$Si), temperature and density conditions for such a clustering are determined. Measured temperatures have been found in the range of 5.5 - 6.0 MeV whereas density values of 0.3 - 0.4 times the saturation density are deduced, i.e., 0.046 to 0.062 $fm^{-3}$. Such a density domain is also predicted by constrained self-consistent mean field calculations. These results constitute a benchmark for alpha clustering from self-conjugate nuclei in relation to descriptions of stellar evolution a…
Systematic Study of Survival Probability of Excited Superheavy Nuclei
用统计模型研究了含$100 \leq Z \leq 134$的超重核对中子发射和裂变的稳定性。特别是对这些SHN的1n沟道中抗裂变的生存概率进行了系统的研究。在目前的计算中，中子分离能和壳层修正能始终取自有限程液滴模型的计算结果，该模型预测了SHN在Z=115和N=179附近的稳定岛。事实证明，在最佳激发能下激发SHN的1n通道中计算的存活概率在Z=115和N=179附近最大化的意义上，这种稳定岛对于激发SHN持续存在。这表明1n沟道中的存活几率主要由核壳效应决定。
Neutron-capture reactions on $^{18}$F in the helium-burning shell play an important role in the production of $^{15}$N during core-collapse supernovae. The competition between the $^{18}$F($n,p/α$)$^{18}$O/$^{15}$N reactions controls the amount of $^{15}$N produced. The strengths of these reactions depend on the decay branching ratios of states in $^{19}$F above the neutron threshold. We report on an experiment investigating the decay branching ratios of these states in order to better constrain the strengths of the reactions.
Yield scaling, size hierarchy and fluctuations of observables in fragmentation of excited heavy nuclei
本文研究了入射能量为32-50 A MeV的Sn +Sn反应产生的单源和80 A MeV的Au+Au碰撞产生的准粒子的多重碎裂性质。这两种类型的源的比较有关Fisher标度，Zipf定律，碎片大小和波动观测。所有数据均观察到Fisher标度。从Fisher标度中提取的赝临界能量在Au +Sn中心碰撞和Au准抛射体之间是一致的。在后一种情况下，它也对应于波动最大的能量区域。由Zipf分析得到的临界能高于Fisher分析得到的临界能。
Heavy elements are formed in nucleosynthesis processes. Abundances of these elements can be classified as elemental abundance, isotopic abundance, and abundance of nuclei. In this work we propose to change nucleon identification from the usual (Z,A) to (Z,N), which allows reading out new information from the measured abundances. We are interested in the neutron density required to reproduce the measured abundance of nuclei assuming equilibrium processes. This is only possible when two stable nuclei are separated by an unstable nucleus. At these places we investigated the neutron density requir…
Particle emission from $^{40}$Ar nuclei excited in fixed-target $^{208}$Pb+$^{40}$Ar UPC at the LHC
Institute of Nuclear Physics PAN（波兰科学院核物理研究所）；Universitá degli Studi di Ferrara（费拉拉大学）；INFN Sezione di Ferrara（意大利国家核物理研究所费拉拉分部）；University of Rzeszów（热舒夫大学）
In highly dissipative collisions between heavy ions, the optimal conditions to investigate different de-excitation channels of hot nuclei such as evaporation, fission or multifragmentation are well known. One crucial issue remains the excitation energy region where fission gives way to multifragmentation. In this paper, the onset of multi-fragment exit channels is investigated in terms of sequential fission. For the first time, the dynamical approach based on solving Langevin transport equations in multidimensional collective coordinate space is used to follow the de-excitation of highly excit…
An increasing number of experimental data indicates the breaking of axial symmetry in many heavy nuclei already in the valley of stability: Multiple Coulomb excitation analysed in a rotation invariant way, gamma transition rates and energies in odd nuclei, mass predictions, the splitting of Giant Resonances (GR), the collective enhancement of nuclear level densities and Maxwellian averaged neutron capture cross sections. For the interpretation of these experimental observations the axial symmetry breaking shows up in nearly all heavy nuclei as predicted by Hartree-Fock-Bogoliubov (HFB) calcula…
We present ab initio predictions for ground and excited states of doubly open-shell fluorine and neon isotopes based on chiral two- and three-nucleon interactions. We use the in-medium similarity renormalization group, in both flow-equation and Magnus formulations, to derive mass-dependent sd valence-space Hamiltonians. The experimental ground-state energies are reproduced through neutron number N=14, beyond which a new targeted normal-ordering procedure improves agreement with data and large-scale multi-reference calculations. For spectroscopy, we focus on neutron-rich 23-26F and 24-26Ne isot…
One of the prominent decay modes of heavy nuclei which are produced in astrophysical environments at temperatures of the order of $10^9$ K is the $α$ ($^4$He) decay. Thermally enhanced $α$ decay rates are evaluated within the standard scheme of a tunneling decay where the $α$ particle tunnels through the potential barrier formed by its interaction with the daughter nucleus. Following the observation that there exist several excited levels with the possibility of an $α$ decay when the daughter nucleus is at a shell closure, we focus in particular on decays producing daughter nuclei with the neu…
Various theories beyond the standard model of particle physics predict the existence of baryon number violating processes resulting in nucleon decay. When occurring within an atomic nucleus, such a decay will be followed by secondary decays of the daughter nucleus unless its ground state is directly populated. In this paper, we estimate branching ratios for processes associated with dinucleon decays of the $^{16}$O nucleus. To this end, we use a simple shell model for the ground state of $^{16}$O. For decays from the 1$s_{1/2}$ configuration, which result in highly excited states in the daught…
采用Fayans { \it et al}的EDF方法，在自洽的TFFS中计算了100多个球奇核的基态和激发态的磁矩.我们把自己限制在有一个中子和一个质子粒子（空穴）的原子核中，这些粒子被添加到魔法或半魔法的核心中。一个简单的模型，没有相互作用的奇核子。在大多数情况下，我们分析，得到了良好的协议与实验数据。考虑了几种情况下，这种简单的模型不工作，有必要超越。对许多不稳定奇核和奇-奇核的磁矩的未知值进行了预测，其中包括60个激发态奇-奇核的磁矩。
We develop a statistical approach for the description of complex nuclei formation from dynamically produced baryons in high energy heavy-ion reactions. We consider a finite highly-excited expanding nuclear system formed after central nucleus-nucleus collisions. This system is sub-divided into primary equilibrated nucleon clusters. The final nuclei are produced after the decay of these excited clusters. By the successful comparison with the FOPI experimental data we prove the possibility of such a local equilibrium in nuclear matter with the temperature corresponding to the phase coexistence re…
Novel chiral-wobbling excitation mode in atomic nuclei
Islamic University of Science and Technology（伊斯兰科学技术大学）；University of Kashmir（克什米尔大学）；Institute of Physics (IOP)（物理研究所（IOP））；Homi Bhabha National Institute（霍米·巴巴国家研究所）；Government Degree College Shopian（肖皮安政府学位学院）；Government Degree College Kulgam（库尔加姆政府学位学院）；Shandong University（山东大学）
We study the ground and excited resonance states of $^{26}$O with a three-body model of $^{24}$O+n+n taking into account the coupling to the continuum. To this end, we use the new experimental data for the invariant mass spectroscopy of the unbound $^{25}$O and $^{26}$O nuclei, and present an update of three-body model calculations for the two-neutron decay of the $^{26}$O nucleus. With the new model inputs determined with the ground state decay of $^{26}$O, we discuss the di-neurtron correlations and a halo nature of this nucleus, as well as the structure of the excited states. For the energy…
Excited states in $^{14}$O have been investigated both experimentally and theoretically. Experimentally, these states were produced via neutron-knockout reactions with a fast $^{15}$O beam and the invariant-mass technique was employed to isolate the 1$p$ and 2$p$ decay channels and determine their branching ratios. The spectrum of excited states was also calculated with the Shell Model Embedded in the Continuum that treats bound and scattering states in a unified model. By comparing energies, widths and decay branching patterns, spin and parity assignments for all experimentally observed level…
A new technique of elucidating $β$-decay schemes of isotopes with large density of states at low excitation energies has been developed, in which a Broad Energy Germanium (BEGe) detector is used in conjunction with coaxial hyper-pure germanium detectors. The power of this technique has been demonstrated on the example of 183Hg decay. Mass-separated samples of 183Hg were produced by a deposition of the low-energy radioactive-ion beam delivered by the ISOLDE facility at CERN. The excellent energy resolution of the BEGe detector allowed $γ$ rays energies to be determined with a precision of a few…
首次系统地研究了83 \leq Z \leq 101范围内奇偶核α衰变精细结构。所用的模型是最近提出的变形核的库仑和邻近势模型（CPPDN），它采用变形库仑势，变形两项邻近势和离心势。计算的部分半衰期，总半衰期和分支比与实验数据进行了比较，是在良好的协议。部分半衰期的标准差为1.08，分支比的标准差为1.21。我们的形式主义也成功地预测角动量阻碍和结构阻碍的转变。本文的研究表明，CPPMDN是一个统一的理论，它成功地解释了基态和同质异能态的α衰变，以及偶偶核、偶奇核和奇偶核的α精细结构。我们的研究表明，母核和子核表面的差异或形变参数的变化以及母核和子核壳层结构的变化，都会影响α衰变几率。
A recent theoretical prediction of a breaking of axial symmetry in quasi all heavy nuclei is confronted to a new critical analysis of photon strength functions of nuclei in the valley of stability. For the photon strength in the isovector giant dipole resonance (IVGDR) regime a parameterization of GDR shapes by the sum of three Lorentzians (TLO) is extrapolated to energies below and above the IVGDR. The impact of non-GDR modes adding to the low energy slope of photon strength is discussed including recent data on photon scattering and other radiative processes. These are shown to be concentrat…
We study the $J/ψ$ photoproduction from nuclei in the near-threshold beam energy region of $E_γ$=5--11 GeV within the nuclear spectral function approach by considering incoherent direct ($γN \to {J/ψ}N$) and two-step ($γp \to P^+_c(4312)$, $P^+_c(4312) \to {J/ψ}p$; $γp \to P^+_c(4440)$, $P^+_c(4440) \to {J/ψ}p$; $γp \to P^+_c(4457)$, $P^+_c(4457) \to {J/ψ}p$) $J/ψ$ production processes. We calculate the absolute excitation functions for the non-resonant and resonant production of $J/ψ$ mesons off $^{12}$C and $^{208}$Pb target nuclei within the different scenarios for in-medium modification of…
We study ground- and excited-state properties of all sd-shell nuclei with neutron and proton numbers 8 <= N,Z <= 20, based on a set of low-resolution two- and three-nucleon interactions that predict realistic saturation properties of nuclear matter. We focus on estimating the theoretical uncertainties due to variation of the resolution scale, the low-energy couplings, as well as from the many-body method. The experimental two-neutron and two-proton separation energies are reasonably well reproduced, with an uncertainty range of about 5 MeV. The first excited 2+ energies also show overall agree…
Two-proton relative momentum ($q_{pp}$) and opening angle ($θ_{pp}$) distributions from the three-body decay of two excited proton-rich nuclei, namely $^{23}$Al $\rightarrow$ p + p + $^{21}$Na and $^{22}$Mg $\rightarrow$ p + p + $^{20}$Ne, have been measured with the projectile fragment separator (RIPS) at the RIKEN RI Beam Factory. An evident peak at $q_{pp}\sim20$ MeV/c as well as a peak in $θ_{pp}$ around 30$^\circ$ are seen in the two-proton break-up channel from a highly-excited $^{22}$Mg. In contrast, such peaks are absent for the $^{23}$Al case. It is concluded that the two-proton emiss…
We have studied the fragment yields emitted from the fragmentation of excited projectile nuclei in peripheral collisions of 136Xe+Pb at 1 GeV/nucleon, and measured with the high-resolution magnetic spectrometer, the Fragment Separator (FRS) of GSI. The mass, charge and isotope distributions of nuclear fragments formed in the reactions were calculated within a statistical ensemble approach and compared to the experimental data. The ensemble of excited projectilelike source nuclei were created in the framework of a previous analysis of similar reactions performed at 600 MeV/nucleon (ALADIN-exper…
