最近获得的$^{197}$ Au $(n,2n)$反应的同分异构横截面的准确数据提供了一个宝贵的机会，可以在对$^{197}$ Au靶核所有可用反应数据的局部一致模型分析中考虑核的有效转动惯量问题。从而得到了$^{196}$ Au核的转动惯量等于刚体转动惯量的确切证明，并提出了$^{194}$ Ir核的半刚体转动惯量的推论.在入射能量高达$\ge$ 40兆电子伏的进一步测量的有用性也得到了证明。
英文摘要：
Recent accurate data obtained for the isomeric cross section of the $^{197}$Au$(n,2n)$ reaction provide a valuable opportunity to consider the question of the effective moment of inertia of the nucleus within a local consistent model analysis of all available reaction data for the $^{197}$Au target nucleus. Thus, a definite proof of a moment of inertia equal to that of the rigid--body has been obtained for $^{196}$Au nucleus while an inference of the half rigid--body value is suggested for the $^{194}$Ir nucleus. The usefulness of further measurements at incident energies up to $\ge$40 MeV has also been proved.
Results of the investigations of the yield of high-spin and low-spin isomers in reactions $^{41}$K($α$,n)$^{44}$Sc, $^{86}$Sr ($α$,n)$^{89}$Zr, $^{112}$Sn($α$,n)$^{115}$Te, and $^{134}$Ba($α$,n)$^{137}$Ce in the energy range of the alpha particles 15 $÷$ 31 MeV based on off-beam measurements of induced activity of members of the isomeric pair are presented. The anomalous behavior of the isomeric cross-section ratios for the first of these reactions is confirmed. Uniquely large isomeric cross-section ratios for the second and third ones are obtained. The features of the fourth reaction, which a…
The cross sections for (γ,xn) reactions at 30 MeV and 40 MeV bremsstrahlung end-point energies on natural rhenium (natRe) targets have been measured by the activation and the off-line γ-ray spectrometric techniques using a High Purity Germanium detector (HPGe). The measured natRe(γ,xn) reaction cross sections were compared to the theoretically calculated cross sections using TALYS 1.9 and EMPIRE 3.2 computer codes. The measurements allowed the determination of the Isomeric Cross section Ratios (ICR) for the 184m,g Re and 182m,gRe isomeric pairs. In addition, we have determined a semi-empirical…
Energy dependence of the isomeric cross section ratio in the $^{58}$Ni$(n,p)^{58}$Co$^{m,g}$ reactions
在2 ~ 15 MeV能量范围内测量了$^{58}$ Ni $(n,p)^{58}$ Co $^{m,g}$反应的激发函数。由实验数据推导出了同分异构截面比R=sigma_m/（sigma_m+sigma_g）与能量的关系。R（E_n）函数的形状和大小由使用一致参数集的模型计算来描述。在低能区准确测量同质异能比的基础上，解决了输入能级方案存在的问题。
Neutron-rich nuclei in the vicinity of the $N=40$ island of inversion are characterized by shell evolution and exhibit deformed ground states. In several nuclei isomeric states have been observed and attributed to excitations to the intruder neutron $1g_{9/2}$ orbital. In the present study we searched for isomeric states in nuclei around $N=40$, $Z=22$ produced by projectile fragmentation at RIBF. Delayed $γ$ rays were detected by the EURICA germanium detector array. High statistics data allowed for an updated decay scheme of $^{60}$V. The lifetime of an isomeric state in $^{64}$V was measured…
The independent cross section ratio for production of nuclei from 197Au targets irradiated with 4 GeV deuterons have been measured by off-line gamma-spectroscopy. On the basis of the measured independent cross section ratio of 198m, gAu the average intrinsic angular momentum of the primary nucleus was estimated by means of a simple statistical-model analysis based on the formalism developed by Huizenga and Vandenbosch.
De-excitation $γ$ rays associated with an isomeric state of $^{186}$Ta were investigated. The isomers were produced in multinucleon transfer reactions between a $^{136}$Xe beam and a natural W target, and were collected and separated by the KEK Isotope Separation System. Two $γ$ transitions with energies of 161.1(2) and 186.8(1) keV associated with an isomeric decay were observed for the first time. The half-life of the isomeric state of the neutral atom $^{186 \rm m}$Ta was deduced as 17(2) s. Based on the comparison with the previous measurements of the isomeric state using the ESR storage r…
Energy dependence of isomeric ratios for alpha-particle-induced reactions on natural platinum up to 50 MeV studied by simultaneous decay curve analysis
The isomeric state of $^{16}$N was studied using the $^{16}$N$^{g,m}$($d$,$^3$He)~proton-removal reactions at \mbox{11.8~MeV/$u$} in inverse kinematics. The $^{16}$N beam, of which 24% was in the isomeric state, was produced using the ATLAS in-fight facility and delivered to the HELIOS spectrometer, which was used to analyze the $^{3}$He ions from the ($d$,$^{3}$He) reactions. The simultaneous measurement of reactions on both the ground and isomeric states, reduced the systematic uncertainties from the experiment and in the analysis. A direct and reliable comparison of the relative spectroscop…
The structure of nuclei around the neutron-rich nucleus 132Sn is of particular interest due to the vicinity of the Z = 50 and N = 82 shell closures and the r-process nucleosynthetic path. Four states in 131Sn with a strong single-particle-like component have previously been studied via the (d,p) reaction, with limited excitation energy resolution. The 130Sn(9Be,8Be)131Sn and 130Sn(13C,12C)131Sn single-neutron transfer reactions were performed in inverse kinematics at the Holifield Radioactive Ion Beam Facility using particle-gamma coincidence spectroscopy. The uncertainties in the energies of …
Isochronous mass spectrometry was applied to measure isomeric yield ratios of fragmentation reaction products. This approach is complementary to conventional gamma-ray spectroscopy in particular for measuring yield ratios for long-lived isomeric states. Isomeric yield ratios for the high-spin I = 19/2 states in the mirror nuclei 53Fe and 53Co are measured to study angular momentum population following the projectile fragmentation of 78Kr at energies of 480A MeV on a beryllium target. The 19/2 state isomeric ratios of 53Fe produced from different projectiles in the literature have also been ext…
The photoneutron reaction $^{181}\rm{Ta}(γ,3n)^{178m,g}\rm{Ta}$ was investigated with the beam from the NSC KIPT electron linear accelerator LUE-40. The measurements were performed using the residual $γ$-activity method. The bremsstrahlung flux-averaged cross-sections $\langle{σ(E_{\rm{γmax}})}\rangle$, $\langle{σ(E_{\rm{γmax}})}\rangle_{\rm{m}}$, $\langle{σ(E_{\rm{γmax}})}\rangle_{\rm{g}}$ and the isomeric ratio of the reaction products $d(E_{\rm{γmax}})$ have been measured. Theoretical values of averaged cross-sections and isomeric ratio were calculated using partial cross-sections from the …
Direct mass measurements of the low-spin $3/2^{(-)}$ and high-spin $13/2^{(+)}$ states in the neutron-deficient isotopes $^{195}$Po, $^{197}$Po, and high-spin $13/2^{(+)}$ state in $^{199}$Po were performed with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE-CERN. These measurements allow the determination of the excitation energy of the isomeric state arising from the $ν$i$_{13/2}$ orbital in $^{195,197}$Po. Additionally, the excitation energy of isomeric states of lead, radon, and radium isotopes in this region were obtained from $α$-decay chains. The new excitation energies complete …
Inspired by the newly discovered isomeric states in the rare-earth neutron-rich nuclei, high-$K$ isomeric states in neutron-rich samarium and gadolinium isotopes are investigated within the framework of the cranked shell model (CSM) with pairing correlation treated by a particle-number-conserving (PNC) method. The experimental multi-particle state energies and moments of inertia are reproduced quite well by the PNC-CSM calculations. A remarkable effect from the high-order deformation $\varepsilon_{6}$ is demonstrated. Based on the occupation probabilities, the configurations are assigned to th…
The bremsstrahlung flux-averaged cross sections for the photoneutron reactions $^{\text{93}}$Nb($γ$,xn;x=1-5)$^{\text{(93-x)m,g}}$Nb were measured in the range of boundary energies of bremsstrahlung $γ$-quanta $E_{γ\text{max}}$=33-93 MeV with a step $ΔE_{γ\text{max}}\approx $ 2 MeV. The isomeric ratios of the average cross-sections of the products of the reactions $^{\text{93}}$Nb ($γ$ ,4n)$^{\text{89m,g}}$Nb and $^{\text{93}}$Nb($γ$,5n)$^{\text{88m,g}}$ Nb were determined in the energy ranges $E_{γ\text{max}}$ = 50-93 and 70-93 MeV, respectively. The experiments were carried out on the beam o…
High-spin states of neutron deficient Trans-Lead nucleus $^{204}$At were populated up to $\sim 8\,{\rm MeV}$ excitation through the $^{12}$C + $^{197}$Au fusion evaporation reaction. Decay of the associated levels through prompt and delayed $γ$-ray emissions were studied to evaluate the underlying nuclear structure. The level scheme, which was partly known, was extended further. An isomeric $16^+$ level with observed lifetime $τ=52 \pm 5\, {\rm ns}$, was established from our measurements. Attempts were made to interpret the excited states based on multi quasiparticle and hole structures involv…
An in-flight beam of $^{16}$N was produced via the single-neutron adding ($d$,$p$) reaction in inverse kinematics at the recently upgraded Argonne Tandem Linear Accelerator System (ATLAS) in-flight system. The amount of the $^{16}$N beam which resided in its excited 0.120-MeV $J^π=0^-$ isomeric state (T$_{1/2}\approx5$ $μ$s) was determined to be 40(5)% at a reaction energy of 7.9(3) MeV/$u$, and 24(2)% at a reaction energy of 13.2(2) MeV/$u$. The isomer measurements took place at an experimental station $\approx30$ m downstream of the production target and utilized an Al beam-stopping foil and…
We report first precision mass measurements of the $1/2^-$ isomeric and $9/2^+$ ground states of $^{101}$In. The determined isomeric excitation energy continues a smooth trend of odd-$A$ indium isotopes up to the immediate vicinity of $N=50$ magic number. This trend can be confirmed by dedicated shell model calculations only if the neutron configuration mixing is considered. We find that the single particle energies are different for different states of the same isotope. The presented configuration-dependent shell evolution, type II shell evolution, in odd-$A$ nuclei is discussed for the first…
Experimental isomeric yield ratios for the 113In(γ,n)112m,gIn reactions on the betatron B25/30 bremsstrahlung gamma beam of energy range 12-25 MeV are measured. Effective cross-sections of (γ,n)-reactions with 112mIn and 114mIn isomers output are calculated. The Penfold-Leiss and Tikhonov methods are applied to solve the Volterra integral equation. The obtained experimental cross-sections are compared with theoretical calculations using the TALYS-1.6 code.
Observation of a dominant $\boldsymbol{0f_{7/2}}$ neutron configuration in the $\boldsymbol{^{32}}$Si $\boldsymbol{J^π=5^-}$ isomeric state
Argonne National Laboratory（阿贡国家实验室）；Louisiana State University（路易斯安那州立大学）；Southern University of Science and Technology（南方科技大学）；University of Notre Dame（圣母大学）；Oak Ridge National Laboratory（橡树岭国家实验室）；North Carolina A&T State University（北卡罗来纳农业与州立大学）；University of Wisconsin - La Crosse（威斯康星大学拉克罗斯分校）；Texas A&M University（德克萨斯农工大学）
Precision mass measurements of neutron-rich rhodium isotopes have been performed at the JYFLTRAP Penning trap mass spectrometer at the Ion Guide Isotope Separator On-Line (IGISOL) facility. We report results on ground- and isomeric-state masses in $^{110,112,114,116,118}$Rh and the very first mass measurement of $^{120}$Rh. The isomeric states were separated and measured for the first time using the phase-imaging ion-cyclotron-resonance (PI-ICR) technique. For $^{112}$Rh, we also report new half-lives for both the ground state and the isomer. The results are compared to theoretical predictions…
A new value for the emission probability of 137.144keV g-ray of 186gRe decay are re-recommended to be 9.47+-0.03 (%). From this new g-ray emission probability, the measured cross sections for 187Re(n,2n)186mRe and 187Re(n,2n)186gRe reactions around 14MeV are evaluated, and the total cross section for 187Re(n,2n)186m+gRe reaction at 14.8MeV is recommended to be 2213+-116 mb. The UNF code are adopted to calculate the total cross sections for 187Re(n,2n)186m+gRe reaction below 20 MeV fitting to the recommended value 2213+-116 mb at 14.8MeV using a set of optimum neutron optical potential paramete…
In this work, we systematically investigate the favored $α$-decay half-lives and $α$ preformation probabilities of both odd-$A$ and doubly-odd nuclei related to ground and isomeric states around the doubly magic cores at $Z=82$, $N=82$ and at $Z=82$, $N=126$, respectively, within a two-potential approach from the view of the valence nucleon (or hole). The results show that the $α$ preformation probability is linear related to $N_\text{p}N_\text{n}$ or $N_\text{p}N_\text{n}I$, where $N_\text{p}$, $N_\text{n}$, and $I$ are the number of valence protons (or holes), the number of valence neutrons …
Island of Inversion in neutron-rich cobalt isotopes revealed from mass measurements
Université de Bordeaux, CNRS/IN2P3, LP2I Bordeaux, UMR 5797（波尔多大学）；Université de Strasbourg, CNRS, IPHC UMR 7178（斯特拉斯堡大学）；Université de Caen Normandie, ENSICAEN, CNRS/IN2P3, LPC Caen UMR6534（诺曼底卡昂大学）；SCK·CEN, Belgian Nuclear Research Centre（比利时核研究中心）；Grand Accélérateur National d’Ions Lourds (GANIL)（重离子国家加速器）；Normandie Univ., UNICAEN（诺曼底大学）；University of Jyväskylä（于韦斯屈莱大学）
An analysis of recent experimental data [J. Khuyagbaatar et al., Phys. Rev. C 104, L031303 (2021)] has established the existence of two fissioning states in $^{253}$Rf: the ground state and a low-lying isomeric state, most likely involving the same neutron single-particle configurations as in the lighter isotone $^{251}$No. The ratio of fission half-lives measured in $^{253}$Rf was used to predict the fission properties of the 1/2$^{+}$ isomeric state in $^{251}$No and draw conclusions as to the stability against fission of even lighter Rf systems. This paper focusses again on the fission prop…
We present the results of precision mass measurements of neutron-rich cadmium isotopes. These nuclei approach the $N=82$ closed neutron shell and are important to nuclear structure as they lie near doubly-magic $^{132}$Sn on the chart of nuclides. Of particular note is the clear identification of the ground state mass in $^{127}$Cd along with the isomeric state. We show that the ground state identified in a previous mass measurement which dominates the mass value in the Atomic Mass Evaluation is an isomeric state. In addition to $^{127/m}$Cd, we present other cadmium masses measured ($^{125/m}…
The decay of odd-odd $^{150}$Pm has been studied by populating the nucleus with the $^{150}$Nd(p,n)$^{150}$Pm reaction at E$_{beam}$ = 8.0 MeV using 97$\%$ enriched $^{150}$Nd target. The presence of an isomeric state with $β$ decay half life of 2.2(1) h could be identified in $^{150}$Pm by following the half lives of the observed $γ$ transitions. The decay of the isomer to the excited levels of $^{150}$Sm has been confirmed by observing the $γ- γ$ coincidence with the VENUS array of six Compton suppressed Clover HPGe detectors. The $β$ decay end-point energies corresponding to the decay from …
The 15N(p,n) reaction is a promising candidate for the production of monoenergetic neutrons with energies of up to 5.7 MeV at the facilities where the T(p,n)3He reaction cannot be used. The characteristic properties of this reaction were studied focusing on its suitability as a source of monoenergetic neutrons for the measurement of differential scattering cross sections in the neutron energy range of 2 MeV to 5 MeV. For this purpose differential and integral cross sections were measured and the choice of optimum target conditions was investigated. The reaction has already been used successful…
Exploration for Astromers near $^{132}$Sn with the Canadian Penning Trap
Argonne National Laboratory（阿贡国家实验室）；Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）；Center for Theoretical Astrophysics, Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室理论天体物理中心）；University of Notre Dame（圣母大学）；Obsidian Research（黑曜石研究公司）；University of Manitoba（曼尼托巴大学）
