Mass Measurements and Implications for the Energy of the High-Spin Isomer in 94Ag
A. Kankainen, V. -V. Elomaa, L. Batist, S. Eliseev, T. Eronen, U. Hager, J. Hakala, A. Jokinen, I. D. Moore, Yu. N. Novikov, H. Penttilä, A. Popov, S. Rahaman, … 展开作者
A. Kankainen, V. -V. Elomaa, L. Batist, S. Eliseev, T. Eronen, U. Hager, J. Hakala, A. Jokinen, I. D. Moore, Yu. N. Novikov, H. Penttilä, A. Popov, S. Rahaman, S. Rinta-Antila, J. Rissanen, A. Saastamoinen, D. M. Seliverstov, T. Sonoda, G. Vorobjev, C. Weber, J. Äystö
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4 pages, 3 figures and 3 tables; v2: updated figures and references, published in Physical Review Letters
Nuclides in the vicinity of 94Ag have been studied with the Penning trap mass spectrometer JYFLTRAP at the Ion-Guide Separator On-Line. The masses of the two-proton-decay daughter 92Rh and the beta-decay daughter 94Pd of the high-spin isomer in 94Ag have been measured, and the masses of 93Pd and 94Ag have been deduced. When combined with the data from the one-proton or two-proton-decay experiments, the results lead to contradictory mass excess values for the high-spin isomer in 94Ag, -46370(170) or -44970(100) keV, corresponding to excitation energies of 6960(400) or 8360(370) keV, respectively.
Background: High-spin isomers at {\approx}9-MeV excitation energies have been reported in several N = 83 isotones near Z = 64. Spin and parity assignments of J{^π} = 49/2+ remain tentative for a number of these states in the odd-A nuclei. Purpose: To study the decay of the (49/2 +) high-spin isomer in 145 Sm, make firm spin and parity assignments to the isomer and states populated in its decay, and investigate the structure of the nucleus. Methods: The 145Sm isomer was populated in the 124Sn(26Mg,5n) reaction. Gamma-ray and conversion-electron data were collected using the Solenogam array. Res…
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…
A recent publication [D.G. Jenkins, Phys. Rev. C \textbf{80}, 054303 (2009)] claims to discredit the experimental observation of two-proton decay of the (21$^+$) high-spin isomer in $^{94}$Ag [I. Mukha \emph{et al.,} Nature (London) \textbf{439}, 298 (2006)]. Its conclusion, which would require a reestablishment of the two-proton emission, is made on the basis of unwarranted assumptions by Jenkins concerning the data analysis of the original work. We provide proof that these assumptions do not correspond to reality, and that therefore the conclusion of the paper is misleading.
Gamow-Teller (GT) transitions from high-spin isomers are studied using the sum-rule approach and the shell model. The GT transition strengths from the high-spin isomeric states show a stronger collectivity than those from the ground states in two $N=Z$ nuclei, $^{52}$Fe and $^{94}$Ag. It is argued that the spin-up and spin-down Fermi spheres involved in the GT transitions from the high-spin isomeric states play important roles. These Fermi spheres are analogous to the isospin-up and isospin-down Fermi spheres for the GT transitions from the ground states in $N>Z$ nuclei and create a strong col…
Over one hundred years have passed since the nuclear isomer was first introduced, in analogy with chemical isomers to describe long-lived excited nuclear states. In 1921, Otto Hahn discovered the first nuclear isomer $^{234m}$Pa. After that, step by step, it was realized that different types of nuclear isomers exist, including spin isomer, K isomer, seniority isomers, and ``shape and fission'' isomer. The spin isomer occurs when the spin change $ΔI$ of a transition is very large. The larger $ΔI$, the lower the electromagnetic transition rates, the longer the half-lives. The K-isomer exists due…
The odd-odd 54;56;58;60;62;64Mn isotopes (Z = 25) were studied using bunched-beam collinear laser spectroscopy at ISOLDE, CERN. From the measured hyperfine spectra the spins and magnetic moments of Mn isotopes up to N = 39 were extracted. The previous tentative ground state spin assignments of 58;60;62;64Mn are now firmly determined to be I = 1 along with an I = 4 assignment for the isomeric states in 58;60;62Mn. The I = 1 magnetic moments show a decreasing trend with increasing neutron number while the I = 4 moments remain quite constant between N = 33 and N = 37. The results are compared to …
Collinear laser spectroscopy has been performed on the $^{79}_{30}$Zn$_{49}$ isotope at ISOLDE-CERN. The existence of a long-lived isomer with a few hundred milliseconds half-life was confirmed, and the nuclear spins and moments of the ground and isomeric states in $^{79}$Zn as well as the isomer shift were measured. From the observed hyperfine structures, spins $I = 9/2$ and $I = 1/2$ are firmly assigned to the ground and isomeric states. The magnetic moment $μ$ ($^{79}$Zn) = $-$1.1866(10) $μ_{\rm{N}}$, confirms the spin-parity $9/2^{+}$ with a $νg_{9/2}^{-1}$ shell-model configuration, in ex…
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…
Mass-separated 187Ta in a high-spin isomeric state has been produced for the first time by multi-nucleon transfer reactions, employing an argon gas stopping cell and laser ionisation. Internal gamma rays revealed a 7.3 s isomer at 1778 keV, which decays through a rotational band with perturbations associated with the approach to a prolate-oblate shape transition. Model calculations show less influence from triaxiality compared to heavier elements in the same mass region. The isomer decay reduced E2 hindrance factor of 27 supports the interpretation that axial symmetry is approximately conserve…
Mass spectrometry of $^{75}$Zn ground and isomeric states from in-trap decay of $^{75}$Cu
Max-Planck-Institut für Kernphysik（马克斯·普朗克核物理研究所）；School of Physics and Astronomy, The University of Manchester（曼彻斯特大学物理与天文学学院）；Physics Department, College of Science, Jouf University（朱夫大学理学院物理系）；Belgian Nuclear Research Centre, SCK CEN（比利时核研究中心SCK CEN）；KU Leuven, Instituut voor Kern- en Stralingsfysica（鲁汶大学核与辐射物理研究所）；GSI Helmholtzzentrum für Schwerionenforschung GmbH（GSI亥姆霍兹重离子研究中心有限公司）；CNRS-TRIUMF International Research Laboratory for Nuclear Physics, Nuclear Astrophysics and Accelerator Technology（法国国家科学研究中心-TRIUMF国际核物理、核天体物理与加速器技术联合实验室）；Université Paris-Saclay, CNRS/IN2P3, IJCLab（巴黎萨克雷大学，法国国家科学研究中心/法国原子能与替代能源委员会，IJCLab）；CERN（欧洲核子研究中心）
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 …
High-K isomers are well known in the rare-earth region and provide unique access to the high spin structures of the nuclei. With the current interest in the study of neutron-rich rare-earth nuclei at Radioactive Ion Beam (RIB) facilities, we present here theoretical results of the band structures of neutron-rich Gd and Dy nuclei, including the high K-isomers. Apart from the already known K-isomers, we predict some more K-isomers and these are suggested for future studies at RIB facilities. Self-consistent Deformed Hartree-Fock and Angular Momentum Projection theories are used to get the intrin…
Energy dependence of isomeric ratios for alpha-particle-induced reactions on natural platinum up to 50 MeV studied by simultaneous decay curve analysis
The rotational properties of the neutron rich Nd and Sm isotopes with mass number $A\approx150$ are systematically investigated using the cranked shell model with pairing correlations treated by a particle-number conserving method, in which the Pauli blocking effects are taken into account exactly. The 2-quasiparticle states in even-even Nd and Sm isotopes with excitation energies lower than 2.5~MeV are systematically calculated. The available data can be well reproduced and some possible 2 and 4-quasiparticle isomers are also suggested for future experiments. The experimentally observed rotat…
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…
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 …
The $Θ_{eff}/Θ_{rig}$ parameter of the spin distribution of the level density was determined for 61 nuclei covering the mass range of 44 to 200. The experimental isomeric cross-section ratios for 25 isomeric pairs were compared with the model calculation to find the best fit to the experimental data. The model calculations were carried out with the TALYS code using the BSFG model for the level density. The reduced $χ^2$ values were calculated to describe the deviation of the experimental data from the model calculation. An $η_d $ was introduced calculating the $Θ_{eff}/Θ_{rig}$ value from the …
The level structures of $^{212}$Ra and $^{213}$Ra have been established via time-correlated $γ$-ray spectroscopy following the $^{204}$Pb($^{12}$C,4$n$)$^{212}$Ra and $^{204}$Pb($^{13}$C,4$n$)$^{213}$Ra reactions. In $^{212}$Ra, levels up to $\sim 6.2$ MeV were identified and firm spin-parity assignments were achieved to a $J^π = 19^+$ isomer with a mean life of 31(3) ns. For $^{213}$Ra the corresponding values were $\sim 4.5$ MeV in excitation energy and $J^π = 33/2^+$. Two isomeric states with $J^π= 23/2^+$, $τ= 27(3)$ ns and $J^π= 33/2^+$, $τ= 50(3)$ ns were discovered in $^{213}$Ra. The ex…
The $β$ intensity distributions of the decays of $^{100\text{gs},100\text{m}}$Nb and $^{102\text{gs},102\text{m}}$Nb have been determined using the Total Absorption $γ$-Ray Spectroscopy technique. The JYFLTRAP double Penning trap system was employed to disentangle the isomeric states involved, lying very close in energy, in a campaign of challenging measurements performed with the Decay Total Absorption $γ$-ray Spectrometer at the Ion Guide Isotope Separator On-Line facility in Jyväskylä. The low-spin isomeric state of each niobium case was populated through the decay of the zirconium parent, …
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…
Attention is fixed on shells in toroidal nuclei in the intermediate mass region using a toroidal single-particle potential. We find that there are toroidal shells in the intermediate mass region with large single-particle energy gaps at various nucleon numbers located at different toroidal deformations characterized by the aspect ratios of toroidal major to minor radius. These toroidal shells provide extra stability at various toroidal deformations. Relative to a toroidal core, Bohr-Mottelson spin-aligning particle-hole excitations may be constructed to occupy the lowest single-particle Routhi…
The decay properties of the ground state and excited states of $^{257}$Rf have been investigated with the detector array GABRIELA at the FLNR, Dubna. The electromagnetic decay of a new excited state in $^{253}$No has been observed. The state lies 750 keV above the ground state and is favourably populated in the alpha decay of the low-lying spin isomer of $^{257}$Rf. It decays to the 9/2$^-$ ground state by an M1 transition and is assigned the 11/2$^-$[725] Nilsson configuration. The presence of this state suggests a possible reinterpretation of the decay of the high-K isomer in $^{253}$No.
The $β$-decay of neutron-rich $^{129}$In into $^{129}$Sn was studied using the GRIFFIN spectrometer at the ISAC facility at TRIUMF. The study observed the half-lives of the ground state and each of the $β$-decaying isomers. The level scheme of $^{129}$Sn has been expanded with thirty-one new $γ$-ray transitions and nine new excited levels, leading to a re-evaluation of the $β$-branching ratios and level spin assignments. The observation of the $β$-decay of the (29/2$^{+}$) 1911-keV isomeric state in $^{129}$In is reported for the first time, with a branching ratio of 2.0(5)$\%$.
