Properties of 187Ta revealed through isomeric decay
P. M. Walker, Y. Hirayama, G. J. Lane, H. Watanabe, G. D. Dracoulis, M. Ahmed, M. Brunet, T. Hashimoto, S. Ishizawa, F. G. Kondev, Yu. A. Litvinov, H. Miyatake,… 展开作者
P. M. Walker, Y. Hirayama, G. J. Lane, H. Watanabe, G. D. Dracoulis, M. Ahmed, M. Brunet, T. Hashimoto, S. Ishizawa, F. G. Kondev, Yu. A. Litvinov, H. Miyatake, J. Y. Moon, M. Mukai, T. Niwase, J. H. Park, Zs. Podolyak, M. Rosenbusch, P. Schury, M. Wada, X. Y. Watanabe, W. Y. Liang, F. R. Xu
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 conserved.
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…
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…
Energy dependence of isomeric ratios for alpha-particle-induced reactions on natural platinum up to 50 MeV studied by simultaneous decay curve analysis
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）
Isomeric states in $^{128}$In and $^{130}$In have been studied with the JYFLTRAP Penning trap at the IGISOL facility. By employing novel ion manipulation techniques, different states were separated and masses of six beta-decaying states were measured. JYFLTRAP was also used to select the ions of interest for identification at a post-trap decay spectroscopy station. A new beta-decaying high-spin isomer feeding the $15^-$ isomer in $^{128}$Sn has been discovered in $^{128}$In at $1797.6(20)$ keV. Shell-model calculations employing a CD-Bonn potential re-normalized with the perturbative G-matrix …
Decay spectroscopy of the odd-proton nuclei $^{249}$Md and $^{251}$Md has been performed. High-$K$ isomeric states were identified for the first time in these two nuclei through the measurement of their electromagnetic decay. An isomeric state with a half-life of $2.8(5)$ ms and an excitation energy $\geq 910$ keV was found in $^{249}$Md. In $^{251}$Md, an isomeric state with a half-life of $1.4(3)$ s and an excitation energy $\geq 844$ keV was found. Similarly to the neighbouring $^{255}$Lr, these two isomeric states are interpreted as 3 quasi-particle high-$K$ states and compared to new theo…
The results of experimental studies of the low-energy isomeric state in the $^{229}$Th nucleus are presented. The work is consisted of several stages. During the first stage $^{229}$Th nuclei were excited with the inverse internal conversion to the low-lying isomeric level in plasma that was formed by laser pulse at the $^{229}$Th-containing target surface. Then thorium ions having excited nuclei were extracted from the plasma by an external electrical field and implanted into thin SiO$_2$ film grown on a silicon substrate (that is a dielectric material with about 9 eV band-gap). Gamma decay o…
Background: The evolution of shell structure around doubly magic exotic nuclei is of great interest in nuclear physics and astrophysics. In the `southwest' region of $^{78}$Ni, the development of deformation might trigger a major shift in our understanding of explosive nucleosynthesis. To this end, new spectroscopic information on key close-lying nuclei is very valuable. Purpose: We intend to measure the isomeric and $β$ decay of $^{75}$Co, with one-proton and two-neutron holes relative to $^{78}$Ni, to access new nuclear structure information in $^{75}$Co and its $β$-decay daughters $^{75}$Ni…
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）
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…
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 …
Efficient production of nuclear isomers is critical for pioneering applications, like nuclear clocks, nuclear batteries, clean nuclear energy, and nuclear γ-ray lasers. However, due to small production cross sections and quick decays, it is extremely difficult to acquire a significant amount of isomers with short lifetimes via traditional accelerators or reactors because of low beam intensity. Here, for the first time, we experimentally present femtosecond pumping of nuclear isomeric states by the Coulomb excitation of ions with the quivering electrons induced by laser fields. Nuclei populated…
The low-lying isomeric state of $^{229}$Th provides unique opportunities for high-resolution laser spectroscopy of the atomic nucleus. We determine the energy of this isomeric state by taking the absolute energy difference between the excitation energy required to populate the 29.2-keV state from the ground-state and the energy emitted in its decay to the isomeric excited state. A transition-edge sensor microcalorimeter was used to measure the absolute energy of the 29.2-keV $γ$-ray. Together with the cross-band transition energy (29.2 keV$\to$ground) and the branching ratio of the 29.2-keV st…
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, …
The first excited isomeric state of Th-229 has an exceptionally low energy of only a few eV and could form the gateway to high-precision laser spectroscopy of nuclei. The excitation energy of the isomeric state has been inferred from precision gamma spectroscopy, but its uncertainty is still too large to commence laser spectroscopy. Reducing this uncertainty is one of the most pressing challenges in the field. Here we present an approach to infer the energy of the isomer from spectroscopy of the electron which is emitted when the isomer de-excites through internal conversion (IC). The experime…
The $β$ decays of the ground state (gs) and isomeric state (m) of $^{96}$Y have been studied with the total absorption $γ$-ray spectroscopy technique at the Ion Guide Isotope Separator On-Line facility. The separation of the 8$^{+}$ isomeric state from the 0$^{-}$ ground state was achieved thanks to the purification capabilities of the JYFLTRAP double Penning trap system. The $β$-intensity distributions of both decays have been independently determined. In the analyses the de-excitation of the 1581.6 keV level in $^{96}$Zr, in which conversion electron emission competes with pair production, h…
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）
The first excited isomeric state of $^{229}$Th possesses the lowest energy among all known excited nuclear states. The expected energy is accessible with today's laser technology and in principle allows for a direct optical laser excitation of the nucleus. The isomer decays via three channels to its ground-state (internal conversion, $γ$ decay and bound internal conversion), whose strengths depend on the charge state of $^{229m}$Th. We report on the measurement of the internal-conversion decay half-life of neutral $^{229m}$Th. A half-life of 7 $\pm$ 1 $μ$s has been measured, which is in the ra…
The $β$ decay of the isomeric and ground state of $^{50}$Sc to the semi-magic nucleus $^{50}_{22}$Ti$_{28}$ has been studied using a $^{50}$Ca beam delivered to the GRIFFIN $γ$-ray spectrometer at the TRIUMF-ISAC facility. $β$-decay branching ratios are reported to 16 excited states with a total of 38 $γ$-ray transitions linking them. These new data significantly expands the information available over previous studies. Relative intensities are measured to less than 0.001$\%$ that of the strongest transition with the majority of $γ$-ray transitions observed here in $β$ decay for the first time.…
Characterizing the atomic mass surface beyond the proton drip line via a-decay measurements of the s1/2 ground state of 165Re and the h11/2 isomer in 161Ta
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…
$^{229}$Th is the only known nucleus with an excited state that offers the possibility for a direct laser excitation using existing laser technology. Its excitation energy has been measured indirectly to be 7.8(5) eV ($\approx$160 nm). The energy and lifetime of the isomeric state make it the presently only suitable candidate for a nuclear optical clock, the uncertainty of the excitation energy is, however, still too large to allow for a direct laser excitation in a Paul trap. Therefore, a major goal during the past years has been an improved energy determination. One possible approach is to m…
Chemical effects on nuclear decay of $^{235}$U isomer in the uranyl form
The University of Osaka（大阪大学）；RIKEN（理化学研究所）；University of Tsukuba（筑波大学）；The University of Electro-Communications（电气通信大学）；Osaka Aoyama University（大阪青山大学）
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…
The new neutron-deficient isotope $^{249}$No was synthesized for the first time in the fusion-evaporation reaction $^{204}$Pb($^{48}$Ca,3n)$^{249}$No. After separation, using the kinematic separator SHELS, the new isotope was identified with the GABRIELA detection system through genetic correlations with the known daughter and granddaughter nuclei $^{245}$Fm and $^{241}$Cf. The alpha-decay activity of $^{249}$No has an energy of 9129(22)$~$keV and half-life 38.3(2.8) ms. An upper limit of 0.2\% was measured for the fission branch of $^{249}$No. Based on the present data and recent information …
