First observation of high-$K$ isomeric states in $^{249}$Md and $^{251}$Md
T. Goigoux, Ch. Theisen, B. Sulignano, M. Airiau, K. Auranen, H. Badran, R. Briselet, T. Calverley, D. Cox, F. Déchery, F. Defranchi Bisso, A. Drouart, Z. Favie… 展开作者
T. Goigoux, Ch. Theisen, B. Sulignano, M. Airiau, K. Auranen, H. Badran, R. Briselet, T. Calverley, D. Cox, F. Déchery, F. Defranchi Bisso, A. Drouart, Z. Favier, B. Gall, T. Grahn, P. T. Greenlees, K. Hauschild, A. Herzáň, R. -D. Herzberg, U. Jakobsson, R. Julin, S. Juutinen, J. Konki, M. Leino, A. Lightfoot, A. Lopez-Martens, A. Mistry, P. Nieminen, J. Pakarinen, P. Papadakis, J. Partanen, P. Peura, P. Rahkila, E. Rey-Herme, J. Rubert, P. Ruotsalainen, M. Sandzelius, J. Sarén, C. Scholey, J. Sorri, S. Stolze, J. Uusitalo, M. Vandebrouck, A. Ward, M. Zielińska, P. Jachimowicz, M. Kowal, J. Skalski
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 theoretical calculations. Excited nuclear configurations were calculated within two scenarios: via blocking nuclear states located in proximity to the Fermi surface or/and using the quasiparticle Bardeen-Cooper-Schrieffer method. Relevant states were selected on the basis of the microscopic-macroscopic model with a deformed Woods-Saxon potential. The most probable candidates for the configurations of $K$-isomeric states in Md nuclei are proposed.
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…
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…
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…
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）
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…
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 …
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 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…
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…
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…
Isomeric states in 59,61Ti have been populated in the projectile fragmentation of a 345 AMeV 238U beam at the Radioactive Isotope Beam Factory. The decay lifetimes and delayed gamma-ray transitions were measured with the EURICA array. Besides the known isomeric state in 59Ti, two isomeric states in 61Ti are observed for the first time. Based on the measured lifetimes, transition multipolarities as well as tentative spins and parities are assigned. Large-scale shell model calculations based on the modified LNPS interaction show that both 59Ti and 61Ti belong to the Island of Inversion at N=40 w…
Mass measurements of fission and projectile fragments, produced via $^{238}$U and $^{124}$Xe primary beams, have been performed with the multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) of the FRS Ion Catcher with a mass resolving powers (FWHM) up to 410,000 and an uncertainty of $6\cdot 10^{-8}$. The nuclides were produced and separated in-flight with the fragment separator FRS at 300 to 1000 MeV/u and thermalized in a cryogenic stopping cell. The data-analysis procedure was developed to determine with highest accuracy the mass values and the corresponding uncertainties for th…
Nuclear properties across the chart of nuclides are key to improving and validating our understanding of the strong interaction in nuclear physics. We present high-precision mass measurements of neutron-rich Fe isotopes performed at the TITAN facility. The multiple-reflection time-of-flight mass spectrometer (MR-ToF-MS), achieving a resolving power greater than $600\,000$ for the first time, enabled the measurement of $^{63-70}$Fe, including first-time high-precision direct measurements ($δm/m \sim 10^{-7}$) of $^{68-70}$Fe, as well as the discovery of a long-lived isomeric state in $^{69}$Fe.…
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…
First observation of multi-phonon $γ$-vibrations in an odd-odd nuclear system
Shandong University（山东大学）；Vanderbilt University（范德堡大学）；Université Claude Bernard Lyon 1（里昂第一大学）；GANIL（法国国家大科学装置重离子加速器联合实验室）；Variable Energy Cyclotron Centre（可变能量回旋加速器中心）；Homi Bhabha National Institute（霍米·巴巴国立研究所）；Government Degree College Shopian（肖皮安政府学位学院）；Islamic University of Science and Technology（伊斯兰科学与技术大学）；University of Kashmir（克什米尔大学）
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…
$^{229}$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…
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…
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。
We perform coincidence measurements between $α$ particles and $γ$ rays from a $^{233}$U source to determine the half-lives of the excited state in a $^{229}$Th nucleus. We first prove that the half-lives of 42.43- and 164.53-keV states are consistent with literature values, whereas that of the 97.14-keV state (93(7) ps) deviates from a previously measured value (147(12) ps). The half-lives of 71.83- and 163.25-keV states are determined for the first time. Based on the obtained half-lives and the Alaga rule, we estimate the radiative half-life of the low-energy isomeric state ($^{229m}$Th) to b…
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.…
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…
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）
