First high-precision direct determination of the atomic mass of a superheavy nuclide
P. Schury, T. Niwase, M. Wada, P. Brionnet, S. Chen, T. Hashimoto, H. Haba, H. Hirayama, D. S. Hou, S. Iimura, H. Ishiyama, S. Ishizawa, Y. Ito, D. Kaji, S. Kim… 展开作者
P. Schury, T. Niwase, M. Wada, P. Brionnet, S. Chen, T. Hashimoto, H. Haba, H. Hirayama, D. S. Hou, S. Iimura, H. Ishiyama, S. Ishizawa, Y. Ito, D. Kaji, S. Kimura, H. Koura, J. J. Liu, H. Miyatake, J. -Y. Moon, K. Morimoto, K. Morita, D. Nagae, M. Rosenbusch, A. Takamine, Y. X. Watanabe, H. Wollnik, W. Xian, S. X. Yan
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Submitted to PRC as Rapid Comm., 5 pages, 4 figures
We present the first direct measurement of the atomic mass of a superheavy nuclide. Atoms of $^{257}$Db ($Z$=105) were produced online at the RIKEN Nishina Center for Accelerator-Based Science using the fusion-evaporation reaction $^{208}$Pb($^{51}$V, 2n)$^{257}$Db. The gas-filled recoil ion separator GARIS-II was used to suppress both the unreacted primary beam and some transfer products, prior to delivering the energetic beam of $^{257}$Db ions to a helium gas-filled ion stopping cell wherein they were thermalized. Thermalized $^{257}$Db$^{3+}$ ions were then transferred to a multi-reflection time-of-flight mass spectrograph for mass analysis. An alpha particle detector embedded in the ion time-of-flight detector allowed disambiguation of the rare $^{257}$Db$^{3+}$ time-of-flight detection events from background by means of correlation with characteristic $α$-decays. The extreme sensitivity of this technique allowed a precision atomic mass determination from 11 events. The mass excess was determined to be $100\,063(231)_\textrm{stat}(132)_\textrm{sys}$~keV/c$^2$. Comparing to several mass models, we show the technique can be used to unambiguously determine the atomic number as $Z$=105 and should allow similar evaluations for heavier species in future work.
Energies from alpha- and proton-decay experiments yield information of capital importance for deriving the atomic masses of superheavy and exotic nuclides. We present a procedure to correct the published decay energies in case the recoiling daughter nuclides were not considered properly in implantation experiments. A program has been developed based on Lindhard's integral theory, which can accurately predict the energy deposition of heavy atomic projectiles in matter.
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 …
Charge and frequency resolved isochronous mass spectrometry in storage rings: First direct mass measurement of the short-lived neutron-deficient $^{51}$Co nuclide
储存环中单个离子的旋转频率测量需要复杂的定时探测器。用于这种检测器的常见方法之一是检测由于所存储的离子的穿透而从薄箔释放的次级电子。提出了一种基于次级电子强度分析的新方法，该方法可以在测量离子旋转频率的同时确定离子的电荷。虽然$^{51}$ Co $^{27+}$和$^{34}$ Ar $^{18+}$离子的质荷比几乎相同，因而不能在储存环中分辨，但应用新方法首次确定了短寿命$^{51}$ Co的质量过剩为ME（$^{51}$ Co）=-27342（48）keV.壳模型计算的$fp$壳核相比，新的数据表明，需要包括同位旋非守恒力。
$^{180m}$Ta is a naturally abundant quasi-stable nuclide and the longest-lived nuclear isomer known to date. It is of interest for, among others, the search for dark matter, for the development of a gamma laser and for astrophysics. So far, its excitation energy has not been measured directly but has been based on an evaluation of available nuclear reaction data. We have determined the excitation energy of this isomer with high accuracy using the Penning-trap mass spectrometer JYFLTRAP. The determined mass difference between the ground and isomeric states of $^{180}$Ta yields an excitation ene…
A novel technique for broadband high-precision mass measurements of short-lived exotic nuclides is reported. It is based on the isochronous mass spectrometry (IMS) and realizes simultaneous determinations of revolution time and velocity of short-lived stored ions at the cooler storage ring CSRe in Lanzhou. The new technique, named as the $Bρ$-defined IMS or $Bρ$-IMS, boosts the efficiency, sensitivity, and accuracy of mass measurements, and is applied here to measure masses of neutron-deficient $fp$-shell nuclides. In a single accelerator setting, masses of $^{46}$Cr, $^{50}$Fe and $^{54}$Ni a…
In the isochronous mass spectrometry (IMS) performed at storage rings, masses of short-lived nuclides are determined through precision measurements of their mean revolution times. However, the distribution of revolution times could be seriously deteriorated by instabilities of the ring's magnetic fields. This becomes a significant obstacle for the particle identifications and mass determinations. A data analysis method is described in this paper which is able to largely remove the uncertainties caused by the magnetic field instabilities in the particle identifications and the mean revolution t…
The absolute atomic mass of $^{208}$Pb has been determined with a fractional uncertainty of $7\times 10^{-11}$ by measuring the cyclotron-frequency ratio $R$ of $^{208}$Pb$^{41+}$ to $^{132}$Xe$^{26+}$ with the high-precision Penning-trap mass spectrometer Pentatrap and computing the binding energies $E_{\text{Pb}}$ and $E_{\text{Xe}}$ of the missing 41 and 26 atomic electrons, respectively, with the ab initio fully relativistic multi-configuration Dirac-Hartree-Fock (MCDHF) method. $R$ has been measured with a relative precision of $9\times 10^{-12}$. $E_{\text{Pb}}$ and $E_{\text{Xe}}$ have …
Offline Commissioning of the St. Benedict Gas Catcher
University of Notre Dame（圣母大学）；École normale supérieure Paris-Saclay（巴黎萨克雷高等师范学院）；Argonne National Laboratory（阿贡国家实验室）；University of Tennessee（田纳西大学）；University of Chicago（芝加哥大学）
Background: $β$-delayed multiple neutron emission has been observed for some nuclei with A$\leq$100, with $^{100}$Rb being the heaviest $β$2n emitter measured to date. So far, only 25 P$_{2n}$ values have been determined for the $\sim$300 nuclei that may decay in this way. Accordingly, it is of interest to measure P$_{2n}$ values for the other possible multiple neutron emitters throughout the chart of the nuclides. It is of particular interest to make such measurement for nuclei with A$>$100 to test the predictions of theoretical models and simulation tools for the decays of heavy nuclei in th…
Accurate mass determination of short-lived nuclides by Penning-trap spectrometers and progress in the spectroscopy of proton-rich nuclei have triggered renewed interest in the isobaric multiplet mass equation (IMME). The energy levels of the members of $T=1/2, 1, 3/2,$ and 2 multiplets and the coefficients of the IMME are tabulated for $A\le 71$. The new compilation is based on the most recent mass evaluation (AME2011) and it includes the experimental results on energies of the states evaluated up to end of 2011. Taking into account the error bars, a significant deviation from the quadratic fo…
Nuclear mass measurements of isotopes are key to improving our understanding of nuclear structure across the chart of nuclides, in particular for the determination of the appearance or disappearance of nuclear shell closures. We present high-precision mass measurements of neutron-rich Ca, Ti and V isotopes performed at the TITAN and LEBIT facilities. These measurements were made using the TITAN multiple-reflection time-of-flight mass spectrometer (MR-ToF-MS) and the LEBIT 9.4T Penning trap mass spectrometer. In total, 13 masses were measured, eight of which represent increases in precision ove…
