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and high-resolution fine-structure spectroscopy for the heaviest nucleiAsai, Masato; Haba, Hiromitsu*; Tsukada, Kazuaki; Sato, Nozomi; Kasamatsu, Yoshitaka*; Kaji, D.*; Morimoto, Koji*; Morita, Kosuke*; Sato, Tetsuya; Toyoshima, Atsushi; et al.
no journal, ,
Alpha-gamma and high-resolution fine-structure spectroscopy of Rf and Lr isotopes was performed to clarify the nuclear structure of superheavy nuclei. rays following the decay of 
Rf were observed for the first time through the - coincidence measurement, and the neutron configuration of the ground state of Rf was assigned. It was found that the ground-state configuration of Rf is different from those of the lighter N = 155 isotones 
Fm and 
Cf. For the Lr isotopes, the proton configurations of the ground and isomeric states in Lr and the ground states of 
Lr and Lr were definitely identified through the high-resolution fine structure spectroscopy. Theoretical calculations based on the macroscopic-microscopic model revealed that the change of the ground-state configuration in the N = 155 isotones is strongly associated with the rapidly decreasing hexadecapole deformation with increasing atomic number.
Nishio, Katsuhisa; Ikezoe, Hiroshi; Hofmann, S.*; Ackermann, D.*; Antalic, S.*; Aritomo, Yoshihiro; Comas, V. F.*; D
llmann, Ch. E.*; Gorshkov, A.*; Graeger, R.*; et al.
no journal, ,
Koura, Hiroyuki
no journal, ,
Nucleus is a composite system consisting of protons and neutrons, and approximately 3000 nuclides have been identified experimentally. However, the existence of much more nuclides is postulated theoretically. How far the area of nuclei extends is an important question in nuclear physics. We have developed an original model based on the macroscopic and mean-field models to describe nuclear masses, called the KTUY (Koura-Tachibana-Uno-Yamada) mass model. By using the KTUY model, we have studied decay modes for alpha-decay, beta-decay, proton emission and spontaneous fission in the wide nuclear mass region. In the extremely heavier nuclear mass region, a large amount of nuclei located over 
is predicted to exist. This region of nuclei with longer lives than 1ns ends or is disconnected at 
. The total number of nuclei having more than 1 ns is estimated to be ten thousands. If we focus on half-lives of 1 ms or longer, number of nuclei would be roughly eight thousands.
Toyoshima, Atsushi; Oe, Kazuhiro; Li, Z.*; Asai, Masato; Sato, Nozomi; Sato, Tetsuya; Kikuchi, Takahiro; Kaneya, Yusuke*; Kitatsuji, Yoshihiro; Tsukada, Kazuaki; et al.
no journal, ,
Electrochemical study of mendelevium (Md) with flow electrolytic column chromatography is presented. The Md isotope was produced in the 
Cm(
B, 4
) reaction at the JAEA tandem accelerator. In applying a negative voltage on the column electrode, Md was eluted with 0.1 M HCl. This behavior is quite similar to that of Sr
and Eu, clearly indicating that most stable Md
is reduced to Md
. We determined the redox potential of Md to be approximately -0.18 V versus a standard hydrogen electrode.
Sato, Nozomi; Asai, Masato; Tsukada, Kazuaki; Sato, Tetsuya; Toyoshima, Atsushi; Li, Z.*; Kikuchi, Takahiro; Kaneya, Yusuke*; Sch
del, M.; Nagame, Yuichiro; et al.
no journal, ,
The first ionization potential (IP) of the last actinide, lawrencium (Lr), is predicted to be lower than those of other actinides. To determine the IP of Lr based on the surface ionization comparison technique, we are developing a surface-ionization-type ion-source coupled to a gas-jet transport system at the Isotope Separator On-Line at the JAEA tandem accelerator facility. In the present study, we measured ionization efficiencies of lanthanides as a function of ion-source temperature to examine the applicability of our apparatus to the IP measurement. It was found that the obtained ionization efficiency of each lanthanide element is affected by an ionization potential as well as a boiling point.