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Gtz, M.*; Yakushev, A.*; G
tz, S.*; Di Nitto, A.*; D
llmann, Ch. E.*; Asai, Masato; Kindler, B.*; Krier, J.*; Lommel, B.*; Nagame, Yuichiro*; et al.
Radiochimica Acta, 110(2), p.75 - 86, 2022/02
Times Cited Count:2 Percentile:29.53(Chemistry, Inorganic & Nuclear)The study of volatile superheavy element carbonyl complexes requires more efficient methods because the yield of transactinide elements decreases with increasing atomic number. This is achieved by using a newly developed double chamber system to separate the recoil chamber and the reaction one, thereby avoiding the decomposition of reactive molecules by the projectile ion beam, which hinders the synthesis of carbonyl complexes. The feasibility of this method was verified by synthesizing 5d metal short-lived isotopes as homologous element isotopes of the light transactinide elements Sg, Bh, Hs, and Mt at the Japan Atomic Energy Agency tandem accelerator and conducting model experiments.
Chiera, N. M.*; Sato, Tetsuya; Eichler, R.*; Tomitsuka, Tomohiro; Asai, Masato; Adachi, Sadia*; Dressler, R.*; Hirose, Kentaro; Inoue, Hiroki*; Ito, Yuta; et al.
Angewandte Chemie; International Edition, 60(33), p.17871 - 17874, 2021/08
Times Cited Count:3 Percentile:21.36(Chemistry, Multidisciplinary)The formation and the chemical characterization of single atoms of dubnium (Db, element 105), in the form of its volatile oxychloride, was investigated using the on-line gas phase chromatography technique, in the temperature range 350 - 600 C. Under the exact same chemical conditions, comparative studies with the lighter homologs of group-5 in the Periodic Table clearly indicate the volatility sequence being NbOCl
TaOCl
DbOCl
. From the obtained experimental results, thermochemical data for DbOCl
were derived. The present study delivers reliable experimental information for theoretical calculations on the chemical properties of transactinides.
Chiera, N. M.; Sato, Tetsuya; Tomitsuka, Tomohiro; Asai, Masato; Ito, Yuta; Shirai, Kaori*; Suzuki, Hayato; Tokoi, Katsuyuki; Toyoshima, Atsushi; Tsukada, Kazuaki; et al.
Journal of Radioanalytical and Nuclear Chemistry, 320(3), p.633 - 642, 2019/06
Times Cited Count:2 Percentile:20.94(Chemistry, Analytical)An isothermal gas-chromatographic (IGC) device has been developed and tested for on-line gas phase studies of volatile oxychlorides of short-lived group-5 transition metals. Radioisotopes of niobium and tantalum, produced in nuclear fusion evaporation reactions, are directly flushed into the IGC setup by an inert gas-jet. Oxychloride compounds are formed by the addition of SOCl and O
. Parameters influencing the formation and transport of NbOCl
and TaOCl
are investigated. For nuclides with half-lives (
) of about 30 s, an overall efficiency of 7% is obtained, rendering the IGC setup suitable for the chemical exploration of
Db(
= 34s).
Chiera, N. M.; Sato, Tetsuya; Tomitsuka, Tomohiro; Asai, Masato; Suzuki, Hayato*; Tokoi, Katsuyuki; Toyoshima, Atsushi; Tsukada, Kazuaki; Nagame, Yuichiro
Inorganica Chimica Acta, 486, p.361 - 366, 2019/02
Times Cited Count:4 Percentile:24.55(Chemistry, Inorganic & Nuclear)The formation of NbOCl and TaOCl
and their adsorption behavior on quartz surfaces was explored by applying an isothermal gas-chromatographic method. Trace amounts of short-lived Nb and Ta isotopes were used. Adsorption enthalpy values (
) at zero surface coverage of -
(NbOCl
) = 102
4 kJ/mol and -
(TaOCl
) = 128
5 kJ/mol were determined by analyzing the chromatographic behavior of the Nb andTa complexes with a Monte-Carlo simulation method based on an adsorption-desorption kinetic model.By applying an empirical correlation, the experimental
values were successively related to the macroscopic standard sublimation enthalpy,
, as a measure of the volatility of each substance. The inferred sublimation enthalpies are in agreement with tabulated thermochemical values. Thus, the linear empirical correlation between
and
for metal-oxychlorides was updated with the inclusion of the present data. According to the predicted
(DbOCl
), a
(DbOCl
) value of 135
2 kJ/mol was extrapolated. The future accomplishment of comparative studies with DbOCl
under the same experimental conditions will provide valuable information on the volatility trend in Group-5 elements, together with an indication on the magnitude of relativistic effects on the electronic structure of dubnium.
Eichler, R.*; Asai, Masato; Brand, H.*; Chiera, N. M.*; Di Nitto, A.*; Dressler, R.*; Dllmann, Ch. E.*; Even, J.*; Fangli, F.*; Goetz, M.*; et al.
EPJ Web of Conferences, 131, p.07005_1 - 07005_7, 2016/12
Times Cited Count:3 Percentile:72.73(Chemistry, Inorganic & Nuclear)In recent years gas-phase chemical studies assisted by physical pre-separation allowed for the productions and investigations of fragile single molecular species of superheavy elements. The latest highlight is the formation of very volatile hexacarbonyl compound of element 106, Sg(CO). Following this success, second-generation experiments were performed to measure the first bond dissociation energy between the central metal atom and the surrounding ligand. The method using a tubular decomposition reactor was developed and successfully applied to short-lived Mo(CO)
, W(CO)
, and Sg(CO)
.
Kaneya, Yusuke*; Tomitsuka, Tomohiro; Sato, Tetsuya; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Mitsukai, Akina; Makii, Hiroyuki; Hirose, Kentaro; Osa, Akihiko; et al.
no journal, ,
Tomitsuka, Tomohiro; Kaneya, Yusuke*; Sato, Tetsuya; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Mitsukai, Akina; Osa, Akihiko; Nishio, Katsuhisa; Nagame, Yuichiro; et al.
no journal, ,
In order to investigate the adsorption behavior of Lawrencium (Lr, Z = 103) on a Tantalum (Ta) surface, we measured ionization efficiencies of Lr under several temperature conditions of the surface ionization. We observed ionization efficiencies of Lr which were lower than those calculated by the Saha-Langmuir equation in lower temperature region. Based on a temperature dependence of the obtained ionization efficiencies, we discuss the adsorption behavior of Lr on the Ta surface.
Kaneya, Yusuke*; Asai, Masato; Sato, Tetsuya; Tomitsuka, Tomohiro; Tsukada, Kazuaki; Toyoshima, Atsushi; Mitsukai, Akina; Makii, Hiroyuki; Hirose, Kentaro; Osa, Akihiko; et al.
no journal, ,
To study the influence of the valence 7p electronic orbital on chemical properties of lawrencium, a measurement of the adsorption enthalpy of lawrencium was carried out. A new method using a surface ionization technique coupled to an on-line isotope separator was developed, which enabled one to measure temperature dependence of lawrencium surface adsorption on a metallic tantalum surface at high temperature up to 2800 K. The temperature dependences of adsorption of lawrencium as well as various lanthanide elements were investigated with this method, and the adsorption enthalpy of lawrencium was successfully extracted.
Tomitsuka, Tomohiro; Tokoi, Katsuyuki*; Sato, Tetsuya; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Chiera, N. M.; Kamada, Hiroki; Nagame, Yuichiro; Goto, Shinichi*
no journal, ,
no abstracts in English
Asai, Masato; Tsukada, Kazuaki; Hirose, Kentaro; Toyoshima, Atsushi; Tomitsuka, Tomohiro; Chiera, N. M.; Ito, Yuta; Makii, Hiroyuki; Nagame, Yuichiro; Nishio, Katsuhisa; et al.
no journal, ,
Spontaneous fissions of neutron-rich heavy actinide isotopes Fm,
Fm, and
Lr have been measured at the JAEA Tandem accelerator facility.
Fm and
Fm were produced in a multinucleon transfer reaction with an
O beam and an extremely rare
Es target with a half-life of 276 days. Reaction products were mass-separated with an on-line isotope separator (ISOL). A transition between the typical asymmetric mass distribution and a very sharp symmetric one was clearly observed between
Fm and
Fm, while the spontaneous fission of
Lr was found to exhibit mixture of three different fission modes.
Kamada, Hiroki*; Asai, Masato; Tsukada, Kazuaki; Sato, Tetsuya; Toyoshima, Atsushi; Nagame, Yuichiro; Mitsukai, Akina; Tomitsuka, Tomohiro*; Andreyev, A. N.; Nishio, Katsuhisa; et al.
no journal, ,
Existence of the previously unknown isomer Np was discovered for the first time.
Np was produced by using the JAEA tandem accelerator. Short-lived reaction products were mass-separated by the on-line isotope separator ISOL, and
and X rays originating from the decay of
Np were observed. The half-life of
Np was determined to be approximately 9 min, and
Np was found to decay via the EC decay as well as the isomeric transition. On the basis of the observed
and X rays and the half-life value, we have evaluated level energy, spin-parity, and proton-neutron configuration of
Np.
Tomitsuka, Tomohiro*; Tokoi, Katsuyuki*; Sato, Tetsuya; Asai, Masato; Chiera, N. M.; Goto, Shinichi*; Osa, Akihiko; Toyoshima, Atsushi; Tsukada, Kazuaki; Nagame, Yuichiro
no journal, ,
Tokoi, Katsuyuki; Sato, Tetsuya; Eichler, R.*; Ito, Yuta; Tomitsuka, Tomohiro; Suzuki, Hayato*; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi*; Chiera, N. M.; et al.
no journal, ,
We developed a new experimental method combining vacuum chromatography and surface ionization, and applied this to investigate adsorption behavior of lawrencium (Lr, Z =103) on a surface of high temperature metallic tantalum. The adsorption behavior of Lr was similar to that of lutetium having low volatility among lanthanide elements. In this work, a Monte Carlo simulation code has been newly developed to study ionization and chromatographic behavior of short-lived atoms. In the presentation, we will report the details of a developed simulation code and calculation results.
Asai, Masato; Tsukada, Kazuaki; Hirose, Kentaro; Toyoshima, Atsushi; Tomitsuka, Tomohiro; Chiera, N. M.; Ito, Yuta; Makii, Hiroyuki; Nagame, Yuichiro; Nishio, Katsuhisa; et al.
no journal, ,
Spontaneous fissions of Fm,
Fm, and
Lr have been measured using an
Es target at the JAEA Tandem Accelerator Facility. These three nuclei show different fission properties: the asymmetric fission, the high total-kinetic-energy (TKE) symmetric fission, and the low TKE symmetric fission, and the mechanisms of these three fissions should be very different. It is of great interest to elucidate how these differences occur. We have produced
Fm in multinucleon-transfer reactions with a
Es target and
O projectiles, and produced
Lr in the
Cm(
N,4n) fusion-evaporation reaction. The reaction products were mass-separated with a gas-jet-coupled on-line isotope separator, and were delivered into a rotating wheel alpha- and fission-fragment detection system. By comparing the mass and TKE distributions deduced from the present experimental data, we will discuss the differences in fission mechanism among
Fm,
Fm, and
Lr.
Tomitsuka, Tomohiro; Tokoi, Katsuyuki; Sato, Tetsuya; Ito, Yuta; Suzuki, Hayato*; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Chiera, N. M.; Goto, Shinichi*; et al.
no journal, ,
In order to experimentally determine the ground state electronic configurations of Superheavy element atoms, we have developed a slow Atomic Beam Source (ABS) using a high-temperature nozzle type cavity. In this study, we conducted an off-line experiment using stable isotopes of Cd to examine the extraction of the Cd beams. A symmetrical beam distribution with respect to the atomic beam edge was obtained. The obtained results, together with Monte-Carlo simulations for atomic beam profiles, will be presented.
Chiera, N. M.; Sato, Tetsuya; Asai, Masato; Suzuki, Hayato*; Tokoi, Katsuyuki; Tomitsuka, Tomohiro; Toyoshima, Atsushi; Tsukada, Kazuaki; Nagame, Yuichiro
no journal, ,
Asai, Masato; Suekawa, Yoshihide*; Higashi, Masato*; Kamada, Hiroki*; Tobe, Teruhisa*; Andreyev, A. N.; Hirose, Kentaro; Ito, Yuta; Makii, Hiroyuki; Nishio, Katsuhisa; et al.
no journal, ,
A new isomer Np with a half-life of
9 min has been discovered. It was produced in the reaction of
U target with
Li beam at JAEA tandem accelerator, and was identified through characteristic X-ray measurement and mass separation with an on-line isotope separator (ISOL). Gamma-ray singles, gamma-gamma coincidence, and internal-conversion electron measurements were performed. It was revealed that the
Np decays mostly through an isomeric E4 transition followed by an M1 transition, and that the spin-parity of the
Np should be 5
. The results are introduced in detail, and the nuclear structure of the
Np are discussed.
Asai, Masato; Tsukada, Kazuaki; Hirose, Kentaro; Toyoshima, Atsushi*; Tomitsuka, Tomohiro*; Chiera, N. M.*; Ito, Yuta; Makii, Hiroyuki; Nagame, Yuichiro*; Nishio, Katsuhisa; et al.
no journal, ,
We have studied spontaneous fission of neutron-rich Fm and Lr isotopes. The neutron-rich Fm isotopes were produced with the Es target and the
O beam delivered by the JAEA tandem accelerator. The neutron-rich Lr isotope were produced with the
Cm target and the
N beam. Reaction products were mass-separated with an on-line isotope separator (ISOL), which enabled us to obtain non-contaminated samples and to measure fission fragments precisely. From the deduced fission-fragment mass and total kinetic energy distributions, we have obtained a new insight into the competition between the symmetric and asymmetric fission which is characteristic in this neutron-rich region.
Nishio, Katsuhisa; Hirose, Kentaro; Makii, Hiroyuki; Orlandi, R.; Kean, K. R.*; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi*; Sato, Tetsuya; Ito, Yuta; et al.
no journal, ,
no abstracts in English
Do, V. K.; Furuse, Takahiro; Murakami, Erina; Aita, Rena; Ota, Yuki; Tomitsuka, Tomohiro; Sano, Yuichi; Akimoto, Yuji*; Endo, Tsubasa*; Katayama, Atsushi; et al.
no journal, ,
The paper presents removal of possible interferences including from an isobar (Nb) and tailings of adjacent peaks for the quantification of
Zr and
Mo using an ICP-MS/MS (Agilent 8900). By using ammonia gas (NH
) as a reaction gas,
Zr and
Mo can be separated from each other and from
Nb owing to the different reactions of those elements with the reaction gas. Based on the characterization results, we propose a measurement scheme aiming at quantification of
Zr and
Mo in environmental samples collected at adjacent location of Fukushima Daiichi Nuclear Power Station.