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Bh in the 
Cm(
Na,5
)Bh reaction and its decay propertiesHaba, Hiromitsu*; Fan, F.*; Kaji, Daiya*; Kasamatsu, Yoshitaka*; Kikunaga, Hidetoshi*; Komori, Yukiko*; Kondo, Narumi*; Kudo, Hisaaki*; Morimoto, Koji*; Morita, Kosuke*; et al.
Physical Review C, 102(2), p.024625_1 - 024625_12, 2020/08
Times Cited Count：6 Percentile：59.56(Physics, Nuclear)
= 100 with a multireflection time-of-flight mass spectrographIto, Yuta*; Schury, P.*; Wada, Michiharu*; Arai, Fumiya*; Haba, Hiromitsu*; Hirayama, Yoshikazu*; Ishizawa, Satoshi*; Kaji, Daiya*; Kimura, Sota*; Koura, Hiroyuki; et al.
Physical Review Letters, 120(15), p.152501_1 - 152501_6, 2018/04
Times Cited Count：60 Percentile：93.36(Physics, Multidisciplinary)Masses of 
Es, 
Fm and the transfermium nuclei 
Md, and 
No, produced by hot- and cold-fusion reactions, in the vicinity of the deformed 
neutron shell closure, have been directly measured using a multi-reflection time-of-flight mass spectrograph. The masses of Es and 
Md were measured for the first time. Using the masses of 
Md as anchor points for 
decay chains, the masses of heavier nuclei, up to 
Bh and Mt, were determined. These new masses were compared with theoretical global mass models and demonstrated to be in good agreement with macroscopic-microscopic models in this region. The empirical shell gap parameter 
derived from three isotopic masses was updated with the new masses and corroborate the existence of the deformed neutron shell closure for Md and Lr.
Tanaka, Taiki*; Narikiyo, Yoshihiro*; Morita, Kosuke*; Fujita, Kunihiro*; Kaji, Daiya*; Morimoto, Koji*; Yamaki, Sayaka*; Wakabayashi, Yasuo*; Tanaka, Kengo*; Takeyama, Mirei*; et al.
Journal of the Physical Society of Japan, 87(1), p.014201_1 - 014201_9, 2018/01
Times Cited Count：18 Percentile：74.47(Physics, Multidisciplinary)Excitation functions of quasielastic scattering cross sections for the 
Ca + 
Pb, 
Ti + Pb, and Ca + Cm reactions were successfully measured by using the gas-filled recoil-ion separator GARIS. Fusion barrier distributions were extracted from these data, and compared with the coupled-channels calculations. It was found that the peak energies of the barrier distributions for the Ca + Pb and Ti + Pb systems coincide with those of the 2n evaporation channel cross sections for the systems, while that of the Ca + Cm is located slightly below the 4n evaporation ones. This results provide us helpful information to predict the optimum beam energy to synthesize superheavy nuclei.
Ca + Cm 
Lv
at RIKEN-GARISKaji, Daiya*; Morita, Kosuke*; Morimoto, Koji*; Haba, Hiromitsu*; Asai, Masato; Fujita, Kunihiro*; Gan, Z.*; Geissel, H.*; Hasebe, Hiroo*; Hofmann, S.*; et al.
Journal of the Physical Society of Japan, 86(3), p.034201_1 - 034201_7, 2017/03
Times Cited Count：28 Percentile：81.43(Physics, Multidisciplinary)The fusion reaction of Ca + Cm Lv was studied using the gas-filled recoil-ion separator GARIS at RIKEN. A total of seven and spontaneous-fission decay chains were observed, which would originate from the reaction products of the element 116, 
Lv and 
Lv. Decay properties observed in the chains are in good agreement with the previously published ones. However, one of the chains showed a discrepancy, indicating the new spontaneous-fission branch in 
Cn or the production of the new isotope 
Lv.
Eichler, R.*; Asai, Masato; Brand, H.*; Chiera, N. M.*; Di Nitto, A.*; Dressler, R.*; D
llmann, 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：72.98(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).
and W(CO)Usoltsev, I.*; Eichler, R.*; Wang, Y.*; Even, J.*; Yakushev, A.*; Haba, Hiromitsu*; Asai, Masato; Brand, H.*; Di Nitto, A.*; Dllmann, Ch. E.*; et al.
Radiochimica Acta, 104(3), p.141 - 151, 2016/03
Times Cited Count：31 Percentile：95.03(Chemistry, Inorganic & Nuclear)Conditions of the production and decomposition of hexacarbonyl complexes of short-lived Mo and W isotopes were investigated to study thermal stability of the heaviest group 6 hexacarbonyl complex Sg(CO). A tubular flow reactor was tested to decompose the hexacarbonyl complexes and to extract the first bond dissociation energies. A silver was found to be the most appropriate reaction surface to study the decomposition of the group 6 hexacarbonyl. It was found that the surface temperature at which the decomposition occurred was correlated to the first bond dissociation energy of Mo(CO) and W(CO), indicating that the first bond dissociation energy of Sg(CO) could be determined with this technique.
Even, J.*; Ackermann, D.*; Asai, Masato; Block, M.*; Brand, H.*; Di Nitto, A.*; Dllmann, Ch. E.*; Eichler, R.*; Fan, F.*; Haba, Hiromitsu*; et al.
Journal of Radioanalytical and Nuclear Chemistry, 303(3), p.2457 - 2466, 2015/03
Times Cited Count：15 Percentile：77.56(Chemistry, Analytical)Rapid In situ synthesis of metal carbonyl complexes has been demonstrated using short-lived isotopes produced in nuclear fission and fusion reactions. The short-lived isotopes with high recoil energy directly react with carbon-monoxides and form carbonyl complexes. Only highly volatile complexes were fast transported in a gas stream to counting and chemistry devices. Short-lived Mo, Tc, Ru, Rh, W, Re, Os, and Ir were found to form volatile carbonyl complexes, while no volataile complex of Hf and Ta were detected. This technique has been applied to a chemical investigation of the superheavy element Sg (atomic number 106), and will be applicable to various fields of nuclear science with short-lived transition metal isotopes.
Even, J.*; Yakushev, A.*; Dllmann, Ch. E.*; Haba, Hiromitsu*; Asai, Masato; Sato, Tetsuya; Brand, H.*; Di Nitto, A.*; Eichler, R.*; Fan, F. L.*; et al.
Science, 345(6203), p.1491 - 1493, 2014/09
Times Cited Count：63 Percentile：83.28(Multidisciplinary Sciences)A new superheavy element complex, a seaborgium carbonyl, has been successfully synthesized, and its adsorption property has been studied using a cryo-thermochromatography and -detection apparatus COMPACT. Nuclear reaction products of short-lived 
Sg preseparated with a gas-filled recoil ion separator GARIS at RIKEN were directly injected into a gas cell filled with He/CO mixture gas, and chemical reaction products of volatile carbonyl complexes were trasported to COMPACT. The Sg carbonyl complex detected with COMPACT was found to be very volatile with adsorption enthalpy of 
50 kJ/mol, from which we have concluded that this complex should be a Sg hexacarbonyl Sg(CO). This is the first synthesis of organometallic compounds of transactinide elements for which only simple inorganic comounds have been synthesized so far.
Chen, J.; Asano, Masaharu; Yamaki, Tetsuya; Yoshida, Masaru
Journal of Power Sources, 158(1), p.69 - 77, 2006/07
Times Cited Count：100 Percentile：92.22(Chemistry, Physical)To develop a highly chemically stable polymer electrolyte membrane for application in a direct methanol fuel cell(DMFC), doubly crosslinked membranes were prepared by chemical crosslinking using bifunctional monomers, such as divinylbenzene(DVB) and bis(p, p-vinyl phenyl) ethane(BVPE), and by radiation crosslinking. The membranes were prepared by grafting of m, p-methylstyrene(MeSt) and p-tert-butylstyrene(tBuSt) into poly(ethylene-co-tetrafluoroethylene)(ETFE) films and subsequent sulfonation. The effects of the DVB and BVPE crosslinkers on the grafting kinetics and the properties of the prepared membranes, such as water uptake, proton conductivity and chemical stability were investigated. Radiation crosslinking was introduced by irradiation of the ETFE base film, the grafted film or the sulfonated membrane. The membrane crosslinked by DVB and BVPE crosslinkers and post-crosslinked by 
-ray irradiation of the corresponding grafted film possessed the highest chemical stability among the prepared membranes, a significantly lower methanol permeability compared to Nafion membranes, and a better DMFC performance for high methanol feed concentration. Therefore, this doubly crosslinked membrane was promising for application in a DMFC where relatively high methanol concentration could be fed.
Chen, J.; Asano, Masaharu; Yamaki, Tetsuya; Yoshida, Masaru
Journal of Applied Polymer Science, 100(6), p.4565 - 4574, 2006/06
Times Cited Count：44 Percentile：75.8(Polymer Science)This study concerns a comparative study of three crosslinkers, divinylbenzene (DVB), 1,2-bis(p,p-vinylphenyl)ethane (BVPE) and triallyl cyanurate (TAC) crosslinked poly(ethylene-co-tetrafluoroethylene) (ETFE)-based radiation-grafted membranes, which were prepared by radiation grafting of p-methylstyrene (MeSt) onto ETFE films and subsequent sulfonation. The effect of the different types and contents of the crosslinkers on the grafting and sulfonation, and the properties such as water uptake, proton conductivity and thermal/chemical stability of the resulting polymer electrolyte membranes was investigated in detail. Introducing crosslink structure into the radiation-grafted membranes leads to a decrease in proton conductivity due to the decrease in water uptake. The thermal stability of the crosslinked radiation-grafted membranes is also somewhat lower than that of the noncrosslinked one. However, the crosslinked radiation-grafted membranes show significantly higher chemical stability characterized in the 3% H
O at 50
C. Among the three crosslinkers, the DVB shows a most pronounced efficiency on the crosslinking of the radiation-grafted membranes, while the TAC has no significant influence; the BVPE is a mild and effective crosslinker, showing the moderate influence between the DVB and TAC crosslinkers.
Chen, J.; Asano, Masaharu; Yamaki, Tetsuya; Yoshida, Masaru
Journal of Materials Science, 41(4), p.1289 - 1292, 2006/02
Times Cited Count：22 Percentile：58.41(Materials Science, Multidisciplinary)The MeSt/tBuSt/DVB-grafted polymer electrolyte membrane showed a high performance for the fuel cell applications. The tBuSt contributed the high chemical stability while the MeSt contributed the high conductivity to the resulted membrane. The DVB crosslinker in the membrane further improved the chemical stability. The new polymer electrolyte membrane with a degree of grafting of 36% showed proton conductivity as high as the Gore-Select membrane, and the durability time was about 3 times longer than that of the traditional styrene/DVB-grafted one. Therefore, the MeSt/tBuSt/DVB-grafted polymer electrolyte membrane was more possible to be used for the fuel cells.
Chen, J.; Asano, Masaharu; Yamaki, Tetsuya; Yoshida, Masaru
Journal of Membrane Science, 269(1-2), p.194 - 204, 2006/02
Times Cited Count：140 Percentile：96.07(Engineering, Chemical)To develop a highly chemically stable polymer electrolyte membrane for application in a direct methanol fuel cell (DMFC), four styrene derivative monomers, m,p-methylstyrene (MeSt), p-tert-butylstyrene (tBuSt), divinylbenzene (DVB) and bis(p,p-vinyl phenyl) ethane (BVPE) were graft copolymerized into poly(ethylene-co-tetrafluoroethylene) (ETFE) films followed by sulfonation and hydrolysis. The latter two monomers were used as crosslinkers. The graft copolymerization was carried out by the -ray preirradiation method. The influence of the preirradiation dose and the grafting kinetics were investigated in detail. Sulfonation of the grafted ETFE films was performed in a chlorosulfonic acid solution, by which the sulfonation ratio reached about 90%. The newly obtained membrane possesses significantly higher chemical stability than the traditional styrene/DVB-grafted membrane and six times lower methanol permeability compared to the Nafion 112 membrane. Therefore, this study reveals the possibility of the developed inexpensive four monomers-grafted membranes, which could provide an attractive alternative as a substitute for the expensive Nafion membranes for DMFC applications.
-proline methyl ester) gel membrane in LiCl solutionChen, J.; Asano, Masaharu; Tsubokawa, Norio*; Maekawa, Yasunari; Yamaki, Tetsuya; Yoshida, Masaru
Journal of Polymer Science, Part B; Polymer Physics, 43(20), p.2843 - 2851, 2005/10
Times Cited Count：0 Percentile：0.01(Polymer Science)Impedance spectra analysis of a thermo-responsive poly(acryloyl--proline methyl ester) (poly(A-ProOMe)) hydrogel membranes in an aqueous solution of LiCl was carried out using a simple equivalent model. The hydrogel membrane was synthesized by -radiation-induced polymerization and crosslinking of A-ProOMe monomer aqueous solution in a glass-cast. By means of the impedance spectra analysis, a novel method for the calculation of the ionic conductivity of the hydrogel membranes in LiCl solution was proposed. The calculated ionic conductivity was in agreement well with the determined value. In addition, effects of temperature and LiCl concentration on the impedance spectra and ionic conductivity of the gel membrane were analysized. Results indicated that the impedance spectra analysis is a very useful tool for evaluating the electric properties of gel membranes in an electrolyte solution. The poly(A-ProOMe) gel membrane in 1.0 M LiCl solution showed a high ionic conductivity of about 0.2 S/cm at 14C. The temperature-dependence of the ionic conductivity was a complex nonlinear form due to the volume phase transition of the thermo-responsive poly(A-ProOMe) gel membrane, and the volume phase transition temperature appeared to be decreased with the increase in the LiCl concentration.
-poly(alkyl vinyl ether) membranes for polymer electrolyte membrane fuel cells by radiation processingChen, J.; Asano, Masaharu; Yamaki, Tetsuya; Yoshida, Masaru
Journal of Membrane Science, 256(1-2), p.38 - 45, 2005/06
New polymer electrolyte membranes having sulfonic acid groups for polymer electrolyte membrane fuel cell applications were prepared by simultaneous radiation-induced grafting method. The poly(tetrafluoroethylene) (PTFE) films, crosslinked by electron-beam radiation at molten temperature, were used as substrates for grafting of two alkyl vinyl ether monomers, propyl vinyl ether (nPVE) and isopropyl vinyl ether (iPVE), under controlled grafting conditions followed by sulfonation reactions. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), water contact angle and Fourier transform infrared (FTIR) were used to characterize the crosslinked PTFE (cPTFE) and grafted cPTFE films. The degree of grafting was found to be dependent on the grafting parameters such as irradiation temperature and Lewis acid catalyst, in which in the presence of Lewis acid catalyst or at a temperature close to the boiling point of each monomer, the grafting reaction significantly accelerated even when the relatively low dose was irradiated. Finally, the grafted cPTFE films were sulfonated in a chlorosulfonic acid solution. In spite of the lower ion-exchange capacity (0.75 mmol/g), the membrane synthesized in this study showed a proton conductivity as high as the Nafion 112.
Yamaki, Tetsuya; Asano, Masaharu; Maekawa, Yasunari; Morita, Yosuke; Suwa, Takeshi; Chen, J.*; Tsubokawa, Norio*; Kobayashi, Kazuhiro*; Kubota, Hitoshi*; Yoshida, Masaru
Radiation Physics and Chemistry, 67(3-4), p.403 - 407, 2003/08
Times Cited Count：76 Percentile：97.02(Chemistry, Physical)no abstracts in English
Li, J.; Maekawa, Yasunari; Yamaki, Tetsuya; Yoshida, Masaru
Macromolecular Chemistry and Physics, 203(17), p.2470 - 2474, 2002/12
Times Cited Count：13 Percentile：42.68(Polymer Science)Chemical modification of the hydrophilic surface of poly(ethylene terephthalate) (PET) was examined by the selective alkylation of the acid salt on the surface using acylbromides as an electrophile with catalytic potassium fluoride. The hydrophobicity of the PET surface increased as the alkylation reaction of the hydrolyzed surface proceeded. The chemical incorporation of the alkylation reagents was confirmed by the fluorine peaks in X-ray photoelectron spectroscopy (XPS) from the fluorinated reagents. Exponential increases were observed in the emission and excitation intensities of fluorescence spectra during the reaction of the surface with a fluorescent reagent. This indicated the esterification of carboxylic acids on the surface without deterioration of the reactions even at the later stages. The relation between changes in contact angles and the fluorescence spectra revealed that the hydrophobicity of a surface was quickly restored at the beginning of a reaction.
Kosako, Toshiso*; *; *; Kawata, Tomio*; *; *; *; Yamaki, J.;
Genshiro Igai No Genshiryoku Shisetsu No Kijun To Shishin (Beikoku), 404 Pages, 1986/00
no abstracts in English
Kosako, Toshiso*; *; *; *; *; *; Yamaki, J.;
Genshiryoku Kagaku Puranto Ni Taisuru Anzen Shinsa Shishin (Eikoku), 75 Pages, 1986/00
no abstracts in English
; Yamaki, J.; Iwamoto, K.
Proc.30th Conf.Remote Systems Technology 1982,Vol.2, p.3 - 9, 1982/00
no abstracts in English
Sakakura, A.; Yamaki, J.; Iwamoto, K.
Proc.30th Conf.Remote Systems Technology l982,Vol.2, p.10 - 15, 1982/00
no abstracts in English
