九州大学 研究者情報
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基本情報 研究活動 教育活動 社会活動
浅井 雅人(あさい まさと) データ更新日:2021.10.30



主な研究テーマ
超重核及び重アクチノイド核の核構造研究
キーワード:超重核、重アクチノイド核、核構造、核分光
1998.04.
超重元素の化学特性の実験的研究
キーワード:超重元素、周期表、化学特性、イオン化エネルギー
1998.04.
超重核の核分裂特性の研究
キーワード:核分裂、対称核分裂、超重核
2016.07.
従事しているプロジェクト研究
119番元素探索実験
2018.06, 代表者:森田浩介, 理化学研究所/九州大学, 理化学研究所(日本).
113番元素Nhの揮発性研究
2016.08, 代表者:A. Yakushev, GSI/HIM, GSI (Germany).
Es-254標的を用いた核分裂・核構造・核化学研究
2017.10, 代表者:西尾勝久, 原子力機構, 原子力機構(日本).
研究業績
主要著書
主要原著論文
1. M. Asai, F. P. Hassberger, A. Lopez-Martens, Nuclear structure of elements with 100 <= Z <= 109 from alpha spectroscopy, NUCLEAR PHYSICS A, 10.1016/j.nuclphysa.2015.06.011, 944, 308-332, 2015.12, Significant technical progress concerning the availability of intense heavy-ion beams and highly-efficient and sophisticated detection devices has made nuclear-structure investigations possible in the region of superheavy nuclei. Exciting new results have been obtained by applying alpha spectroscopy as well as alpha-gamma and internal-conversion-electron coincidence spectroscopy. The present review article gives an overview of the experimental techniques and methods with specific attention to the recent developments of digital signal and data processing giving access to half-life ranges of less than a few microseconds. The presentation of the experimental results and the physics discussion will be focused on nuclear structure systematics in even-Z nuclei along the N = 151, 153, and 155 isotonic lines, where most progress has been achieved in the last 10 years. (C) 2015 Elsevier B.V. All rights reserved..
2. T. K. Sato, M. Asai, A. Borschevsky, T. Stora, N. Sato, Y. Kaneya, K. Tsukada, Ch E. Duellmann, K. Eberhardt, E. Eliav, S. Ichikawa, U. Kaldor, J. V. Kratz, S. Miyashita, Y. Nagame, K. Ooe, A. Osa, D. Renisch, J. Runke, M. Schaedel, P. Thoerle-Pospiech, A. Toyoshima, N. Trautmann, Measurement of the first ionization potential of lawrencium, element 103, NATURE, 10.1038/nature14342, 520, 7546, 209-U153, 2015.04, The chemical properties of an element are primarily governed by the configuration of electrons in the valence shell. Relativistic effects influence the electronic structure of heavy elements in the sixth row of the periodic table, and these effects increase dramatically in the seventh row including the actinides even affecting ground-state configurations(1,2). Atomic s and p(1/2) orbitals are stabilized by relativistic effects, whereas p(3/2), d and f orbitals are destabilized, so that ground-state configurations of heavy elements may differ from those of lighter elements in the same group. The first ionization potential (IP1) is a measure of the energy required to remove one valence electron from a neutral atom, and is an atomic property that reflects the outermost electronic configuration. Precise and accurate experimental determination of IP1 gives information on the binding energy of valence electrons, and also, therefore, on the degree of relativistic stabilization. However, such measurements are hampered by the difficulty in obtaining the heaviest elements on scales of more than one atom at a time(3-5). Here we report that the experimentally obtained IP1 of the heaviest actinide, lawrencium (Lr, atomic number 103), is 4.96(-0.07)(+0.08) electronvolts. The IP1 of Lr was measured with Lr-256. (half-life 27 seconds) using an efficient surface ion-source and a radioisotope detection system coupled to a mass separator. The measured IP1 is in excellent agreement with the value of 4.963(15) electronvolts predicted here by state-of-the-art relativistic calculations. The present work provides a reliable benchmark for theoretical calculations and also opens the way for IP1 measurements of superheavy elements (that is, transactinides) on an atom-at-a-time scale..
3. J. Even, A. Yakushev, Ch E. Duellmann, H. Haba, M. Asai, T. K. Sato, H. Brand, A. Di Nitto, R. Eichler, F. L. Fan, W. Hartmann, M. Huang, E. Jaeger, D. Kaji, J. Kanaya, Y. Kaneya, J. Khuyagbaatar, B. Kindler, J. V. Kratz, J. Krier, Y. Kudou, N. Kurz, B. Lommel, S. Miyashita, K. Morimoto, K. Morita, M. Murakami, Y. Nagame, H. Nitsche, K. Ooe, Z. Qin, M. Schaedel, J. Steiner, T. Sumita, M. Takeyama, K. Tanaka, A. Toyoshima, K. Tsukada, A. Tuerler, I. Usoltsev, Y. Wakabayashi, Y. Wang, N. Wiehl, S. Yamaki, Synthesis and detection of a seaborgium carbonyl complex, SCIENCE, 10.1126/science.1255720, 345, 6203, 1491-1493, 2014.09, Experimental investigations of transactinoide elements provide benchmark results for chemical theory and probe the predictive power of trends in the periodic table. So far, in gas-phase chemical reactions, simple inorganic compounds with the transactinoide in its highest oxidation state have been synthesized. Single-atom production rates, short half-lives, and harsh experimental conditions limited the number of experimentally accessible compounds. We applied a gas-phase carbonylation technique previously tested on short-lived molybdenum (Mo) and tungsten (W) isotopes to the preparation of a carbonyl complex of seaborgium, the 106th element. The volatile seaborgium complex showed the same volatility and reactivity with a silicon dioxide surface as those of the hexacarbonyl complexes of the lighter homologs Mo and W. Comparison of the product's adsorption enthalpy with theoretical predictions and data for the lighter congeners supported a Sg(CO)(6) formulation..
4. M. Asai, K. Tsukada, M. Sakama, H. Haba, T. Ichikawa, Y. Ishii, A. Toyoshima, T. Ishii, I. Nishinaka, Y. Nagame, Y. Kasamatsu, M. Shibata, Y. Kojima, H. Hayashi, Ground-state configuration of the N=157 nucleus No-259, PHYSICAL REVIEW C, 10.1103/PhysRevC.87.014332, 87, 1, 014332-1-6, 2013.01, The ground-state configuration of the N = 157 nucleus No-259 has been identified through alpha-gamma coincidence and alpha-singles measurements. Three gamma transitions were observed for the first time in the alpha decay of No-259, and its decay scheme was established. The neutron 9/2(+)[615] configuration was assigned to the ground state of No-259 as well as to the 231.4 keV level in Fm-255. Ground-state deformations and neutron single-particle energies in Z = 102 isotopes were calculated with the macroscopic-microscopic model. The 9/2(+)[615] orbital was calculated to be the highest among the five orbitals between the N = 152 and 162 deformed shell gaps, which is consistent with the experimental one-quasiparticle energies in N = 153 and 155 isotones, but is inconsistent with the present experimental result of the 9/2(+)[615] ground state at N = 157. To reproduce the 9/2(+)[615] ground state at N = 157, the order of the neutron orbitals should be different between the N = 153 and 157 isotones. DOI: 10.1103/PhysRevC.87.014332.
5. M. Asai, K. Tsukada, H. Haba, Y. Ishii, T. Ichikawa, A. Toyoshima, T. Ishii, Y. Nagame, I. Nishinaka, Y. Kojima, K. Sueki, Neutron one-quasiparticle states in Fm-251(151) populated via the alpha decay of No-255, PHYSICAL REVIEW C, 10.1103/PhysRevC.83.014315, 83, 1, 014315-1-12, 2011.01, Excited states in Fm-251 populated via the alpha decay of No-255 are studied in detail through alpha-gamma coincidence and alpha fine-structure measurements. Five excited states reported previously in Fm-251 are firmly established through the alpha-gamma coincidence measurement, and rotational bands built on one-quasiparticle states are newly established through the alpha fine-structure measurement. Spin-parities and neutron configurations of the excited states in Fm-251 as well as the ground state of No-255 are definitely identified on the basis of deduced internal conversion coefficients, lifetimes of gamma transitions, rotational-band energies built on one-quasiparticle states, and hindrance factors of alpha transitions. It is found that the excitation energy of the 1/2(+)[620] state in N = 151 isotones increases with the atomic number, especially at Z >= 100, while that of the 1/2(+)[631] state decreases at Z = 100. Ground-state deformations and energies of neutron one-quasiparticle states in the N = 151 isotones are calculated using a macroscopic-microscopic model, and the energy systematics of the one-quasiparticle states in the isotones are discussed in terms of the evolution of nuclear deformation involving the hexadecapole (beta(4)) and hexacontatetrapole (beta(6)) deformations..
6. Asai M., Tsukada K., Sakama M., Ichikawa S., Ishii T., Nagame Y., Nishinaka I., Akiyama K., Osa A., Oura Y., Sueki K., Shibata M., Experimental Identification of Spin-Parities and Single-Particle Configurations in 257No and Its alpha-Decay Daughter 253Fm, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.95.102502, 95, 10, 102502-1-4, 2005.09.
7. Asai M, Sakama M, Tsukada K, Ichikawa S, Haba H, Nishinaka I, Nagame Y, Goto S, Kojima Y, Nakahara H, Oura Y, Shibata M, Kawade K, EC and alpha decays of 235Am, EUROPEAN PHYSICAL JOURNAL A, 10.1140/epja/i2004-10044-6, 22, 3, 411-416, 2004.12.
8. Asai M., Sakama M., Tsukada K., Ichikawa S., Haba H., Nishinaka I., Nagame Y., Goto S., Kojima Y., Oura Y., Nakahara H., Shibata M., Kawade K., Proton-neutron configurations in 236g,mAm and its EC-decay daughter 236Pu, EUROPEAN PHYSICAL JOURNAL A, 10.1140/epja/i2004-10096-6, 23, 3, 395-400, 2004.12.
9. Asai M., Sekine T., Osa A., Koizumi M., Kojima Y., Shibata M., Yamamoto H., Kawade K., Energy systematics of low-lying 0+ states in neutron-deficient Ba nuclei, PHYSICAL REVIEW C, 10.1103/PhysRevC.56.3045, 56, 6, 3045-3053, 1997.12.
10. Asai M., Ichikawa S., Tsukada K., Sakama M., Shibata M., Kojima Y., Osa A., Nishinaka I., Nagame Y., Kawade K., Tachibana T., Beta-decay half-lives of new neutron-rich isotopes 167,168Tb and levels in 167,168Dy, PHYSICAL REVIEW C, 10.1103/PhysRevC.59.3060, 59, 6, 3060-3065, 1999.06.
主要総説, 論評, 解説, 書評, 報告書等
主要学会発表等
学会活動
所属学会名
日本放射化学会
日本物理学会
学協会役員等への就任
2020.04, 日本放射化学会, 理事.
学会大会・会議・シンポジウム等における役割
2019.12.01~2019.12.05, The 4 th International Symposium on Superheavy Elements (SHE2019), Organizer.
2017.03.05~2017.03.06, 「第9回停止・低速RIビームを用いた核分光研究会」&「2017超重元素の科学研究会」合同研究会, 主催者(事務局).
2017.01.05~2017.01.06, 東海・重イオン科学シンポジウム―タンデム加速器成果報告会―, 主催者(事務局).
2016.09.13~2016.09.13, 2016超重元素の科学研究会, 主催者(事務局).
2015.05.25~2015.05.29, The 5th International Conference on the Chemistry and Physics of the Transactinide Elements (TAN15), Organizer (Scientific Secretary).
2013.09.19~2013.09.21, 8th Workshop on the Chemistry of the Heaviest Elements (CHE8), Organizer.
2013.07.02~2013.07.03, 「タンデム領域の重イオン科学」研究会, 主催者(事務局).
2006.10.26~2006.10.27, The 6th International Symposium on Advanced Science Research -Frontiers of Nuclear and Radiochemistry- (ASR2006), Organizer.
2001.11.13~2001.11.15, The 2nd International Symposium on Advanced Science Research -Advances in Heavy Element Research- (ASR2001), Organizer (Scientific Secretary).
2001.02.22~2001.02.23, 「第2回重元素核科学」ワークショップ, 主催者(事務局).
学会誌・雑誌・著書の編集への参加状況
2007.12~2008.06, Journal of Nuclear and Radiochemical Sciences, Vol. 8, No. 2, Proceedings of the 6th International Symposium on Advanced Science Research -Frontiers of Nuclear and Radiochemistry- (ASR2006), 国際, 編集委員.
2001.11~2002.06, Journal of Nuclear and Radiochemical Sciences, Vol. 3, No. 2, Proceedings of the 2nd International Symposium on Advanced Science Research -Advances in Heavy Element Research- (ASR2001), 国際, 編集委員.
学術論文等の審査
年度 外国語雑誌査読論文数 日本語雑誌査読論文数 国際会議録査読論文数 国内会議録査読論文数 合計
2021年度      
2020年度      
2017年度      
2016年度      
2010年度      
2006年度    
受賞
平成28年度 科学技術分野の文部科学大臣表彰 科学技術賞 研究部門, 文部科学省, 2016.04.
The First Poster Award, in TAN 07: The 3rd International Conference on the Chemistry and Physics of the Transactinide Elements, The 3rd International Conference on the Chemistry and Physics of the Transactinide Elements (TAN07), Davos, Switzerland, September 23-27, 2007, 2007.09.
研究資金
科学研究費補助金の採択状況(文部科学省、日本学術振興会)
2021年度~2024年度, 基盤研究(B), 代表, 99番元素Es標的を用いた重アクチノイド核の特異な核分裂機構の解明.
2020年度~2024年度, 挑戦的研究(開拓), 代表, 112~116番元素のイオン化エネルギー測定による新たな周期律の構築.
2014年度~2017年度, 基盤研究(B), 代表, 重・超アクチノイ元素の化学結合に寄与する7p$_{1/2}$電子軌道の影響の探索.
2006年度~2007年度, 若手研究(B), 代表, 超重核の殻構造の実験的解明.
2002年度~2003年度, 若手研究(B), 代表, α-γ精密核分光実験による重・超アクチノイド核の核構造研究.

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