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Iimura, Hideki; Mller, P.*; Ichikawa, Takatoshi*; Sagawa, Hiroyuki*; Iwamoto, Akira*
JPS Conference Proceedings (Internet), 6, p.030102_1 - 030102_4, 2015/06
no abstracts in English
Asai, Masato; Tsukada, Kazuaki; Sakama, Minoru*; Haba, Hiromitsu*; Ichikawa, Takatoshi*; Ishii, Yasuo; Toyoshima, Atsushi; Ishii, Tetsuro; Nishinaka, Ichiro; Nagame, Yuichiro; et al.
Physical Review C, 87(1), p.014332_1 - 014332_6, 2013/01
Times Cited Count:6 Percentile:43.37(Physics, Nuclear)The spin-parity and neutron configuration of the ground state of No have been identified through -decay spectroscopy. The No is the nucleus with the largest neutron number whose spin-parities and single-particle configurations have ever been identified. The neutron 9/2[615] configuration was assigned to the ground state of No as well as to the 231.4 keV level in Fm. This allowed us to establish energy spacings and order of the neutron single-particle orbitals in such heaviest nuclear region. The appearance of the 9/2[615] ground state at =157 implies that the order of the neutron orbitals between the =152 and 162 deformed shell gaps should change considerably with increasing neutron number.
Ichikawa, Takatoshi*; Iwamoto, Akira; Mller, P.*; Sierk, A. J.*
Physical Review C, 86(2), p.024610_1 - 024610_8, 2012/08
Times Cited Count:68 Percentile:94.44(Physics, Nuclear)Fission-fragment mass distributions are asymmetric in fission of typical actinide nuclei for nucelon number in the range and proton number in the range . For somewhat lighter systems it has been observed that fission mass distributions are usually symmetric. However, a recent experiment showed that fission of Hg following electron capture on HI is asymmetric. An earlier experiment has shown fission of Hg and nearby nuclei is symmetric, but with hints of asymmetric yield distributions up to about 10 MeV above the saddle-point energy. We calculate potential-energy surfaces for a typical actinide nucleus and for 12 even isotopes in the range Hg-Hg, demonstrating the radical differences between actinide and mervury potential surfaces. We discuss these differences and how the changing potential-energy structure along the mercury isotope chain affects the observed (a)symmetry of the fission fragments. We show that the mechanism of asymmetric fission is very different in proton-rich mercury isotopes compared to the actinide region.
Sato, Nozomi; Haba, Hiromitsu*; Ichikawa, Takatoshi*; Kaji, Daiya*; Kudo, Yuki*; Morimoto, Koji*; Morita, Kosuke*; Ozeki, Kazutaka*; Sumita, Takayuki*; Yoneda, Akira*; et al.
Journal of the Physical Society of Japan, 80(9), p.094201_1 - 094201_7, 2011/09
Times Cited Count:15 Percentile:65.13(Physics, Multidisciplinary)Decay properties of Hs and Hs produced in the Pb(Fe, ) [=1, 2] reactions were studied using a gas-filled recoil ion separator at the linear accelerator facility of RIKEN. A total of 6 decay chains were assigned to Hs. Cross sections for the Hs production in the Pb(Fe,) and Pb(Fe,) reactions were measured to be pb and pb, respectively. The isotope Hs decayed with a half-life of ms by -particle emission and spontaneous fission. The -particle energy of Hs was observed at 10.610.04 and 10.800.08 MeV. The spontaneous fission branch of Hs was found to be .
Asai, Masato; Tsukada, Kazuaki; Haba, Hiromitsu*; Ishii, Yasuo; Ichikawa, Takatoshi*; Toyoshima, Atsushi; Ishii, Tetsuro; Nagame, Yuichiro; Nishinaka, Ichiro; Kojima, Yasuaki*; et al.
Physical Review C, 83(1), p.014315_1 - 014315_12, 2011/01
Times Cited Count:24 Percentile:79.05(Physics, Nuclear)Excited states in Fm populated via the decay of No are studied in detail through - coincidence and fine structure measurements. Spin-parities and neutron configurations of the excited states in Fm as well as the ground state of No are definitely identified on the basis of deduced internal conversion coefficients, lifetimes of transitions, rotational-band energies built on one-quasiparticle states, and hindrance factors of transitions. It is found that the excitation energy of the 1/2[620] state in =151 isotones increases with the atomic number, especially at 100, while that of the 1/2[631] state decreases at =100. Energy systematics of the one-quasiparticle states in the =151 isotones are discussed in terms of the evolution of nuclear deformation involving the hexadecapole and hexacontatetrapole deformations.
Andreyev, A. N.*; Elseviers, J.*; Huyse, M.*; Van Duppen, P.*; Antalic, S.*; Barzakh, A.*; Bree, N.*; Cocolios, T. E.*; Comas, V. F.*; Diriken, J.*; et al.
Physical Review Letters, 105(25), p.252502_1 - 252502_5, 2010/12
Times Cited Count:189 Percentile:97.20(Physics, Multidisciplinary)Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sato, Nozomi*; Sumita, Takayuki*; Yoneda, Akira*; Ichikawa, Takatoshi*; et al.
Journal of the Physical Society of Japan, 78(6), p.064201_1 - 064201_6, 2009/06
Times Cited Count:30 Percentile:78.22(Physics, Multidisciplinary)Decay properties of an isotope Bh and its daughter nucleus Db produced by the Cm(Na,5) reaction were studied by using a gas-filled recoil separator coupled with a position-sensitive semiconductor detector. Bh was clearly identified from the correlation of the known nuclide, Db. The obtained decay properties of Bh and Db are consistent with those observed in the 113 chain, which provided further confirmation of the discovery of 113.
Kaji, Daiya*; Morimoto, Koji*; Sato, Nozomi*; Ichikawa, Takatoshi*; Ideguchi, Eiji*; Ozeki, Kazutaka*; Haba, Hiromitsu*; Koura, Hiroyuki; Kudo, Yuki*; Ozawa, Akira*; et al.
Journal of the Physical Society of Japan, 78(3), p.035003_1 - 035003_2, 2009/03
A new hassium isotopes Hs is directly produced for the first time. The experiment was performed at the linear accelerator (RILAC) facility in RIKEN (the Institute of Physical and Chemical Research) from Jun. 19 to 25. In the 25-h irradiation of Fe on Pb and 46-h irradiation of Fe on Pb, 8 decay chains and 1 decay chain, respectively, were observed. All decay chains were assigned to subsequent decays from Hs. The half-life of Hs is 0.60 ms. In this experiment, the total beam dose was ions for Fe and ions for Fe. The production cross section corresponding to 8 decay events and 1 decay chain was deduced to be 21 pb and 1.6 pb by assuming that the transmission of the system is 80%.
Kaji, Daiya*; Morimoto, Koji*; Sato, Nozomi*; Ichikawa, Takatoshi*; Ideguchi, Eiji*; Ozeki, Kazutaka*; Haba, Hiromitsu*; Koura, Hiroyuki; Kudo, Yuki*; Ozawa, Akira*; et al.
Journal of the Physical Society of Japan, 78(3), p.035003_1 - 035003_2, 2009/03
Times Cited Count:3 Percentile:26.18(Physics, Multidisciplinary)A new neutron deficient hassium (=108) isotope of Hs was identified via two different reactions of Pb(Fe,n) and Pb(Fe,n) by using a gas-filled recoil separator GARIS at June 2008. During the 25-h irradiation of Pb with the Fe beam and 46-h irradiation of Pb with the Fe beam, 8 decay chains and 1 decay chain, respectively, have been observed. The half-life of Hs is 0.60 ms. In this experiment, the total beam doses of the Fe and Fe was 4.110 ions and 6.210 ions, respectively. The production cross sections corresponding to the 8 decay chains and 1 decay chain have been deduced to be 21 pb and 1.6 pb by assuming the transmission of the system to be 80%.
Sato, Nozomi*; Haba, Hiromitsu*; Ichikawa, Takatoshi*; Ideguchi, Eiji*; Kaji, Daiya*; Koura, Hiroyuki; Kudo, Yuki*; Morimoto, Koji*; Morita, Kosuke*; Ozawa, Akira*; et al.
RIKEN Accelerator Progress Report, Vol.42, P. 16, 2009/00
New Decay Properties of Hs and its -decay daughter nuclei were studied by using reactions of Pb(Fe,2n) and Pb(Fe,n) by using a gas-filled recoil ion separator, GARIS at RIKEN. We observed three correlated events in irradiation of Fe on Pb, and eight events in irradiation of Fe on Pb. A half-life was deduced to be 0.90. We assigned these eleven events to be the decays of Hs. We found different decay-chain events of Hs from a previous report. One is a long-lived -decay of Sg with 180ms of half-life. Another is a long-lived -decay of Rf with 10.4s of half-life. For Sg and Rf, the decay of such a long-lived state have not been reported. These are the first observations of isomerism in Sg and Rf.
Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Ishii, Yasuo; Tome, Hayato; Sato, Tetsuya; Nishinaka, Ichiro; Ichikawa, Takatoshi; Ichikawa, Shinichi; et al.
Radiochimica Acta, 95(1), p.1 - 6, 2007/01
Times Cited Count:16 Percentile:71.93(Chemistry, Inorganic & Nuclear)no abstracts in English
Ichikawa, Takatoshi; Iwamoto, Akira
Physical Review C, 71(6), p.067601_1 - 067601_4, 2005/06
Times Cited Count:0 Percentile:0.01(Physics, Nuclear)We estimate the decrease of the Coulomb-barrier height between colliding parters due to charge polarizations in the entrance channel for cold-fusion reactions. Since the Coulomb-repulsion force increases with increasing the proton numbers of the target and projectile such as cold-fusion reactions, it is expected that the charge distribution of the colliding nuclei is changed to some extent. The resulting charge distribution induced by this polarization decreases the interacting Coulomb energy between the colliding partners, whereas their own self energies increase due to the increase of the symmetry energy. We assume that the resulting charge displacements between protons and neutrons are the sum of the surface- and volume-charge components and estimate the extent of the charge polarization with the self energy on the basis of the droplet model. We show the difference between the charge polarization of light and heavy nuclei and the decrease of the Coulomb barrier height for synthesizing superheavy elements.
Ichikawa, Takatoshi; Iwamoto, Akira; Mller, P.*; Sierk, A. J.*
Physical Review C, 71(4), p.044608_1 - 044608_11, 2005/04
Times Cited Count:42 Percentile:89.77(Physics, Nuclear)We estimate the effective fusion barrier in the entrance channel in cold-fusion reactions in a model where the projectile deformation and quadrupole zero-point vibrational energy are taken into account. The effective fusion-barrier height is defined as the barrier energy at the target and projectile separation distance where the system becomes unstable with respect to projectile deformation. We also calculate five-dimensional potential-energy surfaces for the single compound system. For heavy systems the fusion barrier at touching becomes lower than the fission barrier just beyond the ground state of the compound system. Except for reactions in which the projectile is doubly magic or near doubly magic, the calculated quantities are consistent with the observed optimal energies for evaporation-residue formation.
Iwamoto, Akira; Ichikawa, Takatoshi; Mller, P.*; Sierk, A. J.*
Nuclear Physics A, 738, p.499 - 502, 2004/06
Times Cited Count:4 Percentile:30.83(Physics, Nuclear)no abstracts in English
Kaji, Daiya*; Morimoto, Koji*; Sato, Nozomi; Haba, Hiromitsu*; Ichikawa, Takatoshi*; Ideguchi, Eiji*; Koura, Hiroyuki; Kudo, Yuki*; Ozawa, Akira*; Ozeki, Kazutaka*; et al.
no journal, ,
A new neutron deficient hassium () isotope of Hs was identified via two different reactions of Pb(Fe,) and Pb(Fe,) by using the gas-filled recoil separator GARIS. During irradiation of Pb with the Fe beam and irradiation of Pb with the Fe beam, 8 decay chains and 1 decay chain, respectively, were observed. The properties of decay events obtained by irradiation of Fe on Pb match well with those by irradiation of Fe on Pb. The mean -decay energies for the 3 groups are 10.82, 10.55, and 10.37 MeV, respectively. The half-life of Hs is determined to be 0.60 ms.
Morimoto, Koji*; Morita, Kosuke*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sato, Nozomi; Sumita, Takayuki*; Yoneda, Akira*; Ichikawa, Takatoshi*; et al.
no journal, ,
A nuclide, Bh, is the great-grand-daughter of 113 that is produced in the Bi + Zn reaction. The identification was based on a genetic link to the known daughter nucleus Db by alpha-decays. The main purpose of this work is to provide further confirmation of the production and identification of the isotope 113. As a present result, a state in Bh, which decays by an alpha emission with the energies ranging from 9.05 to 9.23 MeV, feeds a state in Db, which decays by alpha emission and by SF with a previously known half-life. The result provided a further confirmation of the production and identification of the isotope of the 113th element, 113, studied by a research group at RIKEN.
Morimoto, Koji*; Morita, Kosuke*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sato, Nozomi; Sumita, Takayuki*; Yoneda, Akira*; Ichikawa, Takatoshi*; et al.
no journal, ,
We performed the experiment to synthesize an isotope of the element 113 produced by a Bi(Zn,n)113 reaction using a gas-filled recoil ion separator (GARIS) at RIKEN. Two decay chains were observed, and assigned to those originating from an isotope 113. Both chains were connected into the previously known decays of Bh and Db via previously unknown decays of 113, Rg, and Mt. Although the Bh was known nuclide, a number of atoms reported so far was limited. In order to study more precise decay property of the Bh, we performed the direct production of Bh by the Cm(Na,5n)Bh reaction. In this experiment, the Bh was clearly identified from the correlation of the nuclide, Db. The obtained decay properties of Bh and Db are consistent with those observed in the 113 chain, which provided further confirmation of the discovery of 113.
Utsuno, Yutaka; Ichikawa, Takatoshi*; Shimizu, Noritaka*; Otsuka, Takaharu*
no journal, ,
no abstracts in English
Tsukada, Kazuaki; Toyoshima, Atsushi; Haba, Hiromitsu*; Asai, Masato; Akiyama, Kazuhiko*; Ishii, Yasuo; Tome, Hayato*; Nishinaka, Ichiro; Sato, Tetsuya; Ichikawa, Takatoshi; et al.
no journal, ,
no abstracts in English
Toyoshima, Atsushi; Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Akiyama, Kazuhiko*; Ishii, Yasuo; Tome, Hayato*; Nishinaka, Ichiro; Sato, Tetsuya; Ichikawa, Takatoshi; et al.
no journal, ,
no abstracts in English