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Ichikawa, Nozomi*; Hamamoto, Takafumi*; Ishidera, Takamitsu; Sasamoto, Hiroshi
NUMO-TR-22-02, p.55 - 57, 2023/03
no abstracts in English
Takubo, Yusaku*; Takayama, Yusuke; Ichikawa, Nozomi*; Ishida, Keisuke*; Fujisaki, Kiyoshi*
NUMO-TR-22-02, p.68 - 71, 2023/03
no abstracts in English
Sato, Tetsuya; Asai, Masato; Borschevsky, A.*; Stora, T.*; Sato, Nozomi*; Kaneya, Yusuke; Tsukada, Kazuaki; D
llmann, C. E.*; Eberhardt, K.*; Eliav, E.*; et al.
EPJ Web of Conferences, 131, p.05001_1 - 05001_6, 2016/12
Times Cited Count：0 Percentile：0.00(Chemistry, Inorganic & Nuclear)Ionization efficiency in a surface ionization process depends on the first ionization potential of the atom. Based on the dependence, the ionization potential of the atom can be determined. We measured ionization efficiencies of fermium, einsteinium, mendelevium, and lawrencium by using a newly developed gas-jet coupled surface ion-source. The ionization potential of the elements have not been determined so far due to their low production rates and/or their short half-lives. Based on a relationship between the ionization efficiency and the ionization potential obtained via measurements of short-lived lanthanide isotopes, the ionization potentials of these actinide elements have been successfully determined.
Sato, Tetsuya; Asai, Masato; Borschevsky, A.*; Stora, T.*; Sato, Nozomi; Kaneya, Yusuke; Tsukada, Kazuaki; Dllmann, Ch. E.*; Eberhardt, K.*; Eliav, E.*; et al.
Nature, 520(7546), p.209 - 211, 2015/04
Times Cited Count：112 Percentile：97.33(Multidisciplinary Sciences)Ionization efficiency in a surface ionization process depends on the first ionization potential of the atom. Based on the dependence, the ionization potential of the atom can be determined. We successfully measured ionization efficiencies of lawrencium (Lr, 
=103) using a gas-jet coupled surface ion-source. The ionization potential of Lr has not been determined owing to its low production rate and its short half-life. Based on a relationship between the ionization efficiency and the ionization potential obtained via measurements of short-lived lanthanide isotopes, the ionization potential of Lr was determined.
gas-jet system coupled to a surface-ionization type ion-source in JAEA-ISOL; Towards determination of the first ionization potential of Lr (Z = 103)Sato, Tetsuya; Asai, Masato; Sato, Nozomi; Tsukada, Kazuaki; Toyoshima, Atsushi; Oe, Kazuhiro*; Miyashita, Sunao*; Kaneya, Yusuke; Osa, Akihiko; Sch
del, M.; et al.
Journal of Radioanalytical and Nuclear Chemistry, 303(2), p.1253 - 1257, 2015/02
Times Cited Count：9 Percentile：57.41(Chemistry, Analytical)We have developed a surface-ionization ion-source coupled to the He/CdI
gas-jet transport system for the Isotope Separator On-Line (ISOL) at the JAEA tandem accelerator for experimental determination of the first ionization potential of lawrencium (Lr, 
). We performed to ionize a short-lived Lr isotope and various lanthanide isotopes. We successfully observed mass-separated ions of 
Lr by using our present system at the first time. The first ionization potential of Lr was evaluated based on a correlation between of effective ionization potential and ionization efficiency of short-lived lanthanide isotopes in our system.
Lr in the 
Cf + 
B, 
Am + 
O, and 
Cm + 
N reactionsSato, Nozomi; Sato, Tetsuya; Asai, Masato; Toyoshima, Atsushi; Tsukada, Kazuaki; Li, Z.*; Nishio, Katsuhisa; Nagame, Yuichiro; Schdel, M.; Haba, Hiromitsu*; et al.
Radiochimica Acta, 102(3), p.211 - 219, 2014/03
Times Cited Count：10 Percentile：58.48(Chemistry, Inorganic & Nuclear)Production cross-sections of the isotope Lr in the Cf + B, Am + O, and Cm + N reactions were measured using a He/KCl gas-jet transport system and a rotating wheel 
-particle detection apparatus. The -particle energy of Lr was distributed from 8.3 to 8.7 MeV and its half-life, 
, was measured to be 
s. The maximum cross sections in the 
Cf(B, 4
)Lr and Am(O, 5)Lr reactions were determined to be 
nb at the beam energy of 63 MeV and 
nb at 96 MeV, respectively. In the Cm(N, 6)Lr reaction, the cross section was measured to be 
nb at 91 MeV.
Sato, Tetsuya; Sato, Nozomi; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Oe, Kazuhiro; Miyashita, Sunao; Schdel, M.; Kaneya, Yusuke*; Nagame, Yuichiro; et al.
Review of Scientific Instruments, 84(2), p.023304_1 - 023304_5, 2013/02
Times Cited Count：17 Percentile：58.90(Instruments & Instrumentation)We have developed the surface ion-source coupled to the He/CdI gas-jet transport system to measure the ionization potential of Lr atatom-at-a-time conditions. We successfully ionized and mass-separated for the first time Lr ions by applying the present ion-source and the ISOL technique. The ionization efficiencies of Lr were estimated to be approximately 42% and 24% at 2600 K on Re and Ta surfaces, respectively. These values were higher than those of Lu in all of ionization condition. The results indicate that the ionization potential of Lr would be lower than that of Lu, 5.4 eV. Therefore, it is concluded that the surface ion-source is a promising apparatus tomeasure the first ionization potential of Lr. Using the present system, determination of the ionization potential of Lr is being performed.
Lr in the Cm + N reactionSato, Nozomi; Sato, Tetsuya; Asai, Masato; Toyoshima, Atsushi; Tsukada, Kazuaki; Li, Z.*; Nishio, Katsuhisa; Nagame, Yuichiro; Schdel, M.; Haba, Hiromitsu*; et al.
RIKEN Accelerator Progress Report, Vol.46, P. 237, 2013/00
Due to the strong relativistic effects, the weakly-bound outermost electron results in a significantly low first ionization potential (IP) of Lr as compared with its neighboring heavy actinides. The isotope Lr, with a relatively long half-life of 27 s, is the suitable candidates for the IP measurement of Lr through the surface ionization method. In the present study, we measured the cross section of the Cm(N, 6)Lr reaction to evaluate the production rate of Lr. A Cm target with 960 
60 
g/cm
thickness was bombarded with a N
beam from the RIKEN AVF Cyclotron. The beam energy was 91 MeV in the middle of the target. The average beam intensity was 1.2 particle-A. Reaction products were transported to the rotating wheel -particle detection system with a He/KCl gas-jet system. The Lr cross section of 271 nb was calculated based on the -particle events between 8.3 and 8.7 MeV.
Hs and 
HsSato, 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：16 Percentile：65.84(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 
.
Bh and 
Db produced in the Cm + 
Na reactionMorita, 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：77.69(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.
HsKaji, 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%.
HsKaji, 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：25.72(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 4.1
10
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%.
Hs, 
Sg, and RfSato, 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 180
ms of half-life. Another is a long-lived -decay of Rf with 10.4
s 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.
Sato, Tetsuya; Sato, Nozomi; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Oe, Kazuhiro; Kaneya, Yusuke*; Kojima, Takayuki*; Nagame, Yuichiro; Schdel, M.; et al.
no journal, ,
The first ionization potential (IP) of the heaviest actinide lawrencium (Lr) is predicted to be lower than those of other actinides. To determine the IP of Lr based on the surface ionization technique, we have developed a surface ionization ion source coupled to a gas-jet transport system for the Isotope Separator On-Line at the JAEA tandem accelerator facility. We measured ionization efficiencies of short-lived lanthanides isotopes as a function of ion-source temperature as a model experiment of Lr.
Sato, Tetsuya; Sato, Nozomi; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Kaneya, Yusuke*; Ichikawa, Shinichi; Nagame, Yuichiro; Schdel, M.
no journal, ,
The first ionization potentials of the heavy elements with atomic number Z 
100 have never measured owing to the low production rates and short half-lives of the nuclides. In order to determine the first IP of the heaviest actinide element, lawrencium (Lr, Z = 103), by the surface ionization comparison method, we have developed a surface ionization ion source coupled with a gas-jet transport system for an ISOL (Isotope Separator On-Line) at the JAEA tandem accelerator facility. From the results of our fundamental experiments by using short-lived lanthanide isotopes, we have decided to apply some improvements to the apparatus to increase surface temperature of the ion source and reduce the cold spots, and achieve stable operation for a long beam time. In the conference, we will mention the current status of the ion source development and the improvements.
Sato, Nozomi; Asai, Masato; Tsukada, Kazuaki; Sato, Tetsuya; Toyoshima, Atsushi; Li, Z.*; Kikuchi, Takahiro; Kaneya, Yusuke*; Schdel, 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.
-
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.
Sato, Nozomi; Asai, Masato; Tsukada, Kazuaki; Sato, Tetsuya; Toyoshima, Atsushi; Li, Z.*; Oe, Kazuhiro; Kikuchi, Takahiro; Kaneya, Yusuke*; Schdel, M.; 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.
HsKaji, 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.
Sato, Nozomi; Asai, Masato; Tsukada, Kazuaki; Sato, Tetsuya; Toyoshima, Atsushi; Li, Z.; Nagame, Yuichiro; Schdel, M.; Ichikawa, Shinichi
no journal, ,
First ionization potentials (IPs) of heavy elements with atomic numbers Z 100 have not been determined up to now. Recently we have been developing a surface ionization type ion source to measure the IP of the heaviest actinide, lawrencium (Lr, Z = 103). The surface ionization comparison technique is a promising approach to measure the IP of Lr on an atom-at-a-time scale. We will present the status of our development for an apparatus for this measurement.
