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Journal Articles

First ionization potentials of Fm, Md, No and Lr; Verification of filling-up of 5f electrons and confirmation of the actinide series

Sato, Tetsuya

Kagaku To Kogyo, 72(10), P. 867, 2019/10

We conducted measurements of the first ionization potential (IP$$_1$$) of the heavy actinide elements, lawrencium (Lr, $$Z = 103$$), nobelium (No, $$Z = 102$$), mendelevium (Md, $$Z = 101$$) and fermium (Fm, $$Z = 100$$) by using a novel method based on a surface ionization process. The IP$$_1$$ measurements have been performed using the ISOL (Isotope Separator On-Line) system equipped with a surface ion-source with short-lived heavy actinide isotopes, $$^{256}$$Lr ($$T_{1/2}$$ = 27s), $$^{257}$$No ($$T_{1/2}$$ = 24.5s), $$^{251}$$Md ($$T_{1/2}$$ = 4.27 min), and $$^{249}$$Fm ($$T_{1/2}$$ = 2.6 min). Our experimental results clearly showed that the IP$$_1$$ of Lr is distinctly low among actinide elements. Moreover, No has the highest IP$$_1$$ among them due to its full-filled 5f and 7s orbitals; the IP$$_1$$ value increased with an atomic number up to No and decreased dramatically at Lr, indicating the similar trend with that of heavy lanthanide elements. Therefore, we concluded Lr would be the last member of the actinide series.

Journal Articles

First ionization potential of the heaviest actinide lawrencium, element 103

Sato, Tetsuya; Asai, Masato; Borschevsky, A.*; Stora, T.*; Sato, Nozomi*; Kaneya, Yusuke; Tsukada, Kazuaki; D$"u$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:100

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.

Journal Articles

Measurement of the first ionization potential of lawrencium by surface ionization method

Sato, Tetsuya

Genshikaku Kenkyu, 61(1), p.96 - 106, 2016/09

We successfully determined the first ionization potential of lawrencium (Lr, Z=103). The result experimentally substantiated for the first time that Lr is the last member of the actinide series. Measured ionization potential suggested that Lr atom would have the electronic configuration which is different from the configuration expected based on the Periodic table. For the measurement, we have developed a novel method applied the surface ionization process. Public responses after the publication are also introduced.

Journal Articles

Does element-103 change the periodic table of elements ?!; The First ionization potential of lawrencium

Sato, Tetsuya

Kagaku, 71(3), p.12 - 16, 2016/03

We successfully confirmed that lawrencium, element 103, would be the last member of actinide series by a measurement of the first ionization potential of lawrencium. Moreover, the electronic configuration expected from the experimental results suggested that lawrencium could have the outermost electronic orbital similar to that of group-13 elements. Our result triggered discussion concerning the position of lawrencium and lutetium on the periodic table of the elements.

Journal Articles

Lawrencium's place at the table

Nagame, Yuichiro

Nature Chemistry, 8(3), P. 282, 2016/03

We summarize the studies of element 103, lawrencium: discovery or synthesis in nuclear reactions, historical argument for recognition as a new element, nuclear and chemical studies of lawrencium isotopes, and recently measured ionization energy. Based on the studies so far performed, we introduce a debate that has emerged over the place in the periodic table.

Journal Articles

The First ionization potential of element 103 successfully measured for the first time substantiated that lawrencium is the last member of actinide series

Sato, Tetsuya

Isotope News, (740), p.16 - 19, 2015/12

We successfully determined the first ionization potential of lawrencium (Lr, Z=103). The result experimentally substantiated for the first time that Lr is the last member of the actinide series. Measured ionization potential suggested that Lr atom would have the electronic configuration which is different from the configuration expected based on the Periodic table.

Journal Articles

Where is an appropriate place for element 103 on the periodic table?; Measurement of the first ionization potential of lawrencium

Sato, Tetsuya

Nippon Genshiryoku Gakkai-Shi, 57(11), p.741 - 744, 2015/11

We have experimentally confirmed that Lr would be the last member of actinides series for the first time by a measurement of the first ionization potential of lawrencium (Lr, element 103). The electronic orbital of Lr atom which is estimated by the result suggests that Lr could have the outermost electronic orbital similar with group-13 elements. This work triggered a discussion concerning positions of Lr and lutetium, lanthanide homologue of Lr.

Journal Articles

Measurement of the first ionization energy of lawrencium (Z = 103) by surface ionization technique

Sato, Tetsuya

Hosha Kagaku, (32), p.34 - 41, 2015/09

In the surface ionization process, an ionization efficiency depends on the first ionization potential of the atom of the element. The ionization potential can be estimated by using the relationship. This method has been developed in order to determine the first ionization potential of lawrencium (Lr, element 103). The value of the ionization potential of Lr have not been measured experimentally due to its low production rate and short half-life. The surface-ionization method is described in detail in this paper.

Journal Articles

Discrepancy in the periodic table appears at element 103; Successful measurement of the first ionization potential of lawrencium, element 103

Sato, Tetsuya; Nagame, Yuichiro; Tsukada, Kazuaki

Kagaku To Kogyo, 68(9), p.824 - 826, 2015/09

We successfully confirmed that lawrencium (Lr, element 103) is the last member of actinide series by a measurement of its first ionization potential. Obtained experimental result suggested that the outermost electronic orbital of Lr atom would have p-orbital similar to elements of group-13. Our result triggered again the discussion of the position of Lr and lutetium, the lanthanide homologue of Lr, on the Periodic Table.

Journal Articles

Successful measurement of the first ionization potential of lawrencium, element 103

Sato, Tetsuya

Saiensu Potaru (Internet), 3 Pages, 2015/07

On April 9th, a press release titled "Measurement of the first ionization potential of lawrencium (element 103) - Unravelling Relativistic Effects in the Heaviest Actinide Element -" was issued. This research result published from Nature was not only introduced in its "News & Views" but also appeared on the cover. I made a commentary on the result and introduced its response for public.

Journal Articles

Measurement of the first ionization potential of lawrencium, element 103

Sato, Tetsuya; Asai, Masato; Borschevsky, A.*; Stora, T.*; Sato, Nozomi; Kaneya, Yusuke; Tsukada, Kazuaki; D$"u$llmann, Ch. E.*; Eberhardt, K.*; Eliav, E.*; et al.

Nature, 520(7546), p.209 - 211, 2015/04

 Times Cited Count:85 Percentile:1.79(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, $$Z$$=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.

Oral presentation

The First ionization potential measurement of lawrencium (Lr, $$Z$$ = 103)

Sato, Tetsuya; Asai, Masato; Kaneya, Yusuke; Tsukada, Kazuaki; Toyoshima, Atsushi; Miyashita, Sunao*; Oe, Kazuhiro*; Osa, Akihiko; Ichikawa, Shinichi; Nagame, Yuichiro; et al.

no journal, , 

The first ionization potentials of the heaviest actinide elements have not been measured until today owing to short half-lives and low production rates of the isotopes. Based on the surface ionization technique, we performed a measurement of the ionization potential of the heaviest actinide element, lawrencium (Lr, $$Z$$ = 103), by using a newly developed surface ion-source installed to the JAEA-ISOL (Isotope Separator On-Line) at the JAEA tandem accelerator facility. We report on an evaluation of the IP value of Lr based on comparison of ionization behavior of $$^{256}$$Lr with that of short-lived lanthanide isotopes on Ta surface at several temperature.

Oral presentation

Measurement of the ionization potential of Lr (Z = 103) by online mass separation

Sato, Tetsuya; Stora, T.*; Asai, Masato; Borschevsky, A.*; Kaneya, Yusuke; Tsukada, Kazuaki; D$"u$llmann, Ch. E.*; Eliav, E.*; Kaldor, U.*; Kratz, J. V.*; et al.

no journal, , 

It is known that an ionization efficiency of an element in surface ionization process depends on temperature, work function of the surface, and the first ionization energy of the atom of the element to be ionized. We determined the first ionization energy of lawrencium (Lr), the last member of the actinide series, using the relationship between the ionization efficiency and the ionization energy. The ionization energy of Lr had not been measured owing to its low production rate and short half-lives so far. The experimental value of the ionization energy is in good agreement of the theoretical one which was calculated using the state-of-the-art relativistic calculation.

Oral presentation

First ionization potentials of heaviest actinides, lawrencium and nobelium

Sato, Tetsuya

no journal, , 

It is known that an ionization efficiency of an element in surface ionization process depends on temperature and a work function of the surface, and the first ionization energy of the atom of the element to be ionized. We determined the first ionization energies of nobelium (No) and lawrencium (Lr) by using the newly developed method based on surface ionization process. The ionization energies have not been measured owing to its low production rate and short half-lives. Concerning Lr, the experimental value of the ionization energy is in good agreement of the theoretical one which calculated using the state-of-the-art relativistic calculation. The value of No is consistent with the value obtained by an extrapolation from lighter actinide elements.

Oral presentation

First ionization potential measurements of heavy actinides, lawrencium and nobelium

Sato, Tetsuya

no journal, , 

The experimental determination of the first ionization potential (IP) yields information on the electronic structure of the element. We successfully ionized and mass-separated $$^{257}$$No and $$^{256}$$Lr with efficiencies ($$I_{rm eff}$$) of (0.5 $$pm$$ 0.1)% and (36 $$pm$$ 7)% at 2800 K, respectively. From these $$I_{rm eff}$$ values, IP values of No and Lr were determined based on the relationship between $$I_{rm eff}$$ and IP. Our values are in good agreement with the predicted ones by theoretical calculations.

Oral presentation

First ionization energy measurements of heaviest actinides, lawrencium and nobelium

Sato, Tetsuya

no journal, , 

We measured the first ionization energy (IE$$_1$$) of nobelium (No, Z = 102) and lawrencium (Lr, Z =103) by exploiting the dependence of the ionization efficiency ($$I_{rm eff}$$) on the IE$$_1$$ in a surface ionization process. The isotopes $$^{257}$$No ($$T_{1/2}$$ = 24.5s) and $$^{256}$$Lr ($$T_{1/2}$$ = 27 s), produced in the reaction $$^{248}$$Cm ($$^{13}$$C, 4n) and $$^{249}$$Cf ($$^{11}$$B, 4n), respectively, were used for studying their ionization. The reaction products recoiling from the targets were transported to a surface ion-source by a He/CdI$$_2$$ gas-jet transport system. The products ionized in the ion-source were mass-separated with JAEA-ISOL. The number of ions collected at the end of the ISOL was determined by $$alpha$$-particle measurements and was used to evaluate $$I_{rm eff}$$ values. With the present system, we successfully ionized and mass-separated $$^{257}$$No and $$^{256}$$Lr with efficiencies of (0.5 $$pm$$ 0.1)% and (36 $$pm$$ 7)% at 2800 K, respectively. From these $$I_{rm eff}$$ values, IE$$_1$$ values of No and Lr were determined based on the relationship between $$I_{rm eff}$$ and IE$$_1$$. Our values are in good agreement with the predicted ones by theoretical calculations.

Oral presentation

Adsorption behavior of lawrencium (Lr) on a tantalum surface

Sato, Tetsuya; Kaneya, Yusuke*; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Mitsukai, Akina*; Osa, Akihiko; Makii, Hiroyuki; Nishio, Katsuhisa; Hirose, Kentaro; et al.

no journal, , 

The ground state electronic configuration of lawrencium (Lr, Z =103) is predicted to be [Rn]$$5f^{14}7s^27p_{1/2}$$, which is different from that of the lanthanide homolog Lu [Xe]$$4f^{14}6s^25d$$ due to strong relativistic effects. According to semi-empirical considerations, volatility of Lr is expected to be higher than that of Lu. We have investigated adsorption behavior of $$^{256}$$Lr, which was produced in the reaction of $$^{249}$$Cf($$^{11}$$B, 4n), on a tantalum (Ta) metal surface using a surface ion-source installed into the isotope separator on-line (ISOL) at the JAEA tandem accelerator facility. The observed adsorption behavior of $$^{256}$$Lr was similar to those of Tb and Lu which have relatively higher adsorption enthalpy on Ta surface. It implies that Lr would have low volatility like such as Lu and Tb.

Oral presentation

Discrepancy in the periodic table appears at element 103; The Periodic table of elements might be restructured

Sato, Tetsuya

no journal, , 

The first ionization potential (IP$$_1$$) of element 103, lawrencium (Lr), has been successfully determined for the first time by using a newly developed method based on a surface ionization process. The measured IP$$_1$$ value is 4.96 $$pm$$ 0.08 eV. This value is the smallest among those of actinide elements and is in excellent agreement with the value of 4.963(15) eV predicted by state-of-the-art relativistic calculations also performed in this work. Our results strongly support that the Lr atom has an electronic configuration of [Rn]$$7s^25f^{14}7p_{1/2}$$, which is influenced by strong relativistic effects. The present work opens the way for studies on atomic properties of heavy elements with atomic number $$Z > 100$$. Moreover, the present achievement has triggered a controversy on the position of lutetium (Lu) and Lr in the Periodic Table of Elements.

Oral presentation

Adsorption behavior of lawrencium (Lr, Z = 103) on a tantalum surface

Sato, Tetsuya; Kaneya, Yusuke*; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Mitsukai, Akina*; Osa, Akihiko; Makii, Hiroyuki; Hirose, Kentaro; Nagame, Yuichiro; et al.

no journal, , 

Our experimental results on the first ionization potential measurement of lawrencium (Lr, element 103) have strongly suggested that the Lr atom has a [Rn]$$7s^25f^{14}7p_{1/2}$$ configuration as a result of the influence of strong relativistic effects. The configuration is different from that expected from the lanthanide homologue, lutetium (Lu). According to a semi-empirical consideration, it is expected that the change of the electronic configuration leads higher volatility of Lr than that of Lu. In this work, adsorption behaviors of Lr and various short-lived rare earth isotopes on a tantalum surface were investigated via observation of their surface ionization efficiencies. It was found that Lr would behave like low volatile rare earth elements such as Lu contrary to the semi-empirical expectation.

Oral presentation

Adsorption of Lawrencium (Z = 103) on a tantalum surface

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.

26 (Records 1-20 displayed on this page)