From SRAFAP to ARCA and AIDA; Developments and implementation of automated aqueous-phase rapid chemistry apparatuses for heavy actinides and transactinides

Schdel, M.*; Nagame, Yuichiro

Radiochimica Acta, 107(7), p.561 - 585, 2019/07

https://doi.org/10.1515/ract-2019-3103

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

Sato, Tetsuya; Asai, Masato; Borschevsky, A.*; Beerwerth, R.*; Kaneya, Yusuke*; Makii, Hiroyuki; Mitsukai, Akina*; Nagame, Yuichiro; Osa, Akihiko; Toyoshima, Atsushi; et al.

Journal of the American Chemical Society, 140(44), p.14609 - 14613, 2018/11

https://doi.org/10.1021/jacs.8b09068

The first ionization potential (IP) yields information on valence electronic structure of an atom. IP values of heavy actinides beyond einsteinium (Es, Z = 99), however, have not been determined experimentally so far due to the difficulty in obtaining these elements on scales of more than one atom at a time. Recently, we successfully measured IP of lawrencium (Lr, Z = 103) using a surface ionization method. The result suggests that Lr has a loosely-bound electron in the outermost orbital. In contrast to Lr, nobelium (No, Z = 102) is expected to have the highest IP among the actinide elements owing to its full-filled 5f and the 7s orbitals. In the present study, we have successfully determined IP values of No as well as fermium (Fm, Z = 100) and mendelevium (Md, Z = 101) using the surface ionization method. The obtained results indicate that the IP value of heavy actinoids would increase monotonically with filling electrons up in the 5f orbital like heavy lanthanoids.

Charge radii and electromagnetic moments of At

Cubiss, J.*; Andreyev, A.; Mitsuoka, Shinichi*; Nagame, Yuichiro; Nishio, Katsuhisa; Ota, Shuya*; Wakabayashi, Yasuo*; 60 of others*

Physical Review C, 97(5), p.054327_1 - 054327_19, 2018/05

https://doi.org/10.1103/PhysRevC.97.054327

Chemical properties of rutherfordium (Rf) and dubnium (Db) in the aqueous phase

Nagame, Yuichiro; Kratz, J. V.*; Schdel, M.*

EPJ Web of Conferences (Internet), 131, p.07007_1 - 07007_8, 2016/12

BB2016-0022.pdf:0.96MB

https://doi.org/10.1051/epjconf/201613107007

Complex chemistry with complex compounds

Eichler, R.*; Asai, Masato; Brand, H.*; Chiera, N. M.*; Di Nitto, A.*; Dressler, R.*; Dllmann, Ch. E.*; Even, J.*; Fangli, F.*; Goetz, M.*; et al.

EPJ Web of Conferences (Internet), 131, p.07005_1 - 07005_7, 2016/12

https://doi.org/10.1051/epjconf/201613107005

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).

Vacuum chromatography of Tl on SiO at the single-atom level

Steinegger, P.*; Asai, Masato; Dressler, R.*; Eichler, R.*; Kaneya, Yusuke*; Mitsukai, Akina*; Nagame, Yuichiro; Piguet, D.*; Sato, Tetsuya; Schdel, M.; et al.

Journal of Physical Chemistry C, 120(13), p.7122 - 7132, 2016/04

https://doi.org/10.1021/acs.jpcc.5b12033

A new experimental method "vacuum chromatography" has been developed to measure adsorption enthalpy of superheavy elements, and its feasibility has been examined using short-lived thallium isotopes. The short-lived thallium isotopes were produced at the JAEA tandem accelerator. The thallium ion beam prepared with an on-line isotope separator which ionized and mass-separated the thallium isotopes was injected into an isothermal vacuum chromatography apparatus. A temperature-dependent adsorption property of thallium atom on SiO surface were measured. The adsorption enthalpy of thallium was determined to be 158 kJ/mol. The thallium is a homolog of element 113. Thus, the vacuum chromatography developed in this study enables us to perform chemical experiments for short-lived superheavy elements with half-lives of a order of one second.

Lawrencium's place at the table

Nagame, Yuichiro

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

https://doi.org/10.1038/nchem.2460

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.

Decomposition studies of group 6 hexacarbonyl complexes, 1; Production and decomposition of Mo(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

https://doi.org/10.1515/ract-2015-2445

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.

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.

Measurement of the first ionization potential of lawrencium, element 103

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

https://doi.org/10.1038/nature14342

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.