Measurement of the first ionization potential of lawrencium, element 103 (original) (raw)

Nature volume 520, pages 209–211 (2015)Cite this article

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Abstract

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 configurations1,2. 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 time3,4,5. Here we report that the experimentally obtained IP1 of the heaviest actinide, lawrencium (Lr, atomic number 103), is electronvolts. The IP1 of Lr was measured with 256Lr (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.

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Figure 1: Schematic experimental set-up used to measure the IP1 of Lr on an atom-at-a-time scale.

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Figure 2: The ionization efficiency (_I_eff) of various short-lived isotopes as a function of the effective IP1 (IP1*) at 2,700 K.

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Acknowledgements

We thank the JAEA tandem accelerator crew for supplying intense and stable beams for the experiments. The 249Cf was made available by H. Nitsche (Univ. California, Berkeley); it was produced in the form of 249Bk through the former Transplutonium Element Production Program at Oak Ridge National Laboratory (ORNL) under the auspices of the Director, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division of the US Department of Energy. Financial support by the Helmholtz-Institut Mainz is acknowledged. This work has been partly supported by the Grant-in-Aid for Scientific Research (C) no. 26390119 of the Ministry of Education, Science, Sports and Culture (MEXT).

Author information

Authors and Affiliations

  1. Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan,
    T. K. Sato, M. Asai, N. Sato, Y. Kaneya, K. Tsukada, S. Ichikawa, Y. Nagame, A. Osa, M. Schädel & A. Toyoshima
  2. Centre for Theoretical Chemistry and Physics, New Zealand Institute for Advanced Study, Massey University, 0745 North Shore MSC, Auckland, New Zealand,
    A. Borschevsky
  3. Helmholtz-Institut Mainz, 55099 Mainz, Germany
    A. Borschevsky, Ch. E. Düllmann, K. Eberhardt & P. Thörle-Pospiech
  4. ISOLDE, CERN, CH-1211 Geneva 23, Switzerland,
    T. Stora
  5. Graduate School of Science and Engineering, Ibaraki University, Mito, Ibaraki 310-8512, Japan,
    Y. Kaneya & Y. Nagame
  6. GSI Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt, Germany
    Ch. E. Düllmann & J. Runke
  7. Institut für Kernchemie, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany,
    Ch. E. Düllmann, K. Eberhardt, J. V. Kratz, D. Renisch, P. Thörle-Pospiech & N. Trautmann
  8. School of Chemistry, Tel Aviv University, 69978 Tel Aviv, Israel
    E. Eliav & U. Kaldor
  9. Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan,
    S. Ichikawa
  10. Graduate School of Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan,
    S. Miyashita
  11. Institute of Science and Technology, Niigata University, Niigata 910-2181, Japan
    K. Ooe

Authors

  1. T. K. Sato
  2. M. Asai
  3. A. Borschevsky
  4. T. Stora
  5. N. Sato
  6. Y. Kaneya
  7. K. Tsukada
  8. Ch. E. Düllmann
  9. K. Eberhardt
  10. E. Eliav
  11. S. Ichikawa
  12. U. Kaldor
  13. J. V. Kratz
  14. S. Miyashita
  15. Y. Nagame
  16. K. Ooe
  17. A. Osa
  18. D. Renisch
  19. J. Runke
  20. M. Schädel
  21. P. Thörle-Pospiech
  22. A. Toyoshima
  23. N. Trautmann

Contributions

T.K.S., M.A., Y.N. and M.S. prepared the main part of the manuscript, A.B., E. E. and U.K. contributed to the theory part, and T.S. to the experimental part. C.E.D. and J.V.K. commented on the manuscript. T.K.S, M.A., T.S., N.S., K.T. and S.I. developed the surface ion-source in the ISOL setup at the JAEA tandem accelerator facility. T.K.S. and M.A. were responsible for data acquisition and analysis. T.S. commented on ion-source optimizations and the data analysis procedure. K.T. prepared the 249Cf target. K.E., J.R., P.T.-P., C.E.D. and N.T. separated and provided the 249Cf for the target. The on-line experiments were performed by T.K.S., M.A., N.S., Y.K., K.T., S. I., S.M., Y.N., K.O., A.O., D.R., M.S. and A.T., while theoretical calculations were carried out by A.B., E.E. and U.K. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence toY. Nagame.

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The authors declare no competing financial interests.

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Sato, T., Asai, M., Borschevsky, A. et al. Measurement of the first ionization potential of lawrencium, element 103.Nature 520, 209–211 (2015). https://doi.org/10.1038/nature14342

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Editorial Summary

The chemistry of element 103

The most dramatic modern revision of Mendeleev's periodic table of elements came in 1944 when Glenn T. Seaborg placed a new series of elements, the actinides (atomic numbers 89–103), below the lanthanides. In this issue of Nature, Yuichiro Nagame and colleagues report the first measurement of one of the basic atomic properties of element 103 (lawrencium), namely its first ionization potential. Lawrencium is only accessible via atom-at-a-time synthesis in heavy-ion accelerators, so experimental investigations of its properties are rare. Nagame and colleagues were able to reduce the number of atoms required to measure the ionization potential from billions to thousands, and these results — in agreement with the latest theoretical calculations — show that the last valence electron in lawrencium is the most weakly bound one in all actinides and any other element beyond group 1 of the periodic table. This signature — in a region of the periodic table where the sheer size of the atoms means that relativistic effects play a crucial role — confirms the end of the actinide series at element 103.

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