title: Measurement of the first ionization potential of lawrencium, element 103.
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 configurations. Atomic s and p1/2 orbitals are stabilized by relativistic effects, whereas p3/2, 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 time. Here we report that the experimentally obtained IP1 of the heaviest actinide, lawrencium (Lr, atomic number 103), is 4.96(+0.08)(-0.07) electronvolts. The IP1 of Lr was measured with (256)Lr (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.
authors: Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan.
authors: T K
authors: TK
authors: Sato
authors: Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan.
authors: M
authors: M
authors: Asai
authors: 1] Centre for Theoretical Chemistry and Physics, New Zealand Institute for Advanced Study, Massey University, 0745 North Shore MSC, Auckland, New Zealand [2] Helmholtz-Institut Mainz, 55099 Mainz, Germany.
authors: A
authors: A
authors: Borschevsky
authors: ISOLDE, CERN, CH-1211 Geneva 23, Switzerland.
authors: T
authors: T
authors: Stora
authors: Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan.
authors: N
authors: N
authors: Sato
authors: 1] Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan [2] Graduate School of Science and Engineering, Ibaraki University, Mito, Ibaraki 310-8512, Japan.
authors: Y
authors: Y
authors: Kaneya
authors: Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan.
authors: K
authors: K
authors: Tsukada
authors: 1] Helmholtz-Institut Mainz, 55099 Mainz, Germany [2] GSI Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt, Germany [3] Institut für Kernchemie, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors: Ch E
authors: ChE
authors: Düllmann
authors: 1] Helmholtz-Institut Mainz, 55099 Mainz, Germany [2] Institut für Kernchemie, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors: K
authors: K
authors: Eberhardt
authors: School of Chemistry, Tel Aviv University, 69978 Tel Aviv, Israel.
authors: E
authors: E
authors: Eliav
authors: 1] Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan [2] Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors: S
authors: S
authors: Ichikawa
authors: School of Chemistry, Tel Aviv University, 69978 Tel Aviv, Israel.
authors: U
authors: U
authors: Kaldor
authors: Institut für Kernchemie, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors: J V
authors: JV
authors: Kratz
authors: Graduate School of Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan.
authors: S
authors: S
authors: Miyashita
authors: 1] Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan [2] Graduate School of Science and Engineering, Ibaraki University, Mito, Ibaraki 310-8512, Japan.
authors: Y
authors: Y
authors: Nagame
authors: Institute of Science and Technology, Niigata University, Niigata 910-2181, Japan.
authors: K
authors: K
authors: Ooe
authors: Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan.
authors: A
authors: A
authors: Osa
authors: Institut für Kernchemie, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors: D
authors: D
authors: Renisch
authors: GSI Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt, Germany.
authors: J
authors: J
authors: Runke
authors: Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan.
authors: M
authors: M
authors: Schädel
authors: 1] Helmholtz-Institut Mainz, 55099 Mainz, Germany [2] Institut für Kernchemie, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors: P
authors: P
authors: Thörle-Pospiech
authors: Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan.
authors: A
authors: A
authors: Toyoshima
authors: Institut für Kernchemie, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors: N
authors: N
authors: Trautmann