First Ionization Potentials of Fm, Md, No, and Lr: Verification of Filling-Up of 5f Electrons and Confirmation of the Actinide Series

• DOI: 10.1021/jacs.8b09068
• Publication Date: 2018-10-25T21:46:14Z
• Authors: Tetsuya K. Sato; Masato Asai; Anastasia Borsche...; Randolf Beerwerth; Yusuke Kaneya; Hiroyuki Makii; Akina Mitsukai; Yuichiro Nagame; Akihiko Osa; Atsushi Toyoshima; Kazuaki Tsukada; Minoru Sakama; Shinsaku Takeda; Kazuhiro Ooe; Daisuke Sato; Yudai Shigekawa; Shin-ichi Ichikawa; Christoph E. Düll...; Jessica Grund; Dennis Renisch; Jens V. Kratz; Matthias Schädel; Ephraim Eliav; Uzi Kaldor; Stephan Fritzsche; Thierry Stora
• Keywords: Thermal ionization

We report the first ionization potentials (IP1) of heavy actinides, fermium (Fm, atomic number Z = 100), mendelevium (Md, 101), nobelium (No, 102), and lawrencium (Lr, 103), determined using a method based on surface process coupled to an online mass separation technique in atom-at-a-time regime. The measured IP1 values agree well with those predicted by state-of-the-art relativistic calculations performed alongside present measurements. Similar well-established behavior for lanthanides, actinides up No increase filling 5f orbital, while that Lr is lowest among actinides. These results clearly demonstrate orbital fully filled at [Rn]5f147s2 configuration has weakly bound electron outside core. In analogy lanthanide series, unequivocally verify actinide series ends Lr.