First ionization potential of the heaviest actinide lawrencium, element 103

Sato, Tetsuya   ; Asai, Masato  ; Borschevsky, A.*; Stora, T.*; Sato, Nozomi*; Kaneya, Yusuke; Tsukada, Kazuaki  ; Dllmann, C. E.*; Eberhardt, K.*; Eliav, E.*; Ichikawa, Shinichi*; Kaldor, U.*; Kratz, J. V.*; Miyashita, Sunao*; Nagame, Yuichiro ; Oe, Kazuhiro*; Osa, Akihiko  ; Renisch, D.*; Runke, J.*; Schdel, M.*; Thrle-Pospiech, P.*; Toyoshima, Atsushi; Trautmann, N.*

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.