Measurement of the ionization potential of Lr (Z = 103) by online mass separation

Sato, Tetsuya   ; Stora, T.*; Asai, Masato  ; Borschevsky, A.*; Kaneya, Yusuke; Tsukada, Kazuaki  ; Dllmann, Ch. E.*; Eliav, E.*; Kaldor, U.*; Kratz, J. V.*; Miyashita, Sunao*; Nagame, Yuichiro ; Oe, Kazuhiro*; Osa, Akihiko  ; Renisch, D.*; Runke, J.*; Schdel, M.*; Toyoshima, Atsushi; Trautmann, N.*

It is known that an ionization efficiency of an element in surface ionization process depends on temperature, work function of the surface, and the first ionization energy of the atom of the element to be ionized. We determined the first ionization energy of lawrencium (Lr), the last member of the actinide series, using the relationship between the ionization efficiency and the ionization energy. The ionization energy of Lr had not been measured owing to its low production rate and short half-lives so far. The experimental value of the ionization energy is in good agreement of the theoretical one which was calculated using the state-of-the-art relativistic calculation.