First direct mass measurements of nuclides around = 100 with a multireflection time-of-flight mass spectrograph

Ito, Yuta*; Schury, P.*; Wada, Michiharu*; Arai, Fumiya*; Haba, Hiromitsu*; Hirayama, Yoshikazu*; Ishizawa, Satoshi*; Kaji, Daiya*; Kimura, Sota*; Koura, Hiroyuki   ; MacCormick, M.*; Miyatake, Hiroari*; Moon, J. Y.*; Morimoto, Koji*; Morita, Kosuke*; Mukai, Momo*; Murray, I.*; Niwase, Toshitaka*; Okada, Kunihiro*; Ozawa, Akira*; Rosenbusch, M.*; Takamine, Aiko*; Tanaka, Taiki*; Watanabe, Yutaka X.*; Wollnik, H.*; Yamaki, Sayaka*

Masses of Es, Fm and the transfermium nuclei Md, and No, produced by hot- and cold-fusion reactions, in the vicinity of the deformed neutron shell closure, have been directly measured using a multi-reflection time-of-flight mass spectrograph. The masses of Es and Md were measured for the first time. Using the masses of Md as anchor points for decay chains, the masses of heavier nuclei, up to Bh and Mt, were determined. These new masses were compared with theoretical global mass models and demonstrated to be in good agreement with macroscopic-microscopic models in this region. The empirical shell gap parameter derived from three isotopic masses was updated with the new masses and corroborate the existence of the deformed neutron shell closure for Md and Lr.