C. E. Porter

Synthesis of the New Element with Z=117

The synthesis of the new chemical element with atomic number Z=117 is presented. The isotopes 293117 and 294117were produced in fusion reactions between 48Ca and 249Bk. The 249Bk was produced in the High Flux Isotope Reactor and chemically separated at Oak Ridge. Decay chains involving eleven new nuclei were identified by means of the Dubna Gas Filled Recoil Separator. The measured decay properties show a strong rise of stability for super-heavy nuclei toward N=184.

Proton Single-Particle States In The Heaviest Actinide Nuclei

The level structure of 249Bk has been investigated by measuring the γ‐ray spectra following the α decay of a chemically and isotopically pure 253Es sample. Alpha‐gamma coincidence measurement was performed using a Si detector for α particles and a 25% Ge detector for γ rays. A gamma‐gamma coincidence measurement was performed with the Gammasphere spectrometer. The Es sample was obtained by extracting the 253Es which grew in a 253Cf source material produced in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. Additional information on the 249Bk levels was obtained from the study of γ rays produced in the β− decay of 249Cm. The 249Cm sample was produced by neutron irradiation of 248Cm. Using the results of the present study and the results of previous 248Cm(α,t) and 248Cm(3He,d) reaction spectra, the following single‐particle states have been identified in 249Bk: 7/2+[633], 0.0 keV; 3/2−[521], 8.78 keV; 1/2+[400], 377.55 keV: 5/2+[642], 389.17 keV; 1/2−[530], 569.19 keV; 1/2−[521], 643....