Study of the properties of the superheavy nuclei Z = 117 produced in the ²⁴⁹Bk + ⁴⁸Ca reaction

¹ Joint Institute for Nuclear Research, RU-141980 Dubna, Russian Federation
² Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
³ Lawrence Livermore National Laboratory, Livermore, California 94551, USA
⁴ Department of Physics and Astronomy, University of Tennessee, Knoxville Tennessee 37996, USA
⁵ Department of Physics and Astronomy Vanderbilt University, Nashville, Tennessee 37235, USA
⁶ Research Institute of Atomic Reactors, RU-433510 Dimitrovgrad, Russian Federation

^a e-mail: voinov_2000@mail.ru

Published online: 20 March 2014

Abstract

The reaction of ²⁴⁹Bk with ⁴⁸Ca have been reinvestigated to provide new evidence for the discovery of element 117 on a larger number of events. The experiments were performed at five projectile energies and with a total beam dose of ⁴⁸Ca of about 4.6×10¹⁹. Two isotopes ^293,294117 were synthesized in the ²⁴⁹Bk+⁴⁸Ca reaction, providing excitation functions and α-decay spectra of the produced isotopes that establishes these nuclei to be the products of the 4n- and 3n-evaporation channels, respectively. Decay properties of ^293,294117 and of all the daughter products agree with the data of the experiment in which these nuclei were synthesized for the first time in 2010. The new ²⁸⁹115 events, populated by α decay of ²⁹³117, demonstrate the same decay properties as those observed for ²⁸⁹115 produced in the ²⁴³Am(⁴⁸Ca,2n) reaction thus providing crossbombardment evidence. In addition, a single decay of ²⁹⁴118 was observed from the reaction with ²⁴⁹Cf – a result of the in-growth of ²⁴⁹Cf in the ²⁴⁹Bk target.