Experiments on the synthesis of element 115 in the reaction<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mi mathvariant="normal">Am</mml:mi><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>243</mml:mn></mml:mrow></mml:mmultiscripts><mml:mo>(</mml:mo><mml:mmultiscripts><mml:mi mathvariant="normal">Ca</mml:mi><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>48</mml:mn></mml:mrow></mml:mmultiscripts><mml:mo>,</mml:mo><mml:mi>x</mml:mi><mml:mi>n</mml:mi><mml:mo>)</mml:mo><mml:mmultiscripts><mml:mn>115</mml:mn><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>291</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>

The results of experiments designed to synthesize element 115 isotopes in the $^{243}\mathrm{Am}+^{48}\mathrm{Ca}$ reaction are presented. With a beam dose of $4.3\ifmmode\times\else\texttimes\fi{}{10}^{18}$ $248\text{\ensuremath{-}}\text{MeV}$ $^{48}\mathrm{Ca}$ projectiles, we observed three similar decay chains consisting of five consecutive $\ensuremath{\alpha}$ decays, all detected in time intervals of about $20\phantom{\rule{0.3em}{0ex}}\mathrm{s}$ and terminated at a later time by a spontaneous fission with a high-energy release (total kinetic energy $\ensuremath{\sim}220\phantom{\rule{0.3em}{0ex}}\text{MeV}$). At a higher bombarding energy of $253\phantom{\rule{0.3em}{0ex}}\text{MeV}$, with an equal $^{48}\mathrm{Ca}$ beam dose, we registered a different decay chain of four consecutive $\ensuremath{\alpha}$ decays detected in a time interval of about $0.5\phantom{\rule{0.3em}{0ex}}\mathrm{s}$, also terminated by spontaneous fission. The $\ensuremath{\alpha}$ decay energies and half-lives for nine new $\ensuremath{\alpha}$-decaying nuclei are given. The decay properties of these synthesized nuclei are consistent with consecutive $\ensuremath{\alpha}$ decays originating from the parent isotopes of the new element 115, $^{288}115$ and $^{287}115$, produced in the $3n$- and $4n$-evaporation channels with cross sections of about $3\phantom{\rule{0.3em}{0ex}}\text{pb}$ and $1\phantom{\rule{0.3em}{0ex}}\text{pb}$, respectively. The radioactive properties of the new odd-$Z$ nuclei $(105--115)$ are compared with the predictions of the macroscopic-microscopic theory. The experiments were carried out at the U400 cyclotron with the recoil separator DGFRS at FLNR, JINR.

Перевод пока недоступен