Production and Decay of Element 114: High Cross Sections and the New Nucleus<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi>Hs</mml:mi><mml:mprescripts/><mml:none/><mml:mn>277</mml:mn></mml:mmultiscripts></mml:math>

Abstract

The fusion-evaporation reaction $^{244}\mathrm{Pu}(^{48}\mathrm{Ca},3\mathrm{\text{\ensuremath{-}}}4n)^{288,289}114$ was studied at the new gas-filled recoil separator TASCA. Thirteen correlated decay chains were observed and assigned to the production and decay of $^{288,289}114$. At a compound nucleus excitation energy of ${E}^{*}=39.8--43.9\text{ }\text{ }\mathrm{MeV}$, the $4n$ evaporation channel cross section was ${9.8}_{\ensuremath{-}3.1}^{+3.9}\text{ }\text{ }\mathrm{pb}$. At ${E}^{*}=36.1--39.5\text{ }\text{ }\mathrm{MeV}$, that of the $3n$ evaporation channel was ${8.0}_{\ensuremath{-}4.5}^{+7.4}\text{ }\text{ }\mathrm{pb}$. In one of the $3n$ evaporation channel decay chains, a previously unobserved $\ensuremath{\alpha}$ branch in $^{281}\mathrm{Ds}$ was observed (probability to be of random origin from background: 0.1%). This $\ensuremath{\alpha}$ decay populated the new nucleus $^{277}\mathrm{Hs}$, which decayed by spontaneous fission after a lifetime of 4.5 ms.