Nuclear structure and reaction studies near doubly magic 270Hs

Abstract

Abstract Fast on-line gas chemical separations of Hs (hassium, element 108) in the form of HsO4 were applied to investigate the reactions 26Mg + 248Cm and 36S + 238U. In an experiment at the gas-filled separator DGFRS the reaction 48Ca + 226Ra was studied. In all cases the product of complete nuclear fusion is 274Hs*. For the first time, the new nuclide 270Hs was produced in the 4n evaporation channel and its decay properties investigated. The nuclide 270Hs was predicted by microscopic-macroscopic calculations to be a deformed doubly magic nucleus and its decay properties are therefore of special interest to theory. Also, much more detailed information was gained on the decay of 269Hs and its daughters, which led to a new assignment of decay properties of the daughter nuclides 265Sg and 261Rf. There is evidence fo r isomeric states in 265Sg and 261Rf, while 266Sg is not an alpha-particle emitter as believed previously, but decays by spontaneous fission (SF) with a rather short half-life. Also, interesting features of the used reaction 26Mg + 248Cm led to the discovery of the nucleus 271Hs in the same experiments. An investigation of the influence of the Q-value on the fusion reaction in relation to the location of the fusion barrier showed, that the high binding energy of 48Ca largely compensates for the lower fusion probability compared to more asymmetric reactions, while 36S is not as promising as a projectile.