Isomeric Measurement For The Neutron-deficient Th Isotopes And The Study Of The Fusion Mechanism Of The Reaction ⁴⁰Ar+¹⁷⁶Hf

The gas-filled recoil separator(SHANS)is an important experimental device used to study the synthesis mechanism and decay characteristics of superheavy nuclei in China.Based on this platform,this work mainly carried out the experimental research on the decay properties of neutron deficient Th isotopes and the fusion reaction mechanism of⁴⁰Ar+¹⁷⁶Hf.The content of this paper mainly includes the following two parts.In the first part,based on Lanzhou heavy ion accelerator,the decay properties of neutron deficient Th isotope was studied by heavy ion fusion evaporation reaction ⁴⁰Ar+¹⁷⁶Hf at the terminal of gas-filled recoil nuclear spectrometer.We investigate the isomeric state in ^213-217Th by using the ER-?-?correlation measurement.The half-life of ^214-217Th deduced in this work are in agreement with literature values.However,the half-life of13/2⁺isomer in ²¹³Th was newly determined to be T_1/2=8.30(82)?s,which fits well with the systematic trend in N=123 odd-A isotones.In the second part,the evaporation residual cross sections of some reaction channels of heavy ion fusion evaporation reaction ⁴⁰Ar+¹⁷⁶Hf were measured by gas-filled recoil nuclear spectrometer.It was found that the yields of ^209,210Ra and ^212,213Ac at the beam energy of 183 Me V and 190 Me V are about two orders of magnitude lower than the theoretical prediction.The capture cross section of the theoretical value was calculated by the Modified Woods-Saxon model(MWS),and the survival probability of composite nuclei is given by the statistical evaporation model(HIVAP).In order to explore the reasons for the deviation between theory and experiment,we used the density-constrained time-dependent Hartree-Fock to study the effect of target nucleus deformation on the fusion process.The results show that the capure probability of fusion reaction is closely to the orientation of deformed target nucleus.