Study On The Properties Of The Nuclear Unfavored α-decay

Theα-decay of nuclei was interpreted as quantum tunneling effect ofα-particle through a potential barrier.Since then various theoretical models have been developed.Among these models,the Generalized Liquid Drop Model proposed by G.Royer in 1980s is one of the models which successfully used to describe the favoredα-decay process.However,many parent nuclei can also decay to the excited states of the daughter nuclei in addition to the favoredα-transitions.Although several nuclei can decay to the ground states of the daughter nuclei,the spin-parity of the nuclear initial and final states is different.When theα-decay modes mentioned above occur,the angular momentum of theα-particles take is not zero. Theseαtransitions are thus called the unfavored cases.It is very significant to investigate the hinderedαtransitions because it is closely related to the internal structure of nuclei.On the other hand,when the parent nuclei decay to the excited states and the members of the ground state rotational band,the excited energy may have influence on theα-decay process.Although the GLDM model has been successfully used to describe the favoredα-decay process,the unfavored hinderedα-transitions have not been investigated within the GLDM model.In order to investigate the unfavored hinderedα-transitions,it is necessary to improve the GLDM model and extend its application.To study the unfavoredα-decay,by taking into account the centrifugal potential energy V_cen(r) and the excited energy E₁₊^* in the framework of the GLDM model,we investigate some aspects as follows:1.The unfavoredα-decay lifetimes around the closed shell are investigated.The lifetimes of the newly discovered nuclide ²⁰⁹Bi and the nuclei near the closed shell of neutron number N=126 are calculated.The experimental decay lifetimes can be reproduced satisfactorily.The application of the improved GLDM model to research unfavoredα-decays has been proved reliable.It is helpful to further improve and consummate the GLDM model and allow ones to make predictions for the future experiments accurately about the investigation of the unfavoredα-decay around the closed shell.2.The branching ratios ofα-decay between 0+→2+α-transition and 0+→0+α-transition of even-even nuclei Ra—Cf are calculated.The results are in good agreement with the experimental data.Some predictions of even-even nuclei(Z=102—112) are made for future experiments.Our results support the method proposed by Sobiczewski et al that a measurement ofαspectroscopy is a feasible one to extract the information of nuclear deformation.3.The branching ratios ofα-decay to the members of the ground state rotational band and excited 0+states of even-even nuclei are calculated.The calculation covers isotopic chains from Hg—Fm in the regions 180＜A＜202 and A≥224.The calculated branching ratios of the a-transitions are in good agreement with the experimental data and some useful predictions are provided for future experiments.