Theoretical Study On The ?-decay Half-life Of Unstable Nuclei

Nuclear ?-decay is one of the most important decay modes of unstable nuclei.Most of the known nuclei are unstable nuclei,so it is very significant to study the decay properties of nuclei.Half-life is an important physical quantity to describe the decay properties of nuclei.As is known,?-decay is a weak interaction process,whereas,the calculation of half-life is related to the properties of the daughter nucleus and parent nucleus.So the study of ?-decay can help to more deeply understand the structure of the nucleus.In addition,the ?-decay has an important effect on nuclear astrophysics,the evolution of the abundance of elements in stars is associated with ?-decay,study on ?-decay is good for understanding some processes in nuclear astrophysics.In this article,??/EC decay half-lives of some even-even medium-mass nuclei are calculated within the extended quasiparticle random-phase approximation(QRPA).The calculat-ed half-lives are found to be in good agreement with the available experimental data and other theoretical predictions,and some useful predictions on ?-decay half-lives are made for some nuclei near the drip lines.In the first chapter,we introduce the background of the study on the ?-decay of unstable nuclei and the main purpose and content of this article.The study on the nuclear ?-decay phenomenon plays an important role in the development of nuclear physics.The first study on ?-decay is made by E.Fermi,?-decay involves the wave function of the parent and the daughter nucleus in his theory,and the solution of wave function is a difficult problem.Because the nucleus is a multi-body system,the number of nucleon varies from tens to hundreds,quantum statistical methods can not be used and the accurate solution is more difficult.So there are many models to describe the nuclear properties,for example,gross theory,shell model,pn quasiparticle random phase approximation.The main purpose of our work is to calculate ?+/EC decay half-lives of some even-even medium-mass nuclei within the extended quasiparticle random-phase approximation(QRPA),including Fermi theory,HFB method,QRPA method,etc.The second chapter is the theoretical background of this article.We introduce the Fermi theory about calculation theory of ?-decay half life.Based on the influence of the size of the transition matrix element in the ?-decay theory,this paper only calculates the allowed ?-decay half-life.According to the variation of the spin of the parent nu-cleus before decay and the daughter nucleus after decay,we only consider the Gamow-Teller ?-decay.The process of ?-decay generally occurs from an initial ground state i of the parent nucleus to some possible final states f in the daughter nucleus.Therefore,it is necessary to solve wave function of the parent and daughter nucleus.Based on the mean field,the Hamiltonian of the nucleus includes the nucleon-nucleon correlation ef-fect.By solving the correlation effect of nucleons within the Hartree-Fock-Bogoliubov transformation,the description on nucleus can be changed from single particle picture to quasi particle representation.The particle-hole and particle-particle components of the Gamow-Teller residual interactions are always taken into account in dealing with the extended QRPA matrix equation.The third chapter is the results of the calculation.The sensitivity of the calculat-ed half-lives to some physical quantities used in the calculations is mainly discussed.We systematically calculated the half-life of ?+-decay and orbital electron capture,and useful predictions on ?-decay half-lives are made for some nuclei near the drip lines.It is found that the calculated half-lives are in good agreement with the available experimental data,and the predicted half-lives are consistent with other theoretical pre-dictions.In general,after calculating the half-life of ?-decay,it has a positive meaning for our further study on ?-decay.In the last chapter,we summarize our previous work and outlooks of our future plan are given.