The Solution And Application Of Branched S-Process Network Equations

On the basis of neutron capture process, this paper mainly presents branched s-process network path about two branched systems of Sm-Eu-Gd and W-Re-Os. Furthermore, we give the solution of s-process branched network equations of these two systems. Then, we discuss the sensitivity analysis of elements neutron capture cross section and reaction flow. And according to the data, we calculate the age of Galaxy with the use of ¹⁸⁷ Re-¹⁸⁷Os cosmochronology.This thesis includes fives chapters which are as follows:This first chapter is an introduction. We introduce the evolution of universe and stars, neutron capture process and the theory of s-process heavy-element formation. Then we present some predecessors' research about branched s-process. Finally, we give the main conclusions and innovation of the thesis.The second chapter introduces the branched s-process network path with the branching point ¹⁵¹Sm in the Sm-Eu-Gd system. According to the s-process path, we gain s-process branched network equation and then simply it. We gain analytical expression of abundance function about initial nuclide ¹⁵⁰Sm. With the use of four-order Runge-Kutta method, we have the abundance curve of all the elements in the Sm-Eu-Gd system. Moreover, we discuss the sensitivity analysis of neutron capture cross section in the branched s-process and come a conclusion that Eu and Eu have great influence on the Sm-Eu-Gd system. Based on the solution of s-process branched network equations, we receive the calculation of reaction flow in the system, and then confirm the branched s-process main path in the Sm-Eu-Gd system.The third chapter discusses branched s-process with branch-point ¹⁸⁵ W about W-Re-Os system. In according with neutron capture process, we have branched s-process network equations of W-Re-Os system. Then we simplify network equations, and get simple equations. Similar to the second chapter, we get analytical expression of abundance function about initial nuclide W of the branched network on the basic of classical s-process. We take advantage of four-order Runge-Kutta method to obtain numerical solution of branched s-process network equations and draw up the abundance curve of elements in the W-Re-Os system. Then we do the sensitivity analysis of neutron capture cross section and draw a conclusion that W has a considerable effect on the W-Re-Os system. After we make use of elements abundance to work out reaction flow of all the branches and make sure branched s-process main path in the W-Re-Os system.The fourth chapter presents calculation of the ages of the Galaxy. According to elements abundance in the W-Re-Os system, we utilize Re-Os cosmochronology to discuss the ages of heavy-element formation. Then we give preliminary estimates of the ages of the Galaxy and the calculation result is consistent with the predecessors'.The fifth chapter gives a systematic analysis of the article conclusion, and we also provide the further outlook.