Study On Capture Cross Section Of Near-barrier Heavy Ion Fusion Reaction

In the 1960s,scientists predicted that nucleus near the number of neutrons N=184 and the number of protons 114 would have long lifetimes,forming an"superheavy nuclei island of stability".Exploring the limit of nuclear mass is one of the hot topics in nuclear physics research,and its research results have an important impact on the fields of physics and chemistry.At present,the heaviest element found by scientists at present is No.118 Og.Among them,there are already 26 synthetic transuranium elements,accounting for about 20%of the total known elements,and the seventh line of the periodic table has been completely filled.The number of nuclear charges for synthetic overweight nuclei is increasing and the requirements for laboratories are increasing.In order to effectively carry out nuclear reaction experiments to synthesize superheavy nuclei,it is very important to be able to accurately calculate the fusion cross section of heavy nuclei.In this paper,the capture cross section of near-barrier heavy ion fusion reaction is calculated by many methods,and the results are compared.Analyze its advantages and disadvantages,and find the best method for calculating the capture cross section.In this paper,WKB method,semi-empirical coupled channel model of barrier distribution and two-step model are used to calculate the capture cross section of heavy ion fusion reaction.WKB method is simple to calculate and can accurately calculate the penetration coefficient of the lower part of the barrier.However,the upper part of the barrier cannot be calculated,and the calculation result is not accurate when the barrier is abruptly changed.The two-step model calculates the capture cross section of heavy ions well,and the calculation results are in good agreement with the experimental values.When element 117 was discovered in the laboratory,the two-step model was used,which was widely accepted.However,the two-step model for calculating the capture section of heavy nuclear reaction needs to adjust parameters according to experimental values.At present,only the cross section of the nuclear reaction capture with incident particles ⁴⁸Caand ⁵⁰Ti can be calculated.With the progress of The Times,in order to synthesize heavier nuclei,it is necessary to select heavier nuclei as incident particles such as ⁵²Cr and 58Fe for fusion reaction.The two-step model is unable to carry out the above calculation and has certain limitations.The semi-empirical coupled path model based on barrier distribution has no limitation on incident particles and is universal.The calculation results of the heavy ion fusion capture cross section are basically consistent with the experimental values and the two-step model calculation results.It is proved that the semi-empirical coupled path model of barrier distribution can repeat the process of calculating the capture cross section of the two step model,and the results can be used in the subsequent calculation of the two step model.During the fusion reaction,different models have different understandings of the internal mechanism of the fusion reaction.When the results of calculating the capture cross section of the same reaction are the same,the capture probability is greatly different.The semi-empirical coupled channel model based on the barrier distribution not only considers the width and height of the barrier,but also considers the coupling of intrinsic degrees of freedom and relative motion that have great influence on the capture probability.The method for calculating the capture cross section of the near barrier fusion reaction of heavy ions is developed.Moreover,the semi-empirical coupling path model of barrier distribution does not require large parameter adjustment.The parameters are adjusted in a certain range,the error is relatively small,and the calculation results are more reliable.This article uses this method to calculate the capture cross section of nuclear reactions with 52Cr and 58Fe as incident particles,and discusses the effects of various factors on the capture cross section of a heavy ion fusion reaction.And the effects of excitation energy and angular momentum on the probability of capture.It is hoped that the data obtained in this article can be verified in the laboratory in the future.