Pairing-energy coefficients of neutron-rich fragments in spallation reactions  

作　　者：牛菲 马春旺 

机构地区：[1]Institute of Particle and Nuclear Physics,Henan Normal University [2]Institute of Modern Physics,Chinese Academy of Sciences

出　　处：《Chinese Physics C》2018年第3期62-68,共7页中国物理C（英文版）

基　　金：Supported by National Natural Science Foundation of China(U1732135);Natural Science Foundation of Henan Province(162300410179);Henan Normal University for the Excellent Youth(154100510007)

摘　　要：The ratio of pairing-energy coefficient to temperature （ap/T） of neutron-rich fragments produced in spallation reactions has been investigated by adopting an isobaric yield ratio method deduced in the framework of a modified Fisher model. A series of spallation reactions, 0.5A and 1A GeV 208Pb ＋ p, 1A GeV 238U ＋ p, 0.5A GeV 136Xe ＋ d, 0.2A, 0.5A and 1A GeV 136Xe ＋ p, and 56Fe ＋ p with incident energy ranging from 0.3A to 1.5A GeV, has been analysed. An obvious odd-even staggering is shown in the fragments with small neutron excess （I=N-Z）, and in the relatively small-A fragments which have large I. The values of ap/T for the fragments, with I from 0 to 36, have been found to be in a range from -4 to 4, and most values of ap/T fall in the range from -1 to 1. It is suggested that a small pairing-energy coefficient should be considered in predicting the cross sections of fragments in spallation reactions. It is also concluded that the method proposed in this article is not good for fragments with A/As〉 85% （where As is the mass number of the spallation system）.The ratio of pairing-energy coefficient to temperature （ap/T） of neutron-rich fragments produced in spallation reactions has been investigated by adopting an isobaric yield ratio method deduced in the framework of a modified Fisher model. A series of spallation reactions, 0.5A and 1A GeV 208Pb ＋ p, 1A GeV 238U ＋ p, 0.5A GeV 136Xe ＋ d, 0.2A, 0.5A and 1A GeV 136Xe ＋ p, and 56Fe ＋ p with incident energy ranging from 0.3A to 1.5A GeV, has been analysed. An obvious odd-even staggering is shown in the fragments with small neutron excess （I=N-Z）, and in the relatively small-A fragments which have large I. The values of ap/T for the fragments, with I from 0 to 36, have been found to be in a range from -4 to 4, and most values of ap/T fall in the range from -1 to 1. It is suggested that a small pairing-energy coefficient should be considered in predicting the cross sections of fragments in spallation reactions. It is also concluded that the method proposed in this article is not good for fragments with A/As〉 85% （where As is the mass number of the spallation system）.

关 键 词：pairing energy neutron-rich isotope spallation reaction asymmetric muclear matter 

分 类 号：O571[理学—粒子物理与原子核物理]