Stuty on the Process of the Fast Neutron Radiative Capture for 40Ca and 208Pb

  • The pre-equilibrium correction for the nuclear reactions induced by fast neutron is considered as follows: the nuclear reaction processes with the exciton number equal to or larger than five can still be described by the statistical theory of the nuclear reaction. The particle emission processes, in which less than five excitons are involved, are calculated by means of the exciton model and the γ emission of one exciton state is calculated by the direct capture mechanism. For the three-exciton state, only the semidirect capture mechanism, which plays the main role in the researched energy region, is taken into account. The interference effect between the direct and semidirect capture is also considered. The radiative capture cross sections for 40Ca and 208Pb in the neutron incident energy region from 3 MeV to 20 MeV are calculated and a better coincidence with the experimental values is obtained. At the same time, the contribution to the (n, γ) reaction cross sections of the γ emissions before and after statistical equilibriums as well as the characteristics of the direct capture, semidirect capture and their interferece terms are discussed.
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  • [1] . Allen B J et al.Advancesin Nucl.Phys.,1978,10:129 2. Raman S et al.Phys.Rev.,1985,C32:183. HUOYu Kun et al.Nucl.Phys.,1983,A406:1 4. Lane A M ,Lynn J E .Nucl.Phys.,1959,5:732 5. Brown G E .Nucl.Phys.,1964,57:339 6. Clement C F .Nucl.Phys.,1965,66:273 7. MA Zhong-Yu et al.Chinese Journal of Nucl.Phys.,1981,3:217(in Chinese) (马中玉等.原子核物理,1981,3:217)8. Oblozinsky P .Phys.Rev.,1987,C2:4079. Oblozinsky P .Phys.Rev.,1990,C4:165210. SHI Xiang-Jun et al.Nucl.Phys.,1987,A466:333 11. LIU JianFeng et al.High Energy Phys.and Nucl.Phys.,1990,5:469(in Chinese) (刘建峰等.高能物理与核物理,1990,5:469) 12. LIUJianFengetal.HighEnergyPhys.andNucl.Phys.,1991,4:349(inChinese) (刘建峰等.高能物理与核物理,1991,4:349)13. Becchetti F D et al.Phys.Rev.,1969,182:119014. Gilbert A ,cameron A G W .Can.j.Phys.,1965,43:1446 15. Dietrich S S et al.Atomic Dataand Nuclear Data Tables,1988,38:199 16. Potokar Metal.Nucl.Phys.,1977,A277:29 17. EXFOR (EXchange FOR mat).Computerized System for the Storage,Retrievaland International Exchange of Experimental Nuclear Reaction Data,Coordinated by the IAEA Nuclear Data Section
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LIU Jian-Feng and ZHAO Wei-Juan. Stuty on the Process of the Fast Neutron Radiative Capture for 40Ca and 208Pb[J]. Chinese Physics C, 2002, 26(11): 1158-1165.
LIU Jian-Feng and ZHAO Wei-Juan. Stuty on the Process of the Fast Neutron Radiative Capture for 40Ca and 208Pb[J]. Chinese Physics C, 2002, 26(11): 1158-1165. shu
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Received: 2001-12-17
Revised: 1900-01-01
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Stuty on the Process of the Fast Neutron Radiative Capture for 40Ca and 208Pb

    Corresponding author: LIU Jian-Feng,
  • Department of Physics, Zhengzhou University, Zhengzhou 450052, China

Abstract: The pre-equilibrium correction for the nuclear reactions induced by fast neutron is considered as follows: the nuclear reaction processes with the exciton number equal to or larger than five can still be described by the statistical theory of the nuclear reaction. The particle emission processes, in which less than five excitons are involved, are calculated by means of the exciton model and the γ emission of one exciton state is calculated by the direct capture mechanism. For the three-exciton state, only the semidirect capture mechanism, which plays the main role in the researched energy region, is taken into account. The interference effect between the direct and semidirect capture is also considered. The radiative capture cross sections for 40Ca and 208Pb in the neutron incident energy region from 3 MeV to 20 MeV are calculated and a better coincidence with the experimental values is obtained. At the same time, the contribution to the (n, γ) reaction cross sections of the γ emissions before and after statistical equilibriums as well as the characteristics of the direct capture, semidirect capture and their interferece terms are discussed.

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