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arXiv 2406.15445nucl-exnucl-th
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$^{243}$Am$(n,2n)$反应中的$^{242m}$Am同核异能素产额

$^{242m}$Am isomer yield in $^{243}$Am$(n, 2n)$ reaction

V. M. Maslov

AI总结:

本研究通过标准动力学方程计算$^{243}$Am$(n,2n)$反应中$^{242g}$Am与$^{242m}$Am的布居和相对产额,并用已有实验数据验证中子谱及阈值行为。

摘要:

$^{243}$Am$(n,2n)$反应会布居半衰期为16小时、自旋$J$为1的$^{242g}$Am基态,或者半衰期为141年、自旋$J$为5的$^{242m}$Am同核异能素态。前一种状态$^{242g}$Am主要通过β衰变生成$^{242}$Cm,或通过电子俘获转变为$^{242}$Pu。$^{242g}$Am的绝对产额与Norris于1983年通过$^{242}$Cm的α活度估算并测得的数据相符。分支比被定义为$^{242}$Am最低内禀态的布居数之比。对剩余核$^{242}$Am的基态$^{242g}$Am和同核异能素态$^{242m}$Am的计算产额,被用于预测同核异能素的相对产额。这些布居由激发态的γ衰变定义,并由标准动力学方程描述。在$^{236}$Np和$^{242}$Am核的情形中,低自旋态与高自旋态的排序不同,这解释了尽管激发能依赖关系相似,但在$(n,2n)$反应阈值附近相对产额形状不同的原因。Drapchinsky于2004年获得的5 MeV和15 MeV下$^{243}$Am$(n,F)$数据,支持了所计算的$^{243}$Am$(n,xnf)$裂变前中子对瞬发裂变中子谱的贡献,以及所计算的馈入$^{242g}$Am和$^{242m}$Am同核异能素态的$^{243}$Am$(n,2n)$遍举中子谱。

英文摘要:

The reaction 243 Am (n, 2n) populates the T of 16 hours ground state 242 g Am with J of 1 or the 242 m Am isomer state J of 5 with T of 141 years. The former state 242 g Am mostly beta decays to 242 Cm, or transmutes to 242 Pu via electron capture. The absolute yield of 242 g Am is compatible with the measured data, estimated by the alpha activity of 242 Cm by Norris in 1983. The branching ratio defined by the ratio of the populations of the lowest intrinsic states of 242 Am. Calculated yields of ground 242 g Am and isomer 242 m Am states of the residual nucleus 242 Am are used to predict the relative yield of isomer. These populations defined by the gamma decay of the excited states, described by the standard kinetic equation. The ordering of the low and high spin states is different in case of 236 Np and 242 Am nuclei, that explains different shapes of relative yields near the (n, 2n) reaction threshold, though the excitation energy dependences are similar. Data of 243 Am (n, F) at 5 MeV and 15 MeV by Drapchinsky in 2004, support calculated 243Am (n,xnf) prefission neutron contribution to prompt fission neutron spectra and calculated exclusive neutron spectra of 243 Am (n, 2n) feeding the 242 g Am and isomer 242 m Am states.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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