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在双核模型的理论框架下系统研究了超重元素Z=116～121的蒸发剩余截面,计算过程中核子扩散由主方程描述,同时考虑了全熔合与准裂变的竞争。计算基本再现了利用热熔合反应48Ca+245Cm,48Ca+249Cf和48Ca+249Bk产生116～118号同位素的合成截面。同样,分别以249Bk,249Cf和243Am为靶,以48Ca,50Ti和58Fe为炮弹,计算了Z=119～121号同位素的生成截面。结果表明,这些超重核的生成截面随着质子数的增大进一步变小。例如,利用58Fe+243Am反应合成121号同位素的最大蒸发剩余截面仅在fb量级。基于对选择的几个反应系统的系统分析,发现双核系统在熔合蒸发过程中偶Z奇N和奇Z偶N复合核分别有强的3n和4n蒸发道。
Under the theoretical framework of dual-core model, the superficial elements Z = 116 ~ 121 are systematically studied. The nucleation diffusion is described by the main equation and the competition between total fusion and quasi-fission is considered. The calculation basically reproduces the synthetic cross-section of the isotopes 116 to 118 produced by the thermal fusion reactions 48Ca + 245Cm, 48Ca + 249Cf and 48Ca + 249Bk. Similarly, using 249Bk, 249Cf and 243Am targets respectively, 48Ca, 50Ti and 58Fe shells were used to calculate the formation cross sections of isotopes Z = 119-121. The results show that the cross section of these superheavy nuclei further decreases with the increase of proton number. For example, the maximum evaporative residual cross-section for the synthesis of isotope 121 using the 58Fe + 243Am reaction is only on the order of fb. Based on the systematic analysis of selected reaction systems, it was found that the dual-core systems have strong 3n and 4n evaporation channels respectively in the Z-odd N and odd-Z-couple nuclei in the process of fusing and evaporating.