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arXiv 0908.1957nucl-th
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准裂变和$^{16}$ O+ $^{184}$ W和PDMATHAAC F+ $^{181}$ Ta反应中蒸发残渣形成的差异

Quasifission and difference in formation of evaporation residues in the $^{16}$O+$^{184}$W and $^{19}$F+$^{181}$Ta reactions

A. K. Nasirov, G. Mandaglio, M. Manganaro, A. I. Muminov, G. Fazio, G. Giardina

摘要:

从理论上研究了导致相同$^{200}$ Pb复合核的$^{19}$ O+ $^{184}$ W和$^{19}$ F+ $^{181}$ Ta反应中的俘获、完全熔合和蒸发残渣生成的激发函数,解释了前者比后者蒸发残渣生成量大的实验数据.观察到的差异是由大的捕获截面在前者和增加的准裂变的贡献,在$^{19}$ F+ $^{181}$ Ta反应在大激发能的裂变样碎片的产量。在$^{16}$ O+ $^{184}$ W反应中形成复合核的几率较大,但在相同的激发能下,两种反应中形成的复合核具有相似的角动量范围。与高激发能下的$^{16}$ O+ $^{184}$ W反应相比,在$^{19}$ F+ $^{181}$ Ta反应中观察到的归一化到熔合截面的蒸发残余截面减小,这是由于在$^{19}$ F诱导反应中,准裂变贡献的快速增加与复合核形成中的阻碍增加有关.给出了这两个反应的蒸发剩余物截面的自旋分布。

英文摘要:

The excitation functions of capture, complete fusion, and evaporation residue formation in the $^{16}$O+$^{184}$W and $^{19}$F+$^{181}$Ta reactions leading to the same $^{200}$Pb compound nucleus has been studied theoretically to explain the experimental data showing more intense yield of evaporation residue in the former reaction in comparison with that in the latter reaction. The observed difference is explained by large capture cross section in the former and by increase of the quasifission contribution to the yield of fission-like fragments in the $^{19}$F+$^{181}$Ta reaction at large excitation energies. The probability of compound nucleus formation in the $^{16}$O+$^{184}$W reaction is larger but compound nuclei formed in both reactions have similar angular momentum ranges at the same excitation energy. The observed decrease of evaporation residue cross section normalized to the fusion cross section in the $^{19}$F+$^{181}$Ta reaction in comparison with the one in the $^{16}$O+$^{184}$W reaction at high excitation energies is explained by the increase of hindrance in the formation of compound nucleus connected with more quick increase of the quasifission contribution in the $^{19}$F induced reaction. The spin distributions of the evaporation residue cross sections for the two reactions are also presented.

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