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多声子激发和转移对Ca+Zr熔合的影响

Influence of multiphonon excitations and transfer on the fusion of Ca+Zr

H. Esbensen, A. M. Stefanini

备注：
36 pager, 13 figures
发表信息：
Phys. Rev. C89, 044616 (2014)
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摘要：

$^{48}$ Ca+ $^{90,96}$ Zr的融合数据进行了分析的耦合通道计算的基础上的M3 Y+排斥，双折叠势。通过应用先前确定的$^{48}$ Ca的核密度，调整锆同位素的中子密度以优化与聚变数据的拟合，而质子密度通过电子散射实验确定。它表明，融合数据可以解释得相当好，包括耦合到一个和两个声子激发的反应核和一个和两个核子转移反应，但也有一些敏感性多声子激发。提取的两种锆同位素的中子皮厚度与反质子测量结果一致。锆同位素的密度与先前确定的$^{40}$ Ca的核密度一起用于计算M3 Y+排斥势并预测$^{40}$ Ca+ $^{90,96}$ Zr的熔合截面。当考虑多声子激发和适度转移的影响时，对$^{40}$ Ca+ $^{90}$ Zr体系的计算截面与实验数据吻合较好.另一方面，对$^{40}$ Ca+ $^{96}$ Zr熔合截面的预测较差，并且对数据的预测不足30%至40%。虽然耦合到传输通道与积极的$Q$值预计将发挥重要作用，他们不能解释的数据，主要是因为预测的库仑势垒是约1.5兆电子伏太高。这种失败的可能原因进行了讨论。

英文摘要：

Fusion data for $^{48}$Ca+$^{90,96}$Zr are analyzed by coupled-channels calculations that are based on the M3Y+repulsion, double-folding potential. By applying a previously determined nuclear density of $^{48}$Ca, the neutron densities of the zirconium isotopes are adjusted to optimize the fit to the fusion data, whereas the proton densities are determined by electron scattering experiments. It is shown that the fusion data can be explained fairly well by including couplings to one- and two-phonon excitations of the reacting nuclei and to one- and two-nucleon transfer reactions but there is also some sensitivity to multiphonon excitations. The neutron skin thicknesses extracted for the two zirconium isotopes are consistent with anti-proton measurements. The densities of the zirconium isotopes are used together with the previously determined nuclear density of $^{40}$Ca to calculate the M3Y+repulsion potentials and predict the fusion cross sections of $^{40}$Ca+$^{90,96}$Zr. The predicted cross sections for $^{40}$Ca+$^{90}$Zr are in reasonable agreement with the data when the influence of multiphonon excitations and a modest transfer is considered. The prediction of the $^{40}$Ca+$^{96}$Zr fusion cross section, on the other hand, is poor and under-predicts the data by 30 to 40%. Although couplings to transfer channels with positive $Q$ values were expected to play an important role, they are not able to explain the data, primarily because the predicted Coulomb barrier is about 1.5 MeV too high. Possible reasons for this failure are discussed.

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