标题： 重离子融合反应中亚屏障能量下线性耦合近似的有效性 显示英文标题

标题： Validity of the linear coupling approximation in heavy-ion fusion reactions at sub barrier energies

摘要： 高能级耦合表面振动相对运动在近势垒能量下重离子融合反应中的作用被研究。 耦合通道方程被求解到所有阶数，并且也在线性耦合和二次耦合近似下求解。 以$^{64}$Ni +$^{92,96}$Zr 反应为例，结果表明所有阶数的耦合能够显著改善与实验测量的融合截面以及复合核平均角动量的符合程度，对于这种重而接近对称的系统而言。 对于如$^{16}$O +$^{112}$Cd、$^{144}$Sm 等不对称系统，也检验了高阶耦合的重要性，此前的融合截面计算似乎表明线性耦合近似是足够的。 结果表明，即使对于那些由线性耦合近似似乎能够很好地再现的实验测量融合截面的系统，当包含高阶耦合时，势垒分布的形状和平均角动量的能量依赖性也可能发生显著变化。 显示英文摘要

摘要： The role of higher order coupling of surface vibrations to the relative motion in heavy-ion fusion reactions at near-barrier energies is investigated. The coupled channels equations are solved to all orders, and also in the linear and the quadratic coupling approximations. Taking $^{64}$Ni + $^{92,96}$Zr reactions as examples, it is shown that all order couplings lead to considerably improved agreement with the experimentally measured fusion cross sections and average angular momenta of the compound nucleus for such heavy nearly symmetric systems. The importance of higher order coupling is also examined for asymmetric systems like $^{16}$O + $^{112}$Cd, $^{144}$Sm, for which previous calculations of the fusion cross section seemed to indicate that the linear coupling approximation was adequate. It is shown that the shape of the barrier distributions and the energy dependence of the average angular momentum can change significantly when the higher order couplings are included, even for systems where measured fusion cross sections may seem to be well reproduced by the linear coupling approximation.