<gamma> - <gamma> Perturbed Angular Correlation Study of dense Kondo effect.

用微扰角关联技术研究了具有密集Kondo效应的Ce化合物中Ce4f电子的自旋涨落。微扰角关联可以提供有关Ce自旋动力学的信息，而不会受到非弹性中子衍射和NMR的限制。用于时差测量的四个探测器系统已经被改造，用1 1/2“NaI(Tl)闪烁体和RCA8575光电倍增管代替两个探测器，用2”闪烁体和Phillips XP-2020光电倍增管，使四个探测器都相同。为了提高装置的精度、稳定性、效率和时间分辨率，设计了一个计算机控制接口和两个新设计的数字脉冲幅度分析器。除了对(La-Ce)Si系统和(La-Ce)&lt；Al_2&gt；系统进行了补充测量外，还测量了(La-Ce)&lt；Ni_2&gt；系统的微扰角相关。(La-Ce)&lt；Ni2&Gt；化合物在整个组成范围和温度范围内都有明显的波动，具有较高的近藤温度。在多轨道Anderson模型的基础上，分析了由角关联衰减因子得到的关联时间。在考虑晶场分裂的情况下，推导出了高温微扰理论与Hnzawa-Yamada理论相一致的插值公式。实验数据被拟合到用于评价&lt；T_K&GT；的内插公式中。得到的&lt；T_K&gt；值比用其他方法估算的值低很多。Kondo系统单重态的超精细耦合常数可能是产生这种差异的原因之一，这是一个有趣的未来问题。

By means of perturbed angular correlation technique, spin fluctuations of Ce 4f electrons have been studied in Ce compounds which exhibit dense Kondo effect. Perturbed angular correlations can afford information about Ce spin dynamics without limitations encountered in inelastic neutron diffraction and NMR.The four detector system for time differential measurements have been remodeled by replacing two detectors with 1 1/2" NaI(Tl) scintillaters and RCA 8575 photomultipliers by two with 2" scintillaters and Phillips XP-2020 photomultipliers so that all four detectors are the same. An interface for computer control of the whole system and newly designed two channel digital pulse hight analysers were assembled to improve accuracy, stability, efficiency and time resolution of the apparatus.In addition to supplementary measurements on (La-Ce)Si system and (La-Ce) <Al_2> system, perturbed angular correlations were measured on (La-Ce) <Ni_2> system. Having pronounced fluctuations in the whole composition range and the temperature range, the (La-Ce) <Ni_2> compounds were found to have relatively high Kondo temperatures. The correlation time obtained from the attenuation facors of angular correlations were analysed on the basis of multiorbital Anderson model. An interpolation formula consistent with the perturbation theory at high temperatures and with the Hnzawa-Yamada theory at OK was deduced taking into account of crystalline field splitting. The experimental data were fitted to the interpolation formula for the evaluation of <T_K> . The obtained <T_K> values are substantially lower than those evaluated by other methods. The hyperfine coupling constant in the singlet ground state of Kondo system which is a possible origin of the discrepancy is an interesting future problem.