Laser Study of interactions of atoms and molecules with high-T_C superconductor surfaces

本研究的目的是阐明原子和分子与高温超导体表面的相互作用。本研究中使用的脉冲分子束的非平衡性质已经被研究[H.Kuze等人，化学物理评论195,400(1992)]：用激光诱导荧光技术检测到了低至2K的旋转温度。结果表明，用Nd：YAG激光器代替原来的XeCl准分子激光器，大大降低了放电噪声。磁偶极子穿过高温超导体中空圆柱体的能量损耗已被实验证明[H.Kuze等人，应用物理学报73,1320(1993)]：损耗分为磁滞损耗和涡流损耗。用一对Helmholtz线圈建立了一个相对简单的装置，研究了YBa2Cu3Ox样品的详细磁行为，无论是烧结样品还是熔融织构样品。用一个新提出的模型很好地解释了观察到的行为，该模型将颗粒超导体视为超导颗粒的集合，并成功地应用于磁偶极子在超导体表面上方横向运动的情况[H.Kuze等，J.Appl.Phys.77,770(1995)]。

The purpose of this research is to elucidate the interaction of atoms and molecules with the surfaces of high-T_C superconductors. The non-equilibrium nature of the pulsed molecular beam employed in this study has already been investigated [H.Kuze et al., Chem.Phys.Lett.195,400 (1992) ] : the rotational temperature as low as 2 K has been detected by means of laser-induced-fluorescence technique. It has turned out that the use of Nd : YAG laser in place of the original XeCl excimer laser greatly contributes to reduce the discharge noise. The energy losses of magnetic dipoles which pass through a hollow cylinder of high-T_C superconductors have been demonstrated experimentally [H.Kuze et al.J.Appl.Phys.73,1320(1993) ] : the losses are categorized into the hysteresis loss and the eddy-current loss. The detailed magnetic behavior of the YBa_2Cu_3O_x samples, either sintered or melt-textured, is investigated using a relatively simple setup based on a pair of Helmholtz coils. The observed behavior is well explained with a newly propsed model in which the granular superconductors are treated as assembly of superconducting grains.This picture has also been applied successfully to the case where a magnetic dipole is made to move laterally above the surface of the superconductor [H.Kuze et al., J.Appl.Phys.77,770 (1995) ].