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

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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) ].