Browsing by Author "Merrill, Robert Louis"
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Item Absolute differential and integral cross sections for charge transfer of state-selected keV oxygen ion with oxygen(2)(1998) Merrill, Robert Louis; Smith, Ken A.Absolute differential and integral charge transfer cross sections have been measured for 0.5, 0.85, 1.5, 2.8, and 5.0 keV O$\sp+$ with O$\sb2$ at scattering angles between 0.01$\sp\circ$ and 3.50$\sp\circ$ in the laboratory frame. The dependence of these cross sections upon the electronic state of the O$\sp+$ ion was investigated. This study was performed using a filter cell technique to derive the cross sections for both the $\rm O\sp+(\sp4S)$ ground state ions and the $\rm O\sp+({\sp2D,\ \sp2P})$ metastable state ions. The charge transfer cross sections involving the $\rm O\sp+({\sp2D,\ \sp2P})$ ions are significantly larger than the corresponding cross sections for the ground state ions. Previously published cross section measurements are compared to the present results for the total integral charge transfer cross sections of state-selected keV O$\sp+$ with O$\sb2$.Item Andreev reflection and spin injection intod-wave,p-wave, ands-wave superconductors(2000) Merrill, Robert Louis; Si, QimiaoThe effect of spin injection into d-wave, p-wave, and s-wave superconductors is studied here. A theory is developed which treats the interplay between the bulk and boundary spin transport, as well as the interplay between pair and single-particle transport at the boundary. This theory is used to study the relationship between Andreev reflection and the linear-response spin-injection characteristics. Among the quantities of interest are, the amount of injected magnetization (m), the induced spin-dependent current (I s), and the induced boundary voltage (Vs). In general, Andreev reflection makes each of these three quantities depend on a different combination of the boundary and bulk contributions. The conditions are identified under which some of these quantities that depend solely on the bulk properties can be isolated. A correlation between the Andreev bound states and the spin-injection characteristics is established, which implies a strong directional dependence of spin injection into high-temperature superconductors and in p-wave superconductors.