Nuclear-magnetic-resonance data for the alkali and noble metals are discussed in terms of Moriya's theory of exchange-enhanced spin-lattice relaxation rates. The available evidence suggests that the relaxation-rate enhancement resulting from collective electron effects is ~20% smaller in lithium and sodium than predicted by the theory for the case of a S-function-potential electron-electron interaction. This small disparity is attributed to a nonzero interaction range whose magnitude is estimated to be less than an atomic radius. During the course of this study, low-temperature Knight-shift and spin-lattice relaxation data have been obtained for 39 K, ^Rb, 87 Rb, and 133 Cs in the respective metals. The results suggest that the exchange enhancements of the conduction-electron spin susceptibilities in these metals are comparable to those in lithium and sodium. Similar conclusions apply in the case of the noble metals.
A mathematical analysis for minority-carrier diffusion in a solar cell base is used to extract bulk lifetime τ and effective back-surface recombination velocity S from measurements of asymptotic decay times of short-circuit current and open-circuit voltage. Since the decay times depend individually on both S and τ, it is necessary to use both current and voltage data for unique results. Experimental measurements of current and voltage transients are presented from variable base resistivity cells, γ-irradiated cells, and cells with intentionally damaged back-surface field regions. Lifetimes determined in these experiments are compared with conventional techniques. The results show that these conventional techniques yield lifetimes in serious error for cells whose diffusion lengths approach base thickness.
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