Self-Transport, Electro-Convection and Effective Self-Diffusion in Liquid Rubidium Metal

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Abstract
Isotope electrotransport in liquid Rb has been measured. Results of earlier measurements of the mass effect μ have been confirmed and their accuracy further improved. μ ranges from 2 x 10-5 at the m.p. to 10-4 at 400°C. Up to about 200°C the temperature dependence of μ is similar to that of the (theoretically computed) self-diffusion coefficient. At higher temperatures the apparent “activation energy” increases. With the aid of electrotransport, electro-convection in the liquid metal has been studied. Analysis of data at three different currents indicates that in horizontal 0.5 mm i.d. capillaries, at less than some 9 Amps, the main source of electro-convection in Rb is an I2 sensitive mechanism, probably electro-osmosis. At higher currents an I4 dependent mechanism may become dominant. A relatively small current independent term may influence the effective self-diffusion. The zero-current values of the effective self-diffusion coefficients are computed. Between 333° and 500°K they can be represented by (Deff) 0=5.7 x 10–4 exp (-1910/R T), with about 15 percent error margin in “activation energy”. These values are in good agreement with self-diffusion coefficients as calculated from experimental viscosity.

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