charged ions are being formed. It would suggest that RuO and Ru02 are mobile surface species that can nucleate into the growing oxide. Ru03+ and Ru04+ already have substantial partial pressures and are chemically less likely to form oxide. The presence of Ru2032+ and possibly Ru203+ would imply that RuO and Ru02 are reaction partners contributing to the oxide. However, a more detailed study is needed to confirm the existence of the singly charge species. Should the high mass peak be the dimer (Ru02)2+, it would confirm the presence of diffusing and reacting Ru02 molecules analogous to the W03 species on oxidizing tungsten. The point will be scrutinized in future studies with a higher resolution instrument. From the above information, the following mechanism is suggested:
A new method has been developed for the determination of interfacial tensions between two fluids from primary drop shape data. The technique is applicable to either pendant or sessile drops. The required data are limited to the x,z coordinates of the drop profile, the density difference between the two fluids, and the magnification. We build upon the work of Rotenberg et al. (Rotenberg, Y.; Boruvka, L; Neumann, A. W. J. Colloid Interface Sci. 1983, 93, 169), whose main innovations were to obviate the accurate measurement of the coordinates of the apex, define the objective function with a line normal from a data point to a calculated drop profile, and use the incrementally loaded Newton-Raphson method. The major difference in the method presented here is the use of rotational discrimination instead of the incrementally loaded Newton-Raphson technique to minimize the objective function. It is shown, by use of numerically generated drop profiles and one set of experimental data for pure water at 25 °C, that this new method is superior to that of Rotenberg et al. on three points. First, it is found that this method requires 4-50 times less processing time per drop profile. Second, a superior error analysis is performed. Third, the new method determines two additional experimental parameters, the aspect ratio and rotational angle of the optical system. Furthermore, by use of the new error analysis, the dependence of the error on the shape of a drop, pendant and sessile, is examined. An "optimum" range of drop shapes is found.
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