P. Fenter et al., Electrical double-layer structure at the rutile-water interface as observed in situ with small-period X-ray standing waves, J COLL I SC, 225(1), 2000, pp. 154-165
X-Ray standing wave (XSW) measurements were made of Rb and Sr adsorbed from
aqueous solutions at the rutile (110)-water interface. These experiments w
ere performed to address the extent to which direct measurements of electri
cal double-layer structure are possible. The experimental results show that
the Bragg XSW technique, using small-period standing waves generated by Br
agg diffraction from the substrate, can precisely measure ion locations wit
hin the condensed layer and the in situ partitioning of ions between the co
ndensed and diffuse layers. Differences in condensed layer ion positions we
re observed for Sr ions (measured in situ) as compared with Rb ions (in sit
u) and also for Sr ions (ex situ). An additional constraint on the ex situ
Sr site geometry was provided by polarization-dependent surface EXAFS measu
rements. Such measurements can provide important constraints for the develo
pment and verification of electrical double-layer theory especially as appl
ied to ion adsorption at the solid-water interface. (C) 2000 Academic Press
.