In situ and non situ surface x-ray scattering studies of in plane Cs+ ordering in Helmholtz planes of Pt(111) surface

In-plane ordering of Cs+ layers in Helmhotlz planes was studied on Pt(111) surface in 0.1 M CsF electrolyte solutions with synchtrotron surface x-ray scattering techniques. The ordering was measured in a new transmission cell, designed for in situ and non situ measurements and high-temperature sample annealing all in the cell without sample transfer steps. At -850 mV vs. Ag/AgCl, (2x2) in-plane scattering peaks were weak under in situ condition and grew rapidly under non situ condition as the surface emersed from the electrolyte. The models for the (2x2) structures are presented and differences between in situ and non situ conditions are discussed.