X-ray scattering of thin liquid films: beyond the harmonic approximation.
We calculate the x-ray scattering from coupled capillary fluctuations of thin liquid films, taking into account an asymmetric interfacial interaction potential. Harmonic expansion of the potential around its minimum produces the well-known Kiessig fringes in both specular reflectivity and longitudinal diffuse scattering. The addition of a cubic term to the expansion, representing the asymmetry, leads to q(z)-dependent changes of the modulation period of the Kiessig fringes. The cubic term produces a relative phase shift between the interference fringes of the specular reflectivity and the off-specular longitudinal diffuse scattering. It is suggested that these effects may be used to estimate, via x-ray scattering, the interfacial potential of thin liquid films.
Institute of Physics and Center for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100080, People's Republic of China. mingli@aphy.iphy.ac.cn
Ming
M
Li
Mark L
ML
Schlossman