The authors present a review of the systematic studies of the structure of macroscopically planar thin films at the air-liquid interface (water, alkali solution and silica hydrosol). A common feature of the considered works is the application of a model-independent approach to the analysis of X-ray reflectometry data, which does not require a priori assumptions about the structure of the object under study. It is shown that the experimental results obtained with the laboratory source in some cases are qualitatively on par with the results of those obtained with the use of synchrotron radiation source. The reproducibility of the effect of spontaneous ordering in films of amphiphilic organic molecules (phospholipids) at the surface of the colloidal solution of silica nanoparticles is demonstrated. The possibility of influencing the kinetics of the in situ formation of a phospholipid film by enriching the liquid substrate with alkali metal ions is also discussed.

The authors present a review of the systematic studies of the structure of macroscopically planar thin films at the air-liquid interface (water, alkali solution and silica hydrosol). A common feature of the considered works is the application of a model-independent approach to the analysis of X-ray reflectometry data, which does not require a priori assumptions about the structure of the object under study. It is shown that the experimental results obtained with the laboratory source in some cases are qualitatively on par with the results of those obtained with the use of synchrotron radiation source. The reproducibility of the effect of spontaneous ordering in films of amphiphilic organic molecules (phospholipids) at the surface of the colloidal solution of silica nanoparticles is demonstrated. The possibility of influencing the kinetics of the in situ formation of a phospholipid film by enriching the liquid substrate with alkali metal ions is also discussed.

Whispering galleries propagating along large-radius concave meniscuses at the surfaces of rotating deionized water as well as hydrosol of similar to 10 nm amorphous silica particles enriched by CsOH were probed by both x-ray reflectometry and x-ray fluorescence for the first time. The measurements were carried out at a wavelength of 1.5405 angstrom of Cu-K-alpha radiation by using a homemade diffractometer with a moving tube-sample-detector system. According to the experimental results, the x-ray beam deflection angle at the sol's surface reaches 4 degrees, which is roughly four times higher than that obtained on the water surface. The rigorous solution of the Helmholtz equation for the whispering gallery reflection mode at the concave liquid surface agrees well with experimental observations. We attribute the difference in the x-ray beam deflection angle for the studied liquids to the difference in their viscosity, which presumably is inversely proportional to the effective surface roughness. (c) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Grazing incidence X-ray reflectometry (GIXRR) and fluorescence (GIXRF) analysis of the metallic-coated diffraction grating has been conducted. The grating has the sinusoidal-type groove profile derived from the atomic-force microscopy measurements. Using the developed methods of GIXRR and GIXRF, we theoretically and experimentally investigate angular dependences of the specular reflected and emitted radiation intensity of the Al-coated 400 mm grating with a Cr adhesion layer of the thickness of ~2 nm on the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> substrate working in extreme conical and classical diffraction mounts for the incident wavelength of ~0.1541 nm and the grazing-incidence angle range of ~0.05-0.5 deg. The specular reflectance (the 0-th order efficiency) as well as the specular fluorescence intensity have been found from solutions of the respective vector Helmholtz equations. In order to determine the fluorescence intensity, we have used the approach based on a method of fundamental parameters using the reciprocity theorem.

X-ray diffraction and fluorescence of whispering galleries (WGs) which propagate along meniscuses of deionized water or silica hydrosols enriched by CsOH have been analyzed for the first time. The measurements have been performed using the diffractometer with a moving tube-detector system. The X-ray beam rotation angle reached a maximum value of 4° on a silica hydrosol sample. The WG mode propagating near the surface of a concave meniscus as well as the fluorescence intensity have been found from a solution of the respective Helmholtz equations. For analysis of intensities of the X-ray scattering and fluorescence we have used a two-layer model of the liquid with the upper non-uniform corrugated layer in which the concentration of levitating Cs+ ions near the surface has a maximum derived from the experiment in the hydrosol depth of ~ 15 nm for SiO2 particle sizes of ~ 5÷7 nm. In order to determine the fluorescence intensity we have used the approach based on a method of fundamental parameters using the reciprocity theorem.

The molecular structure of dimyristoyl phosphatidylserine (DMPS) monolayers on a water substrate in different phase states has been investigated under normal conditions by X-ray reflectometry with a photon energy of ~ 8 keV. According to the experimental data, the transition from a two-dimensional expanded liquid state to a solid gel state (liquid crystal) accompanied by the ordering of the hydrocarbon tails of the DMPS molecule occurs in the monolayer as the surface pressure rises. The monolayer thickness is (20 +/- 3) Angstrom and (28 +/- 2) Angstrom in the liquid and solid phases, respectively, with the deflection angle of the molecular tail axis from the normal to the surface in the gel phase being (26 +/- 8) deg. At least a twofold decrease in the degree of hydration of the polar lipid groups also occurs under two-dimensional monolayer compression. The reflectometry data have been analyzed using two approaches: under the assumption about the presence of two layers with different electron densities in the monolayer and without any assumptions about the transverse surface structure. Both approaches demonstrate satisfactory agreement between themselves in describing the experimental results.