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Total external reflection
About: Total external reflection is a research topic. Over the lifetime, 829 publications have been published within this topic receiving 22213 citations.
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TL;DR: In this paper, the authors used grazing incidence X-ray diffraction (GIXD) to investigate the structural properties of cholesteryl-L-glutamate at the air-water interface.
Abstract: Monomolecular films at the air-water interface can be investigated on the subnanometer scale with grazing incidence X-ray diffraction (GIXD) using synchrotron radiation. This surface semsitive technique utilizes the property of total external reflection of X-rays from a water surface: an evanescent wave generated within the film diffracts in the surface plane giving an image of the film reciprocal lattice. Three applications of GIXD are presented ranging from poorly to highly crystalline thin films. (i) Cholesteryl- L-glutamate forms a crystalline monolayer at the air-water interface within which the glutamate moieties are not closely packed. This system specifically incorporates hydrophobic amino acids from the subphase. (ii) Long-chain cholesteryl esters deposited on the water surface spontaneously self assemble, forming crystalline interdigitated bilayers. The molecular structure, solved at the atomic resolution, was found to be similar to the 3D counterpart. (iii) According to 2-D diffraction theory, the shape of Bragg peaks is related to the mechanical constants of the film. Rigidity of the film can be deduced from a detailed peak analysis for secondary short chain alcohols showing a softening of the monolayer close to melting.
TL;DR: In this paper, the electron dynamics in the field of an electromagnetic wave produced at the vacuum interface upon reflection from the boundary, close to total internal reflection, is considered, and the authors consider electron trajectories of relativistic electrons propagating along the surface.
Abstract: We consider the electron dynamics in the field of an electromagnetic wave produced at the vacuum – transparent medium interface upon reflection from the boundary, close to total internal reflection. The propagation velocity of a constant phase of the electromagnetic wave along the interface can vary from c/n to infinity (c is the speed of light in vacuum, and n is the refractive index of the medium at the interface). In this case, there emerge regions of positive and negative phases of the field with wavelengths, approximately equal to half the wavelength of the original laser beam, which can propagate at a speed close to that of light in vacuum. If a beam of relativistic electrons propagates along the surface, they can gain energy and accelerate, as well as radiate. With closed trajectories of electron motion, a laser synchrotron will be implemented as a result of many acceleration cycles.
TL;DR: In this paper, a theoretical formalism for quantitative description of X-ray diffraction from Langmuir monolayers under conditions of total external reflection has been developed, based on the distorted-wave approximation.
Abstract: A theoretical formalism for quantitative description of X-ray diffraction from Langmuir monolayers under conditions of total external reflection has been developed. The proposed approach, based on the distorted-wave approximation, allows to consider physical mechanisms for plotting diffraction curves and maps (in the reciprocal space) for real monolayers and describe self-consistently specific features of Bragg peaks. The resulting algorithm can easily be implemented on a personal computer, which provides the opportunities to carry out numerical simulation of experimental two-dimensional diffraction intensity maps and determine reliably both the mean values of structural parameters of layers and their rms deviations.
TL;DR: In this article, the electric response of an x-ray mirror enclosed in a gas flow ionization chamber was studied under the conditions of total external reflection for hard x-rays.
Abstract: Electric response of an x-ray mirror enclosed in a gas flow ionization chamber was studied under the conditions of total external reflection for hard x-rays. It is shown that the electric response of the system as a function of the incidence angle is defined by x-ray Fresnel transmissivity and photon-electron attenuation properties of the mirror material. A simple interpretation of quantum yield of the system is presented. The approach could serve as a basis for non-invasive in-situ diagnostics of hard x-ray optics, easy access to complementary x-ray transmissivity data in x-ray reflectivity experiments and might also pave the way to advanced schemes for angle and energy resolving x-ray detectors.
TL;DR: Instrumentation for time-resolved fluorescent X-ray interference has been designed and the integrated fringes were in close agreement with a theoretical estimate based on the interference among transmitted and reflected waves at interfaces in the sample.
Abstract: A fluorescent X-ray interference method can effectively measure nanometer-level conformational changes for non-crystallized molecules and proteins in aqueous conditions. The time-resolved technique can be used to obtain information about the dynamics of molecules and proteins. Instrumentation for time-resolved fluorescent X-ray interference has been designed. A typical interference-fringe pattern was observed with approximately 3 s of X-ray exposure time from K-fluorescent X-rays emitted from a Zn monoatomic layer on an Rh substrate. The primary X-ray beam was polychromed with a mirror for total external reflection of X-rays and was tuned to an energy level at which only Zn K radiation became optimally excited. The glancing angle of the primary X-ray beam was fixed at a glancing angle at which the total intensity of K-fluorescent X-rays emitted from Zn atoms corresponded to the maximum value. The fluorescent X-ray interference fringes were monitored with an imaging plate (IP) as a non-energy-dispersive two-dimensional detector. The exposed interference fringes on the IP were integrated along the direction of the fringes. The integrated fringes were in close agreement with a theoretical estimate based on the interference among transmitted and reflected waves at interfaces in the sample.