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Structure Prediction from Scattering Profiles: A Neutron-Scattering Use-Case
Published in Anuj Karpatne, Ramakrishnan Kannan, Vipin Kumar, Knowledge-Guided Machine Learning, 2023
Cristina Garcia-Cardona, Ramakrishnan Kannan, Travis Johnston, Thomas Proffen, Sudip K. Seal
Crystallographic structure determination and refinement has been the cornerstone of materials science and our understanding of the atomic structure for many decades. The ability to design customized material with targeted mechanical and chemical properties relies on their internal structure. Neutron scattering is a state-of-the-art experimental technique that allows scientists to probe material structures with atomic resolutions by scattering beams of neutrons from them. While calculating the scattering intensities of a given crystal structure is straight forward, obtaining the atomic structure from the scattering intensities is not due to the so-called “crystallographic phase problem”. In a nutshell, the scattering intensities we measure only give us the amplitude of the structure factor F but not the phase value.
Radiometry and Photometry
Published in Antoni Rogalski, Zbigniew Bielecki, Detection of Optical Signals, 2022
Antoni Rogalski, Zbigniew Bielecki
The scattering process causes a redirected radiation beam to propagate in various directions away from the original direction [9]. There are three main types of scattering: Rayleigh, Mie and non-selective. The scattering type depends on a relationship between both scattering particles’ size and the wavelength of the propagating light. Rayleigh scattering is caused by particles with a size much smaller than the light wavelength. In this case, the scattering intensity decreases with the wavelength as ~λ-4. When the particle size is comparable or as large as a radiation wavelength, Mie scattering is observed. Non-selective scattering occurs for a particle with a size larger than the beam wavelength. In this case, Mie theory is approximated by the principles of reflection, refraction and diffraction. The scattering coefficient depends on the concentration Nscat and the effective cross section parameters σscat of the particles and can be described byβscat=σscatNscat.
Fibre Optic Beam Delivery
Published in Chunlei Guo, Subhash Chandra Singh, Handbook of Laser Technology and Applications, 2021
In addition to the self-focusing effect described earlier, two other non-linear effects, stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS), are also observed in fused silica optical fibres with a high peak power. For a full explanation see Nonlinear Fiber Optics by Agrawal [32]. Damage is not a problem with either of these processes; instead, the light is strongly coupled to other wavelengths. Brillouin scattering is an interaction of the laser beam with an acoustic wave, which couples the power into a frequency-shifted beam travelling in the opposite direction to the laser, thus greatly attenuating the light emerging from the output end of the fibre. Raman scattering, meanwhile, is the scattering of a photon from a molecule, with a change in vibrational energy level of the molecule and a consequent increase in the wavelength of the light. With SRS, the scattered beam normally travels in the same direction as the original beam. If a sufficient length of fibre is used, further scattering of the scattered light to longer wavelengths is observed, resulting in a spectrum with a number of broad peaks [33]. Since the scattered light propagates in the same direction as the original laser beam, SRS is not such a problem as SBS in wavelength-sensitive applications, as the power will still emerge from the far end of the fibre. However, the focusing optics at the output end must be free from chromatic aberration over the range of wavelengths produced.
Preconceptual Design of Multifunctional Gas-Cooled Cartridge Loop for the Versatile Test Reactor: Instrumentation and Measurement—Part II
Published in Nuclear Science and Engineering, 2022
Piyush Sabharwall, Kevan Weaver, N. K. Anand, Chris Ellis, Xiaodong Sun, Hangbok Choi, Di Chen, Rich Christensen, Brian M. Fronk, Joshua Gess, Yassin Hassan, Igor Jovanovic, Annalisa Manera, Victor Petrov, Rodolfo Vaghetto, Silvino Balderrama-Prieto, Adam J. Burak, Milos Burger, Alberto Cardenas-Melgar, Daniel Orea, Reynaldo Chavez, Byunghee Choi, Londrea Garrett, Genevieve L. Gaudin, Noah Sutton, Ken William Ssennyimba, Josh Young
Fiber sensors for measuring distributed strain (and temperature) generally rely on an interferometry technique. Light (from either a tunable laser or broadband source) is sent into the fiber under test. Rayleigh scattering is an elastic scattering of light due to the presence of scattering sites that are much smaller than the wavelength of the light. In an elastic scattering process, the wavelength is conserved, and only direction changes. The scattering amplitude is inversely proportional to the wavelength to the fourth power λ−4. This implies that shorter-wavelength light is scattered more intensely. Scattering sites in fiber-optic cables arise due to microscopic local density differences or other inhomogeneity arising from the fiber manufacturing process. When light is transmitted through the cable, some fraction is scattered in a direction 180 deg to the propagation axis (Rayleigh backscatter) and can be analyzed as it returns to the source. Backscattered light is then detected, and changes in the backscattered characteristics can be used to understand quasi-local strain and, in turn, temperature.
The unique asymmetric nano-cluster formation by the uneven hockey-stick-shaped mesogen based on 1,3,4-oxadiazole in Langmuir–Blodgett thin film
Published in Journal of Dispersion Science and Technology, 2022
Alpana Baidya, Bandana Das, Santanu Majumder, Sandip K. Saha, Ranendu K. Nath, Manoj K. Paul
When a photon interacts with a particle it scatters, that is, reflection, refraction, or diffraction. The elastic collision generates two types of scattering, the Rayleigh scattering, and the Mie scattering, depending on the size of the particles. The Rayleigh scattering happens when the particle size is very minute, below the one-tenth of the wavelength of incident radiation and it remains below 50 nm, like air molecules, because the visible light is between 400 and 700 nm. The amount of light that is scattered in Rayleigh scattering is expressed as the extinction coefficient, Q, which is proportional to the ratio between the radius of the particle and the wavelength. The forward and backscattering are almost equal. But Mie scattering occurs when the particle diameter is one-tenth or the full size of the wavelength of incident radiation. Most of the scattering is in the forward direction and little in the backward direction.[25] In Mie scattering the extinction coefficient, Q depends on
Effect of functionality of thiol on the optical properties of liquid crystals/polymer composite films
Published in Liquid Crystals, 2021
Le Zhou, Gang Chen, Wenbo Shen, Cuihong Zhang, Zhang Lanying
The two important indicators of optical diffusers are total transmission and transmission haze [25,26]. Total transmission is defined as transmission of the incident light passing through optical diffusers. Transmission haze is defined as the ratio of transmission of the scattering light and the incident light when the scattering angle of incident light is greater than 2.5° [25,26]. The scattering mechanism of light scattering is based on two types of scattering: Mie scattering and Rayleigh scattering. Rayleigh scattering is applied for small spheres (the scatter sphere’s diameter D is much less than the incident light wavelength λ), while Mie scattering is applied for large spheres (the scatter sphere’s diameter is comparable or a little larger than the incident light wavelength λ) [27]. Liquid crystals (LCs) are anisotropic liquid, compared to isotropic particles, which are applied as scatters with high scattering and transparency, then, LCs/polymer composites with high transmission and strong scattering can be widely applied as optical diffusers.