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Literatura académica sobre el tema "Diffractive scattering processes"

Autor: Grafiati

Publicado: 14 de marzo de 2023

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Artículos de revistas sobre el tema "Diffractive scattering processes"

GAY DUCATI, M. B. y W. K. SAUTER. "GLUON PROPAGATOR IN DIFFRACTIVE SCATTERING". International Journal of Modern Physics A 21, n.º 28n29 (20 de noviembre de 2006): 5861–74. http://dx.doi.org/10.1142/s0217751x06033945.

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In this work, we perform a comparison of the use of distinct gluon propagators with the experimental data in diffractive processes, pp elastic scattering and light meson photo-production. The gluon propagators are calculated through nonperturbative methods, being justified their use in this class of events, due to the smallness of the momentum transfer. Our results are not able to select the best choice for the modified gluon propagator among the analyzed ones. This shows that the application of this procedure in this class of high energy processes, although giving a reasonable fit to the experimental data, should be taken with same caution.

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IACOBUCCI, GIUSEPPE. "DIFFRACTIVE PHENOMENA". International Journal of Modern Physics A 17, n.º 23 (20 de septiembre de 2002): 3204–19. http://dx.doi.org/10.1142/s0217751x02012697.

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The most recent theoretical and experimental results in the field of diffractive scattering are reviewed. A parallel between the two current theoretical approaches to diffraction, the DIS picture in the Breit frame and the dipole picture in the target frame, is given, accompanied by a description of the models to which the data are compared. A recent calculation of the rescattering corrections, which hints at the universality of the diffractive parton distribution functions, is presented. The concept of generalized parton distributions is discussed together with the first measurement of the processes which might give access to them. Particular emphasis is given to the HERA data, to motivate why hard diffraction in deep inelastic scattering is viewed as an unrivalled instrument to shed light on the still obscure aspects of hadronic interactions.

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Mücke, A., J. P. Rachen, Ralph Engel, R. J. Protheroe y Todor Stanev. "Photohadronic Processes in Astrophysical Environments". Publications of the Astronomical Society of Australia 16, n.º 2 (1999): 160–66. http://dx.doi.org/10.1071/as99160.

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AbstractWe discuss the first applications of our newly developed Monte Carlo event generator SOPHIA to multiparticle photoproduction of relativistic protons with thermal and power-law radiation fields. The measured total cross section is reproduced in terms of excitation and decay of baryon resonances, direct pion production, diffractive scattering, and non-diffractive multiparticle production. Non-diffractive multiparticle production is described using a string fragmentation model. We demonstrate that the widely used ‘Δ-approximation’ for the photoproduction cross section is reasonable only for a restricted set of astrophysical applications. The relevance of this result for cosmic ray propagation through the microwave background and hadronic models of active galactic nuclei and gamma-ray bursts is briefly discussed.

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Trzebiński, M. "Diffractive Physics at the LHC". Ukrainian Journal of Physics 64, n.º 8 (18 de septiembre de 2019): 772. http://dx.doi.org/10.15407/ujpe64.8.772.

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Diffractive processes possible to be measured at the LHC are listed and briefly discussed. This includes soft (elastic scattering, exclusive meson pair production, diffractive bremsstrahlung) and hard (single and double Pomeron exchange jets, y +jet, W/Z, jet-gap-jet, exclusive jets) processes as well as Beyond Standard Model phenomena (anomalous gauge couplings, magnetic monopoles).

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ARISAWA, TETSUO. "HEAVY QUARK PRODUCTION BY HARD DIFFRACTIVE SCATTERING". Modern Physics Letters A 09, n.º 03 (30 de enero de 1994): 247–57. http://dx.doi.org/10.1142/s0217732394000265.

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Heavy quark production in hard diffractive scattering is analyzed with evaluation of cross-sections and Monte-Carlo event generations. “Super hard” Pomeron, the existence of which was recently supported by the UA8 collaboration at CERN [Formula: see text] Collider [Formula: see text], is included by proposing a new method of determining Pomeron structures. Detection of (anti-)top quarks in the single diffractive processes is also mentioned.

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KUUSELA, MIKAEL, JERRY W. LÄMSÄ, ERIC MALMI, PETTERI MEHTÄLÄ y RISTO ORAVA. "MULTIVARIATE TECHNIQUES FOR IDENTIFYING DIFFRACTIVE INTERACTIONS AT THE LHC". International Journal of Modern Physics A 25, n.º 08 (30 de marzo de 2010): 1615–47. http://dx.doi.org/10.1142/s0217751x10047920.

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Close to one half of the LHC events are expected to be due to elastic or inelastic diffractive scattering. Still, predictions based on extrapolations of experimental data at lower energies differ by large factors in estimating the relative rate of diffractive event categories at the LHC energies. By identifying diffractive events, detailed studies on proton structure can be carried out.The combined forward physics objects: rapidity gaps, forward multiplicity and transverse energy flows can be used to efficiently classify proton–proton collisions. Data samples recorded by the forward detectors, with a simple extension, will allow first estimates of the single diffractive (SD), double diffractive (DD), central diffractive (CD), and nondiffractive (ND) cross-sections. The approach, which uses the measurement of inelastic activity in forward and central detector systems, is complementary to the detection and measurement of leading beam-like protons.In this investigation, three different multivariate analysis approaches are assessed in classifying forward physics processes at the LHC. It is shown that with gene expression programming, neural networks and support vector machines, diffraction can be efficiently identified within a large sample of simulated proton–proton scattering events. The event characteristics are visualized by using the self-organizing map algorithm.

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Buchmüller, W. y A. Hebecker. "A parton model for diffractive processes in deep inelastic scattering". Physics Letters B 355, n.º 3-4 (agosto de 1995): 573–78. http://dx.doi.org/10.1016/0370-2693(95)00721-v.

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Anisovich, V. V., M. A. Matveev y V. A. Nikonov. "Diffractive hadron production at ultrahigh energies". International Journal of Modern Physics A 30, n.º 11 (16 de abril de 2015): 1550054. http://dx.doi.org/10.1142/s0217751x15500542.

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Diffractive production is considered in the ultrahigh energy region where pomeron exchange amplitudes are transformed into black disk ones due to rescattering corrections. The corresponding corrections in hadron reactions h1 + h3 → h1 + h2 + h3 with small momenta transferred [Formula: see text] are calculated in terms of the K-matrix technique modified for ultrahigh energies. Small values of the momenta transferred are crucial for introducing equations for amplitudes. The three-body equation for hadron diffractive production reaction h1 + h3 → h1 + h2 + h3 is written and solved precisely in the eikonal approach. In the black disk regime final state scattering processes do not change the shapes of amplitudes principally but dump amplitudes by a factor ~ ¼; initial state rescatterings result in additional factor ~ ½. In the resonant disk regime initial and final state scatterings damp strongly the production amplitude that corresponds to σ inel /σ tot → 0 at [Formula: see text] in this mode.

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Badran, R. I. y Dana Al-Masri. "Exploring diffractive features of elastic scattering of 6Li by different target nuclei at different energies". Canadian Journal of Physics 91, n.º 4 (abril de 2013): 355–64. http://dx.doi.org/10.1139/cjp-2012-0466.

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The diffractive aspects of angular distribution have been investigated by analyzing the experimental data for a set of elastic scattering processes of 6Li by different target nuclei at different laboratory energies. The analysis of experimental data of angular distribution for elastic scattering process is performed using both Frahn–Venter and McIntyre models. The theoretical models can reasonably reproduce the general pattern of the data, thus allowing us to extract geometrical parameters from elastic scattering processes. It is found that interpretation of the diffraction features of the data is model-independent. The values of extracted parameters, from both models, are found to be comparable to each other and to those of others. The correlation between the total reaction cross section and the incident laboratory energy for each scattering is discernible and values of total reaction cross section are found to be comparable with those of others.

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Munier, Stéphane. "Diffractive patterns in deep-inelastic scattering and parton genealogy". EPJ Web of Conferences 192 (2018): 00008. http://dx.doi.org/10.1051/epjconf/201819200008.

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We report on our recent observation that the occurrence of diffractive patterns in the scattering of electrons off nuclei obeys the same law as the fluctuations of the height of genealogical trees in branching diffusion processes.

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Tesis sobre el tema "Diffractive scattering processes"

Ozeren, Kemal. "Multiparton scattering amplitudes with heavy quarks : calculational techniques and applications to diffractive processes". Thesis, Durham University, 2008. http://etheses.dur.ac.uk/2291/.

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In this thesis we demonstrate the use of twistor inspired methods in the calculation of gauge theory amplitudes. First, we describe how MHV rules and the BCF recursion relations can be used in QED. Then we apply BGF recursion to the problem of amplitudes with massive fermions in QCD, using the process gg → bbg as an illustration. Central exclusive production is a promising method of revealing new physics at the LHC. Observing Higgs production in this scheme will be hampered by dijet backgrounds. At leading order this background is strongly suppressed by a J(_z) = 0 selection rule. However, at higher orders there is no suppression and so it is important to calculate the contribution to the cross section of these terms. Among the necessary theoretical inputs to this calculation are the loop corrections to gg →bbg and the amplitude describing the emission of an extra gluon in the final state, gg → bbg. We provide analytic formulae for both these ingredients, keeping the full spin and colour information as is required.

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LILIANA, LOSURDO. "Rapidity gap studies in DPE events with the TOTEM-CMS combined apparatus at √s = 8 TeV". Doctoral thesis, Università di Siena, 2018. http://hdl.handle.net/11365/1054153.

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Diffractive scattering processes have two main signatures: one or both incoming protons remain intact after the interaction and one or more rapidity gaps appear as forbidden regions in the rapidity distribution of scattering products. Rapidity gaps are associated to the exchange of pomerons between the interacting protons, the pomeron being described in QCD in terms of an exchange of gluons in a colorless configuration. In the context of diffractive physics, the study of rapidity gaps is then of particular interest. In the work reported in this thesis a study of rapidity gaps has been conducted in Double Pomeron Exchange events produced in pp collisions at √s = 8 TeV, using a dataset collected in July 2012 by the TOTEM experiment at the LHC during a common data taking with the CMS experiment. In DPE events both incoming protons remain intact in the collision and a system of particles is generated in the central zone, separated from the two protons by two rapidity gaps. Thanks to the combined TOTEM-CMS apparatus, which provides an exceptionally large pseudorapidity coverage, the tagging of protons with the TOTEM Roman Pot detectors and the reconstruction of the central system with the CMS apparatus has been performed. The TOTEM T2 telescope also provided the reconstruction of charged particles in the forward region, where no information from CMS is available. The aim of this work was the development of an analysis to study the rapidity gaps in DPE events, and compare them with a sample of DPE events obtained by a Pythia8MBR Monte Carlo simulation. Since such MC sample is based on a pure 2-gluon colorless exchange during the interaction, a deviation of rapidity gap probability could represent an indication of additional exchange not related to pomerons. In this study, an important role was covered by the charged particle tracks reconstructed in the TOTEM T2 telescopes and by final-state stable particles reconstructed and identified by means of a particular algorithm, known as “particle-flow" (PF), combining the information from the CMS subdetectors. They allowed to define in a wide |η| range the two rapidity gaps in DPE event candidates. The evaluation of the size of the rapidity gaps was possible through the direct leading proton measurement by the RP detectors. As first step, an optimization in the selection of PF neutral particles (neutral hadrons and photons) at √s = 8 TeV has been performed in order to suppress most of the detector noise in data, since standard cuts were previously obtained by the CMS Collaboration for data at √s = 7 TeV. The new cuts have been found in each CMS sub-region by using a Zero-Bias sample, collected during the same data taking period of the dataset used for DPE event selection (triggered by the TOTEM RPs). Then, the typical variables for the identification of DPE processes have been introduced: the fractional longitudinal momentum loss of each scattered proton (ξ1,2) reconstructed from the proton tracks; the two values of pseudorapidity ηmin and ηmax (related to the central diffractive system) which characterize the two rapidity gaps; the mass MX of the diffractive system obtained from the RP measurements, and the central mass Mcentral measured from the PF objects in the CMS region. In the next step of this study a selection of DPE event was performed in order to remove/reduce the main sources of background. The dominant background due to elastic events overlapped with pile-up processes has been removed by vetoing on the diagonal (TB/BT) configurations for the protons in the RPs. In order to reduce the pile-up effects in the selected parallel (TT/BB) configurations, we have selected only events with one proton per arm, simultaneously tagged by the two vertical RPs in the 220-station, and with no more than one CMS vertex. Then, by requiring a value of mass of the diffractive system greater than the value of the central mass, it was possible to reject events affected by residual noise and pile-up (NP) effects. After the selection of DPE events, a data driven correction method has been applied bin per bin to the probability distributions of ηmin and ηmax as an iterative procedure in order to correct for NP effects. This procedure has been based on studies on the Zero-Bias sample. In the following step, it was necessary to also consider the contribution of another source of background: the single diffractive process. Detailed studies performed on MC simulation showed that this contribution is dominant (up to about 19%) and is due when a proton produced by the breaking of one of two incoming protons arrives to RP detectors, simulating a leading proton. This contribution has been reduced by requiring activity in the CMS region. Based on MC studies, the iterative method correction has been updated in order to account for the residual SD background. Then, a comparison with MC expectations given by the Pythia8MBR generator was made. Here, a clear enhancement in events with reduced or absent reconstructed rapidity gaps in the very forward regions is observed in DATA, leading to a discrepancy in global normalization of the probability distributions in the central region, where a substantial agreement is found for the shapes. A better agreement between DATA and MC expectations is indeed found in the subsample where forward RGs are required (T2 veto on both sides). This result cannot a priori exclude that the violation of the expected rapidity gaps is due to some other process not characterized by the exchange of colorless objects, or that the MC generator we are considering is not properly modeling the DPE processes. However, further investigation should be performed in order to be sure that the observed behaviour is not due to some subtle residual background effect, or to some detector simulation related effect as well. For instance, it should be interesting to perform a separate study of events with zero and one CMS vertex, which are expected to be characterized by a different background bias.

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Holmberg, Jonas. "Surface integrity on post processed alloy 718 after nonconventional machining". Licentiate thesis, Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-12191.

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There is a strong industrial driving force to find alternative production technologies in order to make the production of aero engine components of superalloys even more efficient than it is today. Introducing new and nonconventional machining technologies allows taking a giant leap to increase the material removal rate and thereby drastically increase the productivity. However, the end result is to meet the requirements set for today's machined surfaces.The present work has been dedicated to improving the knowledge of how the non-conventional machining methods Abrasive Water Jet Machining, AWJM, Laser Beam Machining, LBM, and Electrical Discharge Machining, EDM, affect the surface integrity. The aim has been to understand how the surface integrity could be altered to an acceptable level. The results of this work have shown that both EDM and AWJM are two possible candidates but EDM is the better alternative; mainly due to the method's ability to machine complex geometries. It has further been shown that both methods require post processing in order to clean the surface and to improve the topography and for the case of EDM ageneration of compressive residual stresses are also needed.Three cold working post processes have been evaluated in order to attain this: shot peening, grit blasting and high pressure water jet cleaning, HPWJC. There sults showed that a combination of two post processes is required in order to reach the specified level of surface integrity in terms of cleaning and generating compressive residual stresses and low surface roughness. The method of high pressure water jet cleaning was the most effective method for removing the EDM wire residuals, and shot peening generated the highest compressive residual stresses as well as improved the surface topography.To summarise: the most promising production flow alternative using nonconventional machining would be EDM followed by post processing using HPWJC and shot peening.

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Gautier-Luneau, Isabelle. "Syntheses et etudes structurales de materiaux prepares par voie sol-gel : batio::(3), polysiloxane dope au titane". Toulouse 3, 1988. http://www.theses.fr/1988TOU30037.

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Libros sobre el tema "Diffractive scattering processes"

Diffractive processes in nuclear physics. Oxford: Clarendon Press, 1985.

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Capítulos de libros sobre el tema "Diffractive scattering processes"

OLSSON, J. "DIFFRACTION AND EXCLUSIVE PROCESSES AT HERA". En Elastic And Diffractive Scattering, 292–311. WORLD SCIENTIFIC, 2000. http://dx.doi.org/10.1142/9789812817624_0033.

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Musulmanbekov, G. "DYNAMICAL QUARK STRUCTURE OF HADRONS AND DIFFRACTIVE PROCESSES". En Elastic And Diffractive Scattering, 341–50. WORLD SCIENTIFIC, 2000. http://dx.doi.org/10.1142/9789812817624_0037.

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DAKHNO, L. G. "POMERON IN DIFFRACTIVE PROCESSES γ*(Q2)p → ρ0p AND γ*P → γ*(Q2)P AT LARGE Q2: THE ONSET OF PQCD". En Elastic And Diffractive Scattering, 89–94. WORLD SCIENTIFIC, 2000. http://dx.doi.org/10.1142/9789812817624_0010.

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Blow, David. "Diffraction". En Outline of Crystallography for Biologists. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780198510512.003.0008.

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Diffraction refers to the effects observed when light is scattered into directions other than the original direction of the light, without change of wavelength. An X-ray photon may interact with an electron and set the electron oscillating with the X-ray frequency. The oscillating electron may radiate an X-ray photon of the same wavelength, in a random direction, when it returns to its unexcited state. Other processes may also occur, akin to fluorescence, which emit X-rays of longer wavelengths, but these processes do not give diffraction effects. Just as we see a red card because red light is scattered off the card into our eyes, objects are observed with X-rays because an illuminating X-ray beam is scattered into the X-ray detector. Our eye can analyse details of the card because its lens forms an image on the retina. Since no X-ray lens is available, the scattered X-ray beam cannot be converted directly into an image. Indirect computational procedures have to be used instead. X-rays are penetrating radiation, and can be scattered from electrons throughout the whole scattering object, while light only shows the external shape of an opaque object like a red card. This allows X-rays to provide a truly three-dimensional image. When X-rays pass near an atom, only a tiny fraction of them is scattered: most of the X-rays pass further into the object, and usually most of them come straight out the other side of the whole object. In forming an image, these ‘straight through’ X-rays tell us nothing about the structure, and they are usually captured by a beam stop and ignored. This chapter begins by explaining that the diffraction of light or X-rays can provide a precise physical realization of Fourier’s method of analysing a regularly repeating function. This method may be used to study regularly repeating distributions of scattering material. Beginning in one dimension, examples will be used to bring out some fundamental features of diffraction analysis. Graphic examples of two-dimensional diffraction provide further demonstrations. Although the analysis in three dimensions depends on exactly the same principles, diffraction by a three-dimensional crystal raises additional complications.

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Coppens, Philip. "The Effect of Thermal Vibrations on the Intensities of the Diffracted Beams". En X-Ray Charge Densities and Chemical Bonding. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195098235.003.0004.

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The atoms in a crystal are vibrating with amplitudes determined by the force constants of the crystal’s normal modes. This motion can never be frozen out because of the persistence of zero-point motion, and it has important consequences for the scattering intensities. Since X-ray scattering (and, to a lesser extent, neutron scattering) is a very fast process, taking place on a time scale of 10−18 s, the photon-matter interaction time is much shorter than the period of a lattice vibration, which is of the order Thus, the recorded X-ray scattering pattern is the sum over the scattering of a large number of 1/v, or ≈10−13s. instantaneous states of the crystal. To an extremely good approximation, the scattering averaged over the instantaneous distributions is equivalent to the scattering of the time-averaged distribution of the scattering matter (Stewart and Feil 1980). The structure factor expression for coherent elastic Bragg scattering of X-rays may therefore be written in terms 〈ρ(r)〉, of the thermally averaged electron density: . . . F(H)=∫unit cell〈ρ(r)〉 exp (2πi H ·r) dr (2.1) . . . The smearing of the electron density due to thermal vibrations reduces the intensity of the diffracted beams, except in the forward |S| = 0 direction, for which all electrons scatter in phase, independent of their distribution. The reduction of the intensity of the Bragg peaks can be understood in terms of the diffraction pattern of a more diffuse electron distribution being more compact, due to the inverse relation between crystal and scattering space, discussed in chapter 1. The reduction in intensity due to thermal motion is accompanied by an increase in the incoherent elastic scattering, ensuring conservation of energy. In this respect, thermal motion is much like disorder, with the Bragg intensities representing the average distribution, and the deviations from the average appearing as a continuous, though not uniform, background, generally referred to as thermal diffuse scattering or TDS. A crystal with n atoms per unit cell has 3nN degrees of freedom, N being the number of unit cells in the crystal.

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Glusker, Jenny Pickworth y Kenneth N. Trueblood. "Diffraction". En Crystal Structure Analysis. Oxford University Press, 2010. http://dx.doi.org/10.1093/oso/9780199576340.003.0011.

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A common approach to crystal structure analysis by X-ray diffraction presented in texts that have been written for nonspecialists involves the Bragg equation, and a discussion in terms of “reflection” of X rays from crystal lattice planes (Bragg, 1913). While the Bragg equation, which implies this “reflection,” has proved extremely useful, it does not really help in understanding the process of X-ray diffraction. Therefore we will proceed instead by way of an elementary consideration of diffraction phenomena generally, and then diffraction from periodic structures (such as crystals), making use of optical analogies (Jenkins and White, 1957; Taylor and Lipson, 1964; Harburn et al., 1975). The eyes of most animals, including humans, comprise efficient optical systems for forming images of objects by the recombination of visible radiation scattered by these objects. Many things are, of course, too small to be detected by the unaided human eye, but an enlarged image of some of them can be formed with a microscope—using visible light for objects with dimensions comparable to or larger than the wavelength of this light (about 6 × 10−7 m), or using electrons of high energy (and thus short wavelength) in an electron microscope. In order to “see” the fine details of molecular structure (with dimensions 10−8 to 10−10 m), it is necessary to use radiation of a wavelength comparable to, or smaller than, the dimensions of the distances between atoms. Such radiation is readily available (1) in the X rays produced by bombarding a target composed of an element of intermediate atomic number (for example, between Cr and Mo in the Periodic Table) with fast electrons, or from a synchrotron source, (2) in neutrons from a nuclear reactor or spallation source, or (3) in electrons with energies of 10–50 keV. Each of these kinds of radiation is scattered by the atoms of the sample, just as is ordinary light, and if we could recombine this scattered radiation, as a microscope can, we could form an image of the scattering matter.

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Coppens, Philip. "Fourier Methods and Maximum Entropy Enhancement". En X-Ray Charge Densities and Chemical Bonding. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195098235.003.0007.

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Image formation in diffraction is no different from image formation in other branches of optics, and it obeys the same mathematical equations. However, the nonexistence of lenses for X-ray beams makes it necessary to use computational methods to achieve the Fourier transform of the diffraction pattern into the image. The phase information required for this process is, in general, not available from the diffraction experiment, even though progress has been made in deriving phases from multiple-beam effects. This is the phase problem, the paramount issue in crystal structure analysis, which also affects charge density analysis of noncentrosymmetric structures. For centrosymmetric space groups, the independent-atom model is a sufficiently close approximation to allow calculation of the signs for all but a few very weak reflections. Images of the charge density are indispensable for qualitative understanding of chemical bonding, and play a central role in charge density analysis. In this chapter, we will discuss methods for imaging the experimental charge density, and define the functions used in the imaging procedure. According to Eq. (1.22), the structure factor F(H) is the Fourier transform of the electron density ρ(r) in the crystallographic unit cell. The electron density p(r) is then obtained by the inverse Fourier transformation, or . . . ρ(r)=∫F(H) exp (−2πi H ·r) dH (5.1) . . . in which F(H) are the (complex) structure factors corrected for the anomalous scattering discussed in chapter 1.

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Krishnan, Kannan M. "Transmission and Analytical Electron Microscopy". En Principles of Materials Characterization and Metrology, 552–692. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198830252.003.0009.

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Transmission electron microscopy provides information on all aspects of the microstructure — structural, atomic, chemical, electronic, magnetic, etc. — at the highest spatial resolution in physical and biological materials, with applications ranging from fundamental studies to process metrology in the semiconductor industry. Developments in correcting electron-optical aberrations have improved TEM resolution to sub-Å levels. Coherent Bragg scattering (diffraction), incoherent Rutherford scattering (atomic mass), and interference (phase) are some contrast mechanisms in TEM. For phase contrast, optimum imaging is observed at the Scherzer defocus. Magnetic domains are imaged in Fresnel, Foucault, or differential phase contrast (DPC) modes. Off-axis electron holography measures phase shifts of the electron wave, and is affected by magnetic and electrostatic fields of the specimen. In scanning-transmission (STEM) mode, a focused electron beam is scanned across the specimen to sequentially form an image; a high-angle annular dark field detector gives Z-contrast images with elemental specificity and atomic resolution. Series of (S)TEM images, recorded every one or two degrees about a tilt axis, over as large a tilt-range as possible, are back-projected to reconstruct a 3D tomographic image. Inelastically scattered electrons, collected in the forward direction, form the energy-loss spectrum (EELS), and reveal the unoccupied local density of states, partitioned by site symmetry, nature of the chemical species, and the angular momentum of the final state. Energy-lost electrons are imaged by recording them, pixel-by-pixel, as a sequence of spectra (spectrum imaging), or by choosing electrons that have lost a specific energy (energy-filtered TEM). De-excitation processes (characteristic X-ray emission) are detected by energy dispersive methods, providing compositional microanalysis, including chemical maps. Overall, specimen preparation methods, even with many recent developments, including focused ion beam milling, truly limit applications of TEM.

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Coppens, Philip. "X-ray Diffraction and the Electrostatic Potential". En X-Ray Charge Densities and Chemical Bonding. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195098235.003.0010.

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The distribution of positive and negative charge in a crystal fully defines physical properties like the electrostatic potential and its derivatives, the electric field, and the gradient of the electric field. The electrostatic potential at a point in space, defined as the energy required to bring a positive unit of charge from infinite distance to that point, is an important function in the study of chemical reactivity. As electrostatic forces are relatively long-range forces, they determine the path along which an approaching reactant will travel towards a molecule. A nucleophilic reagent will first be attracted to the regions where the potential is positive, while an electrophilic reagent will approach the negative regions of the molecule. As the electrostatic potential is of importance in the study of intermolecular interactions, it has received considerable attention during the past two decades (see, e.g., articles on the molecular potential of biomolecules in Politzer and Truhlar 1981). It plays a key role in the process of molecular recognition, including drug-receptor interactions, and is an important function in the evaluation of the lattice energy, not only of ionic crystals. This chapter deals with the evaluation of the electrostatic potential and its derivatives by X-ray diffraction. This may be achieved either directly from the structure factors, or indirectly from the experimental electron density as described by the multipole formalism. The former method evaluates the properties in the crystal as a whole, while the latter gives the values for a molecule or fragment “lifted” out of the crystal. Like other properties derived from the charge distribution, the experimental electrostatic potential will be affected by the finite resolution of the experimental data set. But as the contribution of a structure factor F(H) to the potential is proportional to H−2, as shown below, convergence is readily achieved. A summary of the dependence of electrostatic properties of the magnitude of the scattering vector H is given in Table 8.1, which shows that the electrostatic potential is among the most accessible of the properties listed.

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Jolivet, Jean-Pierre. "Precipitation: Structures and Mechanisms". En Metal Oxide Nanostructures Chemistry. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190928117.003.0007.

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The formation of a solid, and especially an oxide, from soluble metal complexes is usually called “precipitation.” This term is a generic name that includes a set of complex and intricate phenomena. The process is governed by thermodynamic, structural, and kinetic contingencies, which should be examined in detail to understand the role of synthesis conditions and their influence on the solid obtained. The chemistry of the process involves a condensation reaction, olation or oxolation, between uncharged hydroxylated complexes. It forms particles of widely variable size over the nano- to micrometric range. These particles are portions of a solid identifiable in using techniques such as X-ray diffraction, absorption, and diffusion, electron microscopy, light-scattering, and various spectroscopies. Of course, these particles have the properties typical of the corresponding bulky solid, but they may be modulated because of the size effect, especially in the nanometric range (Chap. 1). Because of their small size, these objects have a large surface area highlighting their surface physicochemistry, such as ability to disperse in aqueous or nonaqueous medium, to aggregate, and to fix various species from solution, that allows the surface energy to be controlled to adjust the shape and size of these objects (Chap. 5). The crystal structure of polymorphic solids can also be controlled by the choice of the pathway of their formation. Thus, knowledge of the processes involved allows us to exploit the large versatility of the nanostructures synthesized in solution. This chapter has two main objectives. The first is to show that the crystalline structure of the solid may in many cases be anticipated from the characteristics of the precursor in solution, such as functionality, geometry, reactivity, and electron configuration. This point concerns the structural aspect of the formation of the solid. The second objective is to understand why precipitation forms small particles, generally of nano- or micrometric size, and how the crystallization mechanism influences their morphology. These questions concern the kinetics and dynamics of the precipitation phenomenon.

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Actas de conferencias sobre el tema "Diffractive scattering processes"

Boussarie, Renaud, Andrey Grabovsky, Dmitry Yu Ivanov, Lech Szymanowski y Samuel Wallon. "NLO exclusive diffractive processes with saturation". En XXV International Workshop on Deep-Inelastic Scattering and Related Subjects. Trieste, Italy: Sissa Medialab, 2017. http://dx.doi.org/10.22323/1.297.0062.

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Watt, Graeme. "Exclusive Diffractive Processes within the Dipole Picture". En Proceedings of the XVI International Workshop on Deep-Inelastic Scattering and Related Topics. Amsterdam: Science Wise Publishing, 2008. http://dx.doi.org/10.3360/dis.2008.91.

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Kowalski, Henri. "Saturation Model for Exclusive Diffractive Processes, DVCS and F2at HERA". En 15th International Workshop on Deep-Inelastic Scattering and Related Subjects. Amsterdam: Science Wise Publishing, 2007. http://dx.doi.org/10.3360/dis.2007.50.

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BRONA, Grzegorz. "Diffractive processes in pp collisions at 7 TeV measured with the CMS experiment". En XXIII International Workshop on Deep-Inelastic Scattering. Trieste, Italy: Sissa Medialab, 2016. http://dx.doi.org/10.22323/1.247.0067.

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Foster, Andrew. "Status and Prospects of measurements of exclusive and diffractive processes with the ATLAS detector". En XXVI International Workshop on Deep-Inelastic Scattering and Related Subjects. Trieste, Italy: Sissa Medialab, 2018. http://dx.doi.org/10.22323/1.316.0045.

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Blok, Boris. "DGLAP versus perturbative Pomeron in hard diffractive processes large momentum transfer at HERA and LHC". En XVIII International Workshop on Deep-Inelastic Scattering and Related Subjects. Trieste, Italy: Sissa Medialab, 2010. http://dx.doi.org/10.22323/1.106.0057.

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Deisenroth, David C., Leonard M. Hanssen y Sergey Mekhontsev. "High temperature reflectometer for spatially resolved spectral directional emissivity of laser powder bed fusion processes". En Reflection, Scattering, and Diffraction from Surfaces VII, editado por Leonard M. Hanssen. SPIE, 2020. http://dx.doi.org/10.1117/12.2568179.

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Lading, Lars y John Earnshaw. "Surface Light Scattering: Integrated Technology and Signal Processing". En Photon Correlation and Scattering. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/pcs.1996.wb.2.

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Surface light scattering has matured to the extent that it is now possible to envisage the possibility of applying the technique in more demanding environments like microgravity or industrial process monitoring. Such situations will require more compact and robust system designs than the ones that till now have been used in laboratory studies. The generic elements of a system are identified and their impact on system performance is given based on the model presented in.1 We note that proper use of a grating provides a calibration that is independent of the wavelength. This facilitates the use of cheap unstabilised semiconductor lasers2, but the optics may be rather delicate. An implementation with holographic optical elements gives a mechanically very simple and robust system (Fig. 1)3. A concept based on fully integrated optics is obtained by combining a 2D waveguide with diffractive structures for coupling light out of and into the optical “chip”. The waveguide would be combined with the lower hologram. Laser and detectors could be imbedded in the waveguide. Such a system implies a number of conflicting requirements of the integrated optics. A potential solution based on silicon and a rare earth laser is presented. The complexity of the system may be further reduced by the application of intracavity diffractive structures (Fig. 2). By doing this, we essentially eliminate the need for the very high diffraction efficiency required with external diffractive structures and the laser itself may also be used as a detector. However, the simple configuration requires a spacing to the surface that is fixed within a fraction of the optical wavelength.

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Deckelmann, Maximilian, Mark Sippel, Konstantin Lomakin, Gerald Gold, Klaus Helmreich, Bernhard Schmauss, Max Koeppel y Stefan Werzinger. "Using coherent optical frequency domain reflectometry to assist the additive manufacturing process of structures for radio frequency applications". En Reflection, Scattering, and Diffraction from Surfaces VI, editado por Leonard M. Hanssen. SPIE, 2018. http://dx.doi.org/10.1117/12.2320944.

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Baskin, L. M., M. M. Kabardov y N. M. Sharkova. "Fano resonances in the process of multichannel scattering in quantum waveguides with narrows". En Days on Diffraction 2014 (DD). IEEE, 2014. http://dx.doi.org/10.1109/dd.2014.7036419.

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