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Electron Magnetic Circular Dichroism
Electron magnetic circular dichroism (EMCD) (also known as electron energy-loss magnetic chiral dichroism) is the EELS equivalent of XMCD. The effect was first proposed in 2003 and experimentally confirmed in 2006 by the group of Prof. Peter Schattschneider at the Vienna University of Technology. Similarly to XMCD, EMCD is a difference spectrum of two EELS spectra taken in a magnetic field with opposite helicities. Under appropriate scattering conditions virtual photons with specific circular polarizations can be absorbed, giving rise to spectral differences. The largest difference is expected between the case where one virtual photon with left circular polarization and one with right circular polarization are absorbed. By closely analyzing the difference in the EMCD spectrum, information can be obtained on the magnetic properties of the atom, such as its spin and orbital magnetic moment. In the case of transition metals such as iron, cobalt, and nickel, the absorption spectra f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EELS
Eels are ray-finned fish belonging to the order Anguilliformes (), which consists of eight suborders, 19 families, 111 genera, and about 800 species. Eels undergo considerable development from the early larval stage to the eventual adult stage and are usually predators. The term "eel" is also used for some other eel-shaped fish, such as electric eels (genus ''Electrophorus''), spiny eels (family Mastacembelidae), swamp eels (family Synbranchidae), and deep-sea spiny eels (family Notacanthidae). However, these other clades evolved their eel-like shapes independently from the true eels. Eels live both in salt and fresh water, and some species are catadromous. Description Eels are elongated fish, ranging in length from in the one-jawed eel (''Monognathus ahlstromi'') to in the slender giant moray. Adults range in weight from to well over . They possess no pelvic fins, and many species also lack pectoral fins. The dorsal and anal fins are fused with the caudal fin, formin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cobalt
Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal. Cobalt-based blue pigments ( cobalt blue) have been used since ancient times for jewelry and paints, and to impart a distinctive blue tint to glass, but the color was for a long time thought to be due to the known metal bismuth. Miners had long used the name ''kobold ore'' (German for ''goblin ore'') for some of the blue-pigment-producing minerals; they were so named because they were poor in known metals, and gave poisonous arsenic-containing fumes when smelted. In 1735, such ores were found to be reducible to a new metal (the first discovered since ancient times), and this was ultimately named for the ''kobold''. Today, some cobalt is produced specifically from one of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Circular Dichroism
Magnetic circular dichroism (MCD) is the differential absorption of left and right circularly polarized (LCP and RCP) light, induced in a sample by a strong magnetic field oriented parallel to the direction of light propagation. MCD measurements can detect transitions which are too weak to be seen in conventional optical absorption spectra, and it can be used to distinguish between overlapping transitions. Paramagnetic systems are common analytes, as their near-degenerate magnetic sublevels provide strong MCD intensity that varies with both field strength and sample temperature. The MCD signal also provides insight into the symmetry of the electronic levels of the studied systems, such as metal ion sites. History It was first shown by Faraday that optical activity (the Faraday effect) could be induced in matter by a longitudinal magnetic field (a field in the direction of light propagation). The development of MCD really began in the 1930s when a quantum mechanical theory of M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron Vortex Beam
Electrons in free space can carry quantized orbital angular momentum (OAM) projected along the direction of propagation. This orbital angular momentum corresponds to helical wavefronts, or, equivalently, a phase proportional to the azimuthal angle. Electron beams with quantized orbital angular momentum are also called electron vortex beams. Theory An electron in free space travelling at non- relativistic speeds, follows the Schrödinger equation for a free particle, that is i\hbar\frac \Psi(\mathbf,t) = \frac\nabla^2 \Psi(\mathbf,t), where \hbar is the reduced Planck constant, \Psi(\mathbf r , t) is the single-electron wave function, m its mass, \mathbf r the position vector, and t is time. This equation is a type of wave equation and when written in the Cartesian coordinate system (x,y,z), the solutions are given by a linear combination of plane waves, in the form of \Psi_(\mathbf,t)\propto e^ where \mathbf is the linear momentum and E(\mathbf) is the electron energy, given ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beamline
In accelerator physics, a beamline refers to the trajectory of the beam of particles, including the overall construction of the path segment (guide tubes, diagnostic devices) along a specific path of an accelerator facility. This part is either * the line in a linear accelerator along which a beam of particles travels, or * the path leading from particle generator (e.g. a cyclic accelerator, synchrotron light sources, cyclotrons, or spallation sources) to the experimental end-station. Beamlines usually end in experimental stations that utilize particle beams or synchrotron light obtained from a synchrotron, or neutrons from a spallation source or research reactor. Beamlines are used in experiments in particle physics, materials science, life science, chemistry, and molecular biology, but can also be used for irradiation tests or to produce isotopes. Beamline in a particle accelerator In particle accelerators the beamline is usually housed in a tunnel and/or underground, c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmission Electron Microscopy
Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a grid. An image is formed from the interaction of the electrons with the sample as the beam is transmitted through the specimen. The image is then magnified and focused onto an imaging device, such as a fluorescent screen, a layer of photographic film, or a sensor such as a scintillator attached to a charge-coupled device. Transmission electron microscopes are capable of imaging at a significantly higher resolution than light microscopes, owing to the smaller de Broglie wavelength of electrons. This enables the instrument to capture fine detail—even as small as a single column of atoms, which is thousands of times smaller than a resolvable object seen in a light microscope. Transmission electron microscopy is a major analytical method i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atomic Number
The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every atom of that element. The atomic number can be used to uniquely identify ordinary chemical elements. In an ordinary uncharged atom, the atomic number is also equal to the number of electrons. For an ordinary atom, the sum of the atomic number ''Z'' and the neutron number ''N'' gives the atom's atomic mass number ''A''. Since protons and neutrons have approximately the same mass (and the mass of the electrons is negligible for many purposes) and the mass defect of the nucleon binding is always small compared to the nucleon mass, the atomic mass of any atom, when expressed in unified atomic mass units (making a quantity called the "relative isotopic mass"), is within 1% of the whole number ''A''. Atoms with the same atomic number but dif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron Configuration
In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. For example, the electron configuration of the neon atom is , meaning that the 1s, 2s and 2p subshells are occupied by 2, 2 and 6 electrons respectively. Electronic configurations describe each electron as moving independently in an orbital, in an average field created by all other orbitals. Mathematically, configurations are described by Slater determinants or configuration state functions. According to the laws of quantum mechanics, for systems with only one electron, a level of energy is associated with each electron configuration and in certain conditions, electrons are able to move from one configuration to another by the emission or absorption of a quantum of energy, in the form of a photon. Knowledge of the electron configuration of different atoms is useful in understanding the structu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-ray Notation
X-ray notation is a method of labeling atomic orbitals that grew out of X-ray science. Also known as IUPAC notation, it was adopted by the International Union of Pure and Applied Chemistry in 1991 as a simplification of the older Siegbahn notation. In X-ray notation, every principal quantum number is given a letter associated with it. In many areas of physics and chemistry, atomic orbitals are described with spectroscopic notation (1s, 2s, 2p, 3s, 3p, etc.), but the more traditional X-ray notation is still used with most X-ray spectroscopy techniques including AES and XPS. Conversion Uses *X-ray sources are classified by the type of material and orbital used to generate them. For example, CuKα X-rays are emitted from the K orbital of copper. *X-ray absorption is reported as which orbital absorbed the x-ray photon. In EXAFS and XMCD the L-edge or the L absorption edge is the point where the L orbital begins to absorb x-rays. *Auger peaks are identified with three orbital defini ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to react with air under standard conditions because a passivation layer of nickel oxide forms on the surface that prevents further corrosion. Even so, pure native nickel is found in Earth's crust only in tiny amounts, usually in ultramafic rocks, and in the interiors of larger nickel–iron meteorites that were not exposed to oxygen when outside Earth's atmosphere. Meteoric nickel is found in combination with iron, a reflection of the origin of those elements as major end products of supernova nucleosynthesis. An iron–nickel mixture is thought to compose Earth's outer and inner cores. Use of nickel (as natural meteoric nickel–iron alloy) has been traced as far back as 3500 BCE. Nickel was first isolated and classified as an e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in front of oxygen (32.1% and 30.1%, respectively), forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust. In its metallic state, iron is rare in the Earth's crust, limited mainly to deposition by meteorites. Iron ores, by contrast, are among the most abundant in the Earth's crust, although extracting usable metal from them requires kilns or furnaces capable of reaching or higher, about higher than that required to smelt copper. Humans started to master that process in Eurasia during the 2nd millennium BCE and the use of iron tools and weapons began to displace copper alloys, in some regions, only around 1200 BCE. That event is considered the transition from the Bronze Age to the Iron A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
