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Fermi Contact Term
The Fermi contact interaction is the magnetic interaction between an electron and an atomic nucleus. Its major manifestation is in electron paramagnetic resonance and nuclear magnetic resonance spectroscopies, where it is responsible for the appearance of isotropic hyperfine coupling. This requires that the electron occupy an s-orbital. The interaction is described with the parameter ''A'', which takes the units megahertz. The magnitude of ''A'' is given by this relationships : A = -\frac \pi \left \langle \boldsymbol_n \cdot \boldsymbol_e \right \rangle , \Psi (0), ^2\qquad \mbox and : A = -\frac \mu_0 \left \langle \boldsymbol_n \cdot \boldsymbol_e \right \rangle , \Psi(0), ^2, \qquad \mbox where ''A'' is the energy of the interaction, ''μ''''n'' is the nuclear magnetic moment, ''μ''''e'' is the electron magnetic dipole moment, Ψ(0) is the value of the electron wavefunction at the nucleus, and \left\langle \cdots \right\rangle denotes the quantum mechanical spin coupling. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetism
Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments. Magnetism is one aspect of the combined phenomena of electromagnetism. The most familiar effects occur in ferromagnetic materials, which are strongly attracted by magnetic fields and can be magnetized to become permanent magnets, producing magnetic fields themselves. Demagnetizing a magnet is also possible. Only a few substances are ferromagnetic; the most common ones are iron, cobalt, and nickel and their alloys. The rare-earth metals neodymium and samarium are less common examples. The prefix ' refers to iron because permanent magnetism was first observed in lodestone, a form of natural iron ore called magnetite, Fe3O4. All substances exhibit some type of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetostatics
Magnetostatics is the study of magnetic fields in systems where the currents are steady (not changing with time). It is the magnetic analogue of electrostatics, where the electric charge, charges are stationary. The magnetization need not be static; the equations of magnetostatics can be used to predict fast Magnetization reversal, magnetic switching events that occur on time scales of nanoseconds or less. Magnetostatics is even a good approximation when the currents are not static – as long as the currents do not alternating current, alternate rapidly. Magnetostatics is widely used in applications of micromagnetics such as models of magnetic storage devices as in computer memory. Applications Magnetostatics as a special case of Maxwell's equations Starting from Maxwell's equations and assuming that charges are either fixed or move as a steady current \mathbf, the equations separate into two equations for the electric field (see electrostatics) and two for the magnetic fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Dipole
In electromagnetism, a magnetic dipole is the limit of either a closed loop of electric current or a pair of poles as the size of the source is reduced to zero while keeping the magnetic moment constant. It is a magnetic analogue of the electric dipole, but the analogy is not perfect. In particular, a true magnetic monopole, the magnetic analogue of an electric charge, has never been observed in nature. However, magnetic monopole quasiparticles have been observed as emergent properties of certain condensed matter systems. Moreover, one form of magnetic dipole moment is associated with a fundamental quantum property—the spin of elementary particles. Because magnetic monopoles do not exist, the magnetic field at a large distance from any static magnetic source looks like the field of a dipole with the same dipole moment. For higher-order sources (e.g. quadrupoles) with no dipole moment, their field decays towards zero with distance faster than a dipole field does. External mag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John Wiley & Sons
John Wiley & Sons, Inc., commonly known as Wiley (), is an American multinational publishing company founded in 1807 that focuses on academic publishing and instructional materials. The company produces books, journals, and encyclopedias, in print and electronically, as well as online products and services, training materials, and educational materials for undergraduate, graduate, and continuing education students. History The company was established in 1807 when Charles Wiley opened a print shop in Manhattan. The company was the publisher of 19th century American literary figures like James Fenimore Cooper, Washington Irving, Herman Melville, and Edgar Allan Poe, as well as of legal, religious, and other non-fiction titles. The firm took its current name in 1865. Wiley later shifted its focus to scientific, technical, and engineering subject areas, abandoning its literary interests. Wiley's son John (born in Flatbush, New York, October 4, 1808; died in East Orange, New Je ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John David Jackson (physicist)
John David Jackson (January 19, 1925 – May 20, 2016) was a Canadian–American physics professor at the University of California, Berkeley and a faculty senior scientist emeritus at Lawrence Berkeley National Laboratory. A theoretical physicist, he was a member of the United States National Academy of Sciences, National Academy of Sciences, and is well known for numerous publications and summer-school lectures in nuclear and particle physics, as well as his Classical Electrodynamics (book), widely used graduate text on classical electrodynamics. Education Born in London, Ontario, Canada, Jackson attended the University of Western Ontario, receiving a B.Sc. in honors physics and mathematics in 1946. He went on to graduate study at MIT, where he worked under Victor Weisskopf, completing his Ph.D. thesis in 1949. Academic career Jackson held academic appointments successively at McGill University, thanks to Philip Russell Wallace, a prominent Canadian theoretical physicist, (Ja ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zeitschrift Für Physik
''Zeitschrift für Physik'' (English: ''Journal for Physics'') is a defunct series of German peer-reviewed physics journals established in 1920 by Springer Berlin Heidelberg. The series stopped publication in 1997, when it merged with other journals to form the new ''European Physical Journal'' series. It had grown to four parts over the years. History *''Zeitschrift für Physik'' (1920–1975 ), The first three issues were published as a supplement to '' Verhandlungen der Deutschen Physikalischen Gesellschaft''. The journal split in parts A and B in 1975. :*''Zeitschrift für Physik A'' (1975–1997). The original subtitle was ''Atoms and Nuclei'' (). In 1986, it split in ''Zeitschrift für Physik A: Atomic Nuclei'' () and ''Zeitschrift für Physik D''. ''Zeitschrift für Physik A'' now continues as the ''European Physical Journal A''. :*''Zeitschrift für Physik B'' (1975–1997). This is the result of the split of ''Zeitschrift für Physik'' and the merger of ''Ph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enrico Fermi
Enrico Fermi (; 29 September 1901 – 28 November 1954) was an Italian (later naturalized American) physicist and the creator of the world's first nuclear reactor, the Chicago Pile-1. He has been called the "architect of the nuclear age" and the "architect of the atomic bomb". He was one of very few physicists to excel in both theoretical physics and experimental physics. Fermi was awarded the 1938 Nobel Prize in Physics for his work on induced radioactivity by neutron bombardment and for the discovery of transuranium elements. With his colleagues, Fermi filed several patents related to the use of nuclear power, all of which were taken over by the US government. He made significant contributions to the development of statistical mechanics, Quantum mechanics, quantum theory, and nuclear physics, nuclear and particle physics. Fermi's first major contribution involved the field of statistical mechanics. After Wolfgang Pauli formulated his Pauli exclusion principle, exclusion pri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saunders College Publishing
Saunders is an American academic publisher based in the United States. It is currently an imprint of Elsevier. Formerly independent, the W. B. Saunders company was acquired by CBS in 1968, who added it to their publishing division Holt, Rinehart & Winston. When CBS left the publishing field in 1986, it sold the academic publishing units to Harcourt Brace Jovanovich. Harcourt was acquired by Reed Elsevier in 2001. . . Retrieved May 2, 2015. W. B. Saunders published the |
Molecular Orbital
In chemistry, a molecular orbital is a mathematical function describing the location and wave-like behavior of an electron in a molecule. This function can be used to calculate chemical and physical properties such as the probability of finding an electron in any specific region. The terms ''atomic orbital'' and ''molecular orbital'' were introduced by Robert S. Mulliken in 1932 to mean ''one-electron orbital wave functions''. At an elementary level, they are used to describe the ''region'' of space in which a function has a significant amplitude. In an isolated atom, the orbital electrons' location is determined by functions called atomic orbitals. When multiple atoms combine chemically into a molecule, the electrons' locations are determined by the molecule as a whole, so the atomic orbitals combine to form molecular orbitals. The electrons from the constituent atoms occupy the molecular orbitals. Mathematically, molecular orbitals are an approximate solution to the Schrödin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
J-coupling Fermi Contact Mechanism
In nuclear chemistry and nuclear physics, ''J''-couplings (also called spin-spin coupling or indirect dipole–dipole coupling) are mediated through chemical bonds connecting two spins. It is an indirect interaction between two nuclear spins that arises from hyperfine interactions between the nuclei and local electrons. In NMR spectroscopy, ''J''-coupling contains information about relative bond distances and angles. Most importantly, ''J''-coupling provides information on the connectivity of chemical bonds. It is responsible for the often complex splitting of resonance lines in the NMR spectra of fairly simple molecules. ''J''-coupling is a frequency ''difference'' that is not affected by the strength of the magnetic field, so is always stated in Hz. Vector model and manifestations for chemical structure assignments The origin of ''J''-coupling can be visualized by a vector model for a simple molecule such as hydrogen fluoride (HF). In HF, the two nuclei have spin . Four states ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron
The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no known components or substructure. The electron's mass is approximately 1/1836 that of the proton. Quantum mechanical properties of the electron include an intrinsic angular momentum ( spin) of a half-integer value, expressed in units of the reduced Planck constant, . Being fermions, no two electrons can occupy the same quantum state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of both particles and waves: They can collide with other particles and can be diffracted like light. The wave properties of electrons are easier to observe with experiments than those of other particles like neutrons and protons because electrons have a lower mass and hence a longer de Broglie wavele ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
