electron spin


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Related to electron spin: electron spin resonance

Electron spin

That property of an electron which gives rise to its angular momentum about an axis within the electron. Spin is one of the permanent and basic properties of the electron. Both the spin and the associated magnetic dipole moment of the electron were postulated by G. E. Uhlenbeck and S. Goudsmit in 1925 as necessary to allow the interpretation of many observed effects, among them the so-called anomalous Zeeman effect, the existence of doublets (pairs of closely spaced lines) in the spectra of the alkali atoms, and certain features of x-ray spectra. See Spin (quantum mechanics)

The spin quantum number is s, which is always ½. This means that the component of spin angular momentum along a preferred direction, such as the direction of a magnetic field, is ±½ℏ, where ℏ = h/2&pgr; and h is Planck's constant. The spin angular momentum of the electron is not to be confused with the orbital angular momentum of the electron associated with its motion about the nucleus. In the latter case the maximum component of angular momentum along a preferred direction is lℏ, where l is the angular momentum quantum number and may be any positive integer or zero. See Angular momentum, Quantum numbers

Electron magnetic moment

The electron has a magnetic dipole moment by virtue of its spin. The approximate value of the dipole moment is the Bohr magneton μ0 which is equal, in SI units, to eh/4&pgr;m = 9.27 × 10-24 joule/tesla, where e is the electron charge measured in coulombs, and m is the mass of the electron. The orbital motion of the electron also gives rise to a magnetic dipole moment μl that is equal to μ0 when l = 1. See Magneton

The orbital magnetic moment of an electron can readily be deduced with the use of the classical statements of electromagnetic theory in quantum-mechanical theory; the simple classical analog of a current flowing in a loop of wire describes the magnetic effects of an electron moving in an orbit. The spin of an electron and the magnetic properties associated with it are, however, not possible to understand from a classical point of view.

In the Landé g factor, g is defined as the negative ratio of the magnetic moment, in units of μ0, to the angular momentum, in units of ℏ. For the orbital motion of an electron, gl = 1. For the spin of the electron the appropriate g value is gs ≃ 2; that is, unit spin angular momentum produces twice the magnetic moment that unit orbital angular momentum produces. The total electronic magnetic moment of an atom depends on the state of coupling between the orbital and spin angular momenta of the electron.

Atomic beam measurements

With the development of spectroscopy by the atomic beam method, a new order of precision in the measurement of the frequencies of spectral lines became possible. By using the atomic-beam techniques, it became possible to measure gs/gl directly, with the result gs/gl = 2(1.001168 ± 0.000005). The magnetic moment of the electron therefore is not μ0 but 1.001168μ0, or equivalently the g factor of the electron departs from 2 by the so-called g factor anomaly defined as a = (g2 - 2)/2 so that μ = (1 + a)0. Thus the first molecular beam work gave a = 0.001168. See Molecular beams

Calculation of g-factor anomaly

It is not possible to give a qualitative description of the effects which give rise to the g-factor anomaly of the electron. The detailed theoretical calculation of the quantity is in the domain of quantum electrodynamics, and involves the interaction of the zero-point oscillation of the electromagnetic field with the electron. Comparison of theoretical determination of a with its experimental measurement constitutes the most accurate and direct existing test of the theory of quantum electrodynamics. See Atomic structure and spectra, Gyromagnetic ratio, Quantum electrodynamics, Quantum mechanics

electron spin

[i′lek‚trän ′spin]
(quantum mechanics)
That property of an electron which gives rise to its angular momentum about an axis within the electron.
References in periodicals archive ?
The Delft scientists have now shown that a single electron spin and a single photon can be coupled on a silicon chip.
We have demonstrated that a long conduction electron spin lifetime in metallic-like material made up of carbon nanospheres can be achieved at room temperature.
Presentamos excusas a nuestros lectores y al antropOlogo Javier AndrEs Sandoval Andrade puesto que en el Vol 15 No 2 del 2011 de la revista Earth Science research Journal (ESRJ) se publico el articulo titulado "Quaternary dating by electron spin resonance (ESR) applied to human tooth enamel" en el cual no se hace un correcto pie de pagina de la figura 1, ya que no es tomada de (Groot, 1992) como reza la misma, sino que es tomada de la tesis de pregrado titulada DATACION DE RESTOS HUMANOS PREHISPANICOS A TRAVES DE ESMALTE DENTAL USANDO RESONANCIA PARAMAGNETICA ELECTRONICA (EPR) (2010).
Aiming to use electron spins for storing, transporting and processing information, researchers from IBM (NYSE:IBM) and scientists at ETH Zurich revealed the first-ever direct mapping of the formation of a persistent spin helix in a semiconductor.
The IBM scientists used ultra short laser pulses to monitor the evolution of thousands of electron spins that were created simultaneously in a very small spot, said Gian Salis, co-author of the Nature paper and a scientist in the Physics of Nanoscale Systems research group at IBM Research.
This is normally called electron spin resonance; with antimatter we call it positron spin resonance," says Mike Hayden, professor of physics at Simon Fraser University and an ALPHA team member.
EMR, also known as electron paramagnetic resonance (EPR) and as electron spin resonance (ESR), was first introduced more than 60 years ago, developed simultaneously but independently in Russia and England.
John Morton at Oxford University and others, has successfully generated and detected quantum entanglement between electron spin and nuclear spin in phosphorus impurities added to silicon.
The field of spintronics is devoted to create, store, manipulate at a given location, and transport coherent electron spin states through dilute magnetic semiconductors and conventional semiconductor heterostructure [1].
They consider such topics as the non-equilibrium magnetism of single-domain particles for characterizing magnetic nanomaterials, site disorder and finite size effects in rare-earth manganites, processing and the properties of thin manganite films, studying magnetic properties of semiconductors and nanomaterials by different theoretical methods, obtaining magnetic and electric information on organic systems using electron spin resonance, and the orbital dilution effect in the Mott insulating system.
In this book, novel results obtained by physicochemical methods, especially electron spin resonance spectroscopy, are considered for various polymers.
Electron spin resonance (ESR) spectroscopy showed that only MK-1 (n = 1), as well as GGF (n = 7) and GFF (n = 8) which had lower cytotoxicity, produced radicals, suggesting the lack of connection between cytotoxicity and radical production.

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