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

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.

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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The study, titled "Electron spin resonance (ESR) dose measurement in the bone of Hiroshima A-bomb victim," was published April 27 in the journal (http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0192444) PLOS One.
T Pierce, "High resolution magnetic microstructure imaging using secondary electron spin polarization analysis in a scanning electron microscope," Journal of Microscopy, vol.
We apologize to our readers and the antropology Javier Andres Sandoval Andrade because in the Vol 15 Issue 2 year 2011 in the Earth Science Research Journal (ESRJ) published the article entitled "Quaternary dating by electron spin resonance (ESR) applied to human tooth enamel" which there is an incorrect footnote in the Figure 1 as it is not quoted from (Groot, 1992), but it is taken from the undergraduate thesis entitled DATACION DE RESTOS HUMANOS PREHISPANICOS A TRAVES DE ESMALTE DENTAL USANDO RESONANCIA PARAMAGNETICA ELECTRONICA (EPR) (2010).
To use a spintronic device to detect a magnetic field, technicians vary the frequency of the radio waves hitting it; when the frequency matches the rate of electron spin in the material, the direction of the spin flips, and that can be detected.
But according to the 2007 French study, published in the scientific journalNature Physics, the team used a "Femtosecond" laser, which produces super-fast laser bursts to alter electron spin, speeding up the read/write process.
Using Electron Spin Resonance (ESR) spectroscopy, DuPont has developed highly sensitive methods for detecting the metal chelating and radical scavenging activity of plant extracts.
"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.

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