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- Q904043 subject Q5724991.
- Q904043 subject Q6425689.
- Q904043 subject Q7162170.
- Q904043 subject Q8595495.
- Q904043 subject Q9041630.
- Q904043 abstract "In magnetic resonance, a spin echo is the refocusing of spin magnetisation by a pulse of resonant electromagnetic radiation. Modern nuclear magnetic resonance (NMR) and magnetic resonance imaging make use of this effect.The NMR signal observed following an initial excitation pulse decays with time due to both spin relaxation and any inhomogeneous effects which cause different spins in the sample to precess at different rates. The first of these, relaxation, leads to an irreversible loss of magnetisation. However, the inhomogeneous dephasing can be removed by applying a 180° inversion pulse that inverts the magnetisation vectors. Examples of inhomogeneous effects include a magnetic field gradient and a distribution of chemical shifts. If the inversion pulse is applied after a period t of dephasing, the inhomogeneous evolution will rephase to form an echo at time 2t. In simple cases, the intensity of the echo relative to the initial signal is given by e−2t/T2 where T2 is the time constant for spin-spin relaxation.Echo phenomena are important features of coherent spectroscopy which have been used in fields other than magnetic resonance including laser spectroscopy and neutron scattering. Echoes were first detected in nuclear magnetic resonance by Erwin Hahn in 1950, and spin echoes are sometimes referred to as Hahn echoes. In nuclear magnetic resonance and magnetic resonance imaging, radiofrequency radiation is most commonly used.In 1972 F. Mezei introduced spin echo neutron scattering, a technique that can be used to study magnons and phonons in single crystals. The technique is now applied in research facilities using triple axis spectrometers.".
- Q904043 thumbnail HahnEcho_GWM.gif?width=300.
- Q904043 wikiPageExternalLink 872879.
- Q904043 wikiPageExternalLink index.php?option=com_content&view=category&layout=blog&id=103&Itemid=271.
- Q904043 wikiPageWikiLink Q104225.
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- Q904043 wikiPageWikiLink Q3396184.
- Q904043 wikiPageWikiLink Q3492917.
- Q904043 wikiPageWikiLink Q476205.
- Q904043 wikiPageWikiLink Q483666.
- Q904043 wikiPageWikiLink Q5724991.
- Q904043 wikiPageWikiLink Q5739615.
- Q904043 wikiPageWikiLink Q574576.
- Q904043 wikiPageWikiLink Q578430.
- Q904043 wikiPageWikiLink Q6425689.
- Q904043 wikiPageWikiLink Q7162170.
- Q904043 wikiPageWikiLink Q848722.
- Q904043 wikiPageWikiLink Q8595495.
- Q904043 wikiPageWikiLink Q899127.
- Q904043 wikiPageWikiLink Q900475.
- Q904043 wikiPageWikiLink Q9041630.
- Q904043 comment "In magnetic resonance, a spin echo is the refocusing of spin magnetisation by a pulse of resonant electromagnetic radiation. Modern nuclear magnetic resonance (NMR) and magnetic resonance imaging make use of this effect.The NMR signal observed following an initial excitation pulse decays with time due to both spin relaxation and any inhomogeneous effects which cause different spins in the sample to precess at different rates.".
- Q904043 label "Spin echo".
- Q904043 depiction HahnEcho_GWM.gif.