Difference between revisions of "Electron Spin Resonance (ESR)"
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=== Significance === | === Significance === | ||
In ESR | In a standard ESR experiment, the sample is irradiated with the microwave field at the constant frequency (~10GHz), the external magnetic field is slowly changed. Electron spins align with the field, but also can precess around the equilibrium orientation | ||
The frequency of the spin precession depends on the field, it increases (linearly in a simple case) with the field increasing. When the field passes through the point, where the spin precession frequency corresponds to the microwave frequency applied, the sample will absorb microwave radiation ( and the electron spin flips from orientation spin-down to spin-up) | |||
<div id="Flash">ESR animation</div> <swf width="500" height="400">images/2/21/Esr.swf</swf> | <div id="Flash">ESR animation</div> <swf width="500" height="400">images/2/21/Esr.swf</swf> | ||
Revision as of 09:46, 10 November 2010
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Background
Electron Spin Resonance (ESR) also known as Electron Paramagnetic Resonance (EPR) spectroscopy or electron paramagnetic resonance spectroscopy is a technique for studying chemical species that have one or more unpaired electrons. It is analogous to NMR except it deals with spins of electrons rather than the spins of atomic nuclei. It is most useful in studying free radicals or organic complexes having transition metal ions since most stable molecules have all their electrons paired. Most ESR spectra are recorded and published as first derivatives of the original signal.
Significance
In a standard ESR experiment, the sample is irradiated with the microwave field at the constant frequency (~10GHz), the external magnetic field is slowly changed. Electron spins align with the field, but also can precess around the equilibrium orientation
The frequency of the spin precession depends on the field, it increases (linearly in a simple case) with the field increasing. When the field passes through the point, where the spin precession frequency corresponds to the microwave frequency applied, the sample will absorb microwave radiation ( and the electron spin flips from orientation spin-down to spin-up)
<swf width="500" height="400">images/2/21/Esr.swf</swf>