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Electron Spin Resonance
Electron Spin Resonance
Electron spin resonance is a tool for investigating materials with a net spin magnetic moment, arising from unpaired electrons, such as free radicals and paramagnetic substances. When an external magnetic field is applied to paramagnetic substances, magnetic moment of unpaired electrons is able to align parallel and anti parallel to the external field. These two alignment corresponds to different energy levels, with a statistical probability to be populated that depends on the temperature. By applying the microwave radiation to the sample a transition to a higher state can be achieved. The precise energy difference between the two states of an electron depends on the surrounding electrons in the atoms or molecule. In this way the location of the unpaired electron can be investigated. Significance in Carbon nanotubes: ESR signals from carbon nanotubes should be generated by localized spins due to impurities, defect centers and for conduction electrons originating from metallic or semiconducting nanotubes with a small band gap.
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