Conduction Electron Spin Resonance (CESR)
Definition and meaning of Conduction Electron Spin Resonance (CESR) in chemistry.
CESR (conduction electron spin resonance) is a magnetic-resonance technique that detects the resonant absorption of microwave radiation by the spins of delocalized conduction electrons in a metal or other conducting sample held in a static magnetic field.
In more detail
It works on the same physical principle as electron paramagnetic resonance (EPR), but the resonating spins belong to itinerant electrons in a conduction band rather than localized unpaired electrons on a radical or transition-metal ion. Because the microwave field only penetrates a thin skin depth of the conductor, CESR signals often appear as an asymmetric "Dysonian" lineshape (a mix of absorption and dispersion) rather than the symmetric line seen in ordinary EPR. From the linewidth, intensity, and g-factor, chemists and physicists extract the electron spin relaxation time, the Pauli spin susceptibility, and information on electron-phonon coupling.
Key facts
| Full name | Conduction Electron Spin Resonance |
|---|---|
| Field | Physical Chemistry |
| Typical lineshape | Dysonian (asymmetric absorption-dispersion mix) |
| Measures | g-factor, spin relaxation time, Pauli spin susceptibility |
CESR studies of alkali-metal-doped fullerides such as K3C60 show a characteristic Dysonian lineshape whose linewidth and intensity are used to track the conduction-electron spin susceptibility as the material approaches a metal-insulator or superconducting transition.
Frequently asked questions
How does CESR differ from ordinary EPR?
EPR probes localized unpaired electrons, such as those in radicals or transition-metal complexes, while CESR probes delocalized conduction-band electrons in metals; the latter typically shows a skin-depth-distorted Dysonian lineshape instead of a symmetric EPR line.
Why is CESR useful?
It gives a direct, element-specific probe of conduction-electron spin dynamics and Pauli paramagnetism, helping characterize metals, doped semiconductors, and materials near superconducting or magnetic transitions.