CESR
Definition and meaning of CESR in chemistry.
CESR (Conduction Electron Spin Resonance) is a specialized electron paramagnetic resonance technique that detects the resonant absorption of microwave radiation by the spins of delocalized conduction electrons in a metal, doped semiconductor, or conducting material placed in a magnetic field.
In more detail
Unlike ordinary EPR, which probes localized unpaired electrons in radicals or transition-metal complexes and gives symmetric absorption lines, CESR probes mobile conduction electrons that diffuse in and out of the microwave skin depth. This motion produces a characteristic asymmetric "Dysonian" line shape, and the signal intensity tracks the temperature-independent Pauli spin susceptibility rather than Curie-law paramagnetism. CESR thus reveals the electron g-factor, spin relaxation times, and the density of states at the Fermi level, making it valuable for studying electronic structure in metals, conducting polymers, graphite, and doped fullerenes.
Key facts
| Full name | Conduction Electron Spin Resonance |
|---|---|
| Field | Physical Chemistry |
| Line shape | Asymmetric (Dysonian), due to the microwave skin effect |
| Typical samples | Metals, conducting polymers, graphite, doped fullerenes |
CESR measurements on potassium-doped fulleride K3C60 revealed a narrow, asymmetric resonance line consistent with delocalized conduction electrons and confirmed its metallic (rather than insulating) electronic character.
Frequently asked questions
How does CESR differ from standard EPR?
Standard EPR detects localized, immobile unpaired electrons and gives symmetric Lorentzian or Gaussian lines following Curie-law temperature dependence. CESR detects mobile conduction electrons, giving asymmetric Dysonian lines whose intensity reflects the temperature-independent Pauli spin susceptibility.
What does a CESR spectrum tell you?
It yields the conduction-electron g-factor, spin relaxation times (T1 and T2), and, through the Pauli susceptibility, information about the density of electronic states at the Fermi level.