H-1-OVERHAUSER SHIFT IN RADICAL-CATION SALTS

Radical cation salts of planar aromatic pure hydrocarbons are model systems for quasi-one-dimensional organic conductors. The mobility of the conduction electrons leads to a strong motional narrowing of the electron spin resonance (ESR). These narrow lines allow detailed investigations of the Overhauser shift of the ESR. This shift is caused by hyperfine interaction of the conduction electrons with protons and C-13. By a double resonance technique this shift can be measured, and investigations of NMR saturation and nuclear relaxation times are presented. The lineshape of the H-1-resonance is dominated by dipolar proton-proton coupling. We show that the Overhauser shift technique is similar to common CW-NMR but with an improved sensitivity.