High field-high frequency electron spin resonance spectroscopy. Multi-frequency ESR spectroscopy

High field-high frequency electron spin resonance (esr) spectroscopy is applied to the determination of spin parameters for metallofullerenes. The esr measurements combined with multi-frequency microwave are indispensable for unambiguous of the parameters. The magnetic field independent terms in the spin Hamiltonian can be easily distinguished from the dependent ones by using the multi-frequency esr measurements. The orientation-dependent g-tensor of La(a)C82 can be determined by W-band measurements. The fine structures in the high spin system of Eu(a)C82 are clearly analyzed by the combination of W-band spectroscopy with X-band one. In Gd(a)C82 there are two spin sites within a molecule, the high spin site on the Gd3+ ion and the other radical site on the fullerene cage. The exchange interaction is valued by the temperature dependent W-band measurements. The large hyperfine interaction due to La2 dimer nuclei within C80 is investigated for La2(a)C80 anion. (author)