Scuola Int Super Studi Avanzati Via Beirut 4 I-34013 Trieste Italy
Infm I-34014 Trieste Italy
Int Ctr Theoret Phys I-34014 Trieste Italy
European Synchrotron Radiat Facil F-38043 Grenoble France
Max Planck Inst Festkorperforsch D-70569 Stuttgart Germany

We calculate the magnetic susceptibility and g factor of the isolated C-60(-) ion at zero temperature, with a proper treatment of the dynamical Jahn-Teller effect, the associated orbital angular momentum, the Ham-reduced gyromagnetic ratio, and the molecular spin-orbit coupling. A number of surprises emerge. First, the predicted molecular spin-orbit splitting is two orders of magnitude smaller than in the bare carbon atom, due to the large radius of curvature of the molecule. Second, this reduced spin-orbit splitting is comparable to Zeeman energies, for instance, in X-band electron paramagnetic resonance at 3.39 kGauss, and a field dependence of the g factor is predicted. Third, the orbital gyromagnetic factor is strongly reduced by vibron coupling, and so therefore are the effective weak-field g factors of all low-lying states. In particular, the ground-state doublet of C-60(-) is predicted to show a negative g factor of similar to -.01.
 

Physical Review B, 54 17184-17190, 1996.