g-Factors and Discrete Energy Level Velocities in Nanoparticles

We establish relations between the statistics of g factors and the fluctuations of energy in metallic nanoparticles where spin-orbit coupling is present. These relations assume that the electron dynamics in the grain is chaotic. The expressions we provide connect the second moment of the g factor to the root-mean square ``level velocity'' (the derivative of the energy with respect to magnetic field) calculated at magnetic fields larger than a characteristic correlation field. Our predictions relate readily observable quantities and allow for a parameter-free comparison with experiments.