The conduction electron spin resonance (CESR) of Rb3C60 has been obser
ved, and the spin susceptibility is found to be chi(s)=(12.4+/-4)x10(-
4) emu/mole, in agreement with the static measurements. The CESR linew
idth of Rb3C60 is 600G at room temperature. Formerly the ESR of Rb1C60
has been erroneously assigned to Rb3C60. It has a width of 6.5G at 30
0K and shows the polymer to monomer transition at 400K. Below this tem
perature Rb1C60 is a quasi-1D metal with a transition to a spin densit
y wave ground state at 50K.