The nature of electron pairing mechanism and the superconducting transition
temperature (T-c) of alkali metal (Rb) doped fullerenes is studied within
the framework of strong coupling theory. Chemical substitution of alkali me
tal in the:parent compound introduces free electrons in the lowest unoccupi
ed molecular orbital and for Rb3C60, the band is filled up to the Fermi lev
el. The intercage interactions between the adjacent C-60 cages and expansio
n of lattice due to the intercalation of Rb atoms are investigated using ne
arest-neighbor interactions. The free electrons in lowest molecular orbital
are coupled with intermolecular phonons. The renormalized Coulomb repulsiv
e parameter mu* and the attractive coupling strength lambda are obtained fo
r the intermolecular phonon frequency omega(er). T-c is then estimated as 8
.6 K, which is lower as compared with the published data of 30 K. The elect
rons also couple with the intramolecular phonons and introducing them in ad
hoc way, T-c enhances to 34 K. Analytical results on T-c allow one to visu
alise the relative interplay between the strength of inter- and intramolecu
lar phonons. To illustrate the usefulness of the above approach the carbon
isotope effect exponent and the energy gap ratio are estimated which are co
nsistent with the experimental data. The present analysis reveals that both
low frequency intermolecular and high frequency intramolecular phonons par
ticipate in the pairing mechanism, T-c mainly arises from high frequency in
tramolecular phonons.