  Reduction factors (RF), that are needed when modeling vibronic systems by an
effective Hamiltonian in an electronic basis, are calculated for the T_1u x h_g
Jahn-Teller (JT) system. The results obtained will be useful when modeling the
fullerene anion C_60-, which is believed to exhibit a T_1u x h_g JT effect in
its ground state. First-order RF's are calculated using symmetry-adapted
vibronic ground and tunneling states in which the system is allowed to tunnel
between equivalent minima in the potential energy surface. The effect of
anisotropy in the minima is also considered. Second-order RF's are calculated
incorporating coupling to excited harmonic-oscillator states associated with
the minima.
