  We have studied hetero- and homonuclear excited state/ground state collisions
by loading both $^{85}$Rb and $^{87}$Rb into a far off resonant trap (FORT).
Because of the relatively weak confinement of the FORT, we expect the hyperfine
structure of the different isotopes to play a crucial role in the collision
rates. This dependence on hyperfine structure allows us to measure collisions
associated with long range interatomic potentials of different structure: such
as long and short ranged; or such as purely attractive, purely repulsive, or
mixed attractive and repulsive. We observe significantly different loss rates
for different excited state potentials. Additionally, we observe that some
collisional channels' loss rates are saturated at our operating intensities
(~15 mW/cm$^{2}$). These losses are important limitations in loading dual
isotope optical traps.
