  The direct photodissociation of trapped $^{85}$Rb$_2^+$ (rubidium) molecular
ions by the cooling light for the $^{85}$Rb magneto-optical trap (MOT) is
studied, both experimentally and theoretically. Vibrationally excited
Rb$_{2}^{+}$ ions are created by photoionization of Rb$_{2}$ molecules formed
photoassociatively in the Rb MOT and are trapped in a modified spherical Paul
trap. The decay rate of the trapped Rb$_{2}^{+}$ ion signal in the presence of
the MOT cooling light is measured and agreement with our calculated rates for
molecular ion photodissociation is observed. The photodissociation mechanism
due to the MOT light is expected to be active and therefore universal for all
homonuclear diatomic alkali metal molecular ions.
