The collision energy dependence of the Ca*(D-1(2)) + HBr --> CaBr*(A,B) + H reaction cross sections has been measured over the 210-290 meV range using the time-of-flight technique under crossed molecular beam conditions. Both reaction channels show a steep increase with pronounced maximum at low energy, followed by a sharp decline as energy increases. A modified time-dependent Landau-Zener model is employed to describe the transition probability from the entrance neutral to the exit ionic channels, directly leading to reaction products. This model, which incorporates the influence on the reaction dynamics of the time necessary for the rearrangement of the intermediate complex, satisfactorily accounts for the experimentally observed translational features of the excitation functions.