A "harpooning" mechanism is investigated for the chemiluminescent reactions of Ca*(D-1(2)) atoms with HCl (leading to CaCl* in the A state) and with HBr (leading to CaBr* in both the A and B states). A model of the interactions in the entrance channels, which involves an electron jump and leads to a charge-transfer intermediate complex, accounts for the selective dependence of reactivity on the relative orientation between the molecule and the outer electronic orbital of the atom. The dynamical treatment incorporates in the Landau-Zener approach the synchronization between times for nonadiabatic transitions and for triggering the rearrangement of the intermediate collision complex. The treatment accounts for the observed features of the translational energy dependence of the cross sections: The steep initial increase with a pronounced maximum, the sharp decline and also fine details, such as a stairlike behavior.