Resonantly enhanced multiphoton ionization (REMPI) and time-of-flight mass spectroscopy have been used to demonstrate that the reaction of Cl-2 on the low work function Al(111) surface proceeds via a prompt vertical electron harpooning process. Sticking measurements were performed showing that Cl-2 adsorbs via a direct chemisorption process at either high incident translation energy or high surface temperature. However, at glancing incident angles and low surface temperatures (100 K), a precursor-mediated channel predominates. REMPI studies show that fast abstracted Cl was produced via both channels: direct, remotely-dissociated incident Cl-2, and indirect, precursor-mediated Cl-2. For incident Cl-2 of 0.11 and 0.27 eV at 40degrees incident angle and 100 K surface temperature, only the precursor-mediated channel was observed with atomic Cl abstracted product energies of 0.09-0.14 eV. At high surface temperature, 500 K, all incident translational energies and angles yield only the direct channel, with abstracted product energies of 0.19-0.26 eV. (C) 2003 American Institute of Physics.