Reactions of laser-evaporated aluminum atoms with molecular fluorine, chlorine, bromine, and iodine in excess argon during condensation onto a CsI window at 11 +/- 1 K produced the AIX, (X = F, Cl, Br, I and n = 1-3) and Al(2)X(6) molecules, which were characterized by infrared absorption spectroscopy. Low laser power favored the primary reaction product AlX and AlX(2) transient species over the more stable secondary reaction product AlX(3) molecules. Chlorine and bromine isotopic structures substantiated the molecular identifications and vibrational assignments. DFT calculations were done for the AlCln and AlBrn series to support the vibrational assignments. Possible Al2Cl4 structures were also explored by DFT calculations, and evidence is presented for a distorted Cl2AlCl2Al structure. The present study provides further evidence for transient aluminum dihalide radicals for the four halogens.