Time‐resolved optical emission spectroscopy, with a resolution of ∼10 ns, was used to investigate the formation of excited photofragments during KrF laser‐irradiation of trimethylaluminum (TMA) and triethylaluminum (TEA). The gases were introduced into a vacuum chamber as pulsed molecular beams expanding from a free‐jet nozzle. The time‐dependence of the fluorescence intensity was measured at various positions, corresponding to different gas pressures P, along the molecular beam. In the case of TMA, the primary peaks observed were the Al 4s 2S→3p 2P atomic transition and the CH A 2Δ→X 2Π (0,0) band. The CH intensity ICH following a laser pulse decreased exponentially with a 1/e decay time τCH ranging from ∼530 ns, in agreement with the radiative lifetime of CH 2Δ(v=0), in the low pressure region of the molecular beam, to ∼150 ns at high pressures. The decrease in τCH with increasing PTMA was due to collisional quenching. The decay of the Al emission intensity IAl was nonexponential since the radiative lifetime of the Al 2S state, 6.8 ns, was less than the laser pulse width, ∼15 ns. The rise times of IAl and ICH, on the other hand, were both ≪10 ns indicating that CH, like Al, is formed photolytically rather than through subsequent collisions involving photofragments. Substituting TEA for TMA suppressed the CH signal while a new molecular band due to AlH [the (0,0) band of the A 1Π→X 1Σ+ transition] was observed in addition to the atomic Al 2S→2P transition. The rise time of IAlH was also ≪10 ns indicating that it too was formed photolytically. τAlH was ∼80 ns in agreement with the published AlH radiative lifetime. The significance of these results on the mechanisms of TMA and TEA photodecomposition and C incorporation in Al films grown by KrF‐laser photolysis is discussed.