We have studied the photodissociation spectroscopy of weakly bound Al + salkene bimolecular complexes (sethene, spropene, and sbutene) in the 216-320 nm spectral region. Molecular absorption bands are assigned to photoinduced charge transfer transitions to states that correlate with the Al(3s 2 3p) + (alkene) + product channels. Similarities in the absorption spectra for Al + sethene, spropene, and s1-butene suggest similar equilibrium geometries with the metal ion lying above the alkene CdC π-bond in each case. The vibrational resonance structure is assigned to intramolecular modes of the alkene. The absorption spectra for Al + s2-butene are broader with less identifiable structure. A clear threshold for charge transfer dissociation to each alkene ion product gives a limit for the corresponding Al + salkene bond dissociation energy: D 0 ′′-(AlsX) e 9.2, 19.1, 19.8, 24.7, and 28.2 kcal/mol for X ) ethene, propene, 1-butene, cis-2-butene, and trans-2-butene, respectively. Experimental results are in good agreement with ab initio predictions.