The chemical interactions and the 308‐nm laser radiation effects on NH3, C2H4, and CH2I2 adsorbed on Al and oxidized Al surfaces have been studied by x‐ray photoemission, thermal desorption, and time‐of‐flight mass spectrometry. The mass and the translational energy distributions are determined as a function of surface coverage and laser fluence. For NH3 and C2H4, the major radiation effect appears to be laser‐induced thermal desorption. For CH2I2 on Al, the adsorbate electronic excitation effect is evident at both submonolayer and multilayer coverages. At a submonolayer coverage, CH2 radicals and C2H4 molecules are produced and can be desorbed by laser pulses. Part of the products may be trapped on the surface. At a multilayer coverage on Al and any coverage on the oxidized Al, photodissociation leads to CH2I and I formation. At very high coverages, adsorbate‐mediated ‘‘explosive’’ desorption can take place on any substrate. The results yield the characteristic electronic, thermal, and explosive desorption patterns depending on the gaseous exposure, the substrate, and the laser irradiation conditions.