Abstract— Porous Vycor glass samples containing adsorbed molecules were illuminated at 77 K by a mercury lamp jacketed by a filter cutting off wavelengths below 250 nm. Oxygen or carbon dioxide on Vycor produces an asymmetric electron paramagnetic resonance (EPR) signal best described as holes trapped in the glass. Methyl bromide produces an identical EPR signal plus four other lines due to methyl radicals. Evidence is presented that the products result from excitonic energy transfer from the Vycor to the adsorbed materials. Triphenylamine (TPA) adsorbed on Vycor can also be photoionized by similar illumination, and the cation radical TPA+ can be stabilized at 77 K if an electron acceptor is also adsorbed. Attachment of the photoejected electron by carbon dioxide forms CO2‐, and that by methyl bromide leads to methyl radicals. The CH3 radical yield is dependent on the surface separation between the electron donor (TPA) and the acceptor (CH3Br). By monitoring the relative quantum yield of the methyl radicals as a function of distance separating the TPA and CH3Br, it is shown that the photoelectron is capable of migrating on the Vycor glass surface.