[en] A quantum mechanical model has been developed for the transport of very light and small gas molecules through polymers. The experimental results on isotope effects in diffusion, permeation, and solvation of H₂ and D₂ in polymer membranes made of polyethylene terephthalate, polyethylene, and polyvinylchloride can be interpreted by the model. Approximate information about the geometrical dimensions of the normal and activated energy state of polymers can be gained. (author)