Rutherford backscattering has been used to study dye diffusion (using a sulfur atom in the dye as a label) into various polymer films with different glass transition temperatures. Diffusion into the films is induced via dye diffusion thermal transfer printing. Backscatter spectra are initially transformed into depth profiles, which are then fitted to the relevant equations in order to obtain diffusion coefficients. Both the diffusion coefficients and the depth of penetration of the dye are found to be controlled by the glass transition of the acceptor polymer matrix. With the dye-polymer interactions being similar in all samples and independent of polymer glass transition temperature, the diffusion coefficients are seen to be in excellent agreement with free-volume theories of diffusion. Backscatter specta are compared to theoretical simulations to obtain mass fractions for the dye/matrix throughout the polymer film.