We propose that alkali-metal migration in oxide glasses at low temperature occurs through Si${\mathrm{O}}_2$ units structurally relaxed by irradiation. With a combination of percolation and diffusion equations, we are able to explain all experimental data obtained by Pantano et al.

• Received 12 December 1985

DOI:https://doi.org/10.1103/PhysRevLett.56.1940