Self-diffusion involves the motion of atoms that are all of the same type; therefore, it is not subject to observation by compositional changes, as with interdiffusion. Suggest one way in which self-diffusion may be monitored.

One way to monitor self-diffusion is by using radioactive isotopes to trace the movement of atoms in the material. This can be done by introducing a small amount of a radioactive isotope of the element in question to the material. The radioactive atoms will undergo self-diffusion just like the non-radioactive atoms, and their motion can be tracked using radiation detection techniques. For example, an appropriate radioactive isotope can be placed at the surface of a solid sample. As self-diffusion occurs, the radioactive atoms will move from the surface into the bulk of the material. By measuring the changes in radiation intensity at different depths within the material over time, one can determine the rate of self-diffusion for the atoms in question. This method is non-destructive and allows for precise tracking of individual atom movements, making it a suitable technique for monitoring self-diffusion in various materials.