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 selfdiffusion may be monitored.

First, it's important to understand what self-diffusion is. Self-diffusion is the process where atoms of the same type move or exchange positions within a material. In other words, atoms move from one site to another in the same material structure without any compositional changes.

Monitoring self-diffusion can be challenging since there are no compositional changes taking place during this process. Conventional methods used for monitoring diffusion like tracking changes in concentration of atoms or elements cannot be used in this case. Thus, we need an alternative method to observe the motion of the same type of atoms within the material.

One way to monitor self-diffusion is using a radioactive tracer technique. In this method, a small amount of atoms within a material are replaced with their radioactive isotopes. These radioactive atoms will have the same chemical properties as the non-radioactive atoms, but they emit detectable radiation as they undergo decay.

By placing a radiation detector near the material, we can measure the radiation emitted from the radioactive atoms. Over time, as the radioactive atoms move through the material via self-diffusion, the radiation detected at different locations within the material will change. This change in detected radiation can be used to monitor the self-diffusion process and calculate the diffusion coefficients of the atoms in the material. In summary, to monitor self-diffusion, we can use the radioactive tracer technique, which involves replacing a small amount of atoms in a material with their radioactive isotopes and measuring the changes in emitted radiation over time. This method allows us to observe the motion of atoms of the same type within a material, even when there are no compositional changes.