ABSTRACT
Although an obvious and important role of surfaces in vacuum practice is that of the inner wall of the vessel in providing the boundary of the vacuum within, there are a number of processes occurring between gases and surfaces, both inside the vacuum and at its boundary wall, that make the role of surfaces more important than their mere mechanical presence. There are few circumstances in which surfaces play a strictly neutral role. For example, as we shall see shortly, the rebound of gas molecules from surfaces is not as simple as it is modeled to be in the kinetic theory presented in Chapter 3, though the results of that theory (be assured) are correct.
