The collisions of neutral or charged gaseous particles with solid
surfaces govern many physical and chemical phenomena, as has been The
gas/solid phenomena in turn depend on a recognized for a long time.
great variety of processes such as the charge transfer of the gas/solid
interface, adsorption and desorption, the energy transfer between an
incident particle and the surface, etc. Our knowledge of these
processes, however, is only fragmentary. This is partly due to the
difficulty in adequately controlling the ex- perimental conditions.
Consequently, until recently the data were usually so complex that
reliable information about a particular elementary process could not be
deduced. Within the last five to ten years, however, the techniques of
ultra-high vacuum and surface preparation have developed rapidly and
there has been a booming and widespread interest in the role of
gas/solid interactions in such diverse fields as plasma physics,
thermonuclear reactions, thermionic energy conversion, ion propulsion,
sputtering corrosion of the surface of satellites and ion engines, ion
getter pumps, deposition of thin films, etc. This led to extensive
investigations of numerous gas/solid phenomena, such as surface
ionization, sputtering, emission of secondary electrons and ions from
surfaces under atom and/or ion impact, ion neutralization, and the
thermal accomodation of gaseous particles on surfaces. As a result, it
has become possible to gather a variety of valuable information.