Defect trapping of gas atoms in metals

Ion implantation provides a way to controllably introduce both defects and gas atoms into metals. This paper reviews implantation studies of the trapping of hydrogen and helium by simple defects in metals. In particular, the increasingly strong evidence for the role of vacancies as trap centers is examined. Interpreted trap structures and binding energies are summarized. Related effects for lighter particles of elementary charge (muons) and heavier inert gases (Xe) are discussed. (orig.)