Cascade and quasi thermal processes in excited atom sputtering

Current models of sputtered excited atom emission are compared and it is concluded that a direct atom-atom collision model affords a more realistic description than plasma or quasi plasma processes. However, although a formalism is derived for excited atom yields, quantification is not attempted because of present absence of knowledge of (1) collision induced excitation functions, (2) bound-free state excitation and dissociation promoted excitation processes during atomic ejection, and (3) the nature and magnitude of competing de-excitation processes. The influence of quasi thermal processes in producing surface atomic emission via sublimation during space-time extension of the initial cascade is also examined briefly. A formalism is developed to describe how this process may contribute to excited atom emission. (author)