On the kinetic energies of sputtered excited particles, I. Atoms sputtered from Li, LiF, and NaCl

Results relating to the yield, as a function of distance from the target, of photons from excited atoms sputtered from Li, LiF, and NaCl are considered. By using an observation slit of small opening (0.2 mm), there was sufficient spatial resolving power to obtain realistic decay curves even for short-lived states. These curves should, on the assumption that the sputtered excited atoms have an energy distribution proportional to E −2 and an angular distribution which is isotropic, be governed by the relation where z is proportional to (distance)/E*½, E* being the assumed minimum kinetic energy of the distribution of energies characterizing the excited atoms. The E* values lie mainly in the interval 101–102 eV. They are thus well below the values found in some previous work, but still higher than the most probable energies of the overall sputtering process or of secondary ions. This suggests that excitation occurs mainly with atoms in the tail of the sputtered-atom spectrum. Highenergy events (∼ > 103 eV) and thermal sputtering can both be ruled out, as can events of the type which lead to ionization