CLUSTERING DISTANCES CRITICAL TO METAL DIMER FORMATION IN THE SECONDARY ION MASS-SPECTRA (SIMS) OF CESIUM-CHLORIDE

Cs2+ has been measured in SIMS of KCl-CsCl solid solutions in which [Cs]/[K] varies from 10-1 to 10-5. The data indicate that there is a maximum clustering distance, i.e., Cs-Cs distance, above which Cs2+ is not formed. This distance is ∼200 and ∼400 Å for He+ and Ar+ primary ions, respectively, and is independent of primary energy over the range 0.2-3.0 keV. The results are consistent with a mechanism in which bound secondary clusters consisting of atoms from contiguous as well as noncontiguous lattice sites are formed through potential interactions during irreversible adiabatic expansion of an activated region near the surface surrounding the impact site. © 1979 American Institute of Physics.