The sputtering of molecular ions from surfaces in secondary ion mass spectrometry

Abstract

Recently, experimental evidence was reported that the charge state and the sputtering mechanism of molecular ions may be connected. In an attempt to understand this phenomenon, this paper discusses the excess energies and the stability towards electron ejection for molecules formed by the recombination of nonadjacent sputtered atoms. It is shown that since the electron affinities of molecules are usually small, stability of a negative molecular ion against neutralization by autodetachment is possible only when the molecule is formed by lattice fragmentation in most cases. On the otherhand, the ionization potentials of neutral and positive molecular ions are usually large and stability against electron ejection is possible even if they are formed by the recombination of nonadjacent sputtered atoms. © 1982.