Limits of Applicability of the Popcorn Model for Desorption of Large Biomolecules by Fast Ion Impact

Abstract

The popcorn model, introduced to explain fast ion desorption of intact, large biomolecules, is discussed with particular reference to desorption of low mass and very high mass molecules. In the model, desorption of a large biomolecule is shown to result from rapid expansion of the molecule, following excitation of most vibrational modes by the intense low-energy electron flux emanating from the primary ion track. It is shown that the popcorn effect can readily induce desorption of individual molecules as light as 500 u, and also that the high mass limit for desorption may lie beyond that presently attained. It is argued that desorption of molecules with molecular weights as high as 105 might be possible by fast heavy ion impact.