SPUTTERING OF BIOORGANIC SAMPLES

In recent years methods based on particle impact on solid and liquid surfaces have been exploited to extend mass spectrometry to high-molecular-weight organic compounds, like biomolecules. One of the most important aspects of these sputtering methods is that one is able to produce ions of whole organic molecules. So far mainly charged ejecta, as exploited in the mass spectrometry applications, have been studied. Since a couple of years, experimental electronic sputtering yields of neutral intact ejecta are available, showing a cubic dependence on deposited energy. Studies of radial velocity distributions of large organic molecular ions show that the ejection angle is related to the angle of incidence of the primary particle. These experimental findings have been reproduced in molecular dynamics simulations of electronic sputtering of large organic molecules. Also an analytical sputtering formula has been derived which describes sputtering by a particle producing a high energy density, in qualitative agreement with experimental data. © 1990.