The velocity dependence of fast heavy-ion induced desorption of biomolecules

Heavy-ion beams from the Uppsala EN-tandem have been used to induce desorption of ions from samples of glycylglycine, ergosterol and cesium iodide. The experimental technique, involving time-of-flight mass spectroscopy, and the apparatus are described. Secondary ion yields of (M + H)+, M+ and Cs+, where M denotes the molecule, have been measured as a function of the atomic number and velocity of the fast primary ions. The results show that the desorption process is connected to the electronic part of the energy loss of the primary ion. A thermal spike model earlier presented to describe sputtering yields from uranium tetrafiuoride1 induced by MeV fluorine beams is shown to reproduce some general features of the measured yield distributions.