Dependence of the desorption yield for valine on the charge state of the primary ions

The yield for molecular ions desorbed from a valine sample has been measured as a function of the charge state of the incident fast heavy ions. The data can be interpreted in the following way: (i) the yield depends on the square of the primary ion charge, and (ii) desorption takes place not only at the sample surface but also within a layer underneath. The depth of this layer is smaller than the depth needed to achieve charge state equilibrium for the primary ions.