MECHANISM OF MEV ION-INDUCED HYDROGEN DEPLETION FROM ORGANIC LAYERS

In many materials, the loss of hydrogen during elastic recoil detectio n (ERD) analysis and nuclear reaction analysis (NRA) with MeV ions is observed. This phenomenon, which is especially pronounced in organic m aterials, limits the accuracy of the quantitative measurements feasibl e with these techniques. The MeV ion induced depletion was investigate d in an ion beam analysis study, using a wide range of projectiles and energies. From the results we conclude that the evolution of hydrogen from electropolymerized porphyrin layers is molecular, which leads to a model incorporating second order kinetics. With this model, the dep endence of hydrogen content on the primary ion flux is described by on ly the initial amount of hydrogen, the probability of ion induced bond breaking and a characteristic distance within two liberated hydrogen atoms will combine to a hydrogen molecule. When incorporating the ener gy deposited by the primary ion within the ion track into the model, t he observed quadratic dependence of ion induced damage on the stopping power is also explained.