Energy of secondary ions desorbed from insulating films by MeV heavy ions as a function of projectile velocity

Abstract

The influence of projectile velocity on the axial energy distribution and mean axial energy of secondary ions was measured with a double-field time-of-flight method at the GSI accelerator-system. The secondary ions were ejected from thin layers ( ~ 150 nm) of CsI, MgO, CaF2, valine and phenylalanine irradiated with Sn and U projectiles. The mean energy of ions like Cs + and Mg + clearly increases in the velocity range from 0.3 to 1.5 cm/ns, whereas the energy of cluster ions remains almost constant. In most cases an influence of the cluster size on the mean ion energy was not observed. The results are discussed in relevance to desorption models and their significance for the optimum design of time-of-flight mass spectrometers.