INTERACTION OF ATOMIC AND MOLECULAR MEV IONS WITH SURFACE

Secondary ion emission was studied using atomic and molecular ions bom barding organic and metallic targets. The energy of the projectile ion s varied from 200 keV to 3 MeV. Relative yields of positive and negati ve secondary ions desorbed from phenylalanine and aluminum targets wer e identified by time-of-flight mass spectrometry. C(q+), O(q+), N(q), CO+ and CO2+ (0 less-than-or-equal-to q less-than-or-equal-to 7) were the beams used in this study. The yield obtained for [M-H]-, [M+H]+ an d H- and H+ secondary ions indicate the existence of two mechanisms fo r the desorption process: the kinetic and the surface mechanism.