Influence of massive projectile size and energy on secondary ion yields from organic surfaces

We investigated the influence of the projectile size and energy using Au_n^q+ clusters (5 < n < 400, 1 < q < 4) impacting on a glycine target with a 19q-34q keV energy range. We show that both CN⁻ fragment and Gly⁻ molecular ion yields are equivalent for projectiles with n > 9 and increase with the energy per projectile atoms. A maximum yield of 0.5 (50%) for both CN⁻ and Gly⁻ was obtained with the Au₄₀₀⁴⁺ projectile at 136 keV total energy. For Gly⁻, the yield enhancement is linear for Au_n when n > 5. Trends for the CN⁻ fragment are different. A nonlinear yield enhancement proportional to n³ is observed for Au_n when n < 9.