Kinetic energy distributions of neutral In monomers and In-2 dimers sputtered from a polycrystalline indium surface under bombardment with 5 keV/atom Au-1(-) and Au-2(-) projectiles have been investigated by means of laser postionization time-of-flight mass spectrometry. Results show that 5 keVAu(1) bombardment leads to results in full compliance with linear cascade sputtering theory. For polyatomic ion bombardment, we find a clear transition to a collisional spike dominated emission process. The spike contribution appears as a low-energy part in the sputtered flux which increases with increasing projectile nuclearity, and energy. We show that, the velocity spectrum associated with the low-energy contribution is virtually identical for sputtered monomers and dimers. This finding has important implications with respect to the particle emission mechanism under polyatomic projectile bombardment. (c) 2006 Elsevier B.V. All rights reserved.