Cluster formation under bombardment with polyatomic projectiles

We describe a new tandem mass spectrometer which has been designed to inves tigate sputtering phenomena at solid surfaces under bombardment with polyat omic projectile ions with particular emphasis on the detection of neutral a toms and clusters ejected from the surface. The primary ions an generated i n a cluster ion source which is based on pulsed laser ionization of neutral particles sputtered from another solid surface bombarded with 5-keV Xe+ io ns. In order to characterize the sputtering processes initiated by these io ns, neutral atoms and clusters ejected from the target surface are analyzed by means of single photon ionization using an intense pulsed VUV laser in a second, reflectron type time-of-flight (ToF) mass spectrometer. We report on first results obtained with this instrument regarding the self-sputteri ng of a polycrystalline silver surface under bombardment with 8-keV atomic silver ions and polyatomic silver cluster ions. More specifically, the yiel ds of neutral Ag-n clusters with n = 1, ..., 4 as well as the variation of the total sputtering yield have been determined using Ag+, Ag-2(+) and Ag-3 (+) projectile ions. (C) 2000 Elsevier Science B.V. All rights reserved.