Desorption of alkali halides upon collision of neutral SO2 clusters on Au and SiO2 surfaces was investigated. For desorption of halogen species X, an ionic desorption channel of the form of (SO2)(n)X- was identified at room temperature on both surfaces. Temperature programmed redistribution of the surface configuration suppresses this desorption channel. Alkali species are desorbed as (SO2)(n)M+; however, on Au surfaces the signal is accompanied by a (SO2)(n)SO2- signal of the same intensity. No such (SO2)(n)SO2- signal of similar strength was observed for desorption from SiO2. The difference is attributed to the different electronic structure of the two substrates. (C) 2012 Elsevier B. V. All rights reserved.