A combined photoelectron spectroscopy and ab initio theoretical study was carried out to study the microsolvation of the acetate anion. Photoelectron spectra of cold solvated clusters CH3CO2-(H2O)(n) (n = 1-3) at 12 K were obtained and compared with theoretical calculations. The first water is shown to bind to the -CO2- group in a bidentate fashion, whereas both water-water and water-CO2- interactions are shown for n = 2 and 3. Significant rearrangement of the solvation structures is observed upon electron detachment, and water-CH3 interactions are present for all the neutral clusters, CH3CO2( H2O)(n) (n = 1-3). (c) 2009 Elsevier B. V. All rights reserved.