Formation of H3O+ from ethanol clusters induced by intense laser fields (100 fs, similar to 1 x 10(14) W/cm(2), 800 nm) was investigated by time-of-flight mass spectrometry. A positive correlation of H3O+ and (C2H5OH)H+ yields, along with the H-3 nDnO+ (n = 0-3) ratio from deuterium-labeled ethanol, led to the conclusion that H3O+ was efficiently eliminated from (C2H5OH)H+. Ab initio calculation for (C2H5OH)H+ isomers suggests the existence of two timescale regimes of hydrogen exchange processes before decomposition. The rate constant for decomposition was experimentally estimated to be 0.17 of the slower one, corresponding to hydrogen exchange between C2H5 and OH2 sites. (C) 2010 Elsevier B. V. All rights reserved.