An ab initio direct molecular dynamics study of the fragmentation of the unstable, neutral F(H2O) complex has been performed. A photodetachment experiment of the stable F-(H2O) anion complex produces F(H2O) in the vicinity of the transition-state region of the hydrogen abstraction reaction, F + H2O --> FH + OH. Ab initio energy and gradient evaluations in the direct molecular dynamics simulation were done at the QCISD/6-311 +G** level of theory. The product vibrational and rotational states were computed and the mechanism of the reaction examined. The primary products of reaction are vibrationally excited HF and rotationally warm but vibrationally cold (v" = 0) OH. The reaction proceeds through three channels. In order of the frequency of occurrence, these are: (1) direct abstraction of a hydrogen atom by F; (2) dissociation into F + H2O; and (3) direct abstraction of a hydrogen atom by F with subsequent formation of a weakly bound FH-OH complex. (C) 2002 Elsevier Science B.V. All rights reserved.