Vibrational energy transfer from the O-H stretching modes in liquid water is studied by using QM/MM simulations and principal mode analysis (PMA). Two energy relaxation time scales of 0.6-0.7 and 0.3 ps are obtained by decorrelating the vibrational energy into principal modes. The longer time is interpreted as a vibrational energy relaxation (VER) process from the solute to bath, while the shorter time scale is attributed to an intramolecular vibrational energy redistribution (IVR) between the two O-H stretching modes. (c) 2005 Elsevier B.V. All rights reserved.