Spectral diffusion in the OH stretching (nu(OH)) band of water is studied by ultrafast IR-Raman spectroscopy. The nu(OH) transition consists of two overlapping inhomogeneously broadened subbands, a broader (similar to500 cm(-1)) redshifted band and a smaller, narrower (similar to200 cm(-1)) blueshifted band. The blueshifted band, which shows less spectral diffusion, has a longer lifetime (0.75 vs 0.55 ps) and a smaller vibrational frequency blueshift from the ground state (65 vs 90 cm(-1)), is tentatively assigned to water molecules where one hydrogen atom has a broken hydrogen bond. (C) 2003 Elsevier B.V. All rights reserved.