Reply to: Comment on 'Vibrational relaxation and spectral diffusion following ultrafast OH stretch excitation of water', by H.J. Bakker, A.J. Lock, D. Madsen

Both IR and anti-Stokes Raman measurements on OH stretch vibrations ν_OH of water see two time constants, ∼0.3 and ∼0.6 ps. We attribute the former to spectral diffusion and the latter to the ν _OH lifetime. This interpretation is evident from our Raman spectra, which show the ν_OH spectrum changing shape and the ν _OH population decaying. The ν_OH decay is accompanied by the rise (∼0.6 ps) and subsequent fall (∼1.4 ps) of population in the δ_OH bending vibration. Bakker et al. [Chem. Phys. Lett. 385 (2004) 329] assert their IR data indicates an absence of (>100 fs) spectral diffusion, that the faster time constant is the ν_OH lifetime and that the slower is the lifetime of a conjectured intermediate state. The properties of this conjectured intermediate differ significantly from the bending vibration directly observed by us. The intensity analysis by Bakker et al. said to contradict our interpretation relies entirely on ad hoc assumptions about excited-state absorptions. We show these ad hoc assumptions are unfounded and some are unreasonable, and that a plausible explanation for the IR intensities exists that is consistent with our interpretation.