We show the presence of a strong negative feedback effect in the vibrational relaxation of the O-H stretch vibrations of liquid H2O. The vibrational relaxation of an O-H stretch vibration leads to the excitation of strongly coupled low-frequency modes, which induces a deceleration of the relaxation of other still excited vibrations. We present a model for this feedback effect, with which we obtain a consistent interpretation of the experimental results of recently reported femtosecond mid-infrared pump-probe experiments and mid-infrared pump anti-Stokes Raman probe experiments.

Chem. Phys. Lett.
Ultrafast Spectroscopy

Bakker, H., Lock, A. J., & Madsen, D. (2004). Strong feedback effect in the vibrational relaxation of liquid water. Chem. Phys. Lett., 384, 236–241. doi:10.1016/j.cplett.2003.12.022